CN102882522B - Quantum interference device, atomic oscillator and magnetic sensor - Google Patents

Abstract

The invention provides quantum interference device, atomic oscillator and Magnetic Sensor.Described quantum interference device produces electromagnetically induced Transparency Phenomenon, and it is characterized in that, this quantum interference device has: the alkali metal atom of gaseous state, and it has 2 ground state levels and at least 1 excitation level, and described 2 ground state levels have energy difference; And inciding the multipair resonance light pair of alkali metal atom of described gaseous state, resonance light described in each is to 2 kinds of frequencies with the difference on the frequency keeping corresponding to described energy difference, and the centre frequency that resonance light described in each is right is different from each other.

Description

Quantum interference device, atomic oscillator and Magnetic Sensor

The application is the applying date is on February 5th, 2010, and application number is 201010113602.x, and denomination of invention is the divisional application of the application for a patent for invention of " quantum interference device, atomic oscillator and Magnetic Sensor ".

Technical field

The present invention relates to quantum interference device, atomic oscillator and Magnetic Sensor, more particularly, relating to the technology for producing EIT phenomenon efficiently.

Background technology

The atomic oscillator of electromagnetically induced transparent mode (sometimes also referred to as EIT mode, CPT mode) is the oscillator of the phenomenon that make use of as follows, that is: when simultaneously to 2 kinds of resonance light that alkali metal atom illumination wavelength is different, the absorption of 2 kinds of resonance light stops (EIT phenomenon).Figure 24 (a) represents the energy state of 1 alkali metal atom.As everyone knows, when separately irradiating the 1st resonance light of the wavelength with the energy difference be equivalent between the 1st ground state level 23 and excitation level 21 to alkali metal atom or there is the 2nd resonance light of wavelength of the energy difference be equivalent between the 2nd ground state level 24 and excitation level 21, light absorption will be caused.But, when irradiating the 1st resonance light and the 2nd resonance light to this alkali metal atom and difference on the frequency between the 1st resonance light of irradiating and the 2nd resonance light and the energy difference (Δ E12) between the 1st ground state level 23 and the 2nd ground state level 24 are consistent exactly simultaneously simultaneously, the system of Figure 24 (a) is in the coincidence status of 2 ground state levels, i.e. quantum interference state, excite stopping to excitation level 21 transition, produce transparent (EIT) phenomenon.The sharply change of light absorption action when utilizing this phenomenon to detect the wavelength difference between the 1st resonance light and the 2nd resonance light to depart from Δ E12, and it can be used as signal to control, thereby, it is possible to produce high-precision oscillator.In addition, Δ E12 changes, therefore, it is possible to utilize EIT phenomenon to manufacture highly sensitive Magnetic Sensor sensitively with the intensity of external magnetic field or variation.

In addition, in order to improve the signal to noise ratio (S/N) of the optical output signal under EIT phenomenon, as long as increase and the interactional alkali-metal atomic quantity of resonance light.Such as, in patent documentation 1, for the purpose of the S/N improving the output signal of atomic oscillator, disclose such as the following method: increase the thickness being sealed with the air chamber (cell) of gaseous alkali metal atom, or increase the beam diameter inciding the laser of air chamber.No matter any method, in order to increase the region that alkali metal atom contacts with resonance light, as shown in Figure 24 (b) or Figure 24 (c), all increases thickness or the height of air chamber.About used laser, only employ 1 to the occurrence condition (development See condition meeting EIT phenomenon here) the laser of 2 kinds of wavelength.

In addition, in patent documentation 2, (1) discloses the technology of the sensitivity about the atomic oscillator improving EIT (CPT) mode.That is, be characterised in that D1 line as light source.Compared with the situation of D2 line in the past, EIT (CPT) signal strength signal intensity can be improved in theory.Thus, sensitivity/frequency stability is improved.(2) and, use 4 light wave light sources, the P1/2 excitation level (hyperfine structure) utilizing the transition of dual Λ type to make energy be split into 2 interacts simultaneously, thus, improve signal strength signal intensity further, but technology disclosed herein relates to 4 light wave mixing, does not belong to the scope of the technical field that the present invention relates to.

Patent documentation 1: Japanese Unexamined Patent Publication 2004-96410 publication

Patent documentation 2:USP6359916

Pay close attention to each atom of the formation gaseous alkali metal atomic group in air chamber, known have the certain VELOCITY DISTRIBUTION corresponding with respective motion state.If the wavelength inciding the laser of this atomic group only has 2 kinds (a pair), then under the impact of the Doppler effect (Doppler frequency shift) of atomic motion, in fact interactive atom is in the multiple atoms in air chamber, have few part of specific velocity component value in laser incident direction atom, and the ratio contributing to the atom producing EIT is extremely low.There is following problem in the prior art disclosed in patent documentation 1, that is: because atomic oscillator forms under the state that this EIT generation efficiency is low, therefore in order to obtain the absorption spectrum of the larger expectation of signal to noise ratio (S/N), one in the thickness of air chamber or height must be increased, be difficult to realize while maintenance signal to noise ratio miniaturized.That is, the atomic quantity contributing to EIT phenomenon in the per unit volume in air chamber remains unchanged.In addition, also there is identical problem in the technology disclosed in patent documentation 2-(1).

That is, patent documentation 1,2-(1) all only employ 2 kinds of light waves.Alkali atom in air chamber has VELOCITY DISTRIBUTION, there is the doppler spread of the energy accompanied therewith.Therefore, in the Λ type transition only having 2 kinds of light waves, only with few atomic interaction partly, therefore, the EIT of per unit volume produces yield rate extreme difference.Therefore, there is the problem that EIT signal strength signal intensity is weak.

The excitation level of actual alkali atom has hyperfine structure, splits into the energy level with energy different from each other shown in Figure 20.Therefore, can not illustrating with alkali atom to be the EIT phenomenon of object by the simple Λ type 3 energy state system shown in Figure 24 (a), therefore, in fact, in order to produce EIT efficiently, needing to consider such multiple level.But there is such problem, that is: up to now, consider multi-level existence and the research of relation between expanding with the power doppler that above-mentioned atomic velocity distributes still insufficient.

Especially, from apply EIT phenomenon quantum interference device drive condition optimization angularly, as the present invention, consider that when using multipair resonance light right the energy state of excitation level decides the centre frequency of light source (laser) or the modulation condition of decision laser is very important.

Summary of the invention

The present invention is just in view of above-mentioned problem completes, its object is to, there is provided by generating the different multipair resonance light pair of wavelength, make the more gaseous alkali metal atom in air chamber produce the quantum interference device of EIT phenomenon efficiently, and provide small-sized atomic oscillator, Magnetic Sensor or quantum interference transducer by utilizing this quantum interference device.

The present invention, in order to solve completing at least partially of above-mentioned problem, can be used as following mode or application examples realizes.

[application examples 1] quantum interference device at least has: the alkali metal atom of gaseous state; And light source, it is for generation of the resonance light pair of different frequency, the difference on the frequency that this resonance light is corresponding to the energy difference kept between 2 ground state of this alkali metal atom, make described alkali metal atom and described resonance light Thermodynamic parameters, produce electromagnetically induced Transparency Phenomenon (EIT), it is characterized in that, the quantity that described resonance light is right is multipair, and the centre frequency that each resonance light is right is different from each other.

The feature of quantum interference device of the present invention is, the right quantity of excitation laser is 2 to above multipair, and the right centre frequency of each laser is different from each other.Thereby, it is possible in per unit volume, more gaseous alkali metal atom is made to produce EIT phenomenon.

[application examples 2] is characterised in that, with the interactional resonance light of described alkali metal atom to being linearly polarized light.

