A frequency stable, single mode he-ne gas laser

A small helium-neon gas laser was assembled and tested. The unit features temperature-compensated cavity design, electromagnetically tunable cavity length, wide axial mode separation to assure single TEMoonmode operation, control circuitry for frequency sweep and AFC, and rugged coaxial construction. The re-entrant mirror mounts and the invar main-body assure negligible changes of the cavity length during warm-up and with changes of temperature, through proper choice of the respective expansion lengths. The high-gain double-walled plasma tube renders single-ended power output in excess of 200 microwatts at the 6328 Å wavelength.