中红外光学材料的高温性能研究

红外光学材料是红外技术应用的基础之一。适用于3~5μm波段的中波红外光学材料正向高性能、大尺寸、低成本等方面发展,具有广阔的应用前景。介绍了尖晶石陶瓷、蓝宝石晶体和氟化镁多晶等中红外光学材料的基本性质,开展了制备技术、光学性能、力学性能和热学性能的研究,比较了温度对发射率、抗弯强度和热导率的影响。结果表明：尖晶石陶瓷具备较高的发射率;氟化镁多晶抗弯强度较差;蓝宝石晶体综合性能较佳,适用于制备基于高温应用的弧形光学器件。

Ho^(3+)掺杂Sc_2SiO_5激光晶体生长与光谱性能研究

采用提拉法分别生长了具有高光学质量的0.5at%和1.0at%的Ho∶Sc2SiO5(Ho∶SSO)激光晶体。研究表明晶体空间群为C2/c,晶胞参数为a=0.99723 nm,b=0.64261 nm,c=1.16843 nm,β=103.9°。Ho3+在SSO基质中的分凝系数为0.82。Ho∶SSO晶体在2085 nm处发射截面为1.12×10-20cm2,发射光谱呈现一个1850~2150 nm的宽发射带。当粒子数反转比率β=0.25时,增益截面σg即开始出现正增益。综合评估了晶体的激光性能,表明Ho∶SSO晶体是一种有潜力的2μm波段激光介质。

硫化锌体材料制备及其光学性能研究进展

多光谱波段透过型ZnS体材料在整流罩、红外透镜、红外窗口等领域具有广泛应用。本文全面梳理和总结了ZnS体材料制备技术的最新研究进展,包括热压技术、化学气相沉积+热等静压技术等。分析了不同制备方法对ZnS体材料光学性能的影响因素。最后展望了ZnS体材料的未来发展方向。

三温区梯度化学气相沉积ZnS制备

红外热像仪可在全天候条件下实现目标识别,在安防、夜视辅助及红外测温系统等领域应用广泛,但红外热像仪成像质量和效果受制于ZnS红外光学镜头的品质和性能。文中采用自主研制的三温区梯度化学气相沉积(TTG-CVD)及退火热处理制备ZnS块体。采用X射线衍射表征出ZnS块体是立方闪锌矿结构,具有光学各向同性,可以满足后续在红外光学镜头中的设计需求。结合红外透过光谱获得ZnS块体在8~12μm长波红外波段的平均透过率达71.6%。ZnS块体在1.06μm处的折射率均匀性为1.94×10^(-5)。进一步采用光学冷加工和单点金刚石车削等工艺,制作出ZnS红外光学透镜和红外镜头。红外光学镜头在空间频率为20 lp/mm时,在半视场(0.5视场)和0.707视场的调制传递函数(MTF)接近衍射极限。红外成像系统在中心视场、0.707视场由像差引起的弥散斑均方根值(RMS)均小于像元尺寸20μm,系统畸变小于1%,各项指标均达到实际使用要求。

镱钠共掺氟化钙锶混晶近红外光谱与激光参数

研究了15%Yb,20%Na∶CaF_(2)-SrF_(2)混晶(Yb,Na∶CaF_(2)-SrF_(2),CaF_(2)∶SrF_(2)=1∶1)的近红外光谱和激光参数特性。研究显示,Yb,Na∶CaF_(2)-SrF_(2)混晶在974 nm处吸收带宽为22 nm,吸收系数为13.09 cm^(-1),吸收截面为0.31×10^(-20) cm^(2)。Yb^(3+)离子在CaF_(2)-SrF_(2)基质中主发射峰中心波长位于1010 nm,肩峰中心波长位于1036 nm,发射带宽为56 nm,在^(2)F_(5/2)→^(2)F_(7/2)能级之间跃迁对应的荧光寿命为228μs。采用激发波长980 nm时,1010 nm处发射截面为6.52×10^(-20) cm^(2)、1036 nm处发射截面为4.11×10^(-20) cm^(2),分别是915 nm激发时的1.49倍与1.68倍;实现激光输出波长1036 nm处达到布居反转时所需要激发的激活粒子数的最小分数β_(min)为0.34%,在零声子线974 nm处的饱和泵浦功率密度I_(sat)为290.58 kW·cm^(-2)。上述结果表明,Yb,Na∶CaF_(2)-SrF_(2)混晶在近红外波段高能量激光系统中具有潜在应用前景。

