| The laser at 2 ?m has the advantages of low atmospheric extinction ratio,eye-safe,and covering many molecular absorption peaks,such as water molecules,CO2 molecules,N2 O molecules and so on.2 ?m laser is very important in many fields,such as laser remote sensing,laser ranging,spectroscopy,and laser medicine.Especially,pulsed single-longitudinal-mode 2 ?m solid-state laser has become the preferred laser source for Coherent Doppler Lidar and Differential Absorption Lidar.The light source of laser lidar is usually achieved by injection locking technique.Narrow linewidth,high energy,high repetition rate,high peak power,single-longitudinal-mode(SLM)laser can be obtained by injecting a SLM seed laser into a high energy and high repetition rate oscillator.The seed laser is very important to the spectral,model of phase and spatial characteristics of the whole system.Thus,in order to make some contributions to the development of laser source,the main subject of this project intends to high power and anti-misalignment sensitivity of the SLM 2 ?m seed laser with narrow linewidth and high stability.Firstly,this paper introduces the investigation progress in 2 ?m SLM laser,and solid-state laser with corner cube resonator,and analyzes on the advantages and disadvantages of the way to achieve high power 2 ?m SLM laser,and points out the significance in improving the output performance of 2 ?m seed laser for injection-locking.Therefore,it is clear that the research on high power SLM Ho single-doped laser at 2 ?m with high anti-misalignment sensitivity and its stability is meaningful.Then,we introduce the physical and spectral properties of Ho:YAG,Ho:YLF and Ho:YVO4 crystals,and establish thermal models of end pumped rod crystal and bulk crystal.It provides a reference to the designing of end pumped Ho single-doped SLM lasers via the numerical simulations of the temperature field distribution and the thermal lens effect of three crystals.Meanwhile,a continuous rate equation model of Ho single-doped laser is established.The effect of pump spot,cavity loss and transmission of output mirror on the output performance of the laser is theoretically simulated and analyzed,which provides a theoretical basis for the experimental research of Ho single-doped SLM laser.Ho single-doped SLM laser realizing by the F-P etalon method is theoretically analyzed and the output characteristics of Ho single-doped SLM laser are experimentally investigated.Based on the research above,the investigation of high power,tunable,SLM Ho:YLF laser with ring cavity is carried out.The principle of high power Ho:YLF single-longitudinal-mode ring laser is analyzed theoretically.Combined with the analysis of the thermal lens effect of Ho:YLF,the design and stability of the cavity are analyzed.Experimentally,the highest SLM power was 528 m W,and the tuning range of about 178 GHz was realized by inserting a F-P etalon.Output characteristics of SLM laser after the first stage master oscillator power amplifier(MOPA)were also studied,and the highest SLM power of 1.5 W was obtained.In order to improve the anti-misalignment sensitivity of 2 ?m SLM laser,a corner cube prism(CCP)acts as a cavity mirror for reducing the detuning of the resonator caused by the mechanical vibration and the thermal distortion of the laser gain medium.Based on the excellent optical properties of CCP,the anti-misalignment sensitivity of the CCP resonator are theoretically simulated and analyzed,and the feasibility of using the corner cube cavity to improve the anti-misalignment sensitivity of 2 ?m SLM laser is verified.The Ho:YAG crystal with positive lens effect is used as the gain medium,and considering the depolarization characteristic of CCP,a CCP-flat cavity SLM laser is designed to study the output characteristics of SLM laser with single CCP cavity.Experimental results show that the depolarization effect of the CCP can be compensated by inserting a wave-plate,and the maximum SLM power of 478 m W was achieved by the method of intracavity F-P etalons.The research results can provide a reference for the design of the Ho single-doped laser with double CCPs.Finally,the output characteristics of the high power,tunable SLM Ho:YLF laser with double CCPs are studied through theory and experiments.By numerical simulation of the depolarization effect of double CCPs cavity,the influence of the placement of double CCPs on output characteristic is discussed.The negative lens effect of Ho:YLF crystal is compensated and a stable Ho:YLF ring cavity laser with double CCPs is designed.The effect of the CCP detuning on the output power and the relationship between the rotation angle of the quarter-wave plate and the laser transmission were investigated experimentally.The reason for unidirectional operation of the double CCPs Ho:YLF laser based on Faraday effect is theoretical analyzed by the method of optic matrix and transition matrix.The maximum SLM power was 733 m W with the beam quality factor 2M of 1.21 and the tuning range was about 238 GHz. |
PDF Full Text Request