In order to form a holographic grating of the invention, a resist pattern having a groove depth deeper than a desired depth of diffraction grating grooves is engraved in a photoresist layer provided on an optical glass base plate by an exposure method. Then, the photoresist layer is etched by an ion...http://www.google.de/patents/US20010017184?utm_source=gb-gplus-sharePatent US20010017184 - Holographic grating and method of forming the same