多坩埚温度梯度法生长Dy^(3+)∶LaF_(3)晶体及发光特性

采用多坩埚温度梯度法(Multi-crucible temperature gradient technology,MC-TGT)制备了Dy^(3+)掺杂氟化镧(Dy^(3+)∶LaF_(3))晶体。通过电感耦合等离子体发射光谱仪、透射光谱、吸收光谱、荧光光谱等手段对Dy^(3+)在LaF_(3)晶体中的实际掺杂浓度、中红外透过光谱、可见光波段光谱特性等进行了研究。实验结果表明,Dy^(3+)在LaF_(3)晶体中的分凝系数约为0.8;格位浓度随着Dy^(3+)掺杂浓度提高而增加,2%Dy∶LaF_(3)晶体中的格位浓度达5.90×10^(20)ions·cm^(-3)。在1%Dy∶LaF_(3)晶体中,采用400 nm光激发,发光中心波长位于601 nm的发射谱带强度最大,位于511 nm的发射峰最宽,半高宽达152 nm;改用450 nm光激发,最强发射峰移至677 nm,最宽发射峰位于568 nm处。提高Dy^(3+)掺杂浓度到2%,采用400 nm或450 nm光激发,发光中心波长均位于478 nm和571 nm。在透射光谱2.5~9μm范围内,Dy∶LaF_(3)晶体(厚度为0.96 mm)红外波段透过率达85%以上。Dy∶LaF_(3)晶体有望在可见光、中红外等激光领域得到应用。

欠发达地区基本公共服务标准化的有益尝试——记清远市国家医疗卫生基本公共服务标准化试点

广东省清远市人民医院始建于1939年,是广州医科大学附属第六医院、广州医科大学第六临床学院、国家首批三甲医院、全国百佳医院、广东省博士后创新实践基地、国家住院医师规范化培训基地、广东省博士工作站。其"优质高效低耗"医院标准化管理模式成为全国医院改革的一面旗帜。近年来,先后荣获"全国文明单位""全国卫生系统先进集体""全国创建文明行业先进单位""广东省抗击新冠肺炎疫情先进基层党组织""广东省抗击新冠肺炎疫情先进集体"等省级以上荣誉30余个。

Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

Generation of 54 Fs Laser Pulses from a Diode Pumped Kerr-Lens Mode-Locked Yb:LSO Laser

一根二极管抽的 Kerr 透镜锁模式的 femtosecond Yb : LSO 激光试验性地第一次被表明。在有 22.5 nm 的带宽的 1052 nm 的中央波长的 54 fs 激光脉搏以 113 MHz 的重复率被获得。就我们的知识而言，这是曾经从做 Yb 的 orthosilicates 激光家庭生产的最短的脉搏持续时间。

Growth and spectroscopic characteristics of Nd-doped PbWO_4 crystal

Nd-doped PbWO4 crystals are grown by using the modified Bridgman method.The spectroscopic properties of the crystals are investigated.The changes of the absorption band at 350 nm are discussed for samples annealed at 740℃ and 1040℃.The radiative lifetime of the 4 F 3/2 level is calculated by using the Judd-Ofelt theory according to the absorption spectrum of 0.5 at.% Nd-doped PbWO 4 crystal.The spontaneous Raman scattering properties of the crystals are analysed.

Spectroscopic properties of Er/Ce-codoped La_3Ga_5SiO_(14)

The Er-single-doped and Er/Ce-codoped La3Ga5SiO14 polycrystalline powders are synthesized by the solid-phase synthesis method. The room-temperature luminescence spectra of the samples are investigated. The Near-infrared- region spectroscopic properties of Er3＋ ions in the La3GasSiO14 systems are analysed with Judd-Ofelt theory and rate equations. The effective deactivating effect of Ce3＋ ions on Er3＋ ions is confirmed.

Spectra properties of Yb^(3+),Er^(3+):Sc_2SiO_5 crystal

The influence of Er3+ ions on the spectra of Yb^(3+),Er^(3+): Sc_2 SiO_5(SSO) single crystal, which was obtained by Czochralski(Cz) method, is discussed. The absorption coefficient at 980 nm was 13.36 cm^(-1) with a peak absorption cross-section of 1.46 × 10^(-20) cm2. The emission cross-sections at 1034 nm and 1062 nm were 5.5 × 10^(-21) cm^2 and4.9 × 10^(-21) cm^2, respectively. The fluorescence lifetime was estimated as 1.24 ms at 1061 nm. The mechanical properties of SSO single crystal were also presented.

High-Power Continuous-Wave and Acousto-Optical Q-Switched Ho:(Sc_(0.5)Y_(0.5))_2SiO_5 Laser Pumped by Laser Diode

We experimentally investigate the continuous-wave(cw)and acousto-optical(AO)Q-switched performance of a diode-pumped Ho:(Sc_(0.5)Y_(0.5))_2SiO_5(Ho:SYSO)laser.A fiber-coupled laser diode at 1.91m is employed as the pump source.The cw Ho:SYSO laser produces 13.0 W output power at 2097.9 nm and 56.0%slope efficiency with respect to the absorbed pump power.In the AO Q-switched regime,at a pulse repetition frequency of 5 kHz,the Ho:SYSO laser yields 2.1 mJ pulse energy and 21 ns pulse width,resulting in a calculated peak power of 100 k W.In addition,at the maximum output level,the beam quality factor of the Q-switched Ho:SYSO laser is measured to be about 1.6.

