1.3/1.5μm LD End-pumped YVO₄-Nd: YVO₄ Laser

Diode pumped solid state lasers have many advantages such as small construction, light weight, long lifetime and high efficiency. They are widely used in many important fields, such as optical storage, optical storage, optical interconnection, laser manufacturing, medical care and military applications. In the processing of the laser, part of the absorbed pump power will be converted to heat deposited in laser material. It will change the refraction of the crystal, and cause thermal effect in the crystal, which will result in bad laser quality and decline of output power.It is one of the most important questions to reduce the thermal effect and accumulation effectively in the laser medium. Accompanied with the development of thermal bonding technology, composite crystal become an effective method to reduce thermal effect. Because the bonding part is undoped, it can remove the heat more quickly than normal crystal. Another way of reducing thermal effect is direct pumping technology, which can reduce the heat converted from non-radiative transition.Laser at 1.5μm is relatively safe to people's eyes, and especially the laser wavelength lies the "atmospheric window". So it is widely applied in military and civil use. The 1.5μm laser based stimulated Raman scattering is becoming more and more attractive to people because of its compact structure and high output power and efficiency.An LD pumped YVO4-Nd:YVO4 composite crystal laser and a acoustic-optically (AO) Q-switched YVO4-Nd:YVO4/SrWO4 Raman lasers are researched theoretically and experimentally. The content and innovative points of this dissertation are listed as below:1 The influence of the LD pump spot size to the output characteristics of the LD pumped Nd:YVO4 1342 run lasers is investigated. Three different fiber core diameters at 400μm,600um, and 800μm are adopted. It is revealed that the fiber core diameter at 800 um can produce the least heat and output the most laser power. 2 For the first time, characteristics of a YVO4-Nd:YVO4 laser at 1342 nm under direct pumping at 880 nm have been investigated. The results of a 880 nm LD pumped Nd:YVO41342 nm laser, a 808 nm LD pumped YVO4-Nd:YVO4 1342 nm laser and a 808 nm LD pumped Nd:YVO4 1342 nm laser were also obtained and compared with those of the 880 nm LD pumped YVO4-Nd:YVO41342 nm laser. The numerical simulation of the temperature distributions in laser crystals was carried out by use of the finite element analysis method. The conclusion is that the application of composite crystal and 880 nm LD direct pumping can effectively decrease the gradient change of the temperature distribution in laser crystal and increase the average output power and slope efficiency.3 The LD-end-pumped actively Q-switched YVO4-Nd:YVO4/SrWO4 eye-safe Raman lasers has been realized. At an incident LD pump power of 17.1 W and a PRF of 30 kHz, an average output power of 1.6 W is obtained, corresponding to a LD-to-Stokes optical conversion efficiency of 9.7%.