End-pumped optical bistability Tm,Ho:YLF laser

We experimentally demonstrate strong optical bistability in a 2 μm continuous wave Tm,Ho:YLF laser with a bulk crystal. The laser is end-pumped by a 792 nm fiber-coupled laser diode. The bistable region is as wide as 1.6 W and the jump power at the turning point is as high as 82.5 mW when the temperature of the laser crystal is kept at 253 K. The influences of the cavity length and the transmission of the output coupler on the characteristics of optical bistability are obtained. The theoretical analysis shows that the bistable output in the Tm,Ho:YLF lasers comes from the combined effects of the nonlinear saturation of ground state reabsorption, the energy transfer upconversion, and the excited state absorption.     

端面抽运Tm，Ho：YLF激光器双稳特性的理论分析与实验研究

报道了波长为792nm激光二极管端面抽运Tm,Ho：YLF连续激光器的双稳输出特性.在考虑能量传递上转换和基态对2μm激光重吸收的前提下,建立了Tm,Ho：YLF双稳激光器准三能级速率方程理论模型.通过对Tm,Ho：YLF激光器速率方程的求解,理论预见了Tm,Ho：YLF激光器双稳输出的特性,并分析了其产生的机理.进行了激光二极管端面抽运Tm,Ho：YLF激光器双稳输出的实验研究,当激光晶体温度为253K时,双稳区的宽度可达1.6W,跃变点输出功率的跃变量可达82.5mW.通过对比发现理论结果与实验结果比 关键词： 端面抽运 Tm Ho：YLF晶体 连续输出 光学双稳     

激光二极管端面抽运Tm,Ho:YLF激光器双稳特性研究

报道了波长为792 nm激光二极管端面抽运Tm,Ho:YLF连续激光器的双稳输出特性.激光晶体温度为283 K时,双稳区的宽度为100 mW,跃变点输出功率的跃变量为15 mW.实验上还研究了晶体温度对2 μm激光双稳特性的影响,当晶体温度从283 K升高到298 K时,双稳区的宽度由100 mW减小到60 mW,跃变点输出功率的跃变量由15 mW下降到6 mW.通过分析可知,Tm,Ho:YLF连续激光器的双稳输出是由能量转递上转换、激发态吸收以及激光下能级对2 μm输出激光再吸收共同作用的结果. 关键词： 端面抽运 Tm Ho:YLF晶体 连续输出 光学双稳     

Optical bistability effects in a Tm,Ho:YLF laser at room temperature

We demonstrate strong optical bistability in a 2 microm continuous-wave Tm,Ho:YLF laser pumped by a 792 nm laser diode near room temperature. The bistable region is as much as 100 mW wide at 283 K and can be controlled by the temperature of the laser crystal. The influence of crystal temperature on the characteristics of optical bistability is obtained. The influence of the pump-to-mode ratio on the bistable characteristics of the laser is also discussed. To our knowledge this is the first report of optical bistability effects in Tm,Ho:YLF lasers.     

激光二极管纵向抽运（Tm，Ho）：YLF激光器的研究

对激光二极管端面抽运(Tm，Ho)：YLF固体激光器的激光特性进行了研究。根据激光二极管抽运准三能级系统的特性，详尽地分析了能量在Tm^3 离子和Ho^3 离子之间的传递过程，给出了(Tm，Ho)：YLF激光器准三能级的速率方程，对上转换及激光下能级粒子再吸收对激光二极管抽运(Tm，Ho)：YLF激光器运转的影响进行了理论分析，得出了(Tm，Ho)：YLF激光器的阈值抽运功率和斜率效率的解析表达式。同时对(Tm，Ho)：YLF微片激光器的激光特性进行了实验研究，当保持晶体温度为19℃时，阈值抽运功率为425mW，斜率效率为22．5％，最大光—光转换效率为17．4％，并且在将晶体保持在四个不同的温度下，给出了激光输出功率随抽运功率变化的实验结果。将理论与实验结果进行比较，发现吻合得比较好。     