For the resonance light pair penetrated from light source, in the face vertical with the direction of propagation of light, the tip representation of electric vector goes out straight line, this light is called as linearly polarized light.Therefore, if not to the resonance light penetrated from light source to enforcement polarization, then it is linearly polarized light.In addition, polarisation of light state can be considered to the coincidence of 2 vertical linearly polarized lights.Thus, because the resonance light from light source is exactly linearly polarized light originally, does not therefore need the means of carrying out polarization, thus can light-source structure be simplified.

[application examples 3] is characterised in that, with the interactional described resonance light of described alkali metal atom to being circularly polarized light.

For the resonance light pair penetrated from light source, in the face vertical with the direction of propagation of light, the tip representation of electric vector goes out round, this light is called as circularly polarized light.Through experimental verification, when resonance light to when converting circularly polarized light to, the Transmission light intensity of wavelength X 0 increases to common about 6 times.Thereby, it is possible to improve the S/N of the optical output signal under EIT phenomenon.

[application examples 4] is characterised in that, with the interactional described resonance light of described alkali metal atom to being Elliptical circularly polarized light.

For the resonance light pair penetrated from light source, in the face vertical with the direction of propagation of light, the tip representation of electric vector goes out Elliptical circle, this light is called as Elliptical circularly polarized light.And it is known, there is such elliptically polarized light, that is: when in the light path that resonance light is right, when being provided with wavelength plate in the mode vertical with light path and rotating its surface, the polarization state of this elliptically polarized light changes and is change continuously between orthogonal polarized light and circularly polarized light.Therefore, even Elliptical circularly polarized light, the S/N of the optical output signal under EIT phenomenon also can be improved.

[application examples 5] is characterised in that, the light path between described light source and the air chamber having enclosed described alkali metal atom is provided with wavelength plate.

Wavelength plate instigates the many refracting elements producing phase difference between vertical polarized light component.The wavelength plate producing phase difference π (180 °) is called λ/2 plate or half-wave plate, and it is for changing the polarization direction of linearly polarized light.The wavelength plate producing phase difference pi/2 (90 °) is called λ/4 plate or quarter wave plate, it for linearly polarized light being converted to circularly polarized light (Elliptical circularly polarized light), or converts circularly polarized light (Elliptical circularly polarized light) to linearly polarized light on the contrary.In invention, because needs convert linearly polarized light to circularly polarized light or Elliptical circularly polarized light, therefore need to use λ/4 plates, utilizing wavelength plate 40 by the resonance light of the linearly polarized light penetrated from light source to converting circularly polarized light or Elliptical circularly polarized light to, inciding air chamber.Thus, simple structure is only needed can to improve the S/N of the optical output signal under EIT phenomenon.

[application examples 6] is characterised in that, described multipair resonance light is to the occurrence condition meeting electromagnetically induced Transparency Phenomenon, and the luminous intensity that each resonance light is right is near the maximum P0 in the region that EIT signal strength signal intensity linearly increases.

Adopt the light intensity distributions that so multipair resonance light is right, light utilization ratio can be improved.

[application examples 7] is characterised in that, the centre frequency that the intensity distributions that described multipair resonance light is right is right relative to each is Gaussian Profile, and the resonance light corresponding with maximum luminous intensity is the occurrence condition of the electromagnetically induced Transparency Phenomenon that described alkali-metal atomic group near 0 is corresponding to meeting with the velocity component of this light direction, its intensity is the maximum P0 in the range of linearity.

VELOCITY DISTRIBUTION due to alkali metal atom is Gaussian Profile, as long as therefore in advance light intensity distributions right for resonance light is set to Gaussian Profile, simple light drive circuit can be utilized to realize high light utilization ratio.

[application examples 8] is characterised in that, generates described multipair resonance light pair by the synthesis of Modulation and Amplitude Modulation and frequency modulation(FM) or phase-modulation.

This modulation system can control the right light intensity distributions of resonance light with the higher degree of freedom.

[application examples 9] is characterised in that, by having the modulation of the signal of any one waveform in sine wave, triangular wave, sawtooth waveforms, square wave, generates described multipair resonance light pair.

This modulation system can utilize simple light drive circuit with the higher degree of freedom to control the right light intensity distributions of resonance light.

[application examples 10] is characterised in that, there is the drive circuit portion for modulating described light source, this drive circuit portion is separated with other structure member, under the state in the fabrication process or after commercialization, at random can control, set the constant in described drive circuit portion.

About " quantum interference device " that make use of EIT phenomenon, various application product can be expected, the such as high precision measuring device such as high precision oscillator, clock and watch and the quantum interference sensor that is representative with particulate detecting sensors such as Magnetic Sensor, pollen or smog, by adopting this structure, the best EIT signal curve conformed to object can be obtained.

[application examples 11] is characterised in that, when setting the nuclear-spin quantum number of described alkali metal atom as I, the quantum number of the hyperfine structure in the excitation level of the P1/2 of described alkali metal atom or the excitation level of P3/2 is F ', least energy in the region that the scope considering two energy of the doppler spread of F '=I-1/2 and F '=I+1/2 coincides with one another is E1, when ceiling capacity is E2, target energy (the excited first エ ネ ル ギ ー) Eend that excites of any pair of the multipair resonance light centering of described electromagnetically induced transparent (EIT) phenomenon is caused to meet E1 < Eend < E2.

For the resonance light pair corresponding with the Eend meeting this condition, the atom of the velocity component with direction opposite each other can be made to produce EIT simultaneously, therefore power broadening (phenomenon that the live width of power broadening: luminous power stronger EIT signal is larger) is less likely to occur, therefore, increase Q value (inverse of the half breadth of EIT signal), which thereby enhance performance index (defining) below.

[application examples 12] is characterised in that, if the nuclear-spin quantum number of described alkali metal atom is I, the quantum number of the hyperfine structure of the excitation level of described alkali metal atom is F ', under the state then do not overlapped each other in the scope of two energy of the doppler spread considering F '=I-1/2 and F '=I+1/2, when set described the F '=I-1/2 considering described doppler spread energy scope as from E11 to E12 (wherein, E11 < E12), the scope considering the energy of described the F '=I+1/2 of described doppler spread for from E21 to E22 (wherein, E21 < E22) time, the target energy Eend that excites of any pair of the multipair resonance light centering of described electromagnetically induced Transparency Phenomenon is caused only to meet the condition of the one party in E11 < Eend < E12 or E21 < Eend < E22.

When satisfying the condition, while the 3 level system Λ type transition that maintenance is pure, can realize based on the right EIT of multipair resonance light, therefore, it is possible to increase the enhancing effect based on the EIT signal of eclipsing effects.

[application examples 13] this quantum interference device makes multipair resonance light to 1 time or turns back by described alkali metal atom in multiple times, described electromagnetically induced Transparency Phenomenon is detected from described alkali metal atom, it is characterized in that, when set the energy of the excitation level not considering Doppler width as E10, described multipair resonance light right excite target energy to be Eend 0 time, described Eend 0 meets E10 < Eend 0 or Eend 0 < E10.

In this case, can make 1 pair of resonance light on outlet and loop, in air chamber, produce EIT with the alkali metal atom group with rightabout velocity component respectively.Therefore, in such a situa-tion by multipair resonance light to generation EIT time, compared with the situation of non-reflective, utilize the resonance light of half quantity to or the light modulation width of half, identical effect can be obtained.

[application examples 14] this quantum interference device makes multipair resonance light to 1 time or turns back by described alkali metal atom in multiple times, described electromagnetically induced Transparency Phenomenon is detected from described alkali metal atom, it is characterized in that, when set any pair of the multipair resonance light centering causing described electromagnetically induced Transparency Phenomenon excite target energy as Eend time, described Eend only meets the condition of the one party in Eend < E10 or E10 < Eend.

In this case, all resonance light to all having contribution to EIT, and owing to being reflection-type, therefore compared with the situation of non-reflective, only need the resonance light of half quantity to, efficiency is higher.

[application examples 15] is characterised in that, described number of turns is odd-times (goes with return respective total optical path length substantially equal).

