Output mode characteristics of an in-phase locked gain waveguide array CO2 laser

In this paper,experimental and theoretical studies of the output mode characteristics of an in-phase locked gain waveguide array CO 2 laser are reported.The experimental results of the optical oscillation mode frequency,the far-field intensity distribution and the burnt pattern of the sliced waveguide array laser are obtained.A revised mode expression of the rectangle waveguide,which is suited for this waveguide array CO 2 laser,is proposed.The theoretical simulation results based on the revised mode expression are shown to be in good agreement with the experimental results.     

Evaluation of optical propagation and radiation in optical waveguide using a numerical method

We introduce a mathematical model based on a concept of intrinsic mode in order to analyse and synthesise optical wave propagation and radiation occurring in a non-uniform optical waveguide used in integrated optics as optical coupler. The model is based on numerical evaluation of electromagnetic wave by applying an intrinsic field integral to evaluate the field behaviour inside the optical waveguide. To analyse the field distribution inside the non-uniform waveguide and predict the beam propagation of optical energy involved in the propagation process, it is necessary to track the motion of any observation point along the tapered waveguide itself. Physically, the rays of the spectrum undergo reflections on the waveguide boundaries until the cut-off occurs and the phenomena of radiation begin. The numerical results show good agreement with those obtained by classical methods of evaluation used bv other works.     

Study on diffraction characteristics of a planar diamond waveguide

A numerical simulation is performed to study the far-field diffraction properties of planar diamond waveguides.The far-field intensity distributions of a planar air waveguide and a diamond waveguide with different distances are given by numerical calculations.In the experiment,the diffraction patterns on the screen with different distances are recorded using a He-Ne laser as the light source,wherein the laser beam is coupled with and propagates in the diamond waveguide.The simulation results are found to be consistent with the experimental ones.     

Intensity Spatial Profile Analysis of a Gaussian Laser Beam at Its Waist Using an Optical Fiber System

In many applications, it is important to know the waist of a laser beam. However, it is impossible to measure it directly because the intensity is high at the waist. We have used an optical fiber-scan system to characterize the Gauss/an intensity profile of a focused femtosecond laser beam. The measurement system employs a single-mode optical fiber that is fixed on a motorized three-dimensional translation stage to collect the laser energy and the other end is connected to an optical power meter to measure the intensity profile. Using the measure data and geometry formulas, one can calculate the beam waist and far-field divergence angle of a laser beam. The measured beam waist size is essentially consistent with the result of theoretical fit.     

Theoretical analyses on improved beam properties of GaSb-based 2.X-μm quantum-well diode lasers with no degradation in laser parameters

An asymmetric laser heterostructure is developed to improve the beam properties of GaSb-based diode lasers with no degradation in laser parameters.Employing the semivectorial finite difference method,the dependences of beam divergence and optical confinement factor on waveguide width and refractive index step are investigated theoretically.After carefully design,a particular asymmetric laser structure is proposed.Its beam divergence in the fast axis is reduced from 61° to 34° compared with that of the broad-waveguide structure.The optical confinement factor is approximately equal to 0.0362 and comparable to that of the conventional broad-waveguide structure.     

Optical cavity coupled surface plasmon resonance sensing for enhanced sensitivity

A surface plasmon resonance(SPR)sensing system based on the optical cavity enhanced detection tech- nique is experimentally demonstrated.A fiber-optic laser cavity is built with a SPR sensor inside.By measuring the laser output power when the cavity is biased near the threshold point,the sensitivity,defined as the dependence of the output optical intensity on the sample variations,can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity interrogation scheme. This could facilitate ultra-high sensitivity SPR biosensing applications.Further system miniaturization is possible by using integrated optical components and waveguide SPR sensors.     

An optically pumped GaN/AlGaN quantum well intersubband terahertz laser

We propose an optically pumped nonpolar GaN/AlGaN quantum well(QW) active region design for terahertz(THz) lasing in the wavelength range of 30 μm～ 40 μm and operating at room temperature.The fast longitudinal optical(LO) phonon scattering in GaN/AlGaN QWs is used to depopulate the lower laser state,and more importantly,the large LO phonon energy is utilized to reduce the thermal population of the lasing states at high temperatures.The influences of temperature and pump intensity on gain and electron densities are investigated.Based on our simulations,we predict that with a sufficiently high pump intensity,a room temperature operated THz laser using a nonpolar GaN/AlGaN structure is realizable.     

