Experimental Investigation of Thermal Lensing in End-pumped Nd:YVO4 Crystal Using a New Simple Approach

The stability of linear planar resonators involved in solid-state lasers is entirely decided by the thermal lens of the laser crystal. There exists a critical point between stable state and unstable state at which the thermally focusing point falls on the surface of one end mirror. Based on this fact, a new method for measuring the thermal focal length has been presented, and applied to three different Nd3+-doped (2%, 0.8%, and 0.5% ) Nd:YVO4 crystals at various absorbed pump power levels up to 10 W, the results show a good agreement with those of theoretical calculation. It also indicates that the thermal lensing is strongly dependent on the Nd3+-doped concentration, and is affected by crystal surface temperature, especially in the situation of weak thermal lensing.     

腔内倍频Nd:YVO4晶体激光获得的大功率671nm红光

本文报道了由双端泵浦Nd:YVO4晶体产生1342nm基频光，经过非线性晶体LBO腔内产生的671nm的红光光源。泵浦功率19.5W时，产生的671nm的红光平均功率是2.9W。光光转换效率为14.9%。分析了最近泵浦光斑尺寸，最佳聚焦位置，减少热透镜效应对输出功率的影响。双端泵浦结构和准连续运行模式大大减弱了热透镜效应。     

Efficient and compact intracavity-frequency-doubled YVO4/Nd:YVO4/KTP laser through analysis of the interaction length

In this paper, a stable end-pumped intracavity-frequency-doubled green laser was demonstrated. The interaction length of different pump systems before setting up the experiment was analyzed in order to find out an effective pump system. The experimental results indicate that the pump system in our configuration is beneficial to the efficient CW Nd lasers. A continue-grown composite crystal YVO₄/Nd:YVO₄, with Nd³⁺ concentration doping of 0.3 at.%, is used as laser medium. With an incident pump power of 27.5 W, as high as 7.2 W of CW output power at 532 nm was achieved. The optical-to-optical conversion efficiency of 26.2% was obtained in CW modes with a flat-flat cavity design.     

Diode-end-pumped composite Nd:YVO4 yellow laser based on intracavity frequency-doubled self-Raman laser

We report an intracavity frequency-doubled Q-switched self-Raman yellow laser at 587 nm. A composite Nd:YVO₄ crystal was utilized as self-Raman gain medium. The maximum average output power of yellow light obtained was 1.5 W at the incident pump power of 30 W and at a repetition rate of 50 kHz, corresponding to the optical conversion efficiency of 5%. The shortest pulse width, the maximum pulse energy and the highest peak power were measured to be 5.8 ns, 46.7 μJ and 5.9 kW, respectively.     

Passively Q-switched laser operation in a composite Nd:YVO4/Nd:YVO4/Nd:YVO4 crystal with a GaAs saturable absorber

By using a piece of GaAs wafer as the saturable absorber, the performance of the passively Q-switched composite Nd:YVO₄ laser with different output couplers has been demonstrated for the first time as far as we know. The largest continuous wave output power of 1.52 W is obtained at the incident pump power of 5.31 W, giving an optical conversion efficiency of 28.7% and a slope efficiency of 30.2%. The shortest pulse width of 11 ns, the largest single-pulse energy of 2.49 μJ and the highest peak power of 190 W are also obtained.     

一种测量二极管侧面抽运固体激光器热焦距的方法

提出了一种能够简单、准确测量二极管侧面抽运固体激光器热透镜焦距的方法,明确提出采用非对称平平腔测量时,激光晶体端面与腔镜的间距不需要为零,并从实验上证明了方法的可靠性. 应用该方法的测量结果可以优化复合折叠和频黄光激光器的结构,保证两束基频在腔内达到最佳的空间重合,提高腔内和频效率. 关键词： 全固态激光器 Nd∶YAG激光器 热焦距 腔内和频     

