OptiGrate Corp. has unveiled a line of ultranarrow notch and bandpass filters for Raman spectroscopy applications. The filters have a bandwidth of <10 cm—1, which the company says is about 10 times narrower than other notch and bandpass filters commercially available for these applications. The filters enable measurements of ultralow-frequency Raman bands with standard instruments, rather than with the previous complex, bulky and more expensive tools. Applications include nanotechnology, pharmacology and semiconductor processing. Using a single-stage spectrometer, Stokes and anti-Stokes frequencies can be measured down to 4.5 cm—1 with a set of BragGrate filters. The filters are based on reflecting volume Bragg gratings formed in proprietary photosensitive glass material, and they are available for a wide range of Raman laser source wavelengths, including 488, 514, 532, 633, 785 and 1064 nm.