Second Harmonic of Laser Radiation for IR-Range in Mixed Crystals

The results of investigations of the influence of different parameters on conversion efficiency in mixed AgGa0.6In0.4Se2 crystal in conditions of existing experiments are cited. The angular dispersion coefficients for three versions of crystal , differing by a content of indium, have been calculated. A comparison was made of the obtained results on conversion efficiency with analogous results in case of other crystals and with corresponding experimentally measured values. The applied analytical method makes it possible to calculate the optimum parameters of both crystal-converter and a source of radiation for conditions of uncritical phase matching in the concrete experiment. 1. Introduction Recently, the important achievements have been attained in application of nonlinear crystals in the numerous devices of IR-range. One can note among them the prospect CdGeAs2 crystals, available ZnGeP2 crystals, AgGaSe2, and others [1–3]. Selection of nonlinear crystals is determined by requirement of obtaining the high conversion efficiency of pump radiation in a tuning wide spectral range. As one way of solving this problem, it is suggested to use chalcogenide crystals or chalcopyrite structures, for example, , [2]. In similar crystals, by changing parameter , it is possible to realize uncritical phase matching. This condition ensures the absence of walk-off of second harmonic energy, excluding decrease of second harmonic generation caused by birefringence. We have chosen the perspective crystals as a subject of study among crystals of mixed type, owing to a number of its qualities. As showed in the result of experiment [4] by researchers, by choosing indium content, it is possible to perform the uncritical condition of phase matching at second harmonic generation in near and middle IR-range. With this, a value of parameters on wavelength of CO2 laser radiation ？mcm is equal to 0.6. The measured value of quadratic nonlinear susceptibility for AgGa0.6In0.4Se2 crystal is equal to ？pm/V [4]. For comparison, the analogous specified value for AgGaSe2 crystal is equal to 39？pm/V [3, 4]. For the task of application in IR-range of spectrum CO2 lasers (which present a powerful source of optical coherent radiation in the given region of spectrum) play a leading role. If in the middle IR-region of spectrum an efficient generation of radiation for this laser permits realizing tunable coherent radiation, then in the near IR-range it can succeed owing to radiation of second harmonics for CO2 laser. To consider a wide circle of the tasks in a theory for nonlinear waves, it is