Weiran Lin

1079.5- and 1341.4-nm: larger energy from a dual-wavelength Nd:YAlO 3 pulsed laser

On the basis of oscillation conditions of simultaneous multiple-wavelength lasing that we have established, a larger-energy (1079.5 and 1341.4 nm) dual-wavelength Nd:YAlO(3) pulsed laser has been developed. Output energies of 3.71 and 1.39 J with efficiencies of 1.29% and 0.48% for the 1341.4-and 1079.5-nm wavelengths, respectively, have been achieved. To our knowledge, this is the best result among simultaneous dual-wavelength solid-state lasers to date. The temporal and spatial distributions of these beams obtained from a free-running dual-wavelength Nd:YAlO3 pulsed laser have also been measured. Experimental results show that the temporal and spatial overlap of the two beams is quite good for this type of laser.

Second harmonic generation and sum frequency mixing of dual wavelength Nd:YAlO/sub 3/ laser in flux grown KTiOPO/sub 4/ crystal

On the basis of accurately measured refractive indexes, the authors have obtained the Sellmeiers equations for flux grown KTiOPO/sub 4/ (KTP) crystal and used them to calculate the phase matched angles ( theta /sub m/, phi /sub m/) and effective nonlinear coefficients (d/sub eff/) for type I and III second harmonic generation (SHG) and sum frequency mixing (SFM) of radiations at 1.0795 and 1.3414 mu m. The optimum phase matching conditions for 1.0795 and 1.3414 mu m SHG are that theta /sub m/=86.88 and 58.88 degrees , respectively, in an XZ plane ( phi =0) and for SMF of 1.0795 and 1.3414 mu m in the same plane 76.02 degrees . The corresponding d/sub eff/ values calculated from theta /sub m/s are 18.07*10/sup -9/ and 17.42*10/sup -9/ esu. >

Computational model of Q-switch Nd:YAlO3 dual-wavelength laser

A rate equation model with spatial hole-burning effect is built to calculate the Q-switch Nd:YAlO3(Nd:YAP) simultaneous dual wavelength laser. We find that 1341.4 and 1079.5 nm lasers can be simultaneously generated in a linear cavity by controlling the output coupling rates of the two coherent radiations. In contrast, a Y cavity and devices to control relative Q-switch delay were necessary for the dual wavelength Nd:YAG laser in previous work. Also with this model, some optimum parameters’ relationships to pump energy are investigated.

Second‐harmonic generation and sum‐frequency mixing of double‐wavelength Nd:YALO3 laser to 413.7‐nm violet coherent radiation in LiIO3 crystal

A new method to get 413.7‐nm violet coherent radiation by using second‐harmonic generation and sum‐frequency mixing of radiation from a 1341.4‐ and 1079.5‐nm dual‐wavelength Nd:YALO3 laser in a LiIO3 crystal is reported in this communication. First, the 670.7‐nm red coherent radiation is obtained by second‐harmonic generation of 1341.4‐nm radiations in a LiIO3 crystal, and then the 670.7‐ and 1079.5‐nm radiations are mixed again in a second LiIO3 crystal to get 413.7‐nm radiation. The phase‐matching angles are obtained for both nonlinear optical processes. The experimental results agree well with calculated results.

Study of the nonlinear optical properties of 7.5 mol% Nb:KTP crystals

Sellmeiers equations and the equations for the thermal principal refractive index coefficients as a function of wavelength fur 7.5 mol% Nb:KTP crystals are presented. Based on these equations, the nonlinear optical parameters for 7.5 mol% Nb:KTP crystals, especially the angular, spectral, and temperature acceptance bandwidths, are calculated. By comparing these results with KTP and KNbO/sub 3/ crystals, 7.5 mol% Nb:KTP crystals show better performance than KNbO/sub 3/ crystals in generating blue coherent light by direct second-harmonic generation of a semiconductor diode laser.