If the outlet of light is substantially equal with the optical path length in loop, then substantially equal to the quantity of the contributive atom of EIT in speed group different from each other, therefore from the angle of EIT generation efficiency be favourable.

[application examples 16] is characterised in that, atomic oscillator has described quantum interference device.

Atomic oscillator, by having quantum interference device of the present invention, can produce EIT phenomenon under the state that S/N is high, therefore, it is possible to realize the miniaturization of atomic oscillator.

[application examples 17] is characterised in that, Magnetic Sensor has above-mentioned quantum interference device of the present invention.

The frequency of oscillation of atomic oscillator with the energy difference (Δ E12) between 2 of atom ground state levels for benchmark.The value of Δ E12 changes with the intensity of external magnetic field or variation, therefore, implements magnetic field shielding to the air chamber of atomic oscillator, with the impact not by external magnetic field.Therefore, by removing magnetic field shielding and changing the change of reading Δ E12 according to frequency of oscillation, manufacture and measure the intensity of external magnetic field and the Magnetic Sensor of variation.By having quantum interference device of the present invention, EIT phenomenon can be produced under the state that S/N is higher, therefore, it is possible to realize the miniaturization of Magnetic Sensor.

[application examples 18] is characterised in that, quantum interference transducer has described quantum interference device of the present invention.

By having quantum interference device of the present invention, the sensitivity of the various transducers for detecting the external disturbance affecting EIT signal curve and precision can be realized and to improve and miniaturized.

Accompanying drawing explanation

Fig. 1 is the skeleton diagram of the VELOCITY DISTRIBUTION of gaseous alkali metal atom.

Fig. 2 is the figure of the structure of the atomic oscillator that the 1st execution mode of the present invention is shown.

Fig. 3 (a) and (b) are the figure of the frequency spectrum that the resonance light inciding air chamber (gas cell) is shown.

Fig. 4 is the figure of the state of the moving direction that resonance light and the gaseous state alkali metal atom inciding air chamber is shown.

Fig. 5 illustrates that the power doppler based on atomic motion expands the schematic diagram of the relation between resonance light of the present invention.

Fig. 6 is the figure of the structure of the atomic oscillator that the 2nd execution mode of the present invention is shown.

Fig. 7 is the figure of the structure of the atomic oscillator that the 3rd execution mode of the present invention is shown.

Fig. 8 is the figure of the structure of the Magnetic Sensor that embodiments of the present invention are shown.

Fig. 9 (a) is by the figure of the Transmission light intensity to the EIT phenomenon caused of 2 kinds of different resonance light of wavelength, and (b) is the figure of the Transmission light intensity to EIT phenomenon when modulating to 2 kinds of different resonance light of wavelength.

Figure 10 is the figure of the structure of the atomic oscillator that the 4th execution mode of the present invention is shown.

Figure 11 is the figure of the structure of the atomic oscillator that the 5th execution mode of the present invention is shown.

Figure 12 (a) is the figure that atom " speed (one dimension projection) " distribution (maxwell boltzman distribution) is shown, (b) is the figure that atom " speed " distribution (maxwell boltzman distribution) is shown.

Figure 13 (a) is the figure that the high order harmonic component (+component) when sine wave modulation is shown distributes, b () is the figure that the high order harmonic component (+component) when typical square-wave frequency modulation is shown distributes, (c) is the figure that the high order harmonic component (+component) when typical triangular modulation is shown distributes.

Figure 14 (a) be illustrate luminous intensity linear-figure of non linear bifurcation point, (b) is the figure illustrating that laser frequency distributes.

Figure 15 (a) is the dependent figure of laser intensity that EIT signal live width is shown, (b) be illustrate for the relation between EIT signal strength signal intensity with EIT signal live width in the past with the figure compared of the present invention.

Figure 16 is the figure that laser frequency distribution near CsD2 line is shown.

Figure 17 is the figure of the relation illustrated between EIT signal strength signal intensity and live width.

Figure 18 is the figure of the comparison of the EIT signal strength signal intensity illustrated under same live width.

Figure 19 is the figure of the structure that experimental system is shown.

Figure 20 (a) is the energy diagram corresponding with D2 line, and (b) is the energy diagram corresponding with D1 line, (c) be consider doppler spread excitation level near energy diagram.

Figure 21 (a) be consider doppler spread excitation level near energy diagram, (b) be consider doppler spread excitation level near energy diagram.

Figure 22 (a) is the energy diagram near excitation level, b () is the energy diagram near excitation level, (c) is the figure of the configuration structure that the air chamber having enclosed alkali metal atom of the 6th execution mode of the present invention, light source, light path and detector are shown.

Figure 23 (a) is the energy diagram near excitation level, b () is the energy diagram near excitation level, (c) is the figure of the configuration structure that the air chamber having enclosed alkali metal atom of the 7th execution mode of the present invention, light source, light path and detector are shown.

Figure 24 (a) is the figure of the principle of the EIT mode illustrated in the past, and (b), (c) are the figure of the relation illustrated between air chamber in the past and resonance light.

Label declaration

1 centre wavelength generation unit; 2LD; 3EOM; 4EOM; 5 air chambers; 6 photodetectors; 7 frequency control unit unit; 8 voltage-controlled quartz (controlled) oscillators; 9 oscillators; 10 oscillators; 11,12,13 resonance light; 14,15,16 gaseous state Cs atom; 17 blenders; 18,19 modulation signals; 40 wavelength plates; 41 do not implement modulate time be linearly polarized photochemical waveform; 42 do not implement modulate time be circularly polarized photochemical waveform; 43 are linearly polarized photochemical waveform when implementing modulation; 44 implement the waveform photochemical by elliptical polarization during modulation; 45 are circularly polarized photochemical waveform when implementing modulation; 50,51,52,53,54 atomic oscillators.

Embodiment

Below, use execution mode shown in the drawings to describe the present invention in detail.But, as long as no special record, the illustrative examples that the structural element described in present embodiment, kind, combination, shape, its relative configuration etc. are all just simple, its object does not also lie in scope of the present invention is only confined to this.

Here, in advance to below " performance index " that repeatedly occur being defined.Performance index is defined as the inverse (i.e. Q value) of the live width of EIT signal and the long-pending of EIT signal to noise ratio (i.e. S/N).Such as, because S/N and EIT signal strength signal intensity is proportional, if therefore EIT signal strength signal intensity increases, then performance index improves.Main purpose of the present invention is to improve this performance index.

Fig. 1 shows the synoptic diagram of the VELOCITY DISTRIBUTION of inclosure gaseous alkali metal atomic group in a reservoir.

The transverse axis of Fig. 1 represents that the speed of gaseous alkali metal atom, the longitudinal axis represent the ratio of the quantity of the gaseous alkali metal atom with this speed.As shown in Figure 1, gaseous alkali metal atom has the certain VELOCITY DISTRIBUTION corresponding with temperature centered by speed 0.Here, speed represents to atomic velocity component parallel with direction of illumination during gaseous alkali metal atomic group irradiating laser, and the value of the speed with light source geo-stationary is set to 0.Here, the present inventor notices that the speed of gaseous alkali metal atom is very large on the impact of EIT phenomenon.When the speed of gaseous alkali metal atom exists distribution, due to the Doppler effect (Doppler frequency shift) of light, the wavelength of the resonance light namely observed from gaseous alkali metal atom the apparent wavelength of resonance light, produce distribution.Therefore, notice in atomic group, there is a considerable amount of gaseous alkali metal atom as follows, even if that is: irradiate 1 pair of resonance light 1 and 2 simultaneously, these gaseous alkali metal atoms also can not produce EIT phenomenon and will remain.When the method in the past of employing is namely simultaneously to alkali metal atom group irradiation 1 pair of resonance light 1 and 2, being enclosed in the gaseous alkali metal atomic group in air chamber is only a part to the contributive alkali metal atom of EIT phenomenon.Therefore, present inventor has performed research, make not have contributive gaseous alkali metal atom also can contribute to producing EIT phenomenon due to the impact of Doppler effect to EIT phenomenon in the past.Below, the present invention is described in detail.

