CO and CO2 spectroscopy using a 60 nm broadband tunable MEMS-VCSEL at approximately 1.55 microm

The spectroscopic application of a new broadband microelectromechanical-system-tunable vertical cavity surface-emitting laser with single-mode coverage of 60 nm (245 cm(-1)) in a single, continuous sweep is described. The operation of the device is illustrated with high-resolution spectra of CO and CO2 over 110 cm(-1) (27 nm) and 67 cm(-1) (17 nm), respectively, with the CO band shown for high-pressure scans between 1 and 3 bars (0.1-0.3 MPa). The achieved tuning range opens up new opportunities for tunable diode laser absorption spectroscopy. The spectra were compared with HITRAN-derived model calculations. The benefits of a sensor based on this laser are greater speed, laser power, and tuning range.     

10-W-level diode-pumped compact 2.78 microm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 mum from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.     

Continuous-wave Raman laser pumped within a semiconductor disk laser cavity

A KGd(WO?)? Raman laser was pumped within the cavity of a cw diode-pumped InGaAs semiconductor disk laser (SDL). The Raman laser threshold was reached for 5.6 W of absorbed diode pump power, and output power up to 0.8 W at 1143 nm, with optical conversion efficiency of 7.5% with respect to the absorbed diode pump power, was demonstrated. Tuning the SDL resulted in tuning of the Raman laser output between 1133 and 1157 nm.     

Electrically tunable slow and fast lights in a quantum-dot semiconductor optical amplifier near 1.55 microm

We have demonstrated both slow light in the absorption regime and fast light in the gain regime of a 1.55 microm quantum-dot semiconductor optical amplifier at room temperature. The theory with coherent population oscillations and four-wave mixing effects agrees well with the experimental results. We have observed a larger phase delay at the excited state than that at the ground state transition, likely due to the higher gain and smaller saturation power of the excited state.     

Continuous-wave laser at 453 nm based on frequency-doubled diode-pumped Nd:ASL crystal

Efficient and compact is generated by intracavity frequency doubling of a diode-pumped Sr_1−x La _{x − y} Nd _y Mg _x Al_{12 − x} O₁₉(Nd:ASL) laser at 906 nm. With 10.3 W of diode pump power and the frequency-doubling crystal LiB₃O₆ (LBO), a maximum output power of 281 mW in the blue spectra] range at 453 nm has been achieved, corresponding to an optical-to-optical conversion efficiency of 2.7%; the output power stability over 4 h is better than 3.8%.     

Intracavity frequency doubling of a diode-pumped external-cavity surface-emitting semiconductor laser

We present a compact, robust, solid-state blue-light (490-nm) source capable of greater than 5 mW of output in a TEM(00) mode. This device is an optically pumped, vertical external-cavity surface-emitting laser with an intracavity frequency-doubling crystal.     

Intra-cavity second-harmonic and sum-frequency generation in a diode-pumped broadband Yb-doped fibre laser

Intra-cavity nonlinear frequency mixing in a diode-pumped, broadband Yb-doped fibre laser has been investigated. Second-harmonic generation of the fibre output, second-harmonic generation of the residual pump beam and sum frequency mixing between the two was achieved simultaneously, resulting in three colour operation in the blue-green region. Including the nonlinear crystal inside the cavity is also shown to be effective in reducing fluctuations in the output power.     

Continuous-wave laser at 440 nm based on frequency-doubled diode-pumped Nd:GdVO(4) crystal

We present for the first time, to the best of our knowledge, a frequency-doubled Nd:GdVO(4) laser operating in a cw on the pure three-level laser line at 880 nm. We obtained 300 mW at 440 nm for 23 W of incident pump power at 808 nm. Moreover, with a 25% output coupler we obtained a cw power of 1.9 W at the fundamental wavelength at 880 nm.     

Ultrafast laser spectroscopy of semiconductor nanocrystals

A large amount of work has been worldwide directed to understand the properties of semiconductor nanostructures. Ultrafast lasers with pulsewidths of a few femtoseconds allowed the investigation of the dynamics of elementary excitations in semiconductor structures on ultrashort time scales. Recent progress in technology made it possible to fabricate semiconductor nanocrystals (i.e. crystals of nanometer dimensions) of well-defined properties. The purpose of this paper is to review the understanding of carrier relaxation and recombination processes in semiconductor nanocrystals as studied by ultrafast laser spectroscopy. The up-to-date techniques of ultrafast laser spectroscopy as well as the fabrication of semiconductor nanocrystals are discussed in some detail.     

高功率垂直外腔面发射半导体激光器增益设计及制备

垂直外腔面发射半导体激光器(vertical external cavity surface emitting laser, VECSEL)兼具高功率与良好的光束质量,是半导体激光器领域的持续研究热点之一.本文开展了光抽运VECSEL最核心的多量子阱增益区设计,对量子阱增益光谱及其峰值增益与载流子浓度及温度等关系进行系统的理论优化,并对5种不同势垒构型的量子阱增益特性进行对比,证实采用双侧GaAsP应变补偿的发光区具有更理想的增益特性.对MOCVD生长的VECSEL进行器件制备,实现了VECSEL在抽运功率为35 W时输出功率达到9.82 W,并且功率曲线仍然没有饱和;通过变化外腔镜的反射率, VECSEL的激光波长随抽运功率的漂移系数由0.216 nm/W降低至0.16 nm/W,证实外腔镜反射率会影响VECSEL增益芯片内部热效应,从而影响VECSEL激光输出功率.所制备VECSEL在两正交方向上的发散角分别为9.2°和9.0°,激光光斑呈现良好的圆形对称性.     

