Time-resolved Fourier transform intracavity spectroscopy with a Cr2+:ZnSe laser.

Intracavity laser absorption spectroscopy (ICLAS) with an evacuated Cr2+:ZnSe laser is performed with a high-resolution time-resolved Fourier transform interferometer with a minimum detectable absorption coefficient equal to 4 x 10(-9) cm(-1) Hz(-1/2) in the 2.5 microm region. This represents the extreme limit currently reached in the infrared by ICLAS with Doppler-limited resolution. The broad gain band of the crystal allows a spectral coverage at most equal to 125 nm, wide enough to see entire vibration bands. Weak CO2 bands observed up to now only in the Venusian atmosphere are recorded for the first time, to our knowledge, in a laboratory. An H2O detection limit down to 0.9 parts per billion by volume is also demonstrated.