Fig. 2 is the figure of the structure of the atomic oscillator that the 1st execution mode of the present invention is shown.This atomic oscillator 50 utilize based on incidence by 2 to the different coherent light of the wavelength of above (be as described later 3 to) to the optical absorption characteristics of the quantum Interference during resonance light formed, control frequency of oscillation, this atomic oscillator 50 is configured to be had: LD (VCSEL) (coherent source) 2 penetrating each resonance light; Produce the centre wavelength generation unit 1 of the centre wavelength of LD 2; Oscillator 9, its vibration produces 1/2 (4.596GHz) of the frequency (9.2GHz) of the energy difference (Δ E12) being equivalent to 2 different ground state; Oscillator 10, its vibration produces the frequency of about 25MHz; EOM (electron optics modulation element) 3,4, it utilizes the signal of telecommunication to implement frequency modulation(FM) to the resonance light 11 penetrated from LD 2; Air chamber 5, it changes the uptake of light according to the wavelength of the light 12 modulated through EOM 4, is sealed with gaseous state caesium (Cs, alkali metal) atom; Photodetector (optical detecting unit) 6, its detect from air chamber 5 transmitted through light 13; And frequency control unit 7, it is according to the output of photodetector 6, detects the EIT state of air chamber 5, controls output voltage.In addition, the frequency of oscillation of oscillator 10 is set to 25MHz, and this frequency is the value of the typical Doppler width (being such as at room temperature approximately 1GHz) much smaller than Cs atom.Suitably can change this frequency.In addition, about the output frequency of oscillator 9, due to for caesium, the frequency being equivalent to Δ E12 is approximately 9.2GHz (4.596GHz × 2), therefore, the output frequency of oscillator 9 is set to 4.596GHz, and it generates by carrying out frequency multiplication to the frequency that such as under type obtains, and described frequency controls to obtain to voltage-controlled quartz (controlled) oscillator 8 according to the control voltage exported from frequency control unit 7.Further, utilize the frequency of oscillator 10 (25MHz) to modulate EOM3, utilize the frequency of oscillator 9 (4.596GHz) to modulate EOM 4, EOM 3 and EOM 4 is arranged in series in the emitting side of LD 2.Further, the combination of EOM 3 and oscillator 10 and putting in order of the combination of EOM 4 and oscillator 9 also can reverse.

That is, the structure of the atomic oscillator 50 of present embodiment is with difference in the past: for the resonance light 11 penetrate from LD 2, via the EOM 3 as modulating unit, obtains 2 right to the different 2 kinds of resonance light of the wavelength of (3 to) above.In atomic oscillator in the past, only prepare the right of 2 kinds of different resonance light of the 1 pair of wavelength, and frequency is controlled, make the difference on the frequency (wavelength difference) of 2 kinds of resonance light of simultaneously irradiating consistent exactly with the energy difference Δ E12 of each ground state level.But, due to the Doppler effect of resonance light produced because of atomic motion, the resonance light wavelength being enclosed in the Cs atom group in air chamber 5 produces distribution, for 1 for resonance light, just interact with a part of Cs atom moved with the speed meeting the resonance condition corresponding with its wavelength once in a while, the efficiency therefore producing EIT phenomenon is poor.Therefore, in the present embodiment, be configured to by modulating unit, make wavelength different at least 4 (2 resonance light to) resonance light interact with the Cs atom being enclosed in the gaseous state in air chamber 5.Thereby, it is possible to increase the quantity contributing to the Cs atom producing EIT phenomenon in the per unit volume of air chamber 5, EIT signal can be obtained efficiently.

Fig. 3 (a) and (b) are the figure of the frequency spectrum that the resonance light inciding air chamber is shown.Fig. 4 is the figure of the state of the moving direction that resonance light and the gaseous state Cs atom inciding air chamber is shown.

Then, be described with reference to the action of Fig. 3 and Fig. 4 to present embodiment.Centre wavelength generation unit 1 take centre wavelength as the resonance light 11 that the mode of λ 0 (centre frequency f0) produces LD 2.When the resonance light 11 of EOM 3 and 4 couples of LD 2 implements frequency modulation(FM), the resonance light 12 with the frequency spectrum 30 ~ 32 shown in Fig. 3 (a) is imported in air chamber 5.Here, in Fig. 3 (a), the difference on the frequency of A-A ' is 9.2GHz, and for this 1 pair of resonance light, by λ 0 is set to suitable value, the gaseous state Cs atom 15 that the velocity component on the direction of the incident light 12 shown in Fig. 4 is little produces EIT phenomenon.In addition, the difference on the frequency of B-B ' is also 9.2GHz, for this 1 pair of resonance light, has and produces EIT phenomenon with the gaseous state Cs atom 14 of the rightabout velocity component of incident light 12 shown in Fig. 4.In addition, in Fig. 3 (a), the difference on the frequency of C-C ' is also 9.2GHz, for this 1 pair of resonance light, has and produces EIT phenomenon with the gaseous state Cs atom 16 of the velocity component of incident light 12 equidirectional shown in Fig. 4.Like this, the atom in air chamber 5 has multiple VELOCITY DISTRIBUTION.Therefore, when being endowed sideband (sideband) B, B to air chamber 5 incidence as described above during the resonance light 12 of the component of ', C, C ', the difference on the frequency of A-A ', B-B ' and C-C ' is 9.2GHz, these 3 pairs of laser all interact with the gaseous state Cs atom with corresponding velocity component, its result, increases the ratio to the contributive Cs atom of EIT phenomenon.Thereby, it is possible to obtain the EIT signal of the large expectation of signal to noise ratio (S/N).

In addition, in the present embodiment, although the modulating frequency of EOM 4 to be set as 1/2 (4.596GHz) of the difference on the frequency of gaseous state Cs atom, also difference on the frequency 9.2GHz can be set as.The frequency spectrum of resonance light now, as shown in Fig. 3 (b), creates frequency spectrum 33 ~ 35, but does not such as use frequency spectrum 33, but uses frequency spectrum 34 and 35 (also can be frequency spectrum 33 and 34).That is, the difference on the frequency of A-λ 0 is 9.2GHz, and for this 1 pair of resonance light, by λ 0 is set to suitable value, the gaseous state Cs atom 15 that the velocity component on the direction of the incident light 12 shown in Fig. 4 is little produces EIT phenomenon.The difference on the frequency of B-λ 1 is also 9.2GHz, for this 1 pair of resonance light, has and produces EIT phenomenon with the gaseous state Cs atom 14 of the rightabout velocity component of incident light 12 shown in Fig. 4.In addition, the difference on the frequency of C-λ 2 is also 9.2GHz, for this 1 pair of resonance light, has and produces EIT phenomenon with the gaseous state Cs atom 16 of the velocity component of incident light 12 equidirectional shown in Fig. 4.Like this, the atom in air chamber 5 has multiple VELOCITY DISTRIBUTION.Therefore, when as described above to air chamber 5 incidence be endowed sideband B, λ 1, C, λ 2 the resonance light 12 of component time, the difference on the frequency of A-λ 0, B-λ 1 and C-λ 2 is 9.2GHz, these 3 pairs of laser all interact with the gaseous state Cs atom with corresponding velocity component, its result, increases the ratio to the contributive Cs atom of EIT phenomenon.The EIT signal of the large expectation of signal to noise ratio (S/N) can be obtained thus.

