Double Monochromator aka Ultraviolet Tunable Filter
Standoff Raman spectroscopy is an optical sensing technique. Among other things, it can be used to detect and identify chemical, biological and explosive activity. There is an ongoing national and international scientific effort to improve these types of detectors. The goal is to form sensing networks to provide early warning for a variety of chemical, biological, radiological, nuclear or explosive (CBRNe) weapons of mass destruction (WMD).
One potential improvement of these Raman spectroscopy systems is to excite samples with shorter wavelengths of light. UV excitation at 193, 213 or 244 nanometers may increases sensitivity, suppresses fluorescence and provide resonance coupling. These each improve signal-to-noise in the measurement for faster detection of trace.
McPhersons compact double-monochromator Model 275D is ideal for deployment in these sensors. It works as a tunable filter, adjustable Rayleigh edge-rejection and bandpass. It can work to wavelengths as short as 190 nanometers with no special preparation. The double-monochromator has a stable housing and wavelength tuning for easier signal optimization. Diffraction gratings with aberration correction and good efficiency from 190 nanometers ultraviolet to the infrared are available.
Double Spectrometer Applications: