Yaogang Liu

Efficient continuous-wave self-frequency-doubling green diode-pumped Yb:YAl(3)(BO(3))(4) lasers.

Efficient cw self-frequency-doubled green laser output of 160 mW has been obtained from Yb:YAl(3)(BO(3))(4) crystal pumped by 1.4-W incident power from a fiber-coupled 976-nm laser diode. The incident-pump-power-green-output-power conversion efficiency is greater than 11.3%, and the electrical-input-green conversion efficiency is 3.9%. Tunable green output from 513.0 to 545.8 nm is also demonstrated with a quartz birefringent filter.

Diode-laser-array end-pumped intracavity frequency-doubled 3.6 W CW Nd:GdVO4/KTP green laser

Abstract A diode-laser-array end-pumped intracavity frequency-doubled Nd:GdVO 4 /KTP green laser, formed with a three-mirror folded cavity, and capable of generating 3.6 W of CW green radiation with optical conversion efficiency of 22.5%, has been demonstrated. The short term stability of the laser was found to be better than 3%, while the green output beam quality factor was measured to be M 2 =1.55. When the laser was operated at the fundamental wavelength, a maximum output power of 10.1 W was obtained at the incident pump power of 22 W, the average slope efficiency was determined to be 55%.

Waveguide laser film in erbium-doped KTiOPO4 by pulsed laser deposition

Erbium doping into potassium titanyl phosphate (KTiOPO4 or KTP) was performed by pulsed laser deposition. Waveguide laser film in Er-doped KTiOPO4 was formed using both KTiOPO4 and erbium as targets and optically polished KTiOPO4 as a substrate. Rutherford backscattering, photoluminescence spectrometry, x-ray diffraction, and prism coupling method are used to investigate the properties of Er-doped KTiOPO4. The results show that (1) Er-doped KTiOPO4 emits the characteristic photoluminescence of Er3+ around 1.54 μm corresponding to transition between the 4I13/2 and 4I15/2 manifolds of the Er3+ ions in KTiOPO4 host. (2) two bright modes in Er-doped KTiOPO4 were observed. This approach may be useful for direct fabrication of thin film waveguide laser for other optoelectrical materials.

Growth, defects, and properties of GdCa4O(BO3)3 and Nd:GdCa4O(BO3)3 crystals

Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method. The orientation of crystal was precisely determined, and the samples for measurements were prepared. Through synchrotron x-ray topography and high-resolution x-ray diffractometry, the twin structure was discovered. Some properties such as the figure of merit value, and dielectric, piezoelectric, and elastic constants were measured along with a discussion of the anisotropy of the laser properties.

Actively Q-switched intracavity second-harmonic generation of 1.06 μm in BiB3O6 crystal

Abstract We have investigated the acousto-optically Q-switched intracavity second-harmonic generation of 1.06 μm in a 1.9-mm-long BiB3O6 crystal, cut for type-I phase-matching direction of (θ,ϕ)=(168.9°,90°), performed in a diode-end-pumped Nd:YVO4 laser. When the incident pump power was 4.3 W at 30 kHz of pulse repetition frequency, a maximum average green output power of 480 mW , the shortest pulse with FWHM width of 72 ns , the highest single pulse energy of 16 μJ and the maximum peak power of 222 W were obtained, giving the corresponding optical conversion efficiency of 11.2%. The effect of varying temperature in BIBO crystal on the average green output power was also investigated.

PHOTOREFRACTIVE PROPERTIES AND SELF-PUMPED PHASE CONJUGATION OF TETRAGONAL FE-DOPED KTA1-XNBXO3 CRYSTAL

This letter reports the two‐wave mixing experimental results of tetragonal Fe‐doped KTa1−xNbxO3. A 7.3 cm−1 gain coefficient and 42% diffraction efficiency have been obtained. For the first time internally self‐pumped phase conjugation is being observed in this crystal. At room temperature, the conjugate reflectivity measured is 21%.

Growth and properties of KBe2BO3F2 crystal

Single crystals of KBeBO 3 F (KBBF) up to 2 mm in thickness were grown by using a spontaneous nucleation method. The flux was composed of KF and B 2 O 3 , and the optimal ratio for growing KBBF single crystal thicker than 1 mm is suggested to be (1.0-1.5):(5.0):(0.7-1.2) (KBBF:KF:B 2 O 3 ) in molar ratio. The ideal morphology of KBBF is two sets of tabular facets and a set of rhombic facets. Surface morphology was characterized both by optical microscopy and atomic force microscopy. Transmission spectra showed that high transmission was maintained up to 170 nm. Based on refractive index measurements, phase matching curves for types I and II were determined. Using a prism coupling method, the effective fourth harmonic generation for an Nd:YAB laser was realized in an 0.6-mm-thick KBBF sample. The output energy of the 266-nm beam was 0.282 mJ, and the conversion efficiency was 11.8%. A 183.6-nm laser over 1 mW was obtained from a Ti:sapphire second harmonic generation beam in an 0.8-mm KBBF sample. The conversion efficiency reached 2.3%. A 179.4-nm laser was also observed from a 358.7-nm laser by directly frequency doubling. This is the shortest wavelength obtained through nonlinear optical processes in a solid-state laser.

Research on growth and self-frequency doubling OF Nd:ReCOB (Re=Y OR Gd) crystals

Large (up to 45mm in diameter and 50mm in length) ReCa4O(BO3)3 (ReCOB) and Nd:ReCOB (Re=Y or Gd) crystals with high optical quality were grown by well designed procedures. Crystal orientation was carefully determined. Based on the measurements of refractive indices the phase matching (PM) figures for both crystals were calculated. Theoretical calculation of the spatial distribution of the effective nonlinear coefficients, which show an asymmetric feature, was carried out to determine the optimal PM orientations which were experimentally confirmed, i.e. (66.3°, 134.4°) and (64.5°, 33.5°) for GdCOB and YCOB respectively.

Analysis of refractive index profile in KTiOPO4 waveguide formed by 3.0 MeV He+ implantation

Abstract The optical waveguide formation in X-cut KTiOPO 4 was achieved by single energy implantation of 3.0 MeV He + to a total dose of 2.0×10 16 ions/cm 2 at liquid nitrogen temperature. The modes were examined by the prism (LiTaO 3 ) coupling method. The analysis of the refractive index profile in the KTiOPO 4 (100) waveguide was performed based on parametrized index profile reconstruction (PIPR). We have used the TRIM (the transport of ions in matter) code to simulate the energy loss distribution. The result shows that the nuclear collision mostly influences the refractive index profile, but the peak position of the refractive index profile is shallower than that of the nuclear energy loss distribution.

The second-harmonic-generation property of GdCa4O(BO3)3 crystal with various phase-matching directions

Abstract The method to determine the spatial configuration of GdCa4O(BO3)3 (GdCOB) crystal is introduced. Samples are cut in and out of principal planes for type I phase matching. Their second-harmonic-generation (SHG) conversion efficiency is measured by a mode-locked Nd:YAG laser. The intracavity doubling frequency of GdCOB crystal is reported for the first time. At the incident pump power of 10 W, the 532 nm output reaches 1.22 W with the (113.2°, 47.4°)-cut sample. In conclusion, the (113.2°, 47.4°)-cut sample shows more excellent SHG property than those cut in other directions.