Stable frequency offset of parallel rf-excited CO₂ waveguide lasers.

The advantages of waveguide lasers over conventional heterodyne systems for frequency offsetting in high-resolution laser spectroscopy and metrology are described. Results are reported for three geometrically parallel RF-excited waveguide CO₂ lasers operating in the dual case one-resonator configuration with common mirrors. Precise alignment, two-axis tilt, and fine translation of the mirrors are provided by a combination of mechanical and piezoelectric adjusters. Efficient RF power transfer to the discharges was achieved over a wide power range. A He:CO₂:N₂ gas mixture in the proportions 3:1:1 was used at gas pressures in the 40-100-Torr range. The powers obtained from each channel were very neatly equal. Beat signals between neighboring lasers were observed in the far field by the overlap of the adjacent beams. The resonator alignment system permitted precise control of the signatures of each laser. Measurement results are shown for the frequency offset fluctuations for different observation times.