Investigation Of The Thermal Management And Output Characteristics Of Dual-wavelength Yb:YAG Laser

Laser-diode-pumped all solid-state lasers have a rapid escalation in interest to date as the lasers are potentially useful light sources with lots of applications.The dualwavelength laser is one of the hot topics in the areas of the developed laser devices in recent years,which can emit two laser-wavelengths simultaneously and have some important applications in many fields,such as terahertz waves,different absorption radar,blood detection,and optical spectroscopy analysis.Especially,the polarized dual-wavelength lasers have attracted more and more interest due to their special applications in underwater imaging and atmospheric remote sensing.In the thesis,the research status and related progress of dual-wavelength solid-state lasers all over the world were systematically analyzed and summarized to set as background.We choose two different shapes of Yb:YAG laser crystals to carry out the experiments and the main research points of the thesis are as follows:(1)Nd:YAG and Yb:YAG,which are common and widely used in solid-state lasers,are selected to make a comparison.Their physical performances and optical properties were studied to show that Yb:YAG has unique advantages over Nd:YAG crystal in fluorescence lifetime,absorption bandwidth,and doping concentration range.(2)With the help of ANSYS engineering simulation,we obtained the results of the temperature distribution inside Yb:YAG crystal at lasing operation,which is based on the Poisson's equation of heat conduction.At the same pump power,cross-section diagrams of heat distribution of two shapes of laser crystals were simulated and achieved.The experimental results confirmed that thermal effect is the key point suppressing the laser output performance.The heat dissipation effect of the slab crystal is better than that of the bulk crystal at the same pumping and cooling conditions.(3)In our experiment,three different kinds of output couplings of 10%,15%,and 20% were employed to investigate the laser output performance.The 1030 nm and 1050 nm laser output can be separately achieved by using 20% and 10% output coupling,respectively.In addition,the dual-wavelength laser was obtained at 15% output coupling.Our experimental results show the output power from the slab Yb:YAG crystal was obviously higher than that of using a bulk Yb:YAG crystal.(4)The polarization states of the Yb:YAG lasers were experimentally investigated and presented to show their polarization properties at the different wavelengths.The experimental results demonstrated that the 1030 nm laser output can be linearly polarized,and the 1050 nm laser output was randomly polarized.Moreover,the polarization states of dual-wavelength lasers would be depended on the ratio of 1030 and 1050 nm,which can be polarized due to the fraction of 1030 nm laser.The beam spots and power stability of the output lasers were observed experimentally.The 1030 nm,1050nm and dual-wavelength lasers obtained in the experiments have quite good beam qualities,which were close to the fundamental Gaussian mode.The output power stability of RMS is determined to be better than 0.5% in a 30-min operation.In the thesis,the linearly polarized lasers and dual-wavelength Yb:YAG lasers were designed and studied to present their output performances.These simple compact Yb:YAG lasers would meet the practical requirements with good stability.These solidstate linearly polarized and dual-wavelength lasers have important applications in many fields,such as laser communication,high-resolution sensing,nonlinear optical frequency conversion,and beam combination.