Nd：Mg：LiNbO3单晶光学特性的初步研究

本文对Nd:Mg:LiNbO_3单晶的透射光谱、光学均匀性、抗光折变特性、倍频与自倍频特性进行了初步研究.报道了染料激光泵浦的Nd:Mg:LiNbO_3自信频激光实验,实现了非临界位相匹配下的自倍频运转,获得了波长为542.2nm的二次谐波输出.     

Crystal growth, spectroscopic and laser properties of Tm:LuAG crystal

Tm:Lu₃Al₅O₁₂ (Tm:LuAG) crystal was grown by the Czochralski method. The segregation coefficient was measured by Inductively Coupled Plasma Atomic Emission Spectrometer. The cell parameters were analyzed with X-ray powder diffraction experiments. The absorption and fluorescence spectra of Tm:LuAG crystal at room temperature were investigated. With a 20 W fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Tm:LuAG crystal was demonstrated. The maximum output power at 2020 nm was obtained to be 3.04 W, and the slope efficiency was 25.3%.     

Femtosecond laser micromachined optical waveguides in LiTaO3 crystal

By using femtosecond laser micromachining, optical wave guides in both depressed cladding and dual‐line configurations have been produced in LiTaO₃ crystal. The guiding properties and the thermal stability have been investigated for both geometries, which exhibit different performance. Depressed cladding waveguides support guidance along both extraordinary and ordinary index polarizations, while dual‐line waveguides support only extraordinary index polarization. Thermal annealing has been proved to be an effective method to reduce the propagation losses. For the cladding waveguide, the lowest propagation loss was as low as 0.38 dB/cm after the annealing treatment at 400 °C. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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     

Diode-pumped mode-locked femtosecond Tm:CLNGG disordered crystal laser

A diode-end-pumped passively mode-locked femtosecond Tm-doped calcium lithium niobium gallium garnet (Tm:CLNGG) disordered crystal laser was demonstrated for the first time to our knowledge. With a 790 nm laser diode pumping, stable CW mode-locking operation was obtained by using a semiconductor saturable absorber mirror. The disordered crystal laser generated mode-locked pulses as short as 479 fs, with an average output power of 288 mW, and repetition rate of 99 MHz in 2 μm spectral region.     

Low-threshold continuous-wave Tm3+:YAlO3 laser

We describe a continuous-wave, low-threshold Tm:YAlO₃ (Tm:YAP) laser operating at 1945 nm with incident threshold pump powers in the 10–20 mW range. The z-cavity containing a 2-mm-long Tm:YAP crystal with 4 at.% Tm³⁺ concentration was end pumped by a continuous-wave Ti:sapphire laser at 795 nm. Tight focusing of the pump and the laser beams enabled low-threshold operation. The power performance of two different cavity configurations with 5-cm radius (R = 5 cm cavity) and 10-cm radius (R = 10 cm cavity) curved mirrors was tested. The best performance was obtained with the R = 10 cm configuration, where, the incident threshold pump power could be lowered to 10 mW after optimizing the polarization direction of the pump beam and by employing double pumping. Theoretical estimation of the threshold power was in good agreement with the experimental observations. The laser could be further tuned from 1842 to 1994 nm.     

E(transverse optical)-mode properties in the LiTaO3: Nd crystal at room temperature

E(TO)-mode properties in LiTaO₃:Nd crystal were examined by analyzing the Raman spectra measured.E(TO) modes appear in the transverseA ₁ spectrum. Their intensities obviously increase in theE andE+A ₁ mixed-symmetry spectra but decrease in theE spectrum which shows new vibrational modes. In particular, in the transverse-E spectrum of y(xz) geometry, the properties ofE(TO) modes are similar to those of pure LiTaO₃ of the same geometry, whereas in the transverse-E spectrum in x(yz) geometry these modes are turned intoA ₁ (TO) modes. We attribute these properties to both the surface strain produced by mechanical polishing of the sample and the microstructural change of the LiTaO₃ crystal resulting from Nd doping.     

Optical spectroscopy and efficient continuous-wave operation near 2 μm for a Tm, Ho:KYW laser crystal

The growth, spectroscopy and lasing performance of a novel Tm,?Ho:KY(WO₄)₂ crystal are reported. The peak emission cross-section of the Ho^{3+ 5}I₇→⁵I₈ transition and lifetime of the ⁵I₇ excited state were determined to be 4.8×10^?20 cm² and 1.8 ms, respectively, in a spectral range at around 2060 nm. Using a Ti:sapphire laser as a pump source at 802 nm, a maximum slope efficiency of up to 44% has been achieved with a corresponding output power of 460 mW at 2056 nm during continuous-wave operation of a Tm,?Ho:KY(WO₄)₂ laser at room temperature. A tuning range of 1890–2080 nm has been demonstrated.     

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.     

Compact diode end-pumped c-cut Tm,Ho:YAlO3 laser

Cryogenic temperature operation of a c-cut Tm(5%),Ho(0.3%):YAlO₃ laser end-pumping by a fiber-coupled laser-diode is reported. A 2.55 W incident pump power is used to generate 160 mW of laser output, representing a 7.1% optical-to-optical conversion efficiency respect to the incident pump power. In the experiment, three wavelengths—2.04, 2.10, and 2.13 μm oscillation have been observed simultaneously, which is agreement with the inherent a-axis polarization fluorescence spectra of Tm,Ho:YAlO₃. Also single wavelength oscillation performance has been observed which is centered at 2.13 μm.     

