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.

Actively mode-locked electron-beam-sustained-discharge CO laser producing a train of ∼5–15ns (FWHM) spikes following with repetition rate 10MHz for both single-line and multiline mode of operation in the mid-IR range of ∼5μm was experimentally studied. Total laser pulse duration was ∼0.5ms for both mode-locked and free-running laser. Specific output energy in multiline CO laser mode of operation was up to 20Jl−1Amagat−1 and the laser efficiency up to 3.5%. The active mode-locking was achieved for single-line CO laser mode of operation in spectral range 5.2–5.3μm. This sort of radiation can be used for pumping an optical parametric amplifier for optical stochastic cooling in relativistic heavy ion collider, for laser ablation, and for studying vibrational and rotational relaxation of CO and NO molecules.

Actively mode-locked electron-beam-sustained-discharge CO-laser producing similar to 10 ns (FWHM) pulses repetition rate 10 MHz for both single-line and multiline mode of operation was experimentally studied. The total laser pulse duration was similar to 0.5 ms for both mode-locked and free running laser conditions. The specific output energy in multiline CO-laser mode of operation was up to 20 J l(-1) Amagat(-1) and the laser efficiency up to 3.5%. The active mode-locking was achieved for single-line CO-laser mode of operation in the spectral range 5.2-5.3 micron. The radiation can be used for laser ablation, for pumping an optical parametric amplifier in optical stochastic cooling of relativistic heavy ions, and for studying vibrational and rotational relaxation of NO molecules.