Ultrafast opto-terahertz photonic crystal modulator

We present an agile optically controlled switch or modulator of terahertz (THz) radiation. The element is based on a one-dimensional photonic crystal with a GaAs wafer inserted in the middle as a defect layer. The THz electric field is enhanced in the photonic structure at the surfaces of the GaAs wafer. Excitation of the front GaAs surface by ultrashort 810 nm laser pulses then leads to an efficient modulation of the THz beam even at low photocarrier concentrations (approximately 10(16) cm(-3)). The response time of the element to pulsed photoexcitation is about 130 ps.     

32 × 32 SOI CMOS image sensor with pinned photodiode on handle wafer

We have fabricated a 32 × 32 silicon on insulator (SOI) complementary metal oxide semiconductor (CMOS) active pixel image sensor with a pinned photodiode on a handle wafer. The structure of one pixel is a four-transistor type active pixel sensor (APS) which consists of a reset and a source follower transistor on a seed wafer, and is comprised of a photodiode, a transfer gate, and a floating diffusion on the handle wafer. The photodiode could be optimized for better quantum efficiency and low dark currents because its process on the handle wafer is independent of that of transistors on a seed wafer. Most of the wavelengths are absorbed within the visible range, because the optimized photodiode is located on the handle wafer. The image has been captured by the fabricated 32 × 32 SOI CMOS image sensor with array pixels, vertical scanner, horizontal scanner, and delta-difference sampling circuit.     

Nd: Sr_5 (PO_4 )_3 F Crystal Laser Characteristics Using GaAs as Passive Q-switch

1 IntroductionQ- switching Of diode-pumped lasers iS an effective technique because they provideshort duration optical pulses required for laser ranging, nonlinear studies, medidne andother important applications[1--#]. It is obvious that the replacement of an organic dyewith a solid-state one makeS a laser more convenient tO use. Semiconductor materialsare attractive for saturable absorber because Of the large optical nonlinearities that can beobtained, particularly in quantum--well .t..t..…     

Images of the phonon propagation across twist-bonded crystals

We investigate identical but twist-bonded crystals using phonon imaging techniques. As in homogeneous crystals, very anisotropic flux patterns are observed. However, the shape of the pattern depends dramatically on the respective twist angle. The observed phonon images in wafer bonded GaAs/GaAs and Si/Si samples are essentially consistent with the predictions of the acoustic mismatch model for defect-free interfaces, with the exception of GaAs wafers twist bonded at a 45 degrees angle where modes with large shear stress are missing, which indicates strong dislocation scattering.     

面向实时视觉芯片的高速CMOS图像传感器

提出了一种面向实时视觉芯片的高速CMOS图像传感器.该高速图像传感器主要包括CMOS像素单元阵列、相关双采样(CDS)阵列、可编程增益放大(PGA)阵列、单次比较模数转换(ADC)阵列和控制模块.该传感器集成了光信号采集和行并行信号处理等功能,以大于1000 frame/s的速度输出数字信号或数字图像,同时实现了行并行...     

有源层掺杂剂对Ga1-xAlxAs/GaAs双异质结发光管特性的影响

本文研究了由液相外延技术生长的GaAIAs/GaAs双异质结材料制成的发光管,有源层掺杂剂对器件特性的影响结果表明,器件结构和器件制作工艺相同的GaAIAs/GaAs发光管,有源层掺Si可获得较大的光输出功率,而频响特性<15MHz,波长在8700Å以上;对有源层掺Ge器件,光输出功率低于掺Si器件,而频响特性则>15MHz,波长可控制在8200Å~8500Å.深能级测量表明二者有不同的深能级位置,对掺Si(氧沾污)器件,Ec-ET≈0.29eV,而掺Ge器件ET-Ev≈0.42eV.两种掺杂剂对有源层暗缺陷的影响尚无明显区别.     

