US Patent 7986407 Method and apparatus using volume holographic wavelength blockers

The invention disclosed here teaches methods to fabricate and utilize a non-dispersive holographic wavelength blocker. The invention enables the observation of the Raman signal near the excitation wavelength (˜9 cm−1) with the compactness of standard thin film/holographic notch filter. The novelty is contacting several individual volume holographic blocking notch filter (VHBF) to form one high optical density blocking filter without creating spurious multiple diffractions that degrade the filter performance. Such ultra-narrow-band VHBF can be used in existing compact Raman instruments and thus will help bring high-end research to a greater number of users at a lower cost.