Room-temperature Fe:ZnSe laser tunable in the spectral range of 3.7–5.3 µm applied for intracavity absorption spectroscopy of CO₂ isotopes, CO and N₂O

We demonstrate an intracavity absorption spectroscopy system based on a broadband single-crystal pulsed Fe:ZnSe laser. The laser operates at room-temperature and is continuously tunable in the spectral range of 3.76–5.29 µm. The long-wavelength emission up to 5.29 µm is a record achievement for Fe:ZnSe lasers, to the best of our knowledge. The developed laser system is applied for measurements of gaseous absorption inside the laser resonator. We demonstrate sensitive detection of (i) CO 2 isotopes in the atmosphere and in human breath, (ii) CO in breath (after cigarette smoking) and in the smoke of a smoldering paper, and (iii) N 2 O in a gas flow. The achieved detection limits are: 0.1 ppm for 12 CO 2 and 13 CO 2 , 3 ppm for CO, and 1 ppm for N 2 O. The sensitivity of the current system is primarily limited by the short pump-pulse duration of 40 ns. Possibilities for sensitivity enhancement by up to a factor of 10 7 are discussed.