水平腔面发射半导体激光器研究进展

近年来,水平腔面发射半导体激光器具有高功率、高光束质量及易封装集成等优良性能,已成为激光器领域的研究热点。本文详细阐述了几种水平腔面发射半导体激光器的结构设计、工作原理以及激光输出特性,并对该激光器国内外最新研究进展与发展现状进行了总结和论述。在此基础上,对该激光器的研究方向和发展趋势进行了分析与展望。目前,水平腔面发射半导体激光器的激光输出功率可达瓦级,美国Alfalight公司引入曲线形光栅的单一发射器输出功率可达73 W。随着应用领域的不断拓展,中远红外波段水平腔面发射激光器将成为未来的研究焦点。     

Continuous-wave single-frequency 532 nm laser source emitting 130 W into the fundamental transversal mode

The nonlinear effect of second-harmonic generation is an efficient way to realize high-power green laser sources. But when scaling up the harmonic power, many setups reported in the literature have been limited by conversion efficiency degradation or the fundamental laser power. Here we report on the generation of 134 W of cw laser light at a wavelength of 532 nm from a fundamental power of 149 W by second-harmonic generation in an external optical resonator comprising a lithium triborate crystal. The external conversion efficiency was 90%. The harmonic light consisted of a single spectral line. At least 97% of it was emitted into the fundamental transversal mode.     

利用半导体激光器环产生27 GHz的平坦宽带混沌激光

关键词： 激光器 混沌 宽带 环形结构     

Picosecond laser for performance of efficient nonlinear spectroscopy from 10 to 21 microm

Laser tunability from 10 to 21 microm is obtained by use of an optical parametric oscillator based on a KTP crystal followed by a difference-frequency stage with a CdSe crystal. An all-solid-state picosecond Nd:YAG oscillator mode locked by a frequency-doubling nonlinear mirror is used for synchronous pumping.     

Room temperature CW lasing operation of monolithically grown 1.55 μm vertical external cavity surface emitting laser

We report room temperature (20 °C) continuous-wave operation of 1.55 μm vertical-external-cavity surface-emitting lasers. The optically pumped monolithic InP-based structure, grown by metal–organic chemical vapor deposition, includes a InP/InGaAsP Bragg reflector, and an active region with strain compensated quantum wells. Output power up to 4 mW is obtained at 0 °C. The thermal impedance of the structure is deduced from the experimental data.     

High-power, (AlGaIn)(AsSb) semiconductor disk laser at 2.0 microm

We report a high-power (AlGaIn)(AsSb) semiconductor disk laser emitting around 2 microm. With a diamond heat spreader used for thermal management, a maximum output power of just over 5 W and slope efficiencies of over 25% were demonstrated. The output wavelength was tunable over an 80 nm range centered at 1.98 microm. The beam propagation parameter (M2) was measured to be in the range of 1.1 to 1.4 for output powers up to 3 W.     

Continuous-wave Raman generation in a diode-pumped Nd3+:KGd(WO4)2 laser

Continuous-wave Raman generation in a compact solid-state laser system pumped by a multimode diode laser is demonstrated. The Stokes radiation of stimulated Raman scattering at 1.181 microm is generated as a result of self-frequency conversion of the 1.067 microm laser radiation in Nd3+:KGd(WO4)2 crystal placed in the cavity. The Raman threshold was measured at 1.15 W of laser diode power. The highest output power obtained at the Stokes wavelength was 54 mW. The anomalous delay of Raman generation relative to the start of laser generation (the oscillation buildup) due to slow accumulation of Stokes photons in the cavity at low Raman gain and Raman threshold dependence not only on the laser intensity but also on the time of laser action are observed.     

表面等离子体调制单模面发射激光器的研究

对单模面发射半导体激光器的研究随着其应用的不断扩展而引起了人们的广泛的重视,应用多种方法可以提高其输出功率并改善其模式抑制比.利用金属表面等离子体纳米结构调制的方法可以获得单模面发射激光器输出功率的提高,理论计算表明这种方法增强效应可达近50%. 关键词： 表面等离子体 单模面发射激光器 模式选择     

Tunable carbon monoxide overtone laser sideband system for precision spectroscopy from 2.6 to 4.1 microm

We report a source of tunable laser radiation for high-precision molecular spectroscopy in the 2.6- 4.1-microm spectral region. Laser light from a CO overtone laser is mixed with microwaves, generating tunable sidebands of ~1 mW of power. We achieve very high absolute frequency accuracy by frequency-offset locking the CO laser to a CO(2) laser secondary frequency standard. The uncertainty of the laser frequency is less than 30 kHz (Dnu/nu=3x10(-10)) , and the laser linewidth is of the order of 100 kHz. This tunable and ultrastable laser system is suitable for very accurate molecular spectroscopy and metrology in a most interesting wavelength region. We demonstrate an application of the system to saturated-absorption spectroscopy of a rovibrational transition of carbonyl sulfide.     

LiGdF4:Tm3+: spectroscopy and diode-pumped laser experiments

A novel LiGdF₄ crystal doped with Thulium ions has been grown using the Czochralski technique. Three samples with doping concentrations of 0.3 at.%, 8 at.%, and 12 at.% have been extensively spectroscopically analyzed. We also performed room-temperature preliminary laser experiments, pumping the samples with a laser diode at 792 nm obtaining 53% as maximum slope efficiency with a maximum output power of 205 mW and a minimum lasing threshold of 22 mW. The laser emission spectrum in free running condition typically spans between 1990 and 2018 nm.