Femtosecond Laser-Written Waveguides in a Bismuth Germanate Single Crystal

We demonstrate the fabrication of symmetric waveguides in a bismuth germanate （BGO） single crystal using a double line approach by an 80Ohm [emtosecond laser. The optical attenuation of the single mode waveguide is measured to be 4.2 dB/cm at 633nm. The influence of pulse energy and focal depth on the end facet of the irradiated region is also studied. This technique is promising to fabricate buried BGO waveguide arrays used in positron emission tomography systems.     

Configuration of an optical waveguide interconnect mesh network based on EOPCB

<正>An optical waveguide interconnect mesh network scheme for parallel multiprocessor systems based on an electro-optical printed circuit board(EOPCB) with multimode polymer waveguide is proposed.The system consists of 2×2 processor element chips interconnected in a mesh network configuration.An additional layer with optical waveguide structure is embedded in a conventional printed circuit board to construct the EOPCB.Vertical cavity surface emitting laser(VCSEL)/positive intrinsic-negative(PIN) arrays are applied as the optical transmitters/receivers.Three 1×12 VCSEL/PIN parallel optical transmitting/receiving modules are used to provide 32 input/output optical channels required by the 2×2 chip-to-chip optical mesh interconnect system.The data rate in each optical channel is 3.125 Gbps and thus 10 Gbps parallel optical interconnect link for each direction of a chip is obtained.The optical signals from a processor element chip can be transmitted to another chip through optical waveguide interconnect embedded in the board.Thus the optical interconnect mesh network for parallel multiprocessor system can be implemented.     

Narrowband switchable dual-passband atomic filter with four-wave mixing optical amplification

By using Faraday optical filter combined with four-wave mixing (FWM) amplifier, a narrow bandwidth optical amplifying atomic filter with switchable dual-passband is demonstrated experimentally. The two transmission peaks of the filter correspond to the Stokes and anti-Stokes frequencies, exhibiting a Raman gain in 13- and 17-fold, respectively, with bandwidth of ～120 MHz. By properly setting pump laser detuning, switching between filter passbands is realized. We also investigate the dependence of peak transmission on both pump laser intensity and Rb cell temperature. This atomic filter can find practical applications in long-distance laser communications and laser remote-sensing systems.     

磁液磁光双稳特性的研究

本文基于磁液磁致双折射效应,实现了其磁光双稳特性的研究。理论上,建立了其磁光双稳传输模型、进行了计算机模拟,并在此基础上建立了相应的实验分析系统。研究表明:磁液薄膜具有良好的磁光双稳特性,可用作超长波红外波导器件。     

Passive mode-locking by use of waveguide arrays

A novel mode-locking technique is presented in which the intensity-dependent spatial coupling dynamics of a waveguide array is used to achieve temporal mode-locking in a passive optical fiber laser. By use of the discrete, nearest-neighbor spatial coupling of the waveguide array, low-intensity light can be transferred to the neighboring waveguides and ejected (attenuated) from the laser cavity. In contrast, higher-intensity light is self-focused in the waveguide and remains largely unaffected. Numerical studies of this pulse shaping mechanism (intensity discrimination) show that using current waveguide arrays and standard optical fiber technology produces stable and robust mode-locked soliton-like pulses.     

自由载流子吸收损耗控制研究

利用数值方法研究了SOI脊形光波导损耗问题,重点讨论了PIN结构对自由载流子损耗控制的影响情况。研究表明SOI脊形波导在引入PIN结构后,偏置电压、入射光强和本征区宽度是影响自由载流子吸收损耗的主要因素,通过调整PIN结所加偏置电压、入射光强和本征区宽度,可以实现对脊形波导自由载流子吸收损耗的控制。计算结果可为硅基光调制器和拉曼激光器的设计制备提供一定的参考依据。     

An azobenzene functionalized polymer for laser direct writing waveguide fabrication

We report on non-lithographic laser direct writing fabrication of optical waveguides by using a 4′-hydroxy-4-nitroazobene dye-functionalized polymer film. The polymer film reveals permanent change of refractive index at high laser illumination intensity. A focused continuous wave low power green laser beam at 532 nm wavelength is used to directly write waveguide structures on the polymer film. The magnitude of refractive index increase at film surface is about 0.006. One-step laser writing results in graded index waveguides in film depth direction under ambient conditions without pre- and post-processing. As a by-product, the laser writing also results in a very small air valley at the boundary between the laser written and non-written regions which may contribute in part although minimal to the waveguide lateral confinement and can be used for visual observation of waveguide patterns. The fabricated waveguide is found to be stable and easily reproducible.     

