Near-Infrared Raman Spectroscopy with a 783-nm Diode Laser and CCD Array Detector

Abstract

A GaAlAs diode laser operating at 783 nm was combined with an unintensified charge coupled device (CCD) array detector and single grating spectrograph to obtain near-infrared (NIR) Raman spectra. The spectrometer has no moving parts and retains the high sensitivity expected for multichannel, shot-noise-limited detectors. Diode laser excitation permits high-sensitivity Raman spectroscopy with reduced fluorescence interference, in comparison to that produced with conventional visible lasers. The diode laser/CCD approach should exhibit much higher sensitivity than FT-Raman systems operating at 1064 nm, at much lower laser power. The sensitivity of the system was demonstrated by an S/N ratio of 17 for the 981-cm⁻¹ band of 0.01 M (NH₄)₂SO₄, obtained with 30 mW of 783 nm laser power.