Zhao Shengzhi

Low Threshold and High Efficiency Nd:S-VAP Laser

The absorption spectrum of a new sort of crystal Nd:S-VAP was measured, which showed that Nd:S-VAP can be appropriately pumped at 583.0 and 809.0 nm. By using tunable dye-laser (570.0-600.0 nm) as pumping light, the performance of low threshold and high efficiency Nd:S-VAP laser has been realized. The characteristics of the output laser, such as 1.5 nm linewidth, 5 ns pulse width, almost total polarity, up to 50% conversion efficiency, down to 2 mJ threshold energy and so on, were presented. Meanwhile, the prospect of Nd:S-VAP crystal for low threshold, high efficiency miniature laser was discussed.

Thermal lens measurement of a LD end-pumped Nd: GdVO4 laser with stable resonator by a slit-scanning method

A simply method to measure the thermal focal length of a LD end-pumped Nd: GdVO4 solid state laser with a stable resonator is presented. By scanning a slit across the field with expression of multi-mode Gaussian distribution behind the output mirror of lasers, the radius and the M2 factor describing the quality of beam can be measured. The waists of the multi-mode field and the TEM00 mode can be deduced according to the law of multi-mode Gassian beam propagation. Based on the ABCD matrix theory of a stable resonator, the thermal focal length of the active medium can be easily obtained. The thermal focal length of a LD end-pumped Nd: GdVO4 laser has been measured and the experimental results agree with the theoretically analyzed values.

Impulse-Coupling Coefficient of Laser-Surface Interaction in Air

Impulse-copling coefficients, for A1 and Cu samples with finite surface area irradiated in air by 1.06 μm, 10 ns laser pulses produced by a Nd: YAG laser, have been measured experimentally. A modified theoretical model of impulse-coupling is proposed, which significantly improves the agreement between the calculated impulse-coupling coefficient and the measured one.

Xenon Flash Lamp Pumped Self-Frequency Doubling NYAB Q-Switched Laser

By using xenon flash lamp as pumping light source and BDN dye film as passive Q-switch or KD* P crystal as active Q-switch, we have, for the first time, realized Q-switching run from 1.06 μm to 0.53 μm in the NdxY1-xAl3(BO3)4 (NYAB) self-frequency doubling laser and obtained MW/cm2 giant pulse output at 0.53 μm wave length. Meanwhile, the green light output energy and pulse duration were measured under the conditions of different resonator lengths and pumpings. The experimental results are in agreement with the numerical solutions of the Q-switching coupling wave rate equations. Moreover, the ways of improving the green laser output peak power are proposed.

FM-AM Conversion Induced by Polarization Mode Dispersion in Fiber Systems

The conversion of the frequency modulated pulse induced from frequency modulation (FM) to amplitude modulation (AM) by the polarization mode dispersion (PMD) is theoretically and experimentally investigated. When there is no polarizer at the output end of a fiber system, the amplitude modulation depth is stable by 8%. Random amplitude modulation is observed when a polarizer is placed at the output end of the fiber system. The observed minimum and maximum modulation depths in our experiment are 5% and 80%, respectively. Simulation results show that the amplitude modulation is stable by 4% induced mainly by group velocity dispersion (GVD) when there is no polarizer, and the amplitude modulation depth displays the random variation character induced by the GVD and PMD. Lastly, a new fiber system scheme is proposed and little amplitude modulation is observed at the top of the output pulse.