Unmodulated CO2 laser stabilized by means of Stark and photoacoustic spectroscopy

Abstract A high-power CO 2 laser (9P(34)) for use in optically pumping a CH 3 OH laser (70.5 μm) has been stabilized in the vicinity of the center of the CH 3 OH saturated absorption line by means of photoacoustic spectroscopy (PAS). The stabilized pump laser beam is unmodulated because the PAS signal for stabilization was obtained by modulating the Stark field in the external PAS cell filled with CH 3 OH molecules at low pressure. The unmodulated effect is to eliminate the spectrum spread due to the frequency modulation, and is demonstrated in the frequency mixing between the seventh harmonic of the CH 3 OH laser and a CO 2 laser at 10.2 μm. The frequency stability has been estimated quantitatively with reference to a CO 2 laser stabilized on the Lamb dip of 4.3 μm fluorescence.