电光调制的频谱特介—Ⅱ.内腔调制

从内腔电光耦合调制输出光场振幅和光场强度的傅里叶展开出发,研究了内腔电光调制的频谱特性.数值计算得出了内腔电光调制输出功率谱和振幅谱的各谐波幅度,以及不同直流偏压下的调制深度.采用CdTe晶体,进行了CO_2激光的内腔电光调制试验,得到了与理论分析一致物结果.     

GaP直接电光调制特性研究

对淡黄色透明电光晶体ＧａＰ衬底上的共面波导进行了直接电光调制测量．获得了ＧａＰ的输入电压与电光调制输出的线性曲线和２６ｍＶ·Ｈｚ－１２的电压灵敏度,并与ＧａＡｓ直接电光调制特性相对比,分析了ＧａＰ直接电光调制的输出特性     

电光调制的新方法

本文介绍了一种电光调制的新方法。与一般的电光调制过程相比较,具有半波电压低,通光孔径大等优点。实验结果与理论分析极其相符。     

电光调制系统设计

调制是光电系统中的一个重要环节.光辐射的调制是指改变光波振幅、强度、相位或频率、偏振等参数使之携带信息的过程.调制的目的是对所需处理的信号或被传输的信息进行某种形式的变换,使之便于处理、传输和检测.目前用得较多的是电光调制、声光调制等方法.文中介绍的电光调制系统主要是验证电光调制原理以及介绍电光调制在激光通信方面的应用,通过此系统了解晶体电光调制的原理和实验方法,以便在此系统中测量晶体的半波电压、电光系数和消光比等参量.     

光调制平衡电光检测

介绍了一种新的电光检测方法,即光调制平衡电光检测技术.它通过调制探测光信号,利用差分平衡,实现对样品电场的锁相检测.这种方法不调制被测电信号,可彻底消除对被测电场的影响,而且方法简单,便于操作.介绍了光调制平衡电光检测系统及检测原理,以GaP为样品,对静态电场进行了模拟测量.将此方法应用于电光取样技术,测量了GaAs共面波导在频率为3GHz下的微波信号.     

光调制平衡电光检测

介绍了一种新的电光检测方法 ,即光调制平衡电光检测技术 .它通过调制探测光信号 ,利用差分平衡 ,实现对样品电场的锁相检测 .这种方法不调制被测电信号 ,可彻底消除对被测电场的影响 ,而且方法简单 ,便于操作 .介绍了光调制平衡电光检测系统及检测原理 ,以 Ga P为样品 ,对静态电场进行了模拟测量 .将此方法应用于电光取样技术 ,测量了 Ga As共面波导在频率为 3GHz下的微波信号 .     

新型软光电材料-离子液体电光调制特性

采用实验方法研究了新型软光电材料离子液体的电光调制特性。研究表明外加低频交流电信号时, 光功率输出与电信号相同频率振荡, 振幅受调制信号幅度和频率的共同影响, 电压幅度越大, 电压频率越低, 光输出振荡幅度越大; 外加直流电信号时, 光功率输出呈光开关状态。对影响光功率变化的因素, 如离子液体种类、调制部分物理尺寸以及离子液体折射率、电导率等进行了研究分析, 并对实验现象进行初步解释。     

电光调制光标记技术

１引言光纤有着巨大的频带资源和优异的传输性能 ,它是实现高速率、大容量传输的最理想的物理媒质。随着波分复用 (ＷＤＭ)技术的成熟 ,一根光纤中已经能够传输几百Ｇｂｉｔ／ｓ到Ｔｂｉｔ／ｓ的数字信息。传输系统的快速增长对交换系统发展带来压力和动力。通信网中交换系统的规模越来越大 ,运行速率也越来越高 ,未来的大型交换系统将需要处理几百、上千Ｔｂｉｔ／ｓ的信息。但是 ,目前的电子交换和信息处理网络的发展已经接近电子速率的极限 ,其中所固有的ＲＣ参数、钟歪、漂移、串话、响应速度等缺点限制了交换速率的提高 ,这就是所谓的…     

基于电光调制的激光功率稳定系统

本文利用电光普克尔效应 ,设计了一个运用电光调制实现激光腔外稳功率输出系统 ,通过实验 ,验证了该系统的实用性 ,并获得了小于0 2 %的激光功率不稳定度。     

MMIC-calibrated probing by CW electrooptic modulation

This paper describes an electrooptic probing technique using a CW semiconductor-laser beam associated with a fast photodetector. Besides its simplicity, this technique presents some advantages over the sampling one thanks to the presence of a Fabry-Perot effect, namely an enhancement of the electrooptic interaction and a simple solution to the calibration problem. The good validity of the calibration method allows the application of this technique to S-parameter measurements. The S-parameter determination, in modulus and in phase, of an industrial MMIC by the electrooptic method is reported and compared with direct network analyzer measurements     

