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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.

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%.

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.

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.

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.

Using the Sellmeier equations of GdCOB and YCOB, we determined the wavelength range in which non-critical phase matching in GdxY1-xCOB can be realized. Using a 704-5 type optical parametric amplifier, we measured the non-critical phase-matching wavelengths in several GdxY1-xCOB crystals with different compositional parameter x.

There is a special area in KTP crystal, in which the SHG efficiency is obviously increased. In this paper, the KTP crystal is studied by means of Synchrotron Radiation (SR) White Beam Topography, and a planar defect is found in such an area. The lattice is deformed because of the accumulation of impurity in this area, which results in the increase of SHG efficiency. The maximum strain direction is determined to be R=〈010〉 according to the extinction condition of planar defect.