Research On Nd:KLu（WO₄）₂ Crystal Laser Characteristics And Self-Raman Laser Characteristics

Laser technology, semiconductors, atomic energy and computers are the four great science inventions in 20th century, and laser technology is widely applied in industry, physics research, biomedicine, military fields and so on. Laser media include solid, liquid and gas media. Solid-state lasers have many advantages such as compactness, long lifetime, high stability, etc. Solid-state laser media mainly contain rare-earth doped crystals, glasses, ceramics and so on. Among them, rare-earth doped tungstates which are considered as premium laser crystals have attracted much attention. There are several kinds of tungstates which can usually be used in laser fields:KGd（WO₄）₂, KY（WO₄）₂, KLu（WO₄）₂ （KLuW）, CaWO₄, BaWO₄ crystals and so on. Solid-state lasers using rare-earth doped tungstates as laser media have many advantages such as low laser threshold, high conversion efficiency, etc. Moreover, tungstate crystals are good Raman media, and have large third order nonlinear coefficients.KLuW crystal is one of premium tungstates with strong anisotropy, high possibility to dope them with high concentration and high values of the absorption and emission cross sections without fluorescence quenching. With the development of crystal growth technology, big size and high quality KLuW crystals were growth in recent years, therefore studies of rare-earth doped KLuW crystal growth, optical properties and laser characteristics attracted many researchers’ attention.As one of rare-earth doped KLuW crystals, Nd:KLu（WO₄）₂ （Nd:KLuW） crystal has good optical and mechanical properties. This paper focuses on studies of Nd:KLuW 1070 nm laser characteristics, frequency doubled laser characteristics and 1185 nm self-Raman laser characteristics. Moreover, the theoretical calculations were made, and compared with experimental results. The main research contents are as follows:1. Research on Nd:KLuW 1070 nm laser. A b cut Nd:KLuW crystal was used as the laser gain medium to realize continuous and pulsed 1070 nm laser output. For continuous wave operation, the maximum output power was 4.9 W, and the corresponding optical-to-optical conversion efficiency was 41.9%. For actively Q-switching operation, the 1070 nm laser characteristics were studied in different pulse repetition rates. When the pulse repetition rates were 20 kHz,30 kHz and 40 kHz, the maximum average output powers were 2.9 W,3.2 W and 3.5 W, respectively.2. Research on Nd:KLuW 535 nm laser. Continuous and pulsed 535 nm lasers were realized with a b cut Nd:KLuW crystal as the laser gain medium and an LiB₃O₅ crystal as the nonlinear frequency doubling crystal. For continuous wave operation, the obtained maximum output power was 2.4 W and the corresponding optical-to-optical conversion efficiency was 20.5%. For active Q-switching operation, with the pulse repetition rate of 30 kHz, the obtained maximum average output power was 2.6 W and the corresponding conversion efficiency was 26.8%. On the basis of rate equations, the characteristics of the actively Q-switched frequency-doubled Nd:KLu（WO₄）₂ laser were simulated. The theoretical results of the average output power and pulse width were obtained. They were in agreement with the measured data on the whole.3. Research on Nd:KLuW 1185 nm self-Raman laser. With a b cut Nd:KLuW crystal, passively Q-switched 1185 nm self-Raman laser was realized. Two Cr:YAG crystals whose initial transmissions were 92% and 80%, were used in our experiments. With the 80% initial transmission Cr:YAG crystal, the maximum 1185 nm laser output power was 768 mW. The corresponding optical-to-optical conversion efficiency, pulse repetition rate and pulse width were 4.5%,34.2 kHz and 3.6 ns, respectively.