Abstract
The frequency of a CO2 laser for sub-mm laser pumping has been stabilized by the use of a Stark modulated Lamb dip signal of CH3OH. Systematic investigation has been made to obtain a signal-to-noise ratio of the Lamb dip signal as high as possible. A frequency stability better than ±0.5 MHz has been achieved for the 9P(34) and 9P(36) lines of a CO2 laser. As a result, the output power of the optically pumped sub-mm laser also became stable. Power stabilities of ±4% and ±2.5% for about 1 hour have been obtained for the 70.5um line of CH3OH pumped by 9P(34) line and for the 119μm line of CH3OH pumped by 9P(36) line of a CO2 laser, respectively.
