High-speed spatial light modulator

A high-speed, coherent spatial light modulator is under development. It is based on the coupling of a silicon photodiode and electrooptic crystal. The design criteria and theoretical performance are presented. Optical quality oflambda/20rms atlambda = 500nm over a 1 in aperture has been demonstrated. Submicrosecond write and erase rates are predicted. Heat dissipation limits the predicted continuous rate to 2.5 kHz or higher, depending on required optical quality. Calculated phase MTF is 50 percent at 10 cycles/mm.     

High-speed infra-red modulator with multilayered pn-junctions

A high-speed infra-red modulator having a GaAs multilayered pn-junction and resonator structure is proposed. Device operation is based on infra-red interaction with injected carriers at each junction. The performance calculation reveals an amplitude of 50%, and an approximately ? phase modulation depth with expected bandwidth in the gigahertz order.     

High-speed optical modulator for application in instrumentation

The design and characterization of the first integrated optic modulator for a commercial instrument application are described. Alternative forms of modulation, including direct laser current modulation and optical heterodyne techniques, are reviewed for the application, which requires modulation to 20 GHz. The advantages of an integrated optic modulator fabricated using titanium in-diffused lithium niobate are discussed. Performance tradeoffs between x-cut and z-cut LiNbO₃ including bandwidth, modulation efficiency, bias point stability, and acoustic resonances are detailed. The x-cut device is found to give the best overall performance for this instrument application. Device reliability and testing, including temperature cycling, humidity, electrostatic discharge, mechanical shock, and vibration are described for complete packaged and pigtailed devices     

16-arrayed electrooptic polymer modulator

A 16-arrayed polymeric optical modulator is fabricated using an electrooptic (EO) polymer with a large EO coefficient and good thermal stability. The 16-arrayed modulator has lumped-type electrodes with a response time of less than 1 ns. The 16-arrayed modulator has good uniform modulation characteristics between the individual modulators. The deviation of half-wave voltages is 0.2 V and that of insertion losses about 1 dB. Crosstalks range from -28 to -36 dB and extinction ratios are more than 21 dB.     

High-speed GaInAsP/InP buried-heterostructure optical intensity modulator with semi-insulating InP burying layers

GaInAsP/InP buried-heterostructure (BH) optical intensity modulators have been fabricated by the use of Fe-doped semi-insulating InP burying layers. The reduction of a parasitic capacitance due to the semi-insulating burying layers realised a wide modulation bandwidth of 11.2GHz. At a wavelength of 1.53/?m, an attenuation ratio of 20 dB at 26°C was achieved with an applied voltage of ?8.5 V.     

High-speed InGaAsP/InP multiple quantum well, 1.55 mu m singlemode modulator

1.55 mu m single mode ridge waveguide modulators based on electroabsorption in InGaAsP/InP multiple quantum wells (MQW) are reported. A 10 dB extinction ratio was obtained by applying a 2 V drive voltage to a 100 mu m long device with a 3 dB on-state loss. The 3 dB cutoff frequency is 12.5 GHz.<>     

High-speed QPSK modulator and demodulator with subharmonic pumping

The authors describe a subharmonically pumped QPSK modulator and demodulator using pairs of beam-leaded Schottky diodes and appropriate high-pass and low-pass filters on dielectric substrates. A modulator and a demodulator were operated in cascade at a carrier frequency of 13 GHz with a common pump at 6.5 GHz. This circuit showed clean eye diagrams of the recovered data trains up to 1.5 Gb/s with corresponding error rates of less than 10^-11. The circuits can be readily scaled to higher frequencies with a proportional increase of the information rate     

High-speed electroabsorption modulator with strip-loaded GaInAsP planar waveguide