原油含水率测量的光学计量仪

油井含水率是油田开发过程中的一个重要指标。光纤传感器具有体积小、重量轻、抗干扰能力强、实时、高效、准确等优点,将其应用于石油测井,有利于提高勘探效率。介绍测井应用中原油含水率计量仪的结构,分析了光纤传感器对混合液体含水率测量的基本原理。激光在弯曲光纤中的传输效率随外界混合介质折射率的变化而改变,根据光纤输出光功率的大小可以测量外界混合介质的组成成分。通过数值模拟,给出了光纤传感器中光束强度随混合液体含水率的变化现象,计算得到混合液体中含水率测量结果。结果表明,光纤传感器计量仪能实现0%～100%含水量的连续测量。最后基于数值模拟结果讨论了系统设计中的注意事项。     

基于波导、金和氧化锌的随机激光器的研究

通过将金属金嵌入到上下两层波导结构中,与ZnO随机粒子相结合,设计出一种新型结构的随机激光器。采用时域有限差分法(FDTD),数值模拟了该随机激光器系统的光场分布和模式频谱图,并针对金粒子和金薄膜两种情况进行对比分析。结果显示,采用金粒子作夹层时,出射激光模式数量减少,单色性较好;采用金薄膜作夹层时,出射激光光强较大。     

基于振动弛豫理论提高光抽运太赫兹激光器输出功率的研究

以半经典密度矩阵理论和分子振动弛豫理论为基础,研究添加适当比例缓冲气体与适当减小波导芯径对光抽运太赫兹激光器输出光强的影响.计算结果表明,加入适当比例缓冲气体或适当减小波导的芯径均能提高太赫兹激光的输出光强;同时优化两个参数能进一步提高抽运激光能量转化为太赫兹激光能量的效率,延长工作腔中的有效激活区,延缓抽运饱和效应的出现,提高太赫兹激光输出光强.该研究对提高光抽运太赫兹激光器的能量转化效率、提高光抽运太赫兹激光器的输出功率及实现光抽运太赫兹激光器的小型化有重要的指导意义.     

Optical cavity coupled surface plasmon resonance sensing for enhanced sensitivity

A surface plasmon resonance (SPR) sensing system based on the optical cavity enhanced detection tech-nique is experimentally demonstrated. A fiber-optic laser cavity is built with a SPR sensor inside. By measuring the laser output power when the cavity is biased near the threshold point, the sensitivity, defined as the dependence of the output optical intensity on the sample variations, can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity interrogation scheme. This could facilitate ultra-high sensitivity SPR biosensing applications. Further system miniaturization is possible by using integrated optical components and waveguide SPR sensors.     

基于倏逝场耦合的石墨烯波导光传输相位特性仿真与实验研究

石墨烯材料应用到各种光波导器件中正成为新一代光子器件的重要发展方向之一,目前基于石墨烯的光纤和集成光子器件研究越来越受到国内外的重视. 本文建立了一种由微纳光纤耦合光倏逝场,并在石墨烯薄膜中传输的模型. 通过有限元分析法,研究了光在这种石墨烯波导中传输光场的强度分布和相位特性,并通过实验进行了验证. 结果表明,沿着微纳光纤-石墨烯光波导传播的倏逝场的强度分布和相位均受石墨烯材料作用,石墨烯材料能有效聚集和导行波导中传输的高阶模,在单位传输长度上具有更密集的等相位面. 本文提出了一种利用微纳光纤耦合光倏逝场研究石墨烯相位响应特性的新方法,对基于石墨烯波导的新型调制器、滤波器、激光器和传感器等光子器件的设计和应用具有一定的参考意义. 关键词： 石墨烯平面光波导 倏逝波 光场强度 相位