Passive Q-switching of diode-pumped Yb:YAG microchip laser with ion-implanted GaAs

We reported a passive Q-switched diode laser pumped Yb:YAG microchip laser with an ion-implanted semiinsulating GaAs wafer. The wafer was implanted with 400-kev As+ in the concentration of 1016 ions/cm2.To decrease the non-saturable loss, we annealed the ion-implanted GaAs at 500 ℃ for 5 minutes and coated both sides of the ion-implanted GaAs with antireflection (AR) and high reflection (HR) films,respectively. Using GaAs wafer as an absorber and an output coupler, we obtained 52-ns pulse duration of single pulse.     

Ultrafast All-Optical Serial-to-Parallel Conversion and Its Application to Optical Label Processing

A novel scheme for all-optical serial-to-parallel conversion (SPC) is proposed for label recognition of ultrafast asynchronous burst optical packets. Compact SP converter modules were developed using a fiber array or a surfaceemitting planar lightwave circuit, and 1-Tbit/s and 40-Gbit/s SPC for 16-bit optical packets is demonstrated using the modules. The key device in the converter is a spin-polarized surface-reflection all-optical switch (LOTOS) with an ultrafast switching time (250 fs) and an extremely high on/off ratio (>30 dB). Label recognition of 40-Gbit/s 16-bit burst-mode optical packets is experimentally confirmed using an optical clock-pulse generator and a complementary metal-oxide-semiconductor (CMOS) electronics circuit as well as the all-optical SP converter. 1 x 4 self-routing is also demonstrated using 2-channel control signals generated from the CMOS circuit according to a routing table.     

基于光导开关的激光二极管触发三电极气体开关研究北大核心CSCD

为实现激光二极管对气体开关的触发,采用从主回路开关两侧取电的基于光导开关一体化激光二极管触发气体开关结构,并对基于光导开关一体化激光二极管触发三电极气体开关进行了初步实验,实现了激光二极管输出能量83μJ条件下40 kV/8 kA三电极气体开关的可靠触发,证明了技术可行性。但实验中的实测光导开关的工作寿命仅约数百次。     

用于粒子探测器的CMOS FET采样保持电路的设计与仿真(英文)

介绍了一个峰保持电路。该电路适用于silicon strip,Si(Li),CdZn Te and CsI等探测器,实现采样-保持功能。已成功进行了基于CMOSFET的采样-保持电路的设计和仿真,通过使用Proteus的PSPICE仿真器和BSIMV3.3模型参数完成了电路性能的仿真。同时,实现了采样时间可在60ns到4.44s范围内进行选择,该电路具有较好的线性。     

基于4晶体管像素结构的互补金属氧化物半导体图像传感器总剂量辐射效应研究

对基于4晶体管像素结构互补金属氧化物半导体图像传感器的电离总剂量效应进行了研究,着重分析了器件的满阱容量和暗电流随总剂量退化的物理机理.实验的总剂量为200 krad(Si),测试点分别为30 krad(Si),100 krad(Si),150 krad(Si)和200 krad(Si),剂量率为50 rad(Si)/s.实验结果发现随着辐照总剂量的增加,器件的满阱容量下降并且暗电流显著增加.其中辐照使得传输门沟道掺杂分布发生改变是满阱容量下降的主要原因,而暗电流退化则主要来自于浅槽隔离界面缺陷产生电流和传输门-光电二极管交叠区产生电流.实验还表明样品器件的转换增益在辐照前后未发生明显变化,并且与3晶体管像素结构不同,4晶体管像素结构的互补金属氧化物半导体图像传感器没有显著的总剂量辐照偏置效应.     

