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A series of niobium doped KTP (Nb:KTP) crystals has been grown. XRD and DTA experiments show that the Nb:KTP crystal structures do not differ from that of KTP (within experimental error) and that the melting points of the crystals increase with increasing Nb content. Synchrotron radiation topography revealed that the main defects of the crystals were growth sector boundaries, growth striations, inclusions and dislocations. Second harmonic generation experiments were performed using a 12.2% Nb:KTP and the d 15 and d 24 values of crystal were determined to be (3.7 ± 0.4) and (8.3 ± 0.8) x 10 -9 esu, respectively. The relationship between phase-matching angle and Nb content for a 1.064 μm laser was determined and in the case of a 4.0% Nb:KTP crystal, non-critical phase matching was realized.

A GdxY1−xCa4O(BO3)3 (GdxY1−xCOB) crystal, which belongs to rare-earth calcium oxyborate family, is used for non-critical phase-matching of visible and ultraviolet (UV) light. We employ 2.8-MeV He+ ions to form optical waveguides in the Gd0.275Y0.725COB crystal at room temperature. The doses are varied from 1.5×1016 ions/cm2 to 5×1016 ions/cm2. A model 2010 prism coupler is used to measure the modes in Gd0.275Y0.725COB waveguides formed by MeV He+ ion implantation. The refractive index profile is fitted based on the reflectivity calculation method. The shape of refractive index profile is compared with one of nuclear energy loss obtained by TRIM'98 simulation.

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.

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.

EPR spectra of V4+-doped single crystal (V4+/KTP) were observed in X band at room temperature. The analysis on the spectra shows that the V4+ ions may occupy two kinds of crystallographically diffrent sites, each kind of sites contains four magnetically nonequivalent but crystallographically equivalent sites. The angular varitions of EPR hyperfine lines were measured with the external magnetic field in three mutually perpendicular planes. The principal values and direction cosines of the principal axes of the g and A tensors, were computed by a least-squares fitting procedure. These main results reveal that the V enters the lattice to substitute for the Ti ion of KTP to form V site with a tetragonally distorted octahetral symmetry. The orientations of all eight Ti ion sites substituted in an unit cell of KTP have been determined.

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.