A Far Infrared Metal Waveguide Laser System Optically Pumped Using A Modular Carbon Dioxide Dielectric Waveguide Laser

The theory, design, and construction of an optically pumped far infrared laser is described. The pump source consists of a carbon-dioxide waveguide laser which injects several watts of 10 (mu)m wavelength radiation into a metallic waveguide FIR resonator containing a molecule active in the far infrared. The frequency of the pump laser is monitored using a heterodyne technique and can be stabilized on the peak of the optoacoustic absorption signal of the FIR active medium. System operation is verified for known FIR stimulated emissions of optically pumped methyl alcohol. The wide tuning range of the CO(,2) waveguide pump laser allows excitation of CH(,3)OH pump absorption lines located within (+OR-)115 MHz from the CO(,2) emission line center.;The waveguide pump laser is constructed from four identical beryllium oxide waveguide sections connected in series. The modular concept permits the assembly of waveguide lasers with resonator lengths appropriate for specific laser applications. A high voltage trigger pulser is used to initiate the separate discharges. Successful implementation of an optovoltaic probe for frequency stabilization is demonstrated. Waveguide Brewster\u27s window extensions, a variable output coupling waveguide etalon, and a two element external cavity reflector were developed to enhance laser performance.;The pump radiation is conducted into the FIR cavity using an alumina waveguide through a hole in the end mirror with very low power loss and minimal beam divergence. Output FIR radiation was detected using a pyroelectric detector contained within the cavity chamber. The compact detector unit includes an integral optical chopper and quartz lens.;Output power vs gain length data from the modular CO(,2) waveguide laser permitted the calculation of small signal gain and saturation intensity for various laser gas mixtures. The results so obtained extend the known values of these parameters to higher operating pressures and larger helium fractions. Saturation intensity was found to be dependent upon the fraction of CO(,2) in the gas mixture. The discharge current for optimal power output increased with laser gain.;The optically pumped FIR laser system can be used to investigate lasing for unstudied molecules and pump off-set frequencies or as a source of stable coherent FIR radiation suitable for spectroscopic applications