Liu Yao-Gang

Deep ultraviolet harmonic generation with KBe2BO3F2 crystal

A special prism coupling technique with the KBe2BO3F2 crystal is adopted to produce deep ultraviolet light including the fourth harmonic from an Nd:YAG laser, for which a conversion efficiency as high as 10% has been obtained.

Efficient 266 nm Ultraviolet Beam Generation in K2Al2B2O7 Crystal

The ultraviolet beam at 266 nm was obtained by fourth harmonic generation of 1064 nm Nd:YAG laser radiation through a nonlinear crystal K2Al2B2O7 (KABO). The fundamental frequency of a flash-lamp pumped Nd:YAG laser was doubled in a β-Ba2B2O4 crystal to generate a second harmonic output at the wavelength of 532 nm, and then doubled again in the KABO crystal to generate the fourth harmonic output at 266 nm. The optical conversion efficiency from 532 to 266 nm was investigated for the first time, and 13% was achieved.

Anisotropy of Nonlinear-Optical Property of RCOB ( R = Gd, Y) Crystal

The nonlinear-optical coefficients of RCOB (R = Gd, Y) crystals are measured. The spatial distribution of deff (effective nonlinear-optical coefficient) is subsequently determined. Our experiments show that the maximum deff occurs at the second quadrant. The second-harmonic generation efficiency reaches 48% for a 6 mm long, (113.2°, 47.4°)-cut GdCOB, and 41.5% for a 5mm long, (113°, 36.5°)-cut YCOB, respectively. The intracavity frequency doubling of GdCOB is reported for the first time.

Growth, Defects and Non-critical Phase Matching of Nb Doped KTP Crystals

A series of Nb doped KTP crystals are grown with seed flux method and flux pulling method. The results of our investigation on growth, morphology defects of the crystals are reported in this paper. We obtained the relationship between Nb contents and second-harmonic generation angles of the crystals. Noncritical phase matching has been realized by 4% Nb doped KTP crystal for Nd:YAG laser 1.06 μm output.

Growth, Second Harmonic and Sum Frequency Generation Operations of Potassium Titanyl Arsenate Crystal

Potassium titanyl arsenate (KTiOAsO4, KTA) crystals have been grown with flux method. The infrared absorbing edge of KTA crystal is about 5.3 μm. The electric and other properties of KTA were measured. According to the x-ray orientating, KTA crystal samples were prepared to carry on second harmonic generation (SHG) and sum frequency generation (SFG) experiments. The SHG efficiency of KTA for Nd: YAG is 1.7 times larger than that of KTA. At 20°C, the shortest SHG wavelength is 0.5174 μm, and the shortest SFG wavelength is 0.4994 μm.

Formation of the Bicrystal Structure of KTiOPO4 Crystals

In this paper, by comparing the three possible combinations of the basic structure unit TiO6 octahedra, a simple model is proposed to explain the cause of the formation of the bicrystal structure in KTiOPO4 (KTP) crystals. The theoretical morphology of KTP crystal is studied and the rate of the appearance possibilities of different faces are obtained. The relationships between bicrystal structure and crystal properties are discussed.

Growth, Defects and Electrooptic Properties of RbTiOAsO4 Crystal

RbTiOAsO4 (RTA) crystals of high optical quality were grown with flux method. The defects of RTA crystals are mainly growth striations, growth sector boundaries and sometimes ferroelectric domains. The refractive indices and electrooptic coefficients were measured together with dielectric constants, ionic conductivity and direct current resistivities. It is shown that RbTiOAsO4 is not only as good a nonlinear optical crystal as KTiOPO4 but also a superior electrooptic crystal.

WHITE-BEAM X-RAY TOPOGRAPHY STUDY OF KTa 1-x Nb x O 3 CRYSTAL WITH SYNCHROTRON RADIATION

The photorefractive Fe-dopoed KTa 1-x Nb x O 3 (KTN) with a Curie point near room temperature has been topographically studied by Beijing synchrotron radiation white-beam X-ray source. Besides inclusions and the [010] oriented growth bands present in KTN, a set of domains perpendicular to the growth bands is shown, the latter is found to disobey the vanishing rule of planar defects, and to be revealed only by X-ray anomalous scattering. A striking wavelength dependence of the domain contrast is shown by tuning the synchrotron radiation, and the contrast reversal of the domains is demonstrated in antiparallel reflections. The domains are ascertained to be 1800 ones. The origins of formation of the domains and the growth features in KTN are outlined.

Photorefractive Properties of Paraelectric Copper Doped Potassium Tantalate Niobate

The photorefractive properties of Cu doped KTa1-xNbxO3 have been studied by using two-wave mixing method. The diffraction efficiency reaches as high as 52% under an electric field. The dependences of diffraction efficiency on interference angles and applied fields have been studied. The maximum light induced index change is found to be 2.33 × 10-5 and the photorefraction sensitivity calculated is 5 × 10-6 cm2/J. Experimental results demonstrate that electrons are the dominant charge carriers.

Tilted Angle Implantation of Xe Ions in potassium Titanyl Phosphate

200 ke V Xe ions were implanted in potassium titanyl phosphate (KTP) at deferent angles: 0°, 45° and 60°. The lateral spread of Xe ions in KTP was studied by Rutherford backscattering of 2.1 Me V He ions. The result is compared with the theoretical prediction. The lateral spread is found in good agreement with calculated value within 17%.