Research On Thermal Lens Effects In The LD Pumped Tm:YAP Laser

LD pumped all-solid-state laser has widely potential applications due to its small size,lightness, simplicity, long lifespan, high-energy storage, good beam quality, high reliability,compact structure. So, all-solid-state laser has potential applications in modern scientific research, while the high power and good beam quality of laser are affected by the thermal lens effects in solid state laser. As a result, it is necessary to study the thermal lens effects in solid state laser.The thermal lens effects in the LD pumped Tm:YAP all-solid-state laser are studied in this thesis.Firstly, we introduce the structure, type, cooling method, development status of the laser.We also introduce the principle, adverse effects and development status of thermal lens effects in the solid state laser.Secondly, Tm:YAP all-solid-state laser is the content of this thesis. The nature of the Tm:YAP laser crystal is summarized. The continuous-wave single-doped Tm3+ laser operating in room-temperature is the three level system, In the aspect of theory, building the three level laser rate equation model. This model considers the process of up-conversion energy-transfer and cross relaxation. That provides a theoretical basis for the study of the thermal lens effects.Thirdly, we use the rate equation as its theoretical model to study specifically the thermal lens effects in solid state laser. The influences of the thermal lens effects on the laser crystal are simulated with matlab software. The software makes a very thorough analysis on the thermal lens effects through analyzing the effects of average pump beam radius in the laser crystal, pump-to-mode size ratio, radius of curvature output mirror and cavity length on the fractional thermal loading and absorption. Under the premise of considering the change of the fractional thermal loading and absorption with the pump power, analyzing and calculating the thermal focal length versus pump parameters of the cavity.At last, the thermal lens effects in solid state laser will affect the performance of the laser when it is running. Therefore, the influences of thermal lens effects are needed to be considered in the design of the parameters. That is to say it is necessary to consider the diffraction losses caused by the thermal lens effects. Then we analysis the influences of the thermal lens effects on the fractional thermal loading, absorption and the thermal focal length.A compensatory scheme is needed to be proposed to effectively raise laser output power,improve laser beam quality and reduce the influences of the thermal lens effects.