That is, in order to produce the resonance light of at least 2 pairs of resonance light to (be 3 to) here, considering to make the resonance light penetrated from LD 2 produce sideband overlappingly, and utilizing its frequency spectrum.In addition, need to modulate the frequency for modulating resonance light by following 2 frequencies, that is: be equivalent to the 4.596GHz of 1/2 of the frequency (9.2GHz) of the energy difference (Δ E12) of 2 different ground state; And the frequency of value much smaller than the typical Doppler width (being such as at room temperature approximately 1GHz) of Cs atom (being 25MHz here).In addition, need to utilize the EOM being used for modulating light.Therefore in the present embodiment, prepared the oscillator 9 and 10 of generation 2 kinds of frequencies of vibrating respectively, by each frequency, the EOM 3 and 4 that the injection being arranged in series in LD 2 is surveyed has been modulated.Thereby, it is possible to based on the resonance light 11 penetrated from LD 2, produce the resonance light with 3 pairs of frequency spectrums, these 3 pairs of frequency spectrums keep the difference on the frequency of 9.2GHz.

In addition, in the present embodiment, EOM 3 and EOM 4 is respectively provided with 1, but, and also can at the emitting side configured in series EOM 4 of LD 2 and at least 2 EOM 3.Thus, the right quantity of resonance light can be set arbitrarily, and produce with the frequency interval of comb teeth-shaped.

Fig. 5 illustrates that the power doppler based on atomic motion expands the schematic diagram of the relation between resonance light of the present invention.The energy state figure enclosing the gaseous alkali metal atomic group in container shows by such as under type: the excitation level of replacing the energy state figure for 1 atom shown in Figure 24 with can bring suitable with doppler spread.In Fig. 5 20,21, each energy level of 22 is the excitation levels of answering with the atom pair represented by 16,15,14 respectively in Fig. 4.It can thus be appreciated that, for the gaseous alkali metal atomic group with VELOCITY DISTRIBUTION, utilize multiple resonance light to the ratio increased the contributive atom of EIT phenomenon.Therefore, such as, if be substantially equal with power in the past by the power setting distributing to 1 pair of resonance light, then the saturation limit absorbed uprises, and gross power increases, therefore, it is possible to obtain the EIT signal of high-contrast.In addition, at total light irradiation power with in the past substantially equal, the power reduction of every 1 pair of resonance light of the present invention, therefore inhibit the power broadening of EIT signal (phenomenon that the live width of luminous power stronger EIT signal is larger), compared with the past, the good EIT signal that half breadth is narrow can be obtained.Therefore, when being applied to oscillator, compared with the past, can frequency stability be improved.

Fig. 6 is the figure of the structure of the atomic oscillator that the 2nd execution mode of the present invention is shown.To with reference to label be described identical with Fig. 2 of same structure element annotation.The difference of Fig. 6 and Fig. 2 is, deletes EOM 4, and is provided with the blender 17 of the output signal of oscillator 10 and oscillator 9 mixing, utilizes the output signal 18 of blender 17 to drive EOM 3, EOM 3 is configured in the emitting side of LD 2.Thus, the resonance light 12 penetrated from EOM 3 produces the frequency spectrum identical with Fig. 3 (a).

That is, in order to modulate light, employ EOM, but there is following problems, if that is: increase the quantity of frequency spectrum, then correspondingly must increase the quantity of EOM, cost up and number of components increase.Therefore, in the present embodiment, mix the signal that EOM is modulated in advance with blender 17, utilize its output signal 18 to modulate 1 EOM 3.Thus, the quantity of EOM can be controlled, for minimum, can number of components be reduced.

Fig. 7 is the figure of the structure of the atomic oscillator that the 3rd execution mode of the present invention is shown.To with reference to label be described identical with Fig. 6 of identical structural element mark.The difference of Fig. 7 and Fig. 6 is, deletes EOM 3, utilizes the output signal 19 of blender 17 directly to carry out modulation to LD 2 and drives.Thus, the resonance light 11 penetrated from LD 2 produces the frequency spectrum identical with Fig. 3 (a).

That is, centre wavelength generation unit 1 is that the mode of λ 0 produces the resonance light 11 penetrated from LD 2 with centre wavelength.Further, in order to the modulation of centering cardiac wave progress row, except the method for the resonance light 11 penetrated from LD 2 being modulated with EOM, the method for in addition LD 2 itself being modulated.Therefore, in the present embodiment, the output frequency of oscillator 10 and oscillator 9 mixes by blender 17, and itself carries out modulation driving with the mixed signal of blender 17 19 couples of LD 2.Thus, EOM can not be needed.In addition, also can generate the output frequency of oscillator 10 via (also can utilize a part for the circuit of oscillator 9) such as PLL from voltage-controlled quartz (controlled) oscillator 8.In this case, oscillator 10 is not needed yet.

In addition, omit diagram, also the LD in the atomic oscillator of the EIT mode be arranged in the past can be formed as following structure, that is: the surface light emitting laser of each different wave length be configured to array-like.

Fig. 8 is the figure of the structure of the Magnetic Sensor that embodiments of the present invention are shown.To with reference to label be described identical with Fig. 7 of same structure element annotation.The difference of Fig. 8 and Fig. 7 is, is configured with generation source, determined magnetic field 37 near air chamber 5, and has the magnetic field measuring device 36 of the variation of the output signal measuring frequency control unit 7.The frequency of oscillation of atomic oscillator with the energy difference (Δ E12) between 2 of atom ground state levels for benchmark.The value of Δ E12 changes with the intensity of external magnetic field or variation, therefore, implements magnetic field shielding to the air chamber of atomic oscillator, with the impact not by external magnetic field.Therefore, by removing magnetic field shielding and changing the change of reading Δ E12 according to frequency of oscillation, manufacture and measure the intensity of external magnetic field and the Magnetic Sensor of variation.By adopting structure of the present invention, EIT phenomenon can be produced under the state that S/N is higher, therefore, it is possible to realize the miniaturization of Magnetic Sensor.

Fig. 9 (a) is the figure of the Transmission light intensity to EIT phenomenon when modulating to 2 different resonance light of wavelength by the figure of the Transmission light intensity to the EIT phenomenon caused of 2 different resonance light of wavelength, Fig. 9 (b).Known according to Fig. 9 (a), waveform 41 is waveforms of the Transmission light intensity through linearly polarized light from VCSEL, and waveform 42 represents makes this resonance light to Transmission light intensity when being become circularly polarized light by wavelength plate further.Known, waveform 42 adds the level of about 20% relative to waveform 41.In addition, when shown in such as Fig. 9 (b) to resonance light to when modulating, multiple resonance light, to all interacting with the gaseous state Cs atom with corresponding VELOCITY DISTRIBUTION, shows the waveform 43 with multiple peak value.In the present embodiment, such as shown in Figure 10, between LD 2 and air chamber 5, be configured with wavelength plate 40 in the mode vertical with light path, when rotation wave major plate face gradually and when making resonance light become circularly polarized light to 11, confirming in wavelength X 0 place Transmission light intensity is maximum waveform 45.Therefore, confirm, in resonance light in the process changed from linearly polarized light to circularly polarized light, Transmission light intensity becomes waveform 43 (linearly polarized light), waveform 44 (Elliptical circularly polarized light), waveform 45 (circularly polarized light).

That is, for the resonance light penetrated from LD 2 to 11, when with in the direction of propagation vertical plane of light, the tip representation of electric vector goes out round, this light is called as circularly polarized light.Through experimental verification to: when by resonance light to when converting circularly polarized light to, the Transmission light intensity of wavelength X 0 increases to common about 6 times.Thereby, it is possible to improve the S/N of the optical output signal under EIT phenomenon.

In addition, for the resonance light penetrated from LD 2 to 11, in the face vertical with the direction of propagation of light, the tip representation of electric vector goes out Elliptical circle, this light is called as Elliptical circularly polarized light.There is such elliptically polarized light, that is: when in the light path that resonance light is right, when being provided with wavelength plate in the mode vertical with light path and rotating its surface, the polarization state of this elliptically polarized light changes and is change continuously between orthogonal polarized light and circularly polarized light.Therefore, even Elliptical circularly polarized light, the S/N of the optical output signal under EIT phenomenon also can be improved.

