Knowledge Bank

By using a CdTe electrooptic modulator with broad-band antireflection coatings on the ends, an infrared-microwave sideband laser spectrometer has been assembled for operation in the CO laser region. Except for the higher frequency of the infrared radiation, the operation of the spectrometer is very similar to that of our systems in the $CO2$ or $N2O$ laser $regions.2$ The laser is frequency-stabilized and the microwave frequency is stepped by a computer across the X-band (8-12,4 GHz) or the P-band (12,4-18 GHz). Modulation of the spectrometer signal is achieved by chopping the microwave radiation with a PIN diode. The sidebands are split into sample and reference beams and the amplitude of the reference beam controls the sideband power by controlling the attenuation of the PIN diode during the ``on'' portion of its cycle. Although the CO laser power is lower than that of our $CO2$ lasers, the efficiency of the sideband generation is greater at the higher infrared frequency, so the sideband powers in the two frequency regions are comparable. Currently, the CO laser is frequency-stabilized at the top of the gain curve, which limits the reproducibility of the frequency to *-10 MHz. The results of spectroscopic measurements of $N2O,H2CO$, and HCOOH will be described.