Infrared Raman laser with an unstable resonator

An experimental investigation was made of the characteristics of the output radiation of an infrared Raman laser with an unstable resonator emitting pulses of ~5 μsec duration. A comparison of the results obtained with the parameters of a similar laser with a plane-parallel resonator showed that the efficiency of conversion of the pump radiation into the first Stokes component was practically the same in both cases. The divergence of the radiation emitted from the unstable resonator was 7–10 times less than in the plane-parallel case when measured at midamplitude of the distribution of the energy density in the far-field zone and 3–4 times less when measured at midamplitude of the output energy. Wide wings were observed in the angular distribution of the radiation and possible reasons for their existence were considered.