Figure 10 is the figure of the structure of the atomic oscillator that the 4th execution mode of the present invention is shown.4th execution mode is the structure having added wavelength plate 40 and obtain in the structure of Fig. 7.That is, between LD 2 and air chamber 5, wavelength plate 40 is configured with in the mode vertical with light path.Incide wavelength plate 40 from the resonance light of the linearly polarized light of LD 2 injection to 11, be polarized 90 degree of phase places and become circularly polarized light 11a.In addition, wavelength plate 40 can be configured in any position between LD 2 and air chamber 5, near the exit facet that can be positioned at LD 2, near the entrance port that also can be positioned at air chamber 5.

Figure 11 is the figure of the structure of the atomic oscillator that the 5th execution mode of the present invention is shown.5th execution mode is the structure adding wavelength plate 40 and obtain in the structure of Fig. 6.That is, between EOM 3 and air chamber 5, wavelength plate 40 is provided with in the mode vertical with light path.After EOM 3 modulates, become resonance light 12 to 11 from the resonance light of the linearly polarized light of LD 2 injection, incide wavelength plate 40, be polarized 90 degree of phase places and become circularly polarized light 12a.In addition, wavelength plate 40 can be configured in any position between EOM 3 and air chamber 5, near the exit facet that can be configured in EOM 3, near the entrance port that also can be configured in air chamber 5.

That is, wavelength plate instigates the many refracting elements producing phase difference between vertical polarized light component.The wavelength plate producing phase difference π (180 °) is called λ/2 plate or half-wave plate, and it is for changing the polarization direction of linearly polarized light.The wavelength plate producing phase difference pi/2 (90 °) is called λ/4 plate or quarter wave plate, it for linearly polarized light being converted to circularly polarized light (Elliptical circularly polarized light), or converts circularly polarized light (Elliptical circularly polarized light) to linearly polarized light on the contrary.In the present embodiment, because needs convert linearly polarized light to circularly polarized light or Elliptical circularly polarized light, therefore need to use λ/4 plate, utilize wavelength plate 40 to convert the resonance light of the linearly polarized light penetrated from LD 2 to circularly polarized light or Elliptical circularly polarized light to 11, incide air chamber 5.Thus, simple structure is only needed can to improve the S/N of the optical output signal under EIT phenomenon.

Figure 14 (a) illustrates to meet the right luminous intensity (transverse axis) of the 2 light wave resonance light of condition that produce EIT and EIT signal strength signal intensity (Zong Shaft) between the figure of relation.In the region that luminous intensity is very weak, EIT signal strength signal intensity and luminous intensity keep proportionate relationship and substantial linear ground changes.But when luminous intensity exceedes certain point (P0), even if increase luminous intensity, EIT signal strength signal intensity also insignificantly changes (zone of saturation).Consider this point, pay close attention to and there is specific speed (as mentioned above in the alkali metal atom in air chamber, refer to the velocity component parallel with incident light) atomic group (ensemble), from the angle of light utilization ratio, wish the maximum light intensity P0 (luminous intensity maximum in the region that intensity increases linearly) incident intensity being set as EIT signal strength signal intensity does not reach capacity relative to incident intensity.

Alkali metal atom (the such as caesium in the air chamber in region is produced as EIT, Cs) group has the VELOCITY DISTRIBUTION (curve) shown in Figure 12 (b), this curve changes with environmental factors such as pressure and temperatures, if but only pay close attention to the distribution of the velocity component on certain fixed-direction, then as shown in Figure 12 (a), substantially in Gaussian Profile.When the resonance light to incident 2 light waves of this system is to when producing EIT, the energy-producing doppler spread because of this VELOCITY DISTRIBUTION, therefore in typical case, corresponding with the centre frequency of frequency field producing EIT EIT signal intensity profile also (in Gaussian Profile converts through frequency and has the expansion about 1 [GHz]).Therefore, pay close attention to above-mentioned smooth utilization ratio, when being set as making multiple resonance light be near P0 respective luminous intensity, wishing that it is distributed as shown in Figure 14 (b) such, is close to the VELOCITY DISTRIBUTION of atom and the shape of Gaussian Profile.

Semiconductor lasers etc., when being applied in direct current, send the monochromatic light (coherent light) of the frequency (wavelength) corresponding with its current value (Ivias).If when centre wavelength being set to about 852 [nm] and applying " modulation " of 4.6 [GHz] to Ivias (Imod (1)=4.6 [GHz]), the sideband of (4.6 × 2=9.2 [GHz]) is spaced apart both being formed in the both sides of centre wavelength, when this 2 light wave as resonance light to the Cs atomic time incided in air chamber, there is quantum interference and produce EIT phenomenon.Here, known in conjunction with doppler spread above, for the resonance light of 2 light waves for (1 to), considerably less to the Cs atomic quantity in the contributive air chamber of EIT phenomenon.That is, EIT generation efficiency is poor in the past.

Accompanying drawing is used to explain the state of applying electric current and the frequency distribution of laser driving semiconductor laser below.Figure 16 is the figure that the frequency distribution observed when frequency modulation(FM) implemented by the monochromatic semiconductor laser being about 852 [nm] is shown to centre wavelength.In order to alkali metal atom (Cs) is produced EIT as object atoms, Ivias (DC bias current) is set to 852 [nm] left and right making centre wavelength become suitable with Cs excitation energy, then the frequency modulation(FM) Imod (1) of 4.6 [GHz] can be implemented to Ivias, or produce sideband via EOM (electron optics modulation element), generation 1 is the resonance light pair of 2 light waves of 9.2GHz to difference on the frequency each other thus.When modulation Imod (2) (superimposed modulation) to its further overlapping optional frequency (such as 15 [MHz]), 2 light waves are modulated by overlaid frequency 15 [MHz] respectively, produce the frequency distribution with comb (Comb) dentation at the interval of overlaid frequency 15 [MHz].Each 2 original light waves with the frequency distribution of this comb teeth-shaped can be counted as multipair resonance light pair, therefore, as long as make the Cs atom in itself and air chamber have an effect, can produce EIT with the Cs atomic group moved with friction speed, EIT generation efficiency improves (the present invention) further simultaneously.

Figure 16 (a) is 1 of in the past not carrying out like that in 2 light waves of superimposed modulation.B (), (c) are with frequency spectrum time sinusoidal wave next overlapping Imod (2).Modulated frequency is equal to 15 [MHz], but the amplitude condition of the modulation of (b), (c) is different.The two all presents the frequency distribution of comb teeth-shaped, and known, and compared with (b) that be 0.2 [V] with modulated amplitude, the frequency expansion scope of (c) of 1.0 [V] is larger.

Figure 17 is the figure relation between the intensity (longitudinal axis) of the EIT signal of Cs and live width (transverse axis) and existing method compared, above-mentioned relation irradiates multiple resonance light to obtaining by utilizing the Laser Driven considering superimposed modulation Imod of the present invention (2), is irradiated to the laser power of Cs and obtains data by change.(a), (b), (c) of Figure 17 is corresponding with (a), (b), (c) of Figure 16 respectively.Known compared with the past, when identical live width, EIT signal strength signal intensity of the present invention is far longer than in the past, and " performance index " (=Q × (S/N)) of previous definition improves.In the methods of the invention, can also understand, compared with (b), the EIT signal strength signal intensity of (c) be more greatly because: each laser frequency spectrum distribution according to Figure 16 is known, by catching the more Cs atom of VELOCITY DISTRIBUTION in air chamber, and resonance light between interactional efficiency improve, this to generation EIT have contribution.And confirm: in existing method (a), due to EIT signal strength signal intensity cannot be obtained, therefore be difficult to realize 120 [kHz] EIT live width below, be difficult to put forward high q-factor (inverse of EIT signal live width), but in the present invention (b), (c), can further refinement live width, therefore, it is possible to significantly improve performance index.

