Room-temperature Fe:ZnSe laser tunable in the spectral range of 3.7-5.3 µm applied for intracavity absorption spectroscopy of CO isotopes, CO and NO.

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 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) NO in a gas flow. The achieved detection limits are: 0.1 ppm for CO and CO, 3 ppm for CO, and 1 ppm for NO. 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 are discussed.