Rugged fiber-optic Raman probe for process monitoring applications

We report on the development of a simple, rugged fiber-optic probe for proc ess Raman measurements, in which laser line rejection is based on an absorp tive longpass filter made from a direct bandgap CdTe semiconductor. The pro be can be used with a fixed wavelength laser at 830 nm, and Raman spectra c an be recorded down to 200 cm(-1) from the laser line. The filter thickness can be adjusted for final turning of the filter edge, as the edge slope is almost independent of thickness in the range 0.1 to 1 mm. Other properties of the probe, such as its signal-to-noise ratio and signal-to-background r atio, are shown to compare well with those of a state-of-the-art probe base d on holographic notch filter techniques.