LD端面泵浦矩形Nd:YVO_4晶体的热效应研究

建立了矩形激光晶体的热传导模型。通过充分考虑晶体侧面与冷却液之间的对流传热,以及晶体端面与外界的热传导,建立了更为合理的边界条件。利用有限元差分法求解泊松方程,得到激光晶体内温度和温度场分布。研究结果表明,在考虑晶体的侧面对流和端面导热的情况下,得出了更符合实际的晶体温度场分布,计算的热焦距与实验测量结果更为吻合。     

二极管端面抽运的固体激光放大器自身热透镜焦距测量

通过分析激光经过热透镜后光束半径的变化，提出了利用放大器测量热透镜焦距的方法.根据激光束传输与变换理论，得到了热透镜焦距的表达式，并分析了其前提条件和近似偏差.最后，基于上述理论分析，测量了激光二极管端面抽运Tm,Ho∶GdVO₄放大器的热透镜焦距. 关键词： 热透镜焦距 固体激光 激光束传输与变换     

激光二极管抽运Nd:YVO4晶体的三维热效应分析

针对激光二极管抽运的以Nd:YVO4板条晶体为增益介质的激光器件,基于有限容积法数值分析各向异性介质的热传导方程,给出了Nd:YVO4晶体板条结构的热分布数值模型,并分别模拟仿真了808nm半导体激光器双端端面抽运,大面均匀抽运,大面周期分布抽运三种抽运结构,得到了Nd:YVO4板条晶体在这三种抽运结构下的非稳态时不同时刻的温度曲线和稳态时的三维温度分布切面图.     

Investigation of Nd:YVO4/YVO4 composite crystal and its laser performance pumped by a fiber coupled diode laser

Thermal effect control is critical to scale the output power of diode end-pumping solid lasers to several watts up and beyond. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lens for the end-pumping laser crystal. The temperature distribution and thermal lens in Nd:YVO₄/YVO₄ composite crystal was numerically analyzed and compared with that of Nd:YVO4 crystal in this paper. The end-pumping Nd:YVO₄/YVO₄ composite crystal laser was set up and tested with z cavity. The maximum output power of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the pumping power of 16.5 W. The highest optical-optical conversion efficiencies were up to 60% at 1064 nm and 40% at 532 nm, respectively.     

Mid-infrared,wide-tunable,continuous-wave Nd:YVO4/PPMgLN intracavity optical parametric oscillator

We obtain a continuous-wave (CW) Nd:YVO₄/PPMgLN intracavity singly resonant optical parametric oscillator (ISRO). The threshold value of the CW-ISRO system is only 2.8 W at 808 nm. When the pump power is 5.5 W, an idle laser output power of 410 mW, and a signal laser output power of 345 mW have been achieved. By changing the grating periods of the domain structure on the PPMgLN wafer, we enable a wide-tunable mid-infrared spectrum of 2.95–4.16 μm and near-infrared spectrum of 1.43–1.66 μm.     

The thermal effect in diode-end-pumped continuous-wave 914-nm Nd:YVO4 laser

The thermal effect and the heat generation in diode-end-pumped continuous-wave 914-nm Nd:YVO₄ lasers are investigated in detail. A theoretical model of a diode end-pumped solid-state laser is constructed to analyse the influence of fractional thermal loading on the thermal effect in the Nd:YVO₄ laser based on finite element analysis. The thermal focal lengths and the end-surface deformations of laser rods in Nd:YVO₄ quasi-three-level and four-level lasers are measured and compared with the results obtained by ordinary interferometry for the demonstration of higher thermal loading in 914-nm laser. Finally the fractional thermal loading in the Nd:YVO₄ quasi-three-level laser is calculated by matching the experimental and the simulated end deformations.     

A novel orthogonally linearly polarized Nd:YVO4 laser

We presented a novel orthogonally linearly polarized Nd:YVO₄ laser. Two pieces of a-cut grown-together composite YVO₄/Nd:YVO₄ crystals were placed in the resonant cavity with the c-axis of the two crystals orthogonally. The polarization and power performance of the orthogonally polarized laser were investigated. A 26.2-W orthogonally linearly polarized laser was obtained. The power ratio between the two orthogonally polarized lasers was varied with the pump power caused by the polarized mode coupling. The longitudinal modes competition and the corresponding variable optical beats were also observed from the orthogonally polarized laser. We also adjusted the crystals with their c-axis parallele to each other, and a 40.7-W linearly polarized TEM₀₀ laser was obtained, and the beam quality factors were M²_x=1.37 and M²_y=1.25.     

