A. M. Rudra

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.

Generation of tunable 187.9–196-nm radiation in β-Ba 2 BO 4

Tunable 187.9-196-nm vacuum-ultraviolet radiation was generated at room temperature in a beta barium borate crystal by sum-frequency mixing of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the second harmonic of the same Nd:YAG laser. By use of the advantageous noncollinear phase-matching configuration, a peak power of 1.3 kW was obtained at 194 nm with input power densities as low as 79MW/cm(2) for 1064-nm and 0.65MW/cm(2) for 237.3-nm radiation.

EFFICIENT GENERATION OF 200-230-NM RADIATION IN BETA BARIUM BORATE BY NONCOLLINEAR SUM-FREQUENCY MIXING

Tunable ultraviolet radiation in the 200-230-nm region has been generated with beta barium borate crystals by type I sum-frequency mixing of the second harmonic with the fundamental beam from a dye laser pumped by the second harmonic of the same Nd:YAG laser. A noncollinear phase-matching configuration has made it possible to realize conversion efficiency of 21% at 208.3 nm with input power densities as low as 28 MW/cm(2) for the fundamental and 2.4 MW/cm(2) for its second-harmonic radiation. The absorption characteristic of a standard DNA sample has been studied with the generated tunable ultraviolet source, revealing additional features compared with those obtained with a spectrophotometer.

Temperature effects in second harmonic generation in AgGaSe2 crystal

The prospect of temperature tunability in an AgGaSe2 crystal for use in infrared nonlinear optics is explored for the first time. Tunable second harmonic generation from CO2 laser radiation is studied at different temperatures of the crystal. The tuning offered is small and the experimental finding is consistent with dispersion measurement.

Generation of widely tunable mid-infrared radiation by difference frequency mixing in KTP

The crystal potassium titanyl phosphate (KTP) shows promise for generation of tunable infrared radiations throughout the range m. Widely tunable mid-infrared radiations have been generated by nonlinear difference frequency mixing of the Nd:YAG second harmonic and the same pumped tunable dye laser radiation (610 - 710 nm) in a KTP crystal. The system generates more than 14 W mid-infrared peak power at m by difference frequency generation.

Evaluation of AgGaSe2 temperature-dependent nonlinear devices

Variations in refractive indices with temperature, the thermo-optic coefficients and temperature-dependent absorption in AgGaSe2 crystal have been measured. Good agreement between the theory and experiment has been found for the temperature-dependence of phase-matching angles for second-harmonic generation of CO2 laser radiation in this crystal. Hence variations of the phase-matching angle with temperature in some important nonlinear devices have also been estimated.

Generation of 6.8–7.7 µm radiation in lithium iodate

Generation of infrared radiation in ts-infrared transmission window (6.8–7.7 µm) is reported for the first time by non-collinear difference-frequency mixing of the Nd: YAG second harmonic and the same-pumped dye (Rh-610) laser radiation in a lithium-iodate crystal. The spectrum of polythene sheets was run with the generated radiation.

Highly efficient difference-frequency generation in KTP

A conversion efficiency as high as 22%from dye-laser radiation to the near infrared with difference-frequency mixing of Nd:YAG laser radiation and its second-harmonic-pumped dye laser in an only 5 mm long KTP crystal is reported for the generation of tunable near infrared radiation.

Tangentially phase-matched efficient difference frequency generation in beta barium borate crystal

Abstract Tangential phase-matching has been employed for efficient generation of infrared radiation tunable from 2743 nm to 3362 nm by difference frequency mixing of Nd: YAG harmonic (532 nm) radiation and the same pumped dye (DCM) laser in a beta barium borate crystal. Wide acceptance over 532 nm beam has been utilised to obtain conversion efficiency in DFG as high as 20 times than our earlier reported value.

Type-I walk-off compensated second and fourth harmonic generation of Nd:YAG laser radiation from a Li2B4O7 crystal

A type-I walk-off compensation (WOC) arrangement has been made for the second harmonic generation (SHG) and the fourth harmonic generation (FOHG) of commercially available Q-switched Nd:YAG laser radiation, for the first time, using two identically cut Li2B4O7 crystals. The enhancement of the conversion efficiencies has been realized in the WOC arrangement by a factor of 2.71 for the SHG and 2.65 for the FOHG relative to the double-crystal non-walk-off arrangement. The absolute values of the conversion efficiencies obtained for WOC SHG and FOHG are 3.52% and 3.56% respectively, applying input power densities for the fundamental and second harmonic of the Nd:YAG laser beam at only 28.3 MW cm-2 and 11.7 MW cm-2, respectively.