Compact-slab radio-frequency discharge CO laser

Abstract

Carbon monoxide (CO) lasers1 are very attractive sources of mid-IR radiation for laser spectroscopy and multicomponentgas analysis. The spectral range (2.5–4.2μm) of first-overtone (FO) CO lasers (characterized by vibrational transitions from V + 2 → V) covers those of the well-established hydrogen fluoride and deuterium fluoride lasers, but with significantly smaller vibrational-rotational line spacings. Their full output spectra may contain more than 400 emission lines,2 many of which coincide with absorption lines exhibited by a wide range of organic and inorganic materials such as, H2O, CO2, CH4, NO2, NO, SO2, acetone, benzene, andmethanol. FO CO lasers operating at these wavelengths can thus be used to assess the impact of resonances on various media in fields as diverse as, nonlinear spectroscopy, atmospheric remote sensing, and laser chemistry. FO CO lasers are among the best devices for laser-based spectroscopic analysis of multicomponent-gas mixtures.3 In addition, the longerwavelength section of their output spectrum coincides with the atmospheric ‘transparency window.’ Successful applications require the development of compact, sealed-off FO CO lasers. Present-generation FO CO lasers use either fragile glass components, e.g., for continuous-wave (cw) gas-flow high-voltage DC discharge, or very complicated, largescale designs (e.g., for high-voltage electron-beam-sustained discharge or supersonic cooling), and are not suitable for integration in compact multiwavelength-laser gas analyzers.3 One of the most promising approaches to producing compact gas lasers uses radio-frequency (RF) discharge in a slab geometry to pump an activemedium.We developed a cryogenically cooled slab RFdischarge CO laser4, 5 (see Figure 1). Significant operational advantages of our FOCO laser include its slab RF-discharge pumping operation, robust compact stainless-steel design, sealedoff performance, cryogenic cooling of the electrode system Figure 1. Slab radio-frequency discharge first-overtone carbon monoxide (CO)-laser setup. (a) General view. (b) Open view.