Broadband light scattering spectroscopy utilizing an ultra-narrowband holographic notch filter

The broadband spectroscopic analysis over Brillouin, quasi-elastic, and Raman regions arising from the same position of the sample has been achieved by employing an ultra-narrowband holographic notch filter (HNF) and an optical isolator. Recently, HNFs are often employed to reject strong elastic scattering in low-frequency Raman experiments. Meanwhile, the rejected spectral component agrees with the frequency range that can be observed by a triple-pass tandem Fabry–Pérot interferometer. Thus the broadband spectroscopy can be accomplished by introducing the rejected light to the interferometer. This system, in combination with the local symmetry analysis by polarization-direction-resolved Raman spectroscopy, is particularly advantageous for the investigation of spatially inhomogeneous systems.