外电路参数对GaAs光导开关导通过程的影响

通过研究不同外电路参数条件下半绝缘GaAs光导开关的输出电流波形的差异,分析了外电路电参数对GaAs光导开关导通过程和工作模式的影响。实验开关由600μm厚的半绝缘GaAs晶片制成,电极间隙为12 mm。使用波长为1 064 nm,5.2 mJ的激光脉冲进行了开关的触发实验。使用皮尔森电流探头测量开关放电电流波形。实验发现储能电容、回路电感等外电路参数对开关放电电流波形存在决定性影响,回路电感影响了导通电流的上升前沿,储能电容对于开关非线性模式的维持起决定作用,储能电容较大时才能够提供非线性模式维持所需的偏置电场。     

A comparison study of on-chip short pulse generation circuits based on a coplanar waveguide

A few traditional pulse-forming circuits are implemented in a commercial 0.13 μm digital complementary-metal-oxide-semiconductor(CMOS)technology.These circuits,based on a coplanar waveguide,are analyzed and compared through CadenceTM Spectre simulations.The results show that these traditional pulse-forming-line(PFL)based circuits can be implemented in standard CMOS technology for short pulse generations.Further work is needed to explore the potential of the circuit techniques and to minimize parasitic effects.     

Infrared-light interferometry and a phase-stepping algorithm for measuring the three-dimensional topography of components covered with GaAs or Si

White-light scanning interferometry is extended from the visible-light region to the infrared-light region to measure the three-dimensional (3D) topography of components. An infrared-light interference system based on a linnik-type interferometric microscope is developed according to the principle of transmission of semiconductor materials in the infrared-light region. The 3D topography is measured using the components covered with a Si or GaAs wafer based on a phase-stepping algorithm. The 3D topography can be obtained accurately and relative step heights can be determined within an error less than 3% compared with the instrument MSA 400, a well-known commercially available apparatus used in the field of 3D topography measurement.     

Effects of phosphorus diffusion gettering on minority carrier lifetimes of single-crystalline,multi-crystalline and UMG silicon wafer

Phosphorus diffusion gettering, which can effectively reduce the transition-metal impurities in the bulk of Si wafer and enhance the minority carrier lifetime (MCLT), is a well-known process to improve the performances of solar cells. Especially, the appropriate gettering process is further required for manufacturing solar cells using an upgraded metallurgical-grade silicon (UMG Si) wafer. In this work, an improvement in the MCLT of the UMG Si wafer including the single-crystalline and multi-crystalline Si wafer after phosphorus diffusion gettering was confirmed by using the quasi-steady state photo-conductivity (QSSPC) measurement and the microwave photo-conductance decay (μW-PCD) method. The experimental results were compared with the MCLT variations calculated through the simulation of the Fe distributions in the Si wafers. It was also observed that the efficiency of the UMG Si solar cell increased by 0.53% due to the two-step gettering process.     

Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. I. Molecular beam epitaxy

GaAs/Ge/GaAs heterostructures in which the GaAs layer lattice on Ge is rotated at a right angle to the substrate plane are grown by molecular-beam epitaxy (MBE). Such heterostructures are grown in different epitaxial setups for GaAs and for Ge with wafer transfer through air tor the first time. It is proposed to use surfactants (Bi, Sb) to control GaAs layer nucleation on Ge.     

Design of Low-Complexity and High-Speed Coplanar Four-Bit Ripple Carry Adder in QCA Technology

Quantum-dot Cellular Automata (QCA) technology is a suitable technology to replace CMOS technology due to low-power consumption, high-speed and high-density devices. Full adder has an important role in the digital circuit design. This paper presents and evaluates a novel single-layer four-bit QCA Ripple Carry Adder (RCA) circuit. The developed four-bit QCA RCA circuit is based on novel QCA full adder circuit. The developed circuits are simulated using QCADesigner tool version 2.0.3. The simulation results show that the developed circuits have advantages in comparison with existing single-layer and multilayer circuits in terms of cell count, area occupation and circuit latency.     

Two-channel IR gas sensor with two detectors based on LiTaO3 single-crystal wafer

An infrared (IR) single-element detector based on a lithium tantalate (LiTaO₃) single-crystal wafer has been successfully fabricated. The preparation and design of the device are