能量传递上转换对Tm，Ho：YLF调Q激光器上能级寿命的影响

根据激光二极管纵向抽运Tm,Ho：YLF激光器的能级跃迁和能量传递过程，在考虑能量传递上转换(ETU)的情况下，建立了Tm,Ho：YLF主动调Q激光器的准三能级速率方程，得出了激光单脉冲能量的解析表达式.在理论上指出，能量传递上转换不但减小了输出单脉冲能量，而且严重减小了激光上能级寿命.实验上给出了在固定抽运功率下，单脉冲能量随重复频率的变化关系，验证了理论所指出的能量传递上转换减小了激光上能级寿命. 关键词： 二极管抽运 Tm Ho：YLF晶体 能量传递上转换 速率方程     

端面抽运Tm,Ho:YLF激光器热转换系数及热透镜效应的研究

根据激光二极管纵向抽运Tm,Ho:YLF激光器的能级跃迁和能量传递过程，在考虑能量传递上转换和基态重吸收的前提下，建立了准三能级速率方程理论模型.给出了Tm,Ho:YLF激光器的热转换系数的解析表达式，讨论了抽运光斑半径与激光束腰半径的比值对热转换系数的影响.实验上得到了热焦距随抽运功率的变化关系，并将其与理论结果进行了对比，发现符合较好. 关键词： Tm Ho:YLF晶体 能量传递上转换 速率方程 热转换系数     

能量传递上转换对Tm，Ho:YLF激光器阈值的影响

根据激光二极管纵向抽运Tm，Ho：YLF激光器的能级跃迁和能量传递过程，在考虑能量传递上转换的情况下，建立了准三能级阈值速率方程，得出了激光器阈值的解析解.给出了阈值与激光器设计参数的关系，并分析了能量传递上转换对激光器设计参数的依赖关系.实验上得到了不同输出耦合透过率下的激光阈值，验证了理论的合理性. 关键词： 二极管抽运 Tm Ho：YLF晶体 能量传递上转换 速率方程 阈值     

Tm~(3+)/Yb~(3+)共掺激光晶体的本征光学双稳特性分析与参数优化

理论研究了650nm激光雪崩抽运Tm3+/Yb3+共掺激光晶体的本征光学双稳态.基于系统的非线性耦合速率方程理论,数值分析了Tm3+/Yb3+离子能级布居数的本征光学双稳性、系统参数对光学双稳态的影响和双稳迟滞回线的动态变化.数值结果给出了光子雪崩机制下Tm3+/Yb3+共掺激光晶体的可见与红外光谱发光的本征光学双稳态;指出了通过优化Tm3+/Yb3+离子浓度比,选取低声子能晶体基质和采用晶体冷却技术,以及调谐抽运光与Tm3+离子激发态跃迁能隙满足共振频率匹配,可以有效地增强本征光学双稳效应;通过微调谐抽运光波长和控制抽运光强变化速率,可以实现动态调控的本征光学双稳态.     

激光二极管抽运Tm,Ho∶YLF晶体声光调Q激光器

对激光二极管端面抽运Tm,Ho∶YLF晶体声光调Q激光器的激光特性进行了研究。根据粒子跃迁和能量传递过程,在考虑能级传递上转换的前提下,建立了Tm,Ho∶YLF脉冲激光器的速率方程,得到了初始反转粒子数的解析表达式,分析了能量传递上转换效应对激光上能级反转粒子数的影响。在室温下实现了2 μm波长激光的脉冲输出。实验上给出并分析了Tm,Ho∶YLF脉冲激光器的平均输出功率、单脉冲能量和脉冲宽度随抽运功率以及声光Q开关调制频率的变化关系。在抽运功率为2.8 W,重复频率为9 kHz时,获得了平均输出功率为189 mW的激光脉冲,光光转换效率为6.8%。在重复频率为1 kHz时,得到最大单脉冲能量为65 μJ,峰值功率为0.17 kW。     