High-speed modulation of an electrooptic directional coupler

A LiNbO3:Ti directional coupler driven by an RF signal has been tested at 1.06 μm over a large modulation bandwidth. An analytical model has been developed leading to simple usable expressions to describe the theoretical dependence of the frequency spectrum of sinusoidally modulated light. The frequency response has been measured with a scanning Fabry-Perot and also with a high-speed photodiode. Both methods provided results which are in good agreement. The 9 mm long switch exhibited a 2.5 GHz bandwidth; a 16 dB extinction ratio has been achieved with a driving power of approximately 50μW/MHz. The confirmation of practical modulation response expressions shows the advantage of the optical spectrum observation, which is a very simple measurement method without any bandwidth limitation. In addition, this method has the advantage of remaining quite accurate even for large modulation signals.     

Enhanced electrooptic modulation efficiency utilizing slow-waveoptical propagation

The use of slow-wave optical propagation to promote highly efficient electrooptic modulation of light is investigated theoretically. The proposed modulators utilize a traveling wave (TW) design in which a grating integrated with a single-mode waveguide induces coupling between forward- and reverse-propagating waves. This contradirectional coupling leads to a reduction in the average optical propagation speed in the forward direction. The “slow” waveguide structures provide two features which facilitate improved modulator performance over conventional “fast” TW designs: (1) optical/microwave velocity matching in substrates with high electrooptic coefficients and dielectric constants and (2) enhancement of electrooptic phase shift due to the “dwell time” of the light in the modulation region. For the ideal case of perfect velocity matching, these two factors lead to a potential improvement of nearly an order of magnitude in electrical power dissipation over velocity-matched designs in the conventional lithium niobate (LN) substrate material. Additional orders-of-magnitude improvement in the required electrical power could result from the use of tungsten bronze substrates such as strontium barium niobate (SBN), which have such higher electrooptic coefficients than LN. The prediction of a large reduction in electrical power dissipation is confirmed by calculations for specific slow-wave designs utilizing multireflector etalons in SBN, although response speed limitations result from the fact that perfect velocity matching is not achieved     

An external electrooptic sampling technique based on theFabry-Perot effect

Electrooptic sampling has proved itself as the best technique for the measurement of high-speed electronic signals. This is due to its high bandwidth and noninvasiveness. Standard sampling geometries rely on a rotation of polarization within an electrooptic material and subsequent polarization sensitive detection. In this paper, we present results using a simple technique which relies on Fabry-Perot resonances inside the electrooptic material to produce an amplitude modulation. This simplifies the experiment considerably     

Trading coupling loss for modulation efficiency in electrooptic modulators

Phase modulators utilizing the electrooptic effect in Li-NbO3are most efficient if the waveguide, and hence the guided mode, is positioned as closely as possible to the modulation electrode which is located at the surface of the crystal. However, placing the guided wave near the crystal surface tends to deform its shape so that the coupling loss between the waveguide mode and an optical fiber is increased. In this paper, we study the tradeoffs between coupling loss and modulation efficiency that result from moving the waveguide further below the crystal surface.     

High-speed electrooptic modulation in GaAs/GaAlAs waveguide devices

A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO3) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with Vpiof 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used.     

Coherent optical vector modulation for fiber radio using electrooptic microchip lasers

Future communication systems will require high data rates and flexible modulation. Direct optical phase modulation of two microchip lasers by information-bearing signals allows for high-rate delivery via fiber to a basestation. At the basestation, the coherent optical signals are combined with a reference in a photodetector to produce a microwave/millimeter-wave carrier with arbitrary M-ary quadrature amplitude modulation, which can then be transmitted over a wireless channel. Rapid tuning of the microwave/millimeter-wave carrier, the modulation scheme, and the data rate is achievable through this method with no fixed oscillators at the basestation, thus providing for flexible architectures. Results show a high-quality carrier and, for 4- and 16-QAM, with data rates to 200 Mb/s. Extensions to higher data rates are discussed.     

Efficient modulation and coupling of CW junction laser light using electrooptic waveguides

The use of an electrooptical-waveguide modulator to achieve over 80-percent modulation of 7980-Å light from a room temperature laser diode operating at 10 mW CW is reported. The insertion loss of the modulator including couplers is 8.5 dB, and the output beam has high coherence.