Figure 18 is the figure that each EIT signal under 127 [kHz] compares to half value overall with (live width).Confirm: compared with existing method (a), in (c) of the present invention, approximately large than it 14 times of EIT signal strength signal intensity.

Result so far is summarized, can clearly to draw a conclusion.When wanting the live width of refinement power broadening, if reduce laser power (Figure 15 (a)), then EIT signal strength signal intensity and its weaken pro rata (Figure 15 (b)), in the conventional method, become 0 in A point place EIT signal strength signal intensity.That is, the signal live width narrower than the signal live width at A point place cannot be obtained.

But, in the method for the invention, the atomic quantity (density) produced in the contributive air chamber of EIT signal is significantly increased, therefore, under the EIT deration of signal that signal strength signal intensity has disappeared in the conventional method, sufficient signal strength signal intensity (B point) can be obtained.That is, representing that method of the present invention is relative to existing methodical maximum magnification ratio by the value that the EIT signal strength signal intensity at B point place obtains divided by the EIT signal strength signal intensity at A point place, is the index of the improvement effect of S/N.If S/N improves, then performance index improves, and therefore can improve the performance of the various devices that make use of EIT phenomenon with being in proportion with it.Clearly, such as in the atomic oscillator that make use of EIT phenomenon, frequency stability and S/N improve pro rata, if be applied in the quantum interference sensors such as Magnetic Sensor (utilizing the frequency of EIT atomic oscillator to make a response and the character changed to outside magnetic-field-sensitive), then can produce the effect of high sensitivity etc.In addition, in the present invention, improve correspondingly with S/N, even if reduce the size of the above-mentioned air chamber causing EIT phenomenon, also can obtain signal strength signal intensity as in the past, therefore, there is the effect of the further miniaturization that can realize device etc.

In addition, as shown in Figure 15 (b), if obtain sufficient EIT signal strength signal intensity at B point place, then by reducing laser intensity refinement signal live width (getting rid of the impact of power broadening) further further.Such as, represent the lowest signal intensity line as target with chain-dotted line, for method of the present invention, the signal live width at C point place can be realized.Identical with the previous discussion about S/N, line width values is less, and Q value is larger, and therefore the value of performance index becomes large, thus can improve the performance of the various devices that make use of EIT phenomenon.Such as, in the atomic oscillator that make use of EIT phenomenon, by the graph thinning of EIT signal, frequency stability improves, if be applied to the quantum interference sensors such as Magnetic Sensor (utilizing the frequency of EIT atomic oscillator to make a response and the character changed to outside magnetic-field-sensitive), then bring the effects such as high precision int.

From what has been discussed above known, according to the present invention, by suitably selecting the modulator approach of laser, EIT signal strength signal intensity that existing method cannot realize and EIT live width can be obtained, therefore there is such advantage: the EIT signal curve conformed to application purpose can be determined on a large scale.Utilize this advantage, such as at EIT device layout, in the fabrication stage, if utilize the independent settings integratedly such as laser drive circuit IC can control above-mentioned Laser Modulation parameter (modulation waveform, intensity etc., also comprise modulation On/Off) unit, and using other structural element a considerable amount of as universal component, then easily separately can manufacture the EIT device of special object, there is the effect to reduce costs etc.In addition, also can pre-set such unit, that is: product user oneself can utilize this unit, suitably controls, sets above-mentioned Laser Modulation parameter according to environment for use etc.

Figure 13 shows the relation between the modulator approach of laser and Fourier component.A () is Fourier component when carrying out Modulation and Amplitude Modulation (AM) with sine wave, b () is Fourier component when carrying out Modulation and Amplitude Modulation (AM) with square wave, (c) is Fourier component when carrying out Modulation and Amplitude Modulation (AM) with triangular wave.Transverse axis is frequency.Compared with triangular modulation, there is the Fourier component of more high order in square wave modulation.If carry out superimposed modulation with frequency modulation(FM) (FM) or phase-modulation (PM) further to these composite waves, and the superimposed modulation as Imod (2) is carried out to laser, then can obtain arbitrary modulation waveform, and the right intensity distributions of multiple resonance light and adjacent frequency interval can be controlled in high-freedom degree ground.Thereby, it is possible to obtain the effects such as following: the EIT signal system that easily realizing the device performance required by often kind of purposes needs is driven, and precision is also improved.

Figure 19 is the figure of the structure that experimental system of the present invention is shown.It is such example, that is: modulate laser without Imod (1), but make use of EOM (electron optics modulation element).

Figure 20 is the energy diagram of alkali-metal electronic state.Figure 20 (a) is excitation level is P3/2, namely corresponding with so-called D2 line energy diagram, and Figure 20 (b) is excitation level is P1/2, namely corresponding with so-called D1 line energy diagram.Figure 20 (c) represent in the past based on 2 light waves 1 pair of resonance light to or interaction between multipair resonance light of the present invention pair and the alkali metal atom considering doppler spread, be the energy diagram near excitation level when meeting the condition producing EIT phenomenon.

Excitation level P3/2 is made up of hyperfine structure, and within the scope of the usual serviceability temperature of device that make use of EIT phenomenon, the energy relating to the F '=I+1/2, I-1/2 that EIT produces overlaps (Figure 20 (c)) because of doppler spread.In addition, in the region that temperature is high, even the hyperfine structure of excitation level P1/2, sometimes also can there is energy because of doppler spread and overlap.Laser center frequency (centre wavelength) is set, makes the right target energy Eend that excites of as far as possible many resonance light of multiple resonance light centering of the present invention enter this overlapping region.That is, as shown in Figure 20 (c), make to meet E1 < Eend < E2.Here, described F ' represents the quantum number of hyperfine structure, and described I represents nuclear-spin quantum number.

Incide 1 pair of resonance light of this energy overlapping region to the EIT phenomenon causing the 2 kind alkali metal atoms corresponding from different F ' (quantum number of hyperfine structure).That is, for the alkali metal atom of 2 kinds of the velocity component with direction opposite each other different speed groups (ensemble: atomic group), produce EIT simultaneously.When meeting such condition, the luminous intensity (number of photons) that resonance light is right is dispersed in each atomic group, and therefore EIT signal strength signal intensity is not easy to reach capacity, and can irradiate stronger laser, and S/N improves.Especially, when needing to strengthen EIT signal strength signal intensity when air chamber miniaturization, better effects if.In addition, if total luminous intensity of irradiating is constant, then in this overlapping region, interactional mode is there is and disperses in number of photons with the alkali metal atom and photon that make 2 kinds of different speed groups as described above, therefore consequently, for the speed group of a side, inhibit power broadening, the refinement live width of EIT signal (increase of Q value).That is, performance index can be improved.

Figure 21 is the energy diagram of typical P1/2 energy level.Generally, hyperfine structure energy division width larger than D2 line (being typically 0.5 ~ 1GHz) of D1 line, 2 kinds of energy bands of doppler spread do not overlap.As mentioned above, when D2 Line (exciting target level to be P3/2), because the energy division width of hyperfine structure is little, therefore, produce because of doppler spread and can be with coincidence, multipair resonance light pair can be made simultaneously to interact with same atom.In this case, 4 light wave mixing occur, and 3 pure level system Λ type transition go wrong, and EIT efficiency reduces.But generally, hyperfine structure energy division width larger than D2 line (being typically 0.5 ~ 1GHz) of D1 line, 2 kinds of energy bands of doppler spread do not overlap.Therefore, if use D1 line, then while the 3 level system Λ type transition that maintenance is pure, can realize based on the right EIT of multipair resonance light, therefore, it is possible to increase the enhancing effect based on the EIT signal of eclipsing effects.In this case, there are these 2 kinds of methods of E11 < Eend < E12 (Figure 21 (a)) and E21 < Eend < E22 (Figure 21 (b)).

