Nonlinear laser spectroscopy of gases, gas flows, and low temperature plasmas

The potentialities of gas analysis by the methods of active Raman spectroscopy based on coherent four-proton interaction of high-power laser beams with the resonance cubic nonlinearity .are examined. Particular attention is paid to the possibility of measuring the parameters of gas discharges, flows, and flames, and also to the detection of low-level impurities in gases. A comparison is made with the traditional methods of spontaneous Raman spectroscopy. We show that the coherent methods of optical gas analysis possess a number of important advantages over the traditional methods, and show promise in many scientific and technical applications. The review is based on materials published in the scientific literature in the past two or three years, and on materials of domestic and international conferences on laser spectroscopy and gas diagnostics during recent years.