High power external-cavity surface-emitting laser with front and end pump

High power optically pumped vertical-external-cavity surface-emitting lasers with front and end pump are reported. The gain chip consists of 15 repeats of In_(0.26)GaAs/GaAsP_(0.02) multiple quantum wells and 30 pairs of Al_(0.2)GaAs/Al_(0.98)GaAs distributed Bragg reflectors. The maximum output power of 3 W, optical-to-optical conversion efficiency of 22.4%, and slope efficiency of 29.8% are obtained with 5-℃ heatsink temperature under the front pump,while the maximum output power of 1.1 W, optical-to-optical conversion efficiency of 23.2%, and slope efficiency of30.8% are reached with 5-℃ heatsink temperature under the end pump. Influences of thermal effects on the output power of the laser with front and end pump are discussed.     

高速850 nm垂直腔面发射激光器的优化设计与外延生长

利用传输矩阵理论和TFCalc薄膜设计软件分析了分布布拉格反射镜和垂直腔面发射激光器(VCSEL)的反射率谱特性,对比了从谐振腔入射与从表面入射时反射率谱的差异,为白光反射谱表征VCSEL外延片提供了依据.利用Crosslight软件模拟了InGaAs/AlGaAs应变量子阱的增益谱随温度的变化特性及VCSEL器件内部温度分布,设计了增益-腔模调谐的VCSEL.采用金属有机物化学气相淀积设备外延生长了顶发射VCSEL,制作了氧化孔径为7.5μm的氧化限制型VCSEL器件,测试了器件的直流特性、光谱特性和眼图特性;6 mA,2.5 V偏置条件下输出光功率达5 mW,4级脉冲幅度调制传输速率达50 Gbit/s.     

Dual-wavelength Nd:YAG crystal laser at 1074 and 1112 nm

We reported an efficient laser-diode (LD) end-pumped CW dual-wavelength Nd:YAG crystal laser operating at 1074 and 1112 nm simultaneously, for the first time to our knowledge. The maximum output power was 3.15 W with an optical conversion efficiency of 23.6%. Considering the broad absorption of carbonylhemoglobin and hemoglobin located at about 538 and 555 nm, respectively, we proposed that this dual-wavelength laser is an important source for detecting carbon monoxide poisoning by simple frequency doubling.     

Modeling and control of tunable vertical cavity laser diode

Micromachined tunable vertical cavity laser diodes (VCLDs) are advantageous for wavelength division multiplexing applications due to their substantial and continuous wavelength tuning range. The present paper reports the effects of closed loop control on these devices. Such use substantially improves the performance of VCLDs. Results from several simulation studies showed that the overshoot was eliminated, the tuning range significantly increased and voltage displacement function linearized. The deformation of the mirror surface was calculated using the Finite Element method and a mathematical model was computed using the Multiple Model approach.     

Dual-wavelength laser operation at 1061 and 942 nm in Nd:GSAG

A dual-wavelength continuous-wave (CW) diode end-pumped gadolinium scandium aluminum garnet (Nd:GSAG) laser that generates simultaneous laser action at the wavelengths 1061 and 942 nm is demonstrated. A total output power of 589 mW (476 mW at 1061 nm and 113 mW at 942 nm) for the dual-wave-length was achieved at the incident pump power of 18.2 W. The M ² values for 942 and 1061 nm lights were found to be around 1.18 and 1.37, respectively.     

Invited Paper: Design and modeling of a transistor vertical-cavity surface-emitting laser

A multiple quantum well (MQW) transistor vertical-cavity surface-emitting laser (T-VCSEL) is designed and numerically modeled. The important physical models and parameters are discussed and validated by modeling a conventional VCSEL and comparing the results with the experiment. The quantum capture/escape process is simulated using the quantum-trap model and shows a significant effect on the electrical output of the T-VCSEL. The parameters extracted from the numerical simulation are imported into the analytic modeling to predict the frequency response and simulate the large-signal modulation up to 40 Gbps.     

Single polarization, single transverse mode, and widely tunable narrow-linewidth laser from a multimode vertical cavity surface-emitting laser by use of a coupled cavity

A simple method for achieving a widely tunable narrow-linewidth, single polarization state and single transverse mode lasing oscillation from a commercially available multimode vertical cavity surface-emitting laser by use of a coupled cavity is reported. The laser has a wavelength tuning range of more than 5 nm along 850 nm, a side-mode suppression ratio of approximately 15 dB, and an output power of approximately 0.3 mW from a 50-microm multimode optical fiber at a bias current of 15 mA. The laser was operated in a single state of polarization lasing oscillation without any polarization switching.     

光注入和光电反馈联合作用下垂直腔表面 发射激光器的动力学特性研究

基于自旋反转模型, 研究了垂直腔表面发射激光器(VCSEL) 在光注入和光电反馈共同作用下的动力学特性. 研究结果表明: 一个受到主VCSEL光注入的副VCSEL, 在同时存在光电正反馈时, 其输出的两个线偏振模式(X和Y偏振模) 可呈现周期、 倍周期、 多周期、 混沌等丰富的动力学状态, 且两偏振模动力学态的演化路径存在差异. 各动力学状态在由反馈强度f与注入强度η 所构成的参数空间的分布区域随着主、 副VCSEL 的频率失谐Δν(Δν=ν_m-ν_s, ν_m, ν_s 分别为主、 副VCSEL自由运行时的振荡频率) 的变化而发生改变. 当Δν为正失谐时, 呈现混沌的区域相比零失谐和负失谐时有明显的扩展, 即副VCSEL能在更大的参数范围内实现混沌输出. 对于特定的频率失谐, 分析了光电正反馈强度f和光注入强度η对混沌输出带宽的影响. 通过合理选择反馈强度以及注入强度, 可使副VCSEL混沌输出带宽显著增加.     