The expressions of the principal thermal refractive index coefficients of 7.5 mol.% Nb:KTiOPO4 crystals

Abstract Based on the autocollimation method results of the principal refractive indices of 7.5 mol.% Nb:KTiOPO 4 (Nb:KTP) crystals for the wavelengths 539.75, 632.8, 1079.5, and 1341.4 nm at the temperature range from 319.25 to 416.15 K, simple expressions of the thermal refractive index coefficients as a function of wavelengths are presented. They agree well with the measured results and can be used to calculate the principal thermal refractive index coefficients at different wavelengths in 7.5 mol.% Nb:KTP crystals for nonlinear optical device designing.

The thermal refractive index coefficients of 7.5 mol % Nb:KTiOPO4 crystals

The principal refractive indices and thermal refractive index coefficients for Nb:KTiOPO4 (KTP) crystal grown by the top-seed flux method from a starting material containing 7.5 mol % Nb have been measured using the autocollimation method. Using measurements made at wavelengths of 0.53975, 0.6328, 1.0795, and 1.3414 μm, in the temperature range from ambient to 188 °C, it is possible to determine the constants of the Sellmeier equations and the thermal refractive index coefficients as a function of wavelength. Also, the temperature acceptance bandwidth at 90° second harmonic generation noncritical phase matching direction was calculated. Comparison of these results with those for undoped KTiOPO4 [K. Rato, IEEE J. Quantum Electron QE-28, 1974 (1992)] and KNbO3 [B. Zysset, I. Biaggo, and P. Gunter, J. Opt. Soc. Am. B 9, 380 (1992)] implies that Nb-doped KTP crystals are suitable for blue coherent light devices.

High quality beam shaping by square soft-edge diaphragm combined with liquid crystal spatial light modulator

The square soft-edge diaphragm with round angle is designed by Matlab, and is sent to a liquid crystal spatial light modulator by the computer. In order to obtain precompensation for the following laser system, local diaphragm transmission can be adjusted by feedback signals of surface-channel charge-coupled device (SCCD). This method can reduce the diffraction effect and realize no modulation, high stability, high homogeneity, and large scale laser beam. Several parameters of soft-edge diaphragms which affect the laser beam quality are studied systematically, and the optimized values are obtained. The method can avoid the serious modulation of hard edges and provide soft-edge diaphragms of different shapes in a fast and convenient way for the large scale laser beam system.

Tripling the harmonic generation of a 1341.4 nm Nd:YAP laser in LiIO3 and KTP crystals to get 447.1 nm blue coherent radiation

Abstract 447.1 nm blue coherent radiation was achieved in two kinds of crystal by sum frequency mixing of the 1341.4 nm radiation of a Nd:YAP laser and its second harmonic wave, one in a LiIO3 crystal with type I sum frequency mixing and one in a KTP crystal with type II sum frequency mixing. To our knowledge, it is the first time that 447.1 nm blue coherent radiation is obtained by tripling the harmonic generation of 1341.4 nm Nd:YAP laser.

Studies on the phase-matching condition and the cut-off wavelength of Nb :KTiOPO4 crystal

Abstract The measured results of the cut-off wavelengths of KTiOPO 4 (KTP) crystal grown from the raw material containing 7.5 and 13 mol% Nb 2 O 5 (referred as 7.5 and 13 mol% Nb:KTP crystals in this paper) by top-seed flux method are presented as well as those of the optimal phase-matching (PM) angles at 1064 and 1079.5 nm lines for KTP crystals grown from raw material containing different concentrations of Nb 2 O 5 . The Sellmeier’s equation and thermal refractive index coefficients for 7.5 mol% Nb:KTP crystal have been obtained and then the optimum PM angles at 1064 and 1079.5 nm and the cut-off wavelength as well as the nonlinear optical properties are calculated. It is shown that the calculated results of optimum PM angles at 1064 and 1079.5 nm and cut-off wavelength for 7.5 mol% Nb:KTP crystal agree fairly well with the measured results. It is concluded that the noncritical PM condition at 1064 nm line can be satisfied in KTP crystal grown from the raw material containing about 3 mol% Nb 2 O 5 . The cut-off wavelength of 13 mol% Nb:KTP crystal has blue-shifted to 937 nm, achieving 468.5 nm blue coherent radiation.