连续变量量子密钥分发系统中调制器驱动设计

相位调制器与振幅调制器是连续变量量子密钥分发中不可缺少的光调制器件.本文以量子安全通信系统的硬件为平台,设计了LiNbO3相位调制器的驱动电路,性能测试电路,同时给出了振幅调制器的性能监控电路.从理论与实验上对方案的可行性与可靠性进行了验证.     

GaAs脊型波导Mach-Zehnder干涉调制器

半导体电光波导调制器是半导体集成光学中具有代表性的器件之一,在光纤通讯、光信息处理等方面有着广阔的应用前景。它能和半导体激光器、探测器、电子线路等各种光、电元件实现单片集成,使设备和系统减少接口,缩小体积,提高可靠性。随着光通讯的发展,半导体调制器件的研究也越来越受到重视,在理论分析、结构设计、材料研制和器件工艺技术等方面也都取得了很大进展。由于GaAs材料具有良好的电、光性能,首先被用于制作GaAs光波导Mach-Zehnder干涉调制器中。     

Nondestructive measurement of loss performance in channel waveguide devices with phase modulator

A novel method using a phase modulator is proposed for the nondestructive measurement of propagation loss in a channel waveguide. The phase modulator was fabricated on a Ti-diffused LiNbO3 crystal. Tuning the effective optical length of a waveguide by application of an electrical field on the phase modulator, the contrast of the resultant Fabry-Perot resonator in a channel waveguide device can be measured. The associated propagation attenuation coefficients are determined from the experimental results. Coordination of the phase modulator with an optical channel waveguide device not only allows measurement of the bending loss, but improvement in the relative intensity noise owing to the reduction of the reflected power.     

Wideband magneto-optic modulation in a bismuth-substituted yttrium iron garnet waveguide

We present a tunable wideband bismuth-substituted yttrium iron garnet (Bi-YIG) waveguide magneto-optic (MO) modulator. High-speed current transients are used to switch the in-plane magnetization of the film, which modulates an 800 nm optical beam. Large bandwidth optical modulation is achieved by driving the device in a non-resonant mode that is well below the ferromagnetic resonance frequency of the film. The MO modulator has the potential of operating at bandwidths higher than 1 GHz by tuning the applied static magnetic field.     

450kV高功率速调管调制器系统

研制了一套用于新型速调管测试的450 kV高功率调制器系统。根据系统指标分别设计了脉冲变压器、脉冲形成网络以及充电电路等主要部件。同时,针对高功率脉冲开关的要求,对闸流管相关性能进行了比较研究,并对其触发、保护电路作了优化设计。并利用可编程控制器与触摸屏组合方式实现了调制器和速调管的控制与连锁保护。利用电力电子仿真软件Saber对调制器主电路进行了建模与仿真,脉冲电压波形仿真结果与在水负载上进行的满功率试验结果一致:脉冲宽度2.5μs,脉冲前沿1.1μs,脉冲后沿1.7μs。调制器输出脉冲电压450 kV,脉冲电流600 A,满足速调管测试需要。     

Ultra-Broad-Band LiNbO3 Electro-Optic Modulators with Novel Complex Electrode

The characteristics of Z- cut LiNbO3 optical modulators with novel complex electrode are discussed by using the finite element method (FEM) and studied experimentally in this paper. The travelling wave electrode consists of upper and lower parts. It can easily realize phase velocity matching between microwave and optical wave and drastically reduce microwave electrode loss. An electrooptic modulator with larger than 100 GHz bandwidth and half wave voltage 6 V is designed, fabricated and measured. Vπ is 5.1 V and the attenuation coefficient a0 is 0.3 dB/(cm· GHz1/2 ). The experimental results show that the modulator has great potentiality for expanding bandwidth.     

A tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium

A novel tunable and reconfigurable microwave photonic filter based on two cascaded modulators and a dispersive medium is proposed, theoretically discussed and experimentally demonstrated. A single-wavelength LD and a modulator (either a Mach-Zehnder modulator or a phase modulator which can avoid the dc bias drift problem) are used to obtain a multi-wavelength optical source. By adjusting the modulation frequency and the bias voltage on the modulators, the wavelength spacing and the relative amplitude of the optical tones change, thus making the filter tunable and reconfigurable. The experimental results show that the proposed filters have good tunability and reconfigurability and the mainlobe-to-sidelobe ratio of around 25 dB is achieved.     

Several Phase Modulators for Digital Shearography

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Ultrasensitive terahertz/infrared waveguide modulators based on multilayer graphene metamaterials

This paper studies and classifies the electromagnetic regimes of multilayer graphene‐dielectric artificial metamaterials in the terahertz/infrared range. The employment of such composites for waveguide‐integrated modulators is analysed and three examples of novel tunable devices are presented. The first one is a modulator with excellent ON‐state transmission and very high modulation depth: >38 dB at 70 meV graphene's electrochemical potential (Fermi energy) change. The second one is a modulator with extreme sensitivity towards graphene's Fermi energy ‐ a minute 1 meV variation of the latter leads to >13.2 dB modulation depth. The third one is a tunable waveguide‐based passband filter. The narrow‐band cut‐off conditions around the ON‐state allow the latter to shift its central frequency by 1.25% per every meV graphene's Fermi energy change.     

Harmonic and Intermodulation Performance of Fabry-Perot Intensity Modulator

Abstract

In this article, a mathematical model for the transfer function of the Fabry-Perot intensity modulator is presented. The model, basically a cosine-series function, can be used to obtain closed-form expressions for the amplitudes of the harmonic and intermodulation products of the Fabry-Perot intensity modulator driven by a multi-frequency radio frequency voltage. The special case of a Fabry-Perot intensity modulator driven by an equal-amplitude two-frequency radio frequency voltage is considered in detail, and the results are compared, whenever possible, with previously published experimental and numerically obtained results.     

