Research On LD Pumped Yb:YAG Single Frequency Laser Technology

In recent years,the field of laser applications has been further expanded,and all-solid-state lasers have also received increasing attention.Because Yb3+ion has many advantages such as long fluorescence lifetime,simple energy level structure and high quantum efficiency,Yb3+doped crystal materials are favored by researchers.Among Yb3+-doped laser materials,Yb:YAG crystal with a higher crystal field splitting energy,a wider absorption band,and a relatively small thermal load,has become one of the main research directions of LD pumped solid-state laser gain media.In this thesis,a LD pumped Yb:YAG single frequency laser is designed and experimentally studied.The main content of this thesis includes the following aspects:Firstly,the research status and main development trends of Yb:YAG lasers at home and abroad are introduced,and the basic composition and working characteristics of solid-state lasers are discussed in detail.The design scheme of the LD end-pumped Yb:YAG single frequency laser is introduced.The LD with a wavelength of 940 nm is used as the pump source.The birefringent filter composed of PBS and HWP is used to select the longitudinal mode.The frequency tuning is achieved by adjusting the HWP angle.The feasibility analysis of the LD pumped Yb:YAG single frequency laser system is carried out.Second,the characteristics of Yb:YAG crystal are introduced.The influence of the thermal effect of the crystal on the performance of the laser is analyzed,the parameters of the resonant cavity are designed,and the micro-channel cooling system is used to cool the crystal.Finally,the internal thermal effect model of the crystal is established,and the cooling effect of the cooling system is analyzed.Thirdly,a measurement system for the laser beam quality M2 factor is designed,and the CCD is used to obtain the spot images at different transmission distances.Through the image processing system,parameters such as the Gaussian curve distribution of the light spot,the three-dimensional energy distribution map,the far-field divergence angle of the laser beam,the beam waist radius,the beam waist position,and the M2 factor can be obtained.Fourthly,the laser cavity experiment system was established.By tuning the pump power,1030nm single-wavelength oscillation,1030nm and 1050nm dual-wavelength simultaneous oscillation,and 1050nm single-wavelength oscillation can be obtained.The power and temperature characteristics of the laser are studied,and the reasons for the dual-wavelength laser output are analyzed.On this basis,a LD-pumped Yb:YAG single-frequency laser experimental system is established.The birefringent filter composed of PBS and HWP can select the laser single longitudinal mode to achieve a single-frequency laser output of 1030nm.The effect of HWP on the output laser power and polarization state when it rotates around the cavity axis is explored.The laser frequency tuning is performed by changing the inclination angle of HWP,and the frequency tuning amount of 600GHz can be obtained when the inclination angle of HWP is 2°.The quality of the output laser beam is evaluated using the M2 factor measurement system.In summary,in this thesis,a detailed theoretical analysis and experimental study on the LD end-pumped Yb:YAG single-frequency laser technology are carried out,and a stable 1030nm single-frequency laser output was obtained.The laser can be used in the fields of laser interferometry,engineering manufacturing and medical aesthetics.