Generation Of Tunable Laser Sidebands In The Far-Infrared Region

Continuously tunable laser sidebands in the submillimeter and far infrared (FIR) have been generated by mixing radiation from an optically pumped FIR molecular laser with that from millimeter-wave klystrons in a Schottky-barrier diode. An enhancement in conversion efficiency over similar systems reported previously is obtained by using a Michelson interferometer to separate the sidebands from the carrier and by placing the Schottky diode in an open structure corner cube mount. With 4 mW of laser power at 693 and 762 GHz the side-band power was measured to be 101N. This is at least an order of magnitude better than the previously reported results. At higher frequencies, 22 mW of 1627 GHz laser power produced about 7.5 μW of sideband output while 3 mW of 1839 GHz laser power generated about 200 nW of sideband radiation. The lower efficiency at the higher frequencies is due primarily to the mismatch between the laser radiation and the fixed-length diode antenna. Spectral lines have been observed up to 3200 GHz. The molecular absorbtion signals are easily seen using either video or lock-in detection techniques.