Study On 2.09 ?m Twisted-mode Ho:YAG Single-longitudinal-mode Laser

The 2?m single longitudinal mode laser is the spectral region of the atmospheric window,which can be efficiently absorbed by CO2,NO2,H₂ O and other molecules.With its unique properties,it shows great advantages in many applications such as laser medicine and lidar.The laser in free-running mode is generally a multi-longitudinal mode laser.Among several technical methods for obtaining a single longitudinal mode laser,the twisted mode technology obtains single-frequency laser by eliminating the spatial hole burning effect,which has the advantages of simple structure and high output power.Ho:YAG is an isotropic gain medium with excellent comprehensive performance.It is a quasi-two-level structure when using 1.9?m laser pumping.It has low heat generation and meets the technical requirements of the twisted mode technology.It is a good choice as a gain medium for twisted-mode technology,and it is also an effective solution to achieve 2?m laser.Based on this,this dissertation carried out the study of Ho:YAG single longitudinal mode laser based on twisted mode method.First of all,this dissertation introduces and analyzes the research status of 2?m single longitudinal mode solid-state laser and Ho:YAG laser.By studying the energy level structure and dynamic process of the Ho:YAG laser,a rate equation is established and the output performance of the laser is theoretically calculated.The thermal focal length of the crystal at different pump powers are emulated.Secondly,the reason for the multi-longitudinal mode oscillation of the laser under free running is discussed,and the principle of single-frequency laser obtained by the twisted mode technology is explored.According to the technical characteristics of the twisted mode technology,the design work of the Ho:YAG twisted mode laser was carried out,which provided guidance for the subsequent realization of high power and stable single longitudinal mode laser.Finally,based on the theoretical research results of the laser,an experimental study of the single longitudinal mode Ho:YAG twisted mode laser was carried out.The resonant cavity adopts a flat concave cavity structure,a polarizer is used to guide the pump laser into the cavity whose length is 185 mm.When the laser is running freely,at the pump power of 13.4W,the output power of the laser reaches 3.45 W,the laser is multi-longitudinal mode.The single longitudinal mode output of the laser is realized using the twist mode technology.When the the pump laser's power is 7.13 w,the singlefrequency laser at 2097.3nm with a maxim?m power of 720 mw has a slope efficiency of 31.4% and the beam quality factor is 1.15.