Precision Tunable Infrared Source at 10 μM: CO2-Laser/Microwave-Sideband System with an Evenson CO2 Laser and a Cheo Waveguide Modulator

A CO2-laser/microwave-sideband tunable infrared source system has been newly built at the University of New Brunswick (UNB) in Canada. The system employs a high-resolution CO2 laser of Evenson design that lases on a wide range of lines including hot and sequence band lines as well as high-J lines of the regular 9.6 and 10.6 μm bands. The frequency of the CO2 laser is stabilized to the Lamb dip in the 4.3 μm fluorescence signal in an external CO2 cell. Microwave (MW) sidebands are generated in a Cheo-type infrared waveguide modulator driven by a synthesized sweeper and a traveling wave tube (TWT) amplifier. The MW sidebands appear on either side of the CO2 laser line, and are individually separated from the carrier by a tunable Fabry-Perot etalon. The sidebands currently have a typical power of about 1.4 mW and a continuous frequency tuning range of 22 GHz (from ± to ±18 GHz) when 5 W laser power and 15 W microwave power are delivered to the modulator. Details are given on the source construction and measured performance characteristics. Features of the source and its planned applications are discussed.