We describe fabrication and characterization of an electroabsorption (EA) light modulator (LM) with a strip-loaded GaInAsP planar waveguide. The EA LM's were fabricated from hydride vapor-phase-epitaxy (VPE) grown wafers. The electroabsorption, the insertion loss, the electrical properties, and the modulation characteristics were investigated for the EA LM's. The drive voltage at a 99-percent modulation depth has been noticeably reduced to 4.5 V by optimizing the thicknesses of the epitaxial layers. The total capacitance of 1.5 pF was obtained by inserting an insulating film under the wire-bonding pad and by improving the mount design. Consequently, a 3-dB bandwidth of 3.8 GHz has been achieved and a pulse modulation operation under 2 Gbit/s nonreturn-to-zero (NRZ) pseudorandom pattern has also been confirmed. Moreover, the dynamic spectra of the EA modulators were measured for the first time. A spectral broadening factor α has been determined to be 1-4 from a relative strength of the sideband to the carrier and it has been experimentally found to decrease with increasing the electric field inside the absorptive waveguide. As the other measures of merit for the EA LM's, the extinction ratio over 23 dB and the insertion loss of 10-14 dB including a coupling loss due to an end-fire method were obtained. As a whole, these results have exhibited that the EA LM is a promising external modulator which will be monolithically integrated into a gigabit per second optical source with a dynamic single-mode laser.     

High-speed optical FSK modulator for optical packet labeling

We described a novel optical label swapping (OLS) technique for optical packet systems using frequency-shift-keying (FSK) optical labeling. High-speed optical FSK signal can be generated by using an external FSK modulator consisting of four optical phase modulators. The FSK modulator was based on optical single-sideband (SSB) modulation technique, and comprised of traveling-wave electrodes for high-speed frequency switching. We demonstrate 10 Gbps FSK transmission, and simultaneous modulation by FSK and intensity modulation (IM). OLS using double-sideband modulation was also demonstrated, where this technique can be used for a bundled wavelength-domain-multiplexing (WDM) channels without using an array of pumping light sources.     

A mechanically biased electrooptic polymer modulator

Mechanical biasing of an electrooptic polymer modulator is proposed and demonstrated by heterogeneously integrating waveguide structures with a piezoelectric element. Biasing is achieved by changing the path-length of one arms of a Mach-Zehnder interferometer by mechanically bending the waveguide structure. Applying ac voltage to the piezoelectric element generates a pilot tone, which is used to monitor the bias point of the modulator, while applying dc tunes the modulator to quadrature. The method separates the biasing and RF modulation of the device, thus avoiding the need for external biasing components and eliminating electrical bias drift     

非线性液晶聚合物电光调制器

文章描述了透明非线性液晶聚合物的合成，准直和非线性光学性质，给出了液晶事物电光调制器的制作和测试方法及应用。     

High-speed all-optical AND gate using nonlinear transmission ofelectroabsorption modulator

We investigated an all-optical logic AND operation at 10 Gb/s using nonlinear transmission of electroabsorption modulator pumped with two counterpropagating data streams. The transmitted pump itself was used as the output of the optical gate to obtain high extinction ratio, and high-output peak powers. The gate has been tested using 2³¹ -1 long pseudorandom bit sequence. The logical output of the gate has an extinction ratio of more than 10 dB with good eye opening. Our measurements of the gate transmission window show that all-optical logic operation up to 100 Gb/s is feasible     

In-line fibre-optic intensity modulator using electro-optic polymer

An in-line fibre-optic intensity modulator is reported that uses evanescent coupling from a fibre to a thin film of electro-optic polymer deposited onto a fiber half coupler. Modulation depths up to 16 dB and low loss (0-6 dB) have been demonstrated.<>     

High-speed mid-IR modulator using Stark shift in step quantum wells

We show in calculations that there is a capability for high speeds with a low applied voltage in modulators based on intersubband transitions in step quantum wells (QWs). A waveguide based on surface plasmons is assumed to achieve the necessary tight confinement of the optical field. In a structure with 8 GaInAs-AlGaInAs-AlInAs step QWs, we obtain a device capacitance of 14 fF corresponding to a RC limitation of electrical f_{3 dB}=190 GHz. The extinction ratio of 6.6-μm light is 10 dB at an applied voltage of 0.9 V and T=300 K. By simple reasoning, we find that the device capacitance is approximately proportional to the absorption linewidth cubed when the linewidth is considered in the device design. Thus, the linewidth is very decisive for the modulation speed. We propose to place the dopants asymmetrically in the barriers in order to reduce broadening caused by doping induced potential fluctuations. In addition, the doping levels in the outermost barriers of the multi-QW structure are proposed to be reduced and asymmetrical, in order to achieve a uniform electric field over the step QWs, which is shown to increase the achievable f_{3 dB} very markedly     

