| The ultraviolet laser is widely used in the fields of LADAR (Laser Detection and Ranging), laser communications, laser marking technology and molecular mechanism research. In spite of LD (laser-diode) pumped solid-state UV (ultraviolet) laser has been used in the realm of the practical, there is some problems such as the poor performance of beam quality, the instability of output power, the large volume of the water cooler and the inconvenience of the whole device. The purpose of this paper is to improve the performance of the ultraviolet laser, reduce the volume, and improve the beam quality and the reliability to meet the requirements of the industrial and civil.The primary coverage is as follows:(1) The LD pumped Q-switched laser has been analyzed with the rate equation of the four-level system. Based on coupled wave equations, the nonlinear process of frequency doubling and tripling, the efficiency of the nonlinear process and the phase-matching conditions are analyzed.(2) To research and develop compact ultraviolet laser with high stability and high efficiency, a mini type all-solid-state ultraviolet laser device at 355 nm is obtained with laser-diode end-pumped Nd:YVO4 crystal, intracavity frequency doubling and tripling employing two LiB3O5 (LBO) crystals with angle phase matching of type I and type II, respectively. To increase conversion efficiency in the experiment, temperature of the frequency conversion crystals is accurate adjusted by employing Proportion Integration Differentiation (PID) digital temperature control modules with resolution of ±0.01 ℃ to compensate angle phase mismatching which is led in by the fixed crystal clamps. Output indexes of the 355 nm laser are as follows, at repetition frequency is of 15 kHz, the average output power is 1.24 W at the pump power is of 13.33 W, output wavelength of the pump source is 804 nm not at the absorption peak of Nd:YVO4 crystal 808nm, however the conversion efficiency from diode laser to ultraviolet laser is about 9.3%, pulse duration is of 9.8 ns, beam quality factors is Mx2=1.8, My=1.7 and the power instability is 0.45% within 2 hours operation. By adjusting the temperature to compensate for the angle phase mismatch of the nonlinear crystals, it is a technical approach to obtain a compact no-water-cooling ultraviolet laser with high stability and high conversion efficiency.(3) A 266 nm deep ultraviolet laser with good Gaussian profile is reported employing a multi-mirror-reflected cavity. A type I LBO crystal is used to double the fundamental-light (1064-nm) wavelength generated by an actively Q-switched Nd:YVO4 laser with an intra-cavity configuration. Fourth harmonic generation (FHG) wavelength is obtained by a type I BaB2O4 (BBO) crystal. The output power as high as 440 mW at 266 nm is generated under an incident power of 2.26 W at 532 nm, corresponding to the conversion efficiency of 532 nm-266 nm up to 19.5% with the repetition rate of 15 kHz and the pulse duration of 266 nm is 10.7 ns. The multi-mirror-reflected cavity is used to compensing walk-off effect of BBO crystal. The output laser is good Gaussian profile.(4) A 266 nm deep ultraviolet laser is reported with Cr4+:YAG crystal. A type I LiB3O5 (LBO) crystal is used to double the fundamental-light (1064-nm) wavelength generated by an passively Q-switched Nd:YAG laser. Fourth harmonic generation (FHG) wavelength is obtained by a type I KD2PO4 (DKDP) crystal. The output energy as high as 57 μJ at 266 nm is generated under the pumped power of 60 W and the pump pulse duration is 500 μs at the repetition rate of 10 Hz. The 266 nm pulse duration is sub-nanosecond. |
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