Correction to: Statistical and strict momentum conservation

International Journal of Theoretical Physics - The author found a mistake in their published article. The eqs. 9 and 10 are incorrect.     

Erratum to Formation and control of Au and Ag nanoparticles inside borate glasses using femtosecond laser and heat treatment

We report the spectroscopic properties of femtosecond laser-irradiated sodium-alumino-borate glass doped with silver and gold ions. We precipitated gold and silver nanoparticles by laser irradiation and annealing at 400°C for 30 min. The irradiation and annealing treatment produced different absorption and emission characteristics in Au³⁺ doped and Au³⁺, Ag⁺ codoped glasses, and the possible mechanisms of the observed results are discussed. The size of the nanoparticles was estimated by TEM and absorption band analysis.     

Dual-wavelength Nd:YAP laser at 930 and 1341 nm and sum-frequency mixing for an emission at 549 nm

A dual-wavelength continuous-wave (CW) diode end-pumped Nd³⁺:YAlO₃ (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 930 and 1341 nm is demonstrated. A total output power of 778 mW for the dual-wavelength was achieved at the incident pump power of 17.8 W. Furthermore, intracavity sum-frequency mixing at 930 and 1341 nm was then realized in a LBO crystal to reach the yellow-green range. We obtained a total CW output power of 103 mW at 549 nm.     

Dual-wavelength diode-pumped laser operation of N p-cut and N g-cut Tm:KLu(WO4)2 crystals

Simultaneous continuous-wave laser oscillation at two wavelengths has been observed and studied in a diode-pumped monoclinic N _p-cut Tm:KLu(WO₄)₂ for different transmission of the output coupler. The maximum output power reached 1.15 W with a slope efficiency of 20.4 % with respect to the absorbed power for polarization parallel to the N _m optical axis. In an analogous N _g-cut crystal, the dual-wavelength laser operation is accompanied by polarization switching with increasing pump power and the switching point depends on the output coupling. The thresholds are slightly higher, and the slope efficiency reached a maximum of 25.5 % for polarization parallel to N _m at low pump levels, but at high pump levels, the oscillating polarization is parallel to N _p, reaching maximum output power of 3.09 W. Simple modelling with rate equations taking into account reabsorption losses explains qualitatively the complex behavior observed in the continuous-wave laser experiments with this anisotropic biaxial laser crystal.     

Erratum to: Allan-variance measurements of diode laser frequency-stabilized with a thin vapor cell

A novel method of stabilizing laser frequency that uses a sub-Doppler spectrum of atoms in a thin vapor cell has been developed. The extended-cavity diode laser is frequency-locked to a hyperfine component of the Cs D₂ line. The linewidth and the signal-to-noise ratio of the spectrum are systematically investigated to find a cell length that gives best long-term frequency stability. In the Allan-variance measurements on the beat note between two lasers thus stabilized, a frequency stability of 6.2×10^-11 is achieved at an averaging time of 5 s. PACS 42.62.Fi, 42.60.Lh, 39.30.+w     

Polymer ablation: From fundamentals of polymer design to laser plasma thruster

UV-Laser ablation of polymers is a well-established method to structure and deposit polymers, but the mechanisms of ablation are still controversial, i.e. photothermal or photochemical processes. An approach to probe the ablation mechanisms and to improve ablation is to incorporate photoactive groups into the polymer structure.The investigation of the ablation behavior of designed triazene polymers showed that the ablation mechanism is always a combination of both photothermal and photochemical processes, but the ratio can be changed by using different polymers and irradiation wavelengths. Also the quality of structures in the triazene polymers is superior at an irradiation wavelength of 308 nm compared to commercially available polymers.Polymers can be designed not only for UV irradiation, but also for applications in the IR range, but with different requirements. One application for designed polymers in the near-IR range is as fuel for the laser plasma thruster, which is used as propulsion system for small satellites. With commercially available polymers the necessary thrust could not be achieved. A specially designed polymer-absorber system for this application produce more energy in the form of thrust, than the laser delivered.     

Real-time volumetric growth rate measurements and feedback control of three-dimensional laser chemical vapor deposition

Received: 4 June 1997/Accepted: 12 June 1997     

In-situ thin film growth/etch measurement and control by laser light reflectance analysis

In this article, I report in-situ thin film growth and etching measurement and control with ultra high precision. A stack of thin film layers of AlAs/Al_0.1Ga_0.9As to form Bragg reflector for the surface emitting semi-conductor laser was grown by gas source molecular beam epitaxy on a rotating wafer and the growth process was monitored with inclined incident polarized He–Ne laser light reflectance measurement. The multiple thin film layers were preferred to increase the visibility of the oscillating intensity variation signal for feasibility experiments. The inferred growth rate from the reflectance analysis was found to be 0.15 nm/s which remained in agreement with set growth parameters. The laser light reflectance analysis method was also employed for in-situ control and measurement of thin film etching process. The inferred etching rate was found to be 0.75 nm/s by the chemical etchant H₃PO₄:H₂O₂:H₂O::3:1:100. Calibrated optical reflectance signal for growth and etching process is proposed for measuring and control their respective thickness and depth with very high accuracy and precision.