NLIR - Model 7.6 – 12.0 µm -Prototype Spectrometer
The mid-infrared region from 5 µm to 12 µm (2000 cm-1 to 833 cm-1) is very interesting for many industrial and research applications because many molecules have defining absorption lines exactly there. Unfortunately, the detectors (typically HgCdTe) used in FTIR systems for spectroscopy purposes suffer from significant amounts of thermal noise due to its low bandgap. Hence, high levels of input light are needed with long exposure times to achieve a satisfactory signal-to-noise ratio.
NLIR is pushing its technology to cover this extended wavelength region in the future. Currently, the prototype edition of the long-wavelength spectrometer covers 7.6 µm to 12.0 µm (1316 cm-1 to 833 cm-1).
The spectrometer has a free-space input to maximize sensitivity and bandwidth, which on the other hand means that the response at each wavelength is sensitive to the angle of the input light. Hence, this spectrometer is most suited for reference measurements (e.g., ATR, gas cell, coating transmission, etc.) with a fixed light source. The spectrometer can be used for characterization of laser sources, for example time-resolved spectral analysis, but an input power calibration may be necessary.
The spectrometer comes in two editions: an economic, sensitive edition with 20 Hz readout rate and a fast edition with up to 130 kHz readout rate. Tentative values for the sensitivities are 50 pW/nm and 100 pW/nm, respectively. The resolution is approx. 10 cm-1.