Growth and non-critical phase-matching frequency conversion properties of LaxY1−xCOB crystals

Abstract

A new series of nonlinear optical crystals La_xY_1−xCa₄O(BO₃)₃ (La_xY_1−xCOB) with multiple components were grown by using the traditional Czochralski pulling method. X-ray powder diffraction and single-crystal X-ray diffraction experimental results proved that all these crystals formed in the La_xY_1−xCOB solid solution state with a monoclinic structure of space group Cm. The optical birefringence was found to be adjustable by changing the compositional parameter x for the La_xY_1−xCOB crystals. Taking advantage of the optical parametric oscillator laser, the non-critical phase-matching (NCPM) second-harmonic-generation (SHG) and third-harmonic-generation (THG) wavelengths along the Y-axis were determined at ambient temperature. In addition, the relationships between and among the optical birefringence, NCPM wavelength and crystal structure were discussed, and the NCPM SHG and THG of the 1064 nm laser were further achieved from the La_0.120Y_0.880COB and La_0.140Y_0.860COB crystals by adjusting the temperature, respectively. Using a 1064 nm Nd:YAG laser as the fundamental light source, the angular acceptance, temperature acceptance, and optical conversion efficiencies were determined and found to be on the order of 107.6 mrad, 18.3 °C and 48.8% for SHG of the La_0.120Y_0.880COB crystal, respectively, and 126.8 mrad, 68.6 mrad, 10.6 °C and 32.4% for THG of the La_0.140Y_0.860COB crystal, respectively. It is demonstrated that La_xY_1−xCOB is a promising NLO crystal for NCPM frequency conversion applications in the visible and ultraviolet spectral regions.