Comparison of Laser Performances of 5at.% Yb：Gd2xY2（1-x）SiO5 Crystals between Different Cutting Directions

We investigate the laser actions of 5at% Yb：Gd2xY2（1-x）SiO5 （Yb：GYSO; x = 0.1） crystals with different cutting directions, parallel and vertical to the growth axis. Our results show that the cutting direction of the sample plays an astonished role in the laser operation. The sample cut vertically to the growth axis possesses the favourable lasing characteristics. Its output power reaches 3.13 W at 1060nm with a slope efficiency of 44.68Yo when the absorbed pump power is 8.9 W. In contrast, the sample cut parallel reaches only 1.65 W at 1044 nm with a slope efficiency of 33.76% with absorbed pump power of 7.99 W. The absorption and emission spectra of the two samples are examined and the merit factor M is calculated. Our analysis is in agreement well with the experimental results. The wavelength tuning range of the superior sample covers from 1013.68 nm to 1084.82nm.

A 1.7-ps pulse mode-locked Yb^(3+):Sc_2SiO_5 laser with a reflective graphene oxide saturable absorber

By using a reflective graphene oxide as saturable absorber, a diode-pumped passively mode-locked Yb^3＋：Sc2Si O5（Yb：SSO） laser has been demonstrated for the first time. Without extra negative dispersion compensation, the minimum pulse duration of 1.7 ps with a repetition rate of 94 MHz was obtained at the central wavelength of 1062.6 nm. The average output power amounts to 355 m W under the absorbed pump power of 15 W. The maximum peak power of the mode-locking laser is up to 2.2 k W, and the single pulse energy is 3.8nJ.

Study on incident laser modulation using surface micro-defects on KH_2PO_4 crystal

KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries （e.g., width, morphology, and depth of defects） are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 p-m. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μm for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.

Diode-pumped laser performance of Tm:Sc2SiO5 crystal at 1971 nm

The 4-at.% Tm：Sc_2SiO_5 （Tm：SSO） crystal is successfully obtained by the Czochralski method. The optical properties and thermal conductivity of the crystal are investigated. The broad continuous wave（CW） laser output of（100）-cut Tm：SSO with the dimensions of 3 mm×3 mm×3 mm under laser diode（LD）-pumping is realized. The full width at half maximum（FWHM） of the laser emitting reaches up to 21 nm. The laser threshold of Tm：SSO is measured to be 0.43 W. Efficient diode-pumped CW laser performance of Tm：SSO is demonstrated with a slope efficiency of 25.9% and maximum output power of 934 mW.

Diode-Pumped Soliton and Non-Soliton Mode-Locked Yb:GYSO Lasers

Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1−xYx)2SiO5(x=0.5)lasers are demonstrated.Pulses as short as 1.4 ps are generated for the soliton mode−locked operation,with a pair of SF10 prisms as the negative dispersion elements.The central wavelength is 1056 nm and the repetition rate is 48 MHz.For the non-soliton mode locking,the output power could achieve∼1.2 W,and the pulse width is about 20 ps.The critical pulse energy in the soliton-mode locked operation against the Q-switched mode locking is much lower than the critical pulse energy in the non-soliton mode-locked operation.

Kerr-Lens Self-Mode-Locked Laser Characteristics of Yb:Lu_(2)SiO_(5) Crystal

A diode-pumped Kerr-lens self-mode-locked laser is achieved by using Yb:Lu2SiO5(Yb:LSO)crystal without additional components.Under the incident pump power of 14.44 W,a self-mode-locked output power of 2.98 W is obtained in the five-mirror cavity,corresponding to an optical-optical efficiency of 20.6%.Pulses as short as 8.2 ps are realized at 1059 nm,with the corresponding pulse energy and peak power of 28.9 nJ and 3.5 kW,respectively.A pair of SF10 prisms are inserted into the laser cavity to compensate for the group velocity dispersion.The pulse width is compressed to 2.2 ps with an average output power of 1.25 W.

端面泵浦渐变浓度Nd∶YAG温度场数值仿真研究

采用高功率半导体激光端面泵浦技术,在均一浓度Nd∶YAG中心轴沿泵浦光通光方向可产生温度梯度,引起热透镜效应,降低激光输出功率与光束质量。本文结合静态热场数值仿真,建立Nd∶YAG在方形平顶光泵浦条件下的热源方程,研究渐变浓度Nd∶YAG在高功率激光泵浦下的温度分布。当初始泵浦功率为1000 W、泵浦脉宽时间为46μs、重复频率为1 kHz时,均一浓度Nd∶YAG的吸收系数为5.8 cm-1,其中心轴沿通光方向的温度由185℃逐次下降到2、4、6、8 mm处的106、51、29、26℃;相应地,每经过2 mm,温度下降率分别为39.5、27.5、11.0、1.5℃/mm。与此相对应,本文构建出一款渐变浓度Nd∶YAG整体式结构,每段厚度均为1 mm,总长度为4 mm。将4段Nd∶YAG的吸收系数依次调控为1.5、2.1、3.3、9.7 cm-1,则沿泵浦光通光方向的中心轴温度基本维持在86.5℃,在渐变浓度Nd∶YAG中实现沿泵浦光传输方向的温度均匀分布。