Tunable Far Infrared Laser Spectroscopy

using C02 laser difference generation in metal-insulator-metal diodes either from the difference between a fixed frequency C02 laser and a tunable waveguide laser, or from the difference between two fixed frequency C02 lasers plus microwave sidebands. is being used to make highly accurate FIR frequency measurements of stable species to serve as frequency and wavelength calibration standards; to measure frequencies of transient species (including molecular ions) for astronomical searches; and to study line broadening and line shape parameters especially for atmospheric spectroscopy applications. Tunable far-infrared (FIR) radiation has been generated Our tunable FIR source INTRODUCTION Tunable far-infrared (FIR) radiation has been generated with four different techniques: harmonics of microwave oscillators ( l ) , C02 laser difference frequency generation in GaAs (2), FIR laser plus microwave sidebands ( 3 ) , and the C02 laser difference generation in a metalinsulator-metal diode ( 4 , s ) described in this paper. tunable FIR source to make highly accurate FIR frequency measurements of stable species to serve as frequency and wavelength calibration standards ( 6 ) , to measure frequencies of transient species (including molecular ions) for astronomical searches (7-11), and to study line broadening and line shape parameters (12) especially for atmospheric spectroscopy applications. We are using two related techniques of synthesizing tunable far infrared radiation: either from the difference between a fixed We are using our “Contribution of the U.S. Government, not subject to copyright. Work supported by NASA Contract W-15,047 An earlier version of this paper was submitted to the 11th International Conference on Infrared and Millimeter Waves, and was available only to delegates at the conference. 43 A . C . P . Alves et al. (eds.). Frontiers ofLaser Spectroscopy of Gases, 43-SI