激光热透镜焦距测量实验及其公式改进

通过平平非稳腔法对激光热透镜焦距进行了实验测量,研究了不同抽运光束腰位置对热透镜焦距的影响.从理论上引入抽运光远场发散角和束腰位置,对端面抽运激光晶体热透镜焦距公式进行了改进.     

纳秒电光调Q Nd:YVO4激光器

介绍了一种新颖的短腔电光调Q窄脉宽激光器,通过分析影响脉宽的主要因素,确定了激光器的结构及参数。在准连续端面泵浦条件下,采用掺杂原子分数为1.0%、沿a轴切成布儒斯特角的Nd:YVO4晶体作为增益介质,直接获得偏振光振荡,有效缩短了腔长。在物理腔长20 mm时,采用退压式电光主动调Q结构,减小了插入损耗,获得了脉冲宽度为1.049 ns、单脉冲能量为0.32 mJ、光束质量平方因子为1.9的稳定激光输出。     

Theoretical and experimental study of a laser-diode-pumped actively Q-switched Nd:YVO4 laser with acoustic–optic modulator

By considering the Gaussian spatial distribution of the intracavity photon density and initial population-inversion density as well as the longitudinal distribution of the photon density along the cavity axis and turnoff time of the acoustic–optic Q-switch, the coupled equations of an LD-pumped actively Q-switched Nd:YVO₄ laser with acoustic–optic modulator are given. These coupled rate equations are solved numerically on a computer, and the dependences of pulse width, single-pulse energy and peak power on incident pump power are obtained. In the experiment, a laser-diode-pumped actively Q-switched Nd:YVO₄ laser with acoustic–optic modulator is realized, and the experimental results are in fair agreement with the numerical solutions.     

激光二极管端面抽运的1.34μm Nd:YVO4平凹腔型激光器

理论上分析了端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的各项参数；实验 上实现了LD端面抽运的1.34μm Nd:YVO₄平凹腔型激光器的运转. 关键词： 固体激光 4晶体')" href="#">Nd:YVO₄晶体 平凹腔     

Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd:YVO4 Laser

The interrelation between the phase matching condition for second harmonic generation (SHG) and the electro-optic Q-switching in KTP was numerically analyzed. A diode-pumped Q-switched Nd: YVO4/KTP green laser was reported, where the KTP crystal was simultaneously used as both an electrooptic Q-switcher and a frequency-doubling crystal in type Ⅱ phase matching.Compared with the conventional frequency-doubling and Q-switching configuration, low loss and high efficiency characteristics were realized by using a single KTP crystal. The Q-switched green laser pulse with a peak power of 762 W and a pulse width of 12 ns was obtained with 1 W pump power.     

1097 nm Nd:YVO4 self-Raman laser

An acousto-optically Q-switched self-Raman laser emitting at 1097 nm is demonstrated with a c-cut Nd:YVO₄ crystal, using a fiber-coupled 880 nm diode laser as the pumping source. Raman laser performances in concave-plane and plane-plane oscillating cavities are studied and compared. With an absorbed diode power of 12.4 W and a pulse repetition rate of 50 kHz, the highest output power of 1.45 W is obtained from the plane-plane cavity, corresponding to an optical-to-optical conversion efficiency of 11.7%.     

全固态单纵模脉冲Nd:YVO_4环形激光器

设计并研制了全固态调Q脉冲单纵模Nd:YVO4环形激光器。利用880nm激光二极管端面抽运Nd:YVO4晶体,通过四镜环形谐振腔中插入声光调Q晶体、标准具,并优化激光谐振腔的结构,获得了重复频率为200Hz、脉宽为26.6ns的单纵模脉冲1.064μm激光输出。当泵浦功率为15 W时,单纵模激光输出的单脉冲能量为570μJ、脉冲能量稳定性优于3%。