A Simple Technique for Obtaining a Stable Frequency Sweep in a Waveguide CO2 Laser

A simple technique for obtaining a stable frequency sweep in a waveguide-type CO₂ laser is described. The laser was compact, and contained a Stark cell inside its cavity, and the Stark spectrum in NH₂D was observed in the frequency range at the 10.6 μm P(20) laser transition. The frequency of the laser was stabilized at the center of the inverted Lamb dip in one of the Stark components, and a stability as high as 2.1× 10^-11 was obtained at an integration time τ of 250 s. The stabilized laser frequency was swept by slowly varying the d.c. electric field applied to the NH₂D molecules. It was swept for the whole frequency range of the single longitudinal-mode oscillation (195 MHz) while maintaining a traceability to the center frequency of the inverted Lamb dip of as high as 5.5× 10^-10\cdotτ^-1/2 for 1 s{≤q}τ{≤q}100 s.