Optically Pumped Molecular Laser

    OPML is an integrated Far Infrared laser system made by Edinburgh Instruments. It consists of two cavities CO₂ and FIR designed to give high out put power in 9-11 micron (about 80 lines) with good frequency and amplitude stability coupled with powerful FIR emission in the 40 micron to 1.22 mm region. The CO₂ section of the laser is operated in a flowing gas mode to obtain highest output power. The laser gain section is a single arm water discharge tube sealed with Brewster angled ZnSe windows in air cooled mounts. The CO₂ resonator consists of a partially reflecting ZnSe output coupling mirror and a blazed diffraction grating. The output coupler is mounted on a piezo-electric transducer which allows fine control of the cavity length (and hence output frequency). The FIR part of the laser system is mounted on the common invar rod frame. It comprises a ZnSe input Brewster window which forms a vacuum seal at one end of the laser, a flat chromium gold coated stainless steel input mirror at one end of the laser and a dichroic output coupler from which the FIR power is extracted to other end. A water cooled oversized pyrex waveguide of 35 mm inside diameter is used. The stabilization of the system is done by using a part of FIR power and feed that back to the CO₂ piezo-electric transducer which stabilize the CO₂ and hence FIR laser. Because any change in the CO₂ laser produces changes in the FIR portion of the laser. Presently we are using two FIR gases CH₃OH and HCOOH which are able to give 10 strong FIR lines.

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