Axial Transmissive f /1.8 Imaging Raman Spectrograph with Volume-Phase Holographic Filter and Grating

An axial transmissive Raman spectrograph is described. The instrument employs volume-phase holograms as the laser line rejection filter and transmission grating. The on-axis configuration and the use of a high-spatial-frequency transmission grating allows nearly diffraction-limited imaging and pixel-limited resolution at f1.8. The performance of the instrument is demonstrated for fiber-optic probe and microprobe Raman spectroscopy.