Figure 22 (c) is the figure of the configuration structure that the air chamber having enclosed alkali metal atom of the 6th execution mode of the present invention, light source, light path and detector are shown.Here, the light sent by LASER Light Source incides air chamber, produces EIT phenomenon with alkali metal atom, afterwards, the light of being turned back by means such as reflections, to advancing in the other direction, is again produced EIT phenomenon thus, is then directed in photodetector with the alkali metal atom in air chamber.This is so-called reflection-type.Now, as shown in Figure 22 (a), (b), when the energy of the excitation level not considering Doppler width is set to E10, if selected in the monochromatic mode of target energy Eend0 and E10 unequal (E10 < Eend0 or Eend0 < E10) that excites of above-mentioned light source, then can make 1 pair of resonance light on outlet and loop, in air chamber, produce EIT with the alkali metal atom group with rightabout velocity component respectively.Therefore, in such a situa-tion by multiple resonance light to generation EIT time, compared with the situation of non-reflective, utilize the resonance light of half quantity to or the light modulation width of half, identical effect of the present invention can be obtained.Therefore, according to this structure, the design that laser driver etc. generate the right mechanism of multipair resonance light becomes easier, and power consumption during device drive reduces, and utilizes energy-conservation.

Figure 23 (c) is the figure of the configuration structure that the air chamber having enclosed alkali metal atom of the 7th execution mode of the present invention, light source, light path and detector are shown.Here, the light sent from LASER Light Source incides air chamber, produces EIT phenomenon with alkali metal atom, afterwards, by means such as reflections, makes, in light Multiple through then out air chamber, to be directed in photodetector after causing EIT phenomenon.This is so-called multipath reflection type.Now, as shown in Figure 23 (a), (b), if selected in the mode of all any one conditions exciting target energy Eend only to meet in Eend < E10 or E10 < Eend that multiple resonance light of EIT phenomenon can be caused right, then 1 pair of resonance light can be made on outlet and loop in air chamber, to produce EIT with the alkali metal atom group with rightabout velocity component respectively.In addition, by adopting multipath reflection type, optical path length becomes longer, thus coherence time increases, and EIT signal strength signal intensity is stronger, and live width is thinner.This is conducive to improving performance index.In addition, when the order of reflection of light being set to odd-times and the optical path length in the outlet of light and loop is roughly equal, in speed group different from each other, almost equal to the quantity of the contributive atom of EIT, therefore, be favourable from the angle of EIT generation efficiency.Therefore, under this condition by multiple resonance light to when causing EIT, compared with the situation of non-reflective, utilize the resonance light of half quantity to or the light modulation width of half, identical effect can be obtained.Therefore, according to this structure, the design that laser driver etc. generate the right mechanism of multipair resonance light becomes easier, and power consumption during device drive reduces, and is conducive to energy-conservation.

Claims (18)

1. a quantum interference device, it produces electromagnetically induced Transparency Phenomenon, it is characterized in that,

This quantum interference device has:

The alkali metal atom of gaseous state, it has 2 ground state levels and at least 1 excitation level, and described 2 ground state levels have energy difference; And

Incide the multipair resonance light pair of the alkali metal atom of described gaseous state,

Resonance light described in each keeps 2 kinds of frequencies of the difference on the frequency corresponding to described energy difference to having,

The centre frequency that resonance light described in each is right is different from each other.

2. quantum interference device according to claim 1, is characterized in that,

Described multipair resonance light is to being linearly polarized light.

3. quantum interference device according to claim 1, is characterized in that,

Described multipair resonance light is to being circularly polarized light.

4. quantum interference device according to claim 1, is characterized in that,

Described multipair resonance light is to being Elliptical circularly polarized light.

5. quantum interference device according to claim 1, is characterized in that,

The right light source of the described multipair resonance light of injection and enclosed described gaseous state alkali metal atom air chamber between light path on be provided with wavelength plate.

6. quantum interference device as claimed in any of claims 1 to 5, is characterized in that,

Described multipair resonance light is to the occurrence condition meeting electromagnetically induced Transparency Phenomenon, and the luminous intensity that each resonance light is right is near the maximum P0 in the region that EIT signal strength signal intensity linearly increases.

7. quantum interference device as claimed in any of claims 1 to 5, is characterized in that,

The centre frequency that the intensity distributions that described multipair resonance light is right is right relative to each is Gaussian Profile, and the resonance light corresponding with maximum luminous intensity is the occurrence condition of the electromagnetically induced Transparency Phenomenon that described alkali-metal atomic group near 0 is corresponding to meeting with the velocity component of this light direction, its intensity is the maximum P0 in the range of linearity.

8. quantum interference device according to claim 1, is characterized in that,

Described multipair resonance light pair is generated by the synthesis of Modulation and Amplitude Modulation and frequency modulation(FM) or phase-modulation.

9. quantum interference device according to claim 1, is characterized in that,

By having the modulation of the signal of any one waveform in sine wave, triangular wave, sawtooth waveforms, square wave, generate described multipair resonance light pair.

10. quantum interference device as claimed in any of claims 1 to 5, is characterized in that,

This quantum interference device has the drive circuit portion for modulating light source, and described drive circuit portion is separated with other structure member, under the state in the fabrication process or after commercialization, at random can control, set the constant in described drive circuit portion.

11. quantum interference devices as claimed in any of claims 1 to 5, is characterized in that,

When set the nuclear-spin quantum number of described alkali metal atom as the quantum number of the hyperfine structure in the P1/2 excitation level of I, described alkali metal atom or P3/2 excitation level be F ', least energy in the region that coincides with one another of the scope that considers two energy of the doppler spread of F '=I-1/2 and F '=I+1/2 is E1, ceiling capacity is E2 time, cause the target energy Eend that excites of any pair of the multipair resonance light centering of described electromagnetically induced Transparency Phenomenon to meet E1 < Eend < E2.

12. quantum interference devices as claimed in any of claims 1 to 5, is characterized in that,

If the nuclear-spin quantum number of described alkali metal atom is I, the quantum number of the hyperfine structure of the excitation level of described alkali metal atom is F ', under the state then do not overlapped each other in the scope of two energy of the doppler spread considering F '=I-1/2 and F '=I+1/2, when setting the scope of energy of described the F '=I-1/2 considering described doppler spread as from E11 to E12, consider the scope of the energy of described the F '=I+1/2 of described doppler spread for from E21 to E22, and E11 < E12, during E21 < E22, the target energy Eend that excites of any pair of the multipair resonance light centering of described electromagnetically induced Transparency Phenomenon is caused only to meet the condition of the one party in E11 < Eend < E12 or E21 < Eend < E22.

13. quantum interference devices as claimed in any of claims 1 to 5, this quantum interference device makes multipair resonance light to 1 time or turns back by described alkali metal atom in multiple times, detect described electromagnetically induced Transparency Phenomenon from described alkali metal atom, the feature of this quantum interference device is

When set the energy of the excitation level not considering Doppler width as E10, described multipair resonance light right excite target energy to be Eend0 time, described Eend0 meets E10 < Eend0 or Eend0 < E10.

14. quantum interference devices as claimed in any of claims 1 to 5, this quantum interference device makes multipair resonance light to 1 time or turns back by described alkali metal atom in multiple times, detect described electromagnetically induced Transparency Phenomenon from described alkali metal atom, the feature of this quantum interference device is

When set any pair of the multipair resonance light centering causing described electromagnetically induced Transparency Phenomenon excite target energy as Eend time, described Eend only meets the condition of the one party in Eend < E10 or E10 < Eend.

15. quantum interference devices according to claim 13, is characterized in that,

Described number of turns is odd-times.

16. 1 kinds of atomic oscillators, is characterized in that, this atomic oscillator has the quantum interference device in claim 1 to 5 described in any one.

17. 1 kinds of Magnetic Sensors, is characterized in that, this Magnetic Sensor has the quantum interference device in claim 1 to 5 described in any one.

18. 1 kinds of quantum interference transducers, is characterized in that, this quantum interference sensor is had the right the quantum interference device in requirement 1 to 5 described in any one.