High-speed 8:1 multiplexer and 1:8 demultiplexer implemented withAlGaAs/GaAs HBTs

An 8:1 multiplexer (MUX) and 1:8 demultiplexer (DMUX) implemented with AlGaAs/GaAs heterojunction bipolar transistors are described. The circuits were designed for lightwave communications, and were demonstrated to operate at data rates above 6 Gb/s. These are among the fastest 8-b MUX-DMUX circuits ever reported. Each contains about 600 transistors and consumes about 1.5 W. The pair provides features such as resettable timing, data framing, and clock recovery circuitry, and a built-in decision circuit on the DMUX. Emitter-coupled logic (ECL) compatible input/output (1/O) signals are available. The circuits were implemented with bi-level current mode logic (CML) and require a -5.2-V power supply and a +1-V bias for ECL compatibility     

基于SOPC的弹光调制干涉信号高速数据采集

针对弹光调制干涉信号频率高的特点及实时处理的要求,设计一种基于SOPC(System on a Programmable Chip)技术的可脱离PC环境的弹光调制干涉信号高速数据采集平台。采用硬件设计和软件编程测试控制系统各部分IP核的方法,实现对弹光调制干涉信号的高速实时采集,将采集到的数据以DMA传输方式存储到两片DDR3 SDRAM。在FPGA控制下,软核处理器（Micro Blaze）将采集到的干涉信号进行实时处理。对卤钨灯光源经调制后的干涉信号进行实时采集和处理验证实验,其中系统各部分IP核的控制逻辑可以根据实际需求进行调整,满足实验实时处理的要求;实验结果表明,该系统可以对最大光程差为69.608μm的干涉信号进行实时采集与存储,采集的信号波形与实际弹光特性相一致。     

High-speed traveling-wave directional coupler switch/modulator for λ = 1.32 µm

We have designed and fabricated a Ti:LiNbO3waveguide traveling-wave directional coupler switch/modulator operating atlambda = 1.32 mum that exhibits a 3 dB modulation bandwidth of 7.2 GHz, a switching voltage of 4.5 V, and power per unit bandwidth of 7.6 mw/ GHz. Using short drive pulses, optical pulsewidths as short as 58 ps have been generated and directly measured with a high-speed InGaAs/InP p-i-n photodiode. Thick (sim 2.8 mum) electroplated gold has been used to produce a small gap (5 μm) and low-loss coplanar strip electrode. The 1.5 cm long, 15 μm wide electrode has a dc resistance of 7 Ω and a total microwave power loss of ∼4dB at 5 GHz.     

Demonstration of wavelength-insensitive biasing using an electrooptic polymer modulator

Wavelength-insensitive biasing (WIB) of an optical intensity modulator was demonstrated using the photobleaching technique to control the initial phase difference of the electrooptic polymer modulator. The WIB technique reduced the wavelength sensitivity of the bias point at 1550 nm by a factor of 17.     

Optimization design of optical waveguide in Mach-Zehnder electro-optical polymer modulator

In order to reduce transmission loss of the optical waveguide in Mach-Zehnder (M-Z) electro-optical (EO) polymer modulator,the basic iterative formula of semi-vector finite-difference beam propagation method (FD-BPM) is obtained from the scalar wave equation. The transition waveguide is combined with S-type bend branch waveguide for the M-Z EO modulator in the branch waveguide. The effects of structure parameters such as ridge width,length of the branch waveguide and interferometer spacing on the transmission loss are systematically studied by using the semi-vector FD-BPM method. The structure is optimized as an S-sine bend branch waveguide,with rib width w=7μm,length of branch waveguide L=1200μm and interferometer spacing G=22 μm. The results show that the optimized structure can reduce transmission loss to 0.083 dB,which have a certain reference value to the design of optical waveguide in M-Z polymer modulator.