Compact, broadly tunable, mid-IR source for the spectroscopicinvestigation of molecular reference lines in the 27- to 33-THz range

摘要

We report on the improvement of a tunable, high resolution, diodenlaser-based, difference-frequency spectrometer using annAgGaS2 nonlinear crystal. We use a type-II cut crystal as anpart of the improvement compared with a type-I cut, which was used innour preliminary setup. The two tunable laser-diodes are operating nearnΛ3=778 nm (pump) and Λ2=842 nmn(signal) with a sub-100-kHz linewidth. The high resolution spectrometernis being developed as an alternative to CO2 lasernspectrometers in the 9- to Il-Μm range. Using a dual-arm cavity tonenhance the two radiation powers, and with 35 mW in front of the 778-nmnarm and 100 mW in front of the 842 nm arm, about 70 nW of the tunablen10-Μm radiation are generated. This power level is enough toninvestigate the linear absorption spectroscopy of SF6.nDoppler-limited spectra over 2 GHz, are recorded, showing the widencontinuous tunability of the spectrometer