Single frequency optical bistability operation in end-pumped Tm,Ho:YLF lasers

Single-frequency bistability performances from a Tm,Ho:YLF laser with two Fabry?CPerot etalons near room temperature is reported. For the first time to our knowledge, the single-frequency bistability at 2.05???m is displayed in the laser operation with the bistable region width of 0?C580 mW and the jump power of 0?C78 mW, which can be tuned by regulating the length of the laser resonator. The maximum single frequency output power of 180 mW is obtained at the pump power of 2?W, and the laser frequency can be continuously tuned 1.25?GHz. The single frequency bistability laser can be used in laser lidar systems and all-optical switching systems.     

电光调Q脉冲Ho:YLF激光器实验研究

2μm低重复频率高峰值功率高光束质量激光在中长波光参量非线性频率变换等领域具有较为广阔的应用前景。采用L型谐振腔结构,使用42 W的掺Tm光纤激光器泵浦Ho:YLF晶体。基于磷酸钛氧铷（RTP）电光调Q技术,实现了重复频率50 Hz、脉冲宽度18 ns、脉冲能量13.5 mJ、峰值功率0.75 MW的2.05μm Ho:YLF固体激光输出。光束的水平方向和竖直方向M2因子分别为1.4和1.1。该Ho:YLF固体激光器采用光纤激光器泵浦,具有结构紧凑的特点,为更高能量的Ho激光输出奠定了基础。     

激光二极管抽运(Tm,Ho)∶YLF激光器光谱特性实验分析

Ho∶YLF晶体的5I7和5I8斯塔克能级分裂数较多,形成2047~2070nm宽的增益谱带,对于可调谐2μm激光及宽带激光放大器研究具有重要意义。理论上分析了(Tm,Ho)∶YLF晶体的能级结构,并对晶体掺杂浓度和长度进行了优化。实验研究了激光二极管抽运微片Tm(原子数分数0.06),Ho(原子数分数0.004)∶YLF激光谱线可调谐特性,调谐范围2.0656~2.0671μm。利用(Tm,Ho)∶YLF晶体的宽增益谱特性,将其作为激光二极管抽运激光放大器,成功地将2.048μm(Tm,Ho)∶GdVO4激光功率放大了2.5倍。实验上测量了(Tm,Ho)∶YLF晶体在强抽运条件下480~492nm及530~550nm可见波段的上转换蓝绿光荧光谱。     

Theoretical and experimental study of a single frequency Tm,Ho:YLF laser

We present a theoretical and experimental analysis of a diode-pumped single frequency Tm,Ho:YLF laser. A new model for a diode-pumped Tm,Ho:YLF quasi-three-level laser is described. The influence of energy-transfer up-conversion (ETU) and ground-state re-absorption (GSA) has been taken into account. When the incident pump power is 2.8 W, a maximum single frequency output power of 118 mW is obtained from the Tm,Ho:YLF laser at room temperature. The line narrowing elements used are two solid etalons. The single frequency laser can be used as a seed laser for either a larger oscillator or an amplifier. The theoretical results are in good agreement with experimental data.     

激光二极管抽运（Tm，Ho）：YLF微片激光器的实验研究

从理论上分析了准三能级(Tm，Ho)：YLF晶体的增益与温度关系，晶体温度的降低和长度的缩短有利于减小重吸收损耗对激光器运行性能的影响。在室温条件下，用2．7w波长为792nm激光二极管端面抽运Tm(原子数分数0．06)，Ho(原子数分数0．004．)：YLF微片激光器，阈值抽运功率为450W，当入射到晶体内的激光二极管功率为1．88W时，2μm激光最大输出功率为328mW，斜率效率为22．5％，光—光转换效率达17．4％。为达到激光最佳运行条件，还探讨了激光二极管波长，抽运光偏振方向以及晶体温度对Tm，Ho激光器性能的影响。     

