SPECTROSCOPIC APPLICATIONS OF SUBMILLIMETER GENERATION BY AN ALL-SOLID-STATE, OPTICAL, HETERODUNE SOURCE

Author Institution: Division of Chemistry and Chemical Engineering, California Institute of Technology; Division of Geological and Planetary Sciences, California Institute of TechnologyA compact, narrow-linewidth, tunable source of submillimeter-wave radiation has been developed for spectroscopy and other high-resolution application. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown (LTG) GaAs photomixer. Resonant optical feedback is employed to stabilize the center frequencies and narrow the linewidths of the DBR lasers. The heterodyne linewidth (FWHM) of two optically locked DBR lasers is 50kHz on the 20 ms time-scale and 2 MHz on the 10 s time-scale; free-running DBR lasers have linewidths of 40 MHz and 90MHz on such time-scales. Detection limits of $4 \times 10^{-5} Hz^{-1/2}$ (noise/total power, averaged over 100 data points at an acquisition rate of 1 points) have been achieved. Applications to VRT spectroscopy of $N_{2}-D_{2}O$ will be presented