G. C. Bhar

Study of laser induced damage threshold and effect of inclusions in some nonlinear crystals

Abstract The paper reports the comparative studies on the laser-induced single-shot and multiple-shot surface damage thresholds of nonlinear crystals, viz. Urea, 3-methyl-4-nitropyridine-1 oxide (POM), l -arginine phosphate (LAP) and β-barium borate (BBO) crystals. The measurements were made using radiation of 1064 nm and its second harmonic generation, i.e. 532 nm from a Q-switched Nd:YAG laser of pulse width 10 ns. In addition, the effect of Na+ impurity incorporated during growth in BBO crystal in different concentration (wt.%) has also been studied, and attempted to be correlated with various factors. We also measured the absorption coefficients of these crystals at different wavelengths. The Scanning Electron Microscope coupled with Energy Dispersive X-Ray Analyzer (SEM-EDX) has been employed to study the inclusions/impurities present in the crystals.

A simple model for evaluation of refractive indices of some binary and ternary mixed crystals

Abstract In view of the importance of binary and ternary mixed crystals for heterojunction LED and solar-cell applications, a method for evaluating the high-frequency refractive indices of such crystals is presented using a modified Penn-gap model. The theoretical predictions agree quite well with the experimental results. The model is also applied to evaluate the temperature and pressure coefficients of refractive indices of binary and ternary crystals. The close agreement between the calculated and experimental values justifies the validity of the approach.

Noncritical second harmonic generation of CO2 laser radiation in mixed chalcopyrite crystal

We have generated a tunable second harmonic of CO2 laser radiation noncritically for the first time in a potential mixed chalcopyrite crystal AgGaxIn1−xSe2. Wide angular acceptance and increased conversion as compared to AgGaSe2 have been observed and the tuning characteristics have been explained using the dispersion data of its two end crystals.

Nonlinear optical laser devices using GaSe

Tunable second-harmonic generation of CO2 laser radiation and tunable upconversion of infrared radiation from CO2-laser radiation in a GaSe crystal are demonstrated. The capability of low infrared-signal detection in this crystal is also explored and compared with the AgGaS2 crystal.

Temperature-tunable second-harmonic generation in zinc germanium diphosphide

Second‐harmonic generation of tunable CO2 laser radiation is reported and analyzed in ZnGeP2 both by angular and temperature tunings. Temperature tuning can thus be advantageously employed in this crystal for nonlinear devices.

Efficient generation of mid-infrared radiation in an AgGaxIn 1− xSe 2 crystal

Efficient generation of mid-infrared radiation by noncritically phase-matched second-harmonic generation is demonstrated in a mixed chalcopyrite crystal, AgGa(x)In(1-x)Se(2), and compared with that in an AgGaSe(2) crystal. Nonlinear coeff icients d(36) of AgGa(x)In(1-x)Se(2) and AgGaSe(2) crystals have also been derived.

Temperature effects in AgGaS 2 nonlinear devices

Refractive indices of AgGaS2 crystal are measured at different temperatures using the classical minimum deviation technique and are fitted in appropriate dispersion relations. The variation of pump laser wavelength for noncritical upconversion of signal at 10.6 μm with the change in crystal temperature has been verified using the above data. Temperature tunable infrared generation by noncritically phase-matched difference-frequency mixing has been predicted from 3 to 18 μm.

Temperature-dependent Sellmeier coefficients and coherence lengths for some chalcopyrite crystals

Temperature-dependent Sellmeier equations are useful for determining optical-design parameters of nonlinear optical devices. These coefficients as a function of temperature are calculated for three chalcopyrite crystals: ZnGeP2, CdGeP2, and CuGaS2. Coherence lengths for second harmonic generation as well as its temperature derivative are also presented for these crystals.

Linear and nonlinear optical properties of ZnGeP2 crystal for infrared laser device applications: revisited.

Measurement of refractive indices in the spectral bands 9-11 microm and 1.32 microm from a cw CO2 laser and a Q-switched Nd:YAG laser, respectively, is reported in a ZnGeP2 crystal. A new set of Sellmeier dispersion relations has been derived from the measured refractive indices data in this crystal. Second-harmonic generation (SHG) of CO2 laser radiation in this crystal is also reported. It is also seen that the previously reported phase-matching data for others experiments in SHG and optical parametric devices is explained satisfactorily with this new set of Sellmeier dispersion relation.

Widely tunable deep ultraviolet generation in CLBO

Abstract In a single cut cesium lithium borate (CsLiB6O10 or CLBO) crystal we have generate deep UV radiation tunable from 195 to 265 nm (with a gap from 210 to 226 nm due to crystal cut limitation). Radiation in the 195–210 nm region is generated by noncollinear sum-frequency mixing of Nd:YAG laser radiation with the second harmonic (239–262 nm) of the dye laser radiation. However, radiation in the region of 210–237.5 nm and 236.8–265 nm is generated by third harmonic and second harmonic generation of the dye laser, respectively. All three interactions for coverage of the said range are made in the same cut CLBO crystal Type-I, θ=80° and ϕ=45°. The shorter wavelength tuning is phase-matching limited. A conversion efficiency of 14% is realised in our 5.5 mm long crystal for the generation of 241.7 nm radiation by Type-I second harmonic generation with a fundamental input beam intensity as low as 14.6 MW/cm2.