强流电子加速器中气体开关与真空二极管的光学特性

 利用光纤传感器与光电二极管相结合的方法,对强流电子加速器中气体火花开关以及真空二极管的发光特性进行了研究,对影响光电二极管测量的因素进行了理论计算与模拟研究。在气体开关导通电压1.7 MV,二极管电压1.07 MV,电流18 kA时,进行了多次实验,得到了发光特性与击穿电压、电流的关系。同时,对利用光学检测方法测量主开关或真空二极管电压、电流大小得可行性进行了分析。     

用声光调制器实现的1 W Nd∶YAG单纵模环形激光器

鉴于单向环形腔是目前获得较大功率单纵模激光最有效的方式之一,为使环形腔单向运行,需要在环形腔内插入对正反2个方向的光产生损耗差的光学元件。采用激光二极管泵浦Nd∶YAG晶体,用声光调制器作为光学二极管使环形腔单向运行,实现四镜矩形环形腔单纵模激光器。实验中谐振腔的稳定性由增益介质的热透镜保证,声光调制器给正反2个方向的光提供损耗差,这使得在竞争过程中有较大损耗的光不能运行从而获得单向输出。实验获得了连续功率1 W、光束质量因子M2为1.21 的1.06 m单纵模激光。     

集成光学Mach—Zehnder型模数转换器

简述了M-Z干涉调制器型A/D转换器的原理,报道了实验样品的设计参数、制备工艺和实验现象观察,介绍了性能测试的方法和结果.     

金属覆盖介质波导在截止点附近的光学特性

本文提出一种适合于截止点附近计算含金属覆盖层介质波层的近似解析方法，详细；地讨论在截止点附近的光波导的模式传播特性 和光电调制特性，并结合有效折射率方法讨论了止型脊形波导调制器的截止条件。     

High speed all-silicon optical modulator

Electrorefractive effect is experimentally demonstrated in an all-silicon optical structure. A highly doped Si P⁺ layer is embedded in the intrinsic region of a PIN diode integrated in a SOI waveguide. Holes are confined at equilibrium around the P⁺ layer. By applying a reverse bias to the diode, electrical field sweeps the carriers out of the active region. Free carrier concentration variations are responsible for local refractive index variations leading to an effective index variation of the waveguide optical mode and to an optical absorption variation. As a figure of merit, the product V_πL_π, determined from the measured effective index variation, is equal to 3.1 V cm. Furthermore, the device performances have theoretically been investigated. Estimations show that V_πL_π as small as 1 V cm are feasible using optimized structures. Response times lower than 2 ps are predicted, which gives the possibility to achieve very high-speed modulation. Furthermore, a temperature increases from 300 to 400 K does not change the index variation amplitude, and despite the carrier mobility reduction, response times are still lower than 2 ps.     

Polarization-independent terahertz wave modulator based on graphene-silicon hybrid structure

In this study, we propose and demonstrate a broadband polarization-independent terahertz modulator based on graphene/silicon hybrid structure through a combination of continuous wave optical illumination and electrical gating.Under a pump power of 400 mW and the voltages ranging from-1.8 V to 1.4 V, modulation depths in a range of-23%–62% are achieved in a frequency range from 0.25 THz to 0.65 THz. The modulator is also found to have a transition from unidirectional modulation to bidirectional modulation with the increase of pump power. Combining the Raman spectra and Schottky current–voltage characteristics of the device, it is found that the large amplitude modulation is ascribed to the electric-field controlled carrier concentration in silicon with assistance of the graphene electrode and Schottky junction.     

Lyot filter based multiwavelength fiber ring laser actively mode-locked at 10 GHz using an electroabsorption modulator

A multiwavelength fiber ring laser comprising of a Lyot filter and hybrid gain medium is presented. A wavelength channel spacing of 100 GHz is achieved by appropriate tuning of the Lyot filter length. Four wavelength channels are simultaneously mode-locked at 10 GHz using an electroabsorption modulator. We highlight how the intra-cavity modulator can affect the stability of the mode-locked laser spectrum when used in conjunction with a Lyot filter. We show that, due its reduced polarization sensitivity, an electroabsorption modulator significantly improves the stability of the mode-locked laser spectrum when compared to using a Mach-Zehnder modulator.     

高压隔离电参数测量的新方法

介绍了用铌酸锂(LiNbO₃)高速光强度调制器测量HL-2A装置ECRH系统高压隔离电参数的新方法,测量结果表明：隔离100kV高压的响应时间小于0.1μs,线性误差小于1%,并对器件存在的问题和实际应用的可行性进行了分析。     

15GHz马赫－陈德尔型Ti：LiNbO_3行波幅度电光调制器

比较了四种马赫－陈德尔调制器的结构特性，表明Ｚ切共面波导（ＣＰＷ）是最好的一种结构。用阶跃倒相电极设计了新型电光光波导幅度调制器，研制了包装式带尾光纤的有５段例相电极的马赫－陈德尔调制器。在１．５３２μｍ波长上，该器件调制带宽为１４．８ＧＨｚ，半波电压为１４Ｖ，消光比为２１．３ｄＢ，光纤－器件－光纤插入损耗７．６ｄＢ。     

A method of generating single optical pulse in nanosecond range with the joint uses of electro-optic modulator and nonlinear material

Optics has already been established as a successful candidate in data processing. Lots of all-optical data processors are proposed in the last few decades. Again it is well-known that, in many situations, an optical single pulse is very much useful to trigger an optical data processing circuit. In this communication the authors propose a method of generating a sub-nanosecond optical pulse using electro-optic modulator and nonlinear material.