CO laser system

Master oscillator–laser amplifier CO laser system generating nanosecond pulses

The laser levels of the CO molecule get populated as the result of a comparatively slow exchange of vibrational energy between molecules. For this reason, the CO laser operating on vibrational–rotational transitions in the mode-synchronization regime was considered to be little efficient until recently. But high-power nanosecond pulses of radiation at wavelengths near 5 μm became requested for solving a complicated science and technology problem, stochastic cooling of relativistic ions in colliders. We demonstrated that at an active synchronization of modes a cryogenic electroionization CO laser facility can generate a train of radiation pulses ~5 to 15 ns in duration at their recurrence frequency of 10 MHz, equal to the recurrence frequency of ion clusters in the Relativistic Heavy Ion Collider (Brookhaven National Laboratory, USA). Herewith, the radiation peak power reached 120 kW at the generation of multi-frequency radiation (~20 spectral lines) and 70 kW in the frequency selective regime at the generation on one line corresponding to the vibrational-rotational transition 9->8 P(11). To increase the peak power of CO laser radiation, a master oscillator–laser amplifier system was developed at the output of which the power increased to 380 kW in the multi-frequency regime and to 130 kW in the frequency selective regime. Studies of the amplification of short radiation pulses showed that, due to a high rotational relaxation rate, the intensity of radiation amplification saturation on one spectral line in the Co laser amplifier was ~14 kW cm^‑2 and exceeded by more than one order of magnitude the intensity of amplification saturation of a continuous multifrequency CO laser radiation. Owing to the development of this laser system, the efficiency of transformation of CO laser radiation frequency in nonlinear crystals was increased; in particular, the internal efficiency of second harmonic generation of a CO laser reached a record value of 25%.

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