High-power single-frequency tunable CW Er-fiber laser pumped Cr2+:ZnSe laser

We demonstrate an Er-fiber-laser-pumped, CW, high-power, single-longitudinal-mode Cr2+:ZnSe laser, tunable in the 2- 3 mm spectral region. The laser is operating in a single longitudinal mode regime with a linewidth of 80-130 MHz over a 120 nm tuning range around 2.5 mm, and delivers up to 150 mW of output power. The laser design is very compact and is based on Kogelnik/Littman cavity configuration with the total optical length of the folded cavity of 10 cm. The narrow-linewidth output spectrum can be quickly scanned over a 10 nm spectral range with a repetition rate of 220 Hz by a piezo-controlled tuning mirror which allows for an extremely fast wavelength tuning of the output spectrum over a large number of absorption spectral lines of trace gases of interest. As a test experiment, we performed a Dopplerlimited- resolution intracavity laser absorption spectroscopy of ro-vibrational transitions of the n3 and n1 bands of H2O with minimum detectable absorption coefficient of ~3x10-7 cm-1, which corresponds to 9 parts per billion by volume water vapor detection limit. The laser is currently in active stage of development and its further optimization will allow for full 2-3 mm fast tuning range and Watt-level output powers. This laser is being designed as a seeding source for an OPG-OPA-based, highly sensitive trace-gas sensor system for real-time detection of gas traces of biological pathogens and explosives in the molecular fingerprint mid-IR spectral region of 2-10 mm.