A compact high efficient diode-double-passing-pumped mid-IR Tm:YLF laser at room temperature

A new compact high efficient diode-double-passing-pumped Tm:YLF laser at room temperature is presented. Using a crystal of 3 mm × 3 mm × 12 mm 4% doping Tm:YLF and double-end-double-passing pumping cavity structure without complex optical splitter pumping system, 5.6 W CW 1907.6 nm laser is obtained at 26.2 W 792 nm pumping laser. The slope efficiency is as high as 37.8% and the spectrum width is 2 nm. The relationship between cavity length and output laser is also analyzed. Experiments verify that the highest energy and convertion efficiency can be reached by optimizing the oscillator cavity length. Finally, we used this Tm:YLF laser to pump Ho:YAG crystal at room temperature and achieved 1.65 W 2.1 μm output laser with slope efficiency 67%.     

端面抽运Tm，Ho∶YLF连续激光器的参数优化与实验研究

研究了激光二极管端面抽运Tm,Ho∶YLF连续激光器的输出特性,并对激光器的参数进行了优化.在考虑能量传递上转换的前提下,通过准三能级速率方程推导出了连续抽运Tm,Ho∶YLF激光器输出功率与抽运功率关系的表达式.对激光晶体的粒子掺杂浓度、晶体长度、激光束腰半径与抽运光束腰半径比值以及输出镜透过率等激光器参数进行了优化.实验上得到了激光输出功率随抽运功率的变化关系,并将其与理论结果进行了比较,发现比较吻合,从而验证了理论模型的合理性. 关键词： Tm Ho∶YLF晶体 速率方程 能量传递上转换 参数优化     

Short-term frequency characteristics of 2 µm single frequency Solid-state lasers

The Short term frequency stability characteristics of 2 μm single frequency Solid-state lasers was investigated. The two laser systems of 2 μm single longitudinal mode oscillation Tm, Ho:YLF microchip laser and Ho:YAG NPRO laser were designed and constructed. The Short term frequency stability of these two laser were measured with the fiber delay self-beating heterodyne method. The 3dB width of the relative frequency fluctuation of Tm, Ho:YLF microchip laser and Ho:YAG NPRO laser were measured to be 895 and 736 Hz with 500 m fiber optical (2.5 μs delay). The proportional relation between the lasing fluctuation and the delay time were 358 and 263 Hz/μs, respectively. The vibration experiment was presented and it indicated that the NPRO Ho:YAG was more terrible to the influence of vibration, which is important in the practical application of wind measurement lidar.     

Tm,Ho双掺调Q激光系统理论与实验研究

本文针对Tm,Ho双掺的激光系统,利用速率方程理论,得出了激光各能级的反转粒子数分布规律.通过计算预测出了超过1 ms的时间有巨脉冲的光子输出,脉冲能量为88.4 mJ,脉冲宽度为426 ns.实验采用环形腔声光调Q,Tm,Ho:LuLF为激光介质,三向侧面抽运.自由运转和调Q状态的斜率效率分别为6.36%和2.9%.注入能量3.25 J时,自由运转激光能量103.2 mJ,调Q激光能量为30.3 mJ,对应光-光效率为3.17%,0.93%;注入能量3.5 J时,自由运转激光能量为129.3 mJ,调Q激光能量35.9 mJ,对应光-光效率为3.69%,1.02%.最大的动静比为32.8%.激光脉冲宽度为417.2 ns.如果环形腔能够单向运转,那么得到的激光能量和光-光转换效率都将增大一倍,与预测结果更加一致.     

600-mJ,double-pulse 2-microm laser

An efficient double-pulse Ho:Tm:YLF 2-microm laser with total Q-switched output energy of 600 mJ has been demonstrated. A double-pulse pair is obtained per pump pulse. By operation of the laser in a double-pulse format, the residual energy stored among the Tm ions is transferred to the Ho atoms that were de-excited by the extraction of the first Q-switched pulse. Thus, the overall laser efficiency is increased by 61%.