Z P Wang

Thermal characterization of lowly Nd 3+ doped disordered Nd:CNGG crystal

Thermal properties of a lowly Nd(3+)-doped disordered Nd:CNGG crystal have been symmetrically investigated. At room temperature, the specific heat, thermal diffusion coefficient and density were determined to be 0.595 J/g.K, 1.223 mm(2)/s and 4.718 g/cm(3), corresponding the thermal conductivity of 3.43 W/m.K. By measuring the thermal lens at different pump power, the thermal-optical coefficient was calculated to be 9.2x10(-6) K(-1) for the first time to our knowledge. All the thermal properties recovered that this material can be used in the moderate and even high pump power.

Thermal and laser properties of Nd:Lu 3 Sc 1.5 Ga 3.5 O 12 for high power dual-wavelength laser

We measured the thermal properties of Nd:Lu₃Sc₁.₅Ga₃.₅O₁₂ (Nd:LuSGG) crystal, including the thermal expansion coefficient, specific heat, and thermal diffusion coefficient. The calculated thermal conductivity is 4.4 W/mK at room temperature. A high-power continuous-wave and passively Q-switched Nd:LuSGG laser was also demonstrated. Continuous-wave output power of 6.96 W is obtained which is the highest power with this material. For the first time to our knowledge, the passively Q-switched Nd:LuSGG laser is reported with the shortest pulse width, largest pulse energy, and highest peak power are achieved to be 5.1 ns, 62.5 μJ, and 12 kW, respectively. By spectral analysis, it has been found that the Nd:LuSGG laser was located at 1059 nm under low pump power, and became dual-wavelength at 1061.5 and 1059 nm when the incident pump power is over 2.27 W. The generating mechanism of dual-wavelength laser is also discussed.

Growth and characterization of self-Q-switched Nd:Cr:YVO 4 crystal

A Nd:Cr:YVO4 crystal was grown by the Czochralski method for the first time to our knowledge. Its structure and cell parameter have been studied by X-ray powder diffraction (XRPD) analysis. Polarized absorption spectra were measured at room temperature, which showed that the absorption bands display polarization character and an absorption band of Cr5+ ions at 1110 nm enables the crystal to be a self-Q-switched laser material. We also found that the absorption of Cr5+ ions became much larger and its self-Q-switched laser performance became much better when the Nd:Cr:YVO4 crystal was annealed because the annealing induces more Cr ions to become those with + 5 valence. In the self-Q-switched laser, the maximum output power, shortest pulse width, and largest pulse energy were obtained to be 120 mW, 85.8 ns, and 0.79 μJ, respectively.

Continuous-wave and passively Q-switched Nd:LYSO lasers

Continuous-wave (CW) and passively Q-switched performance of a Nd-doped oyorthosilicate mixing crystal, (Nd0.005Lu0.4975Y0.4975)2SiO5 (Nd:LYSO), were reported. As a result, new dual-wavelength all-solid-state lasers at 1075 and 1079 nm were achieved. When the absorbed pump power was 3.87 W, the CW laser produced 1.1 W output, corresponding to an optical conversion efficiency of 28.4% and a slope efficiency of 32.4%. By using a Cr4+:YAG wafer as the saturable absorber, we achieved Q-switching operation of Nd:LYSO crystal. The maximal average output power, shortest pulse width, largest pulse energy and highest peak power were measured to be 294 mW, 27.5 ns, 34.3 μJ and 1.18 kW, respectively. By difference frequency, these dual-wavelength lasers have potential applications for the generation of a broadband coherent radiation from 0.7–1.3 THz.

High efficiency angular non-critical phase matching for Ti:sapphire laser realized on LaCa4O(BO3)3 single crystals

Angular non-critical phase-matching (A-NCPM) second harmonic generation (SHG) for a Ti:sapphire laser was realized on LaCa4O(BO3)3 (LaCOB) single crystals, grown by the Czochralski pulling method. Properties including the wavelength, bandwidth, effective nonlinear optical (NLO) coefficient (deff), and acceptance angle were evaluated. At ambient temperature of 20 °C, the type-I NCPM (808 nm wavelength) was obtained along the y axis of LaCOB crystals, where the effective nonlinear optical coefficient (deff), PM waveband, and angular acceptance were found to be of the order of 0.59 pm/V, 803~818 nm and 50.6 mrad cm1/2 (ΔL), respectively. Moreover, high single-pass SHG conversion efficiency (44.6%) was achieved for 24.8 mm long Y-cut samples at 808 nm, using a mode-locked Ti:sapphire fundamental laser.

