Precision tunable infrared source at 10 μM: CO_2-laser/microwave-sideband system with an evenson CO_2 laser and a Cheo waveguide modulator

摘要

A CO_2-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 CO_2 laser of Evenson design that laser 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 CO_2 laser is stabilized to the Lamb dip in the 4.3 μm fluorescence signal in an external CO_2 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 CO_2 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 ±7 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.