Optical spectroscopy of Er:YSGG laser crystal

Er:YSGG single crystals with good optical quality were grown by Czochralski method. X-ray diffraction (XRD) measurements show that the crystal lattice parameters of the 30 at.% Er³⁺-doped YSGG crystal were a=b=c=12.4640±0.0065 Å, α=β=γ=90°. The doping concentration of Er³⁺ in YSGG was calculated. The absorption spectrum and photoluminescence spectra of Er:YSGG crystal were studied at room temperature. Based on Judd-Ofelt (J-O) theory, the J-O intensity parameters Ω_t (t=2, 4, 6), the experimental and theoretical oscillator strengths were calculated using the absorption spectrum. The intensity parameters Ω_t (t=2,4,6) obtained to be Ω₂=0.23×10⁻²⁰ cm², Ω₄=0.86×10⁻²⁰ cm², Ω₆=0.37×10⁻²⁰ cm², respectively. With these intensity parameters, the line strengths, oscillator strengths, transition probabilities, fluorescence branching ratios and radiation lifetimes were calculated. The photoluminescence spectra and excitation spectrum of Er:YSGG were measured and studied.     

Linear and nonlinear optical properties of MgO:LiTaO3

We derive new temperature dependent Sellmeier equations for the extra-ordinary and ordinary refractive indices of 0.5% MgO-doped stoichiometric LiTaO₃ crystal. The equations are based on quasi phase-matched frequency conversion measurements, as well as on interferometric measurements of the thermal expansion and thermal dispersion. These equations fit experimental data over wide spectral ranges: 0.35–6 μm for the extra-ordinary wave and 0.375–3.75 μm for the ordinary wave, from room temperature up to 200°C. The nonlinear optical measurements set lower-limit values for the d ₃₃, d ₂₂, and d ₂₄ elements of the second-order susceptibility tensor χ ⁽²⁾ of 12.9, 1.54, and 0.46 pm/V, respectively. The interferometric measurements enable one to determine the linear and quadratic expansion coefficients of 1.45762e?5 1/°C, and 2.68608e?8 (1/°C)², respectively. The Sellmeier equations are in good agreement with previously published data.     

Crystal growth,spectroscopic characterization and laser operation of Tm3+ and Ho3+ codoped LiLuF4 crystal

Laser crystal Tm³⁺ and Ho³⁺ codoped LiLuF₄ with high optical quality was grown by Czochralski technique. Its absorption and fluorescence spectra were investigated. A continuous wave output power of 1.12 W at 2066 nm was obtained with a slope efficiency of 24% by use of diode pumping. In the Q-switched mode, a slope efficiency of 18.9% and a maximum average power of 0.65 W were obtained.     

脉冲激光沉积Ag:BaTiO3纳米复合薄膜及其光学特性

在MgO(100)基片上利用脉冲激光沉积技术制备了掺有Ag纳米颗粒的BaTiO3复合薄膜.通过X射线衍射对薄膜的结构进行了表征,利用透射电子显微镜对Ag纳米颗粒的尺寸、形态进行了观测,X射线光电子能谱结果表明Ag呈金属态.在410-500 nm范围内观测到了Ag纳米颗粒引起的等离子振荡峰,随着后处理温度和Ag颗粒浓度的增加,吸收峰发生红移,并出现了双峰现象.     

The optical properties of Yb3+ ions in LiTaO3:Nd,Yb crystals

3+ ions excited by energy transfer from Nd³⁺ ions in LiTaO₃:Nd, Yb crystals are presented. The emission band of Yb³⁺ ions is broad, due to the strong phonon-coupling and to the relative large Stark-splitting of the ground ²F_7/2 multiplet. The emission cross-section was evaluated by the reciprocity method, and a value of 0.53×10^-20 cm² was obtained. The gain coefficients derived for the inversion parameters in the range 0.05 to 0.5 indicate positive gain in the 985–1070 nm range. Received: 17 March 1997/Revised version: 10 June 1997     

Optical properties and laser potential of dysprosium doped YAl 3 (BO 3 ) 4 (YAB) crystal

The absorption and emission spectra were measured at 5 and 300 v K. The positions of the selected Dy 3+ levels and their Stark components, determined from optical spectra at 5K, are presented. In this work an attempt is made to assess the potential of dysprosium doped YAl 3 (BO 3 ) 4 crystal as a laser active material operating near 570 v nm. The emission cross-section of a potential laser line at 570 v nm connected with 4 F 9/2 M 6 H 13/2 transition was estimated.     

Diode pumped actively mode-locked Tm:YAlO3 laser

CW acousto-optical mode-locked diode pumped Tm:YAlO₃ laser at 1.936 μm was experimentally studied. Lasing with output power ～100 mW, pulse repetition rate 103.4 MHz and laser pulse durations in the range of 30–200 ps was realized. The problem of laser intensity stabilization is discussed.