Andrey Yu. Kozlov

Novel mode-locked carbon monoxide laser system achieves high accuracy

Extending the emission range of gas lasers is an attractive proposition, for example, in laser spectroscopy, atmosphere sensing, laser media diagnostics, initiating chemical reactions, and separating elemental isotopes. In this context, carbon monoxide (CO) lasers offer several advantages over other sources of IR radiation, including control of output energy and pulse duration over a wide dynamic range. Moreover, they ensure high average power in repetitively pulsed modes. An electric discharge CO laser can operate on every spectral line from among a few hundred in both fundamental ( 4.7–8.2 m)1 and firstovertone ( 2.5–4.2 m) spectral bands.2–4 In addition, parametric frequency conversion (i.e., frequency doubling, or sum or difference frequency generation) of CO laser radiation using a single nonlinear crystal can cover both midand far-IR spectral ranges. However, to achieve high-frequency conversion efficiency, CO laser radiation must have high peak power. The first mode-locked (i.e., pulsing) laser was reported decades ago. But it had a peak power of only a few kilowatts because it operated at room temperature. No efforts have been made since then to obtain substantially higher power. We have developed a cryogenically cooled, electron-beamsustained-discharge (EBSD) mode-locked CO laser that produces a train of 5–15ns full width at half-maximum spikes with a pulse repetition rate of 10MHz in the mid-IR range of 5 m.5 We obtained maximum output power of up to 120kW for a multiline mode and 70kW for a single-line mode of operation. As suggested elsewhere,6 such radiation could be used to pump an optical parametric amplifier for stochastic cooling in a relativistic heavy-ion collider (see Figure 1). Figure 1. Imaginary layout of the optical stochastic cooling system for the relativistic heavy-ion collider (Brookhaven National Laboratory, US). The storage ring measures 4km. CO: Carbon monoxide. : Wavelength. OPA: Oscillator-power amplifier. : Wavelength.

Compact-slab radio-frequency discharge CO laser

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.

Small signal gain in a pulsed CO laser amplifier operating on oxygen containing gas mixtures

Small signal gain temporal behavior in pulsed CO laser amplifier operating with oxygen rich gas mixtures CO:He:O2 and CO:N2:O2 was experimentally studied. The rich content of oxygen in helium mixture (CO:He:O2=1:4:2) resulted in ~8-fold increase of the maximum gain on low vibrational transitions (10-9) and strong absorption on high ones (21-20). A high efficient pulsed CO laser operating with gas mixture in which oxygen substituted for nitrogen was launched.