Passively Q-switched Nd:YAG ceramic laser towards large pulse energy and short pulse width

A large pulse energy and high peak power passively Q-switched ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has been demonstrated with Cr4+:YAG crystals as the saturable absorbers. By employing a continuous wave (CW) laser-diode (LD) as the pump source, as high as 11.3 W CW output power of 1064 nm was obtained under the pump power of 21.6 W, with an optical conversion efficiency of 52.3%. Inserting different initial transmissions Cr4+:YAG as saturable absorbers, under the incident pump power of 15.6 W, the largest pulse energy, shortest pulse width, and highest peak power are measured to be 188 µJ, 3.16 ns, and 59.5 kW, respectively. As we has known, this is the best passively Q-switched results ever reported by Nd:YAG ceramic material.

The performance of 1329 nm CW and passively Q-switched Nd:LGGG laser with low Lu-doping level

The Nd:(LuxGd1?x)3Ga5O12 (Nd:LGGG) laser operating at 1329?nm in both the continuous wave (CW) and the passively Q-switched (PQS) regimes has been successfully demonstrated. With an absorbed pump power of 18.8?W, a maximum CW output power of 3.7?W was obtained, corresponding to an optical?optical conversion efficiency of 19.6% and a slope efficiency of 20.9%. The PQS laser performance was obtained using a V3+:YAG crystal as the saturable absorber. The maximum average output power, shortest pulse width, largest pulse energy and highest peak power were 0.75?W, 25.9?ns, 43.6??J and 1.7?kW, respectively. The results indicate that a Nd:LGGG crystal with a low Lu-doping level (0.66?at.%) could be a novel potential laser gain medium suitable for laser diode pumping and PQS operation at a wavelength of 1.3??m.

Nonlinear optical characterizations of monoclinic LaxGd1?xCa4O(BO3)3 (x = 1, 0.09, 0.13) single crystals

The 1064 nm optimal spatial phase matching (PM) direction for LaCa4O(BO3)3 (LaCOB) crystals was found to be (113.5°, 43.8°) with deff of 1.34 pm V−1, angular acceptance of 0.9 mrad cm and walk-off angle of 14.9 mrad, and more than a 56% second-harmonic generation (SHG) conversion efficiency was realized on a sample (4 × 4 × 6 mm3) cut in this direction, by using a 1064 nm Nd : YAG pico-second laser. The angular noncritical phase-matching (A-NCPM) wavelengths along the y and z axes for LaxGd1−xCOB (x = 0.09, 0.13) crystals were measured. Using a nanosecond laser, the type-I single-pass A-NCPM SHG conversion efficiency along y axis reached 30.2% by taking advantage of the longer crystal sample (4 × 4 × 27 mm3).

Raman characteristics of Nd:LuxY1?xVO4 series crystals

An efficient self-stimulated Raman laser of Nd:LuxY1−xVO4 (x = 0.1, 0.26, 0.41, 0.61, 0.67 and 0.8) series crystals was demonstrated for the first time. Compared to YVO4, the relative Raman gain coefficients were determined by studying their spontaneous Raman scattering spectra. With the largest thermal conductivity, excellent energy storage capability and moderate Raman gain coefficient, the Nd:Lu0.26Y0.74VO4 crystal presented the best Raman laser performance: 2.3 W average output power, 71 μJ single pulse energy and 26.3 kW peak power. The results indicated that the Nd:Lu0.26Y0.64VO4 crystal should be an excellent self-Raman laser material.

A diode-pumped passively Q-switched c-cut Nd:Lu0.1Y0.9VO4 laser

The continuous wave and pulsed laser performances of a laser-diode-end-pumped c-cut Nd:Lu0.1Y0.9VO4 crystal have been demonstrated for the first time. The small emission cross section and appropriate upper level lifetime result in the c-cut Nd:Lu0.1Y0.9VO4 crystals having excellent pulsed laser performance. When the pulse repetition rate was 6.4 kHz, the shortest pulse width, the largest pulse energy and the highest peak power were found to be 1.9 ns, 104.7 μJ and 55.1 kW, respectively, using a Cr4+:YAG crystal as the saturable absorber. These results were much better than those for an a-cut Nd:Lu0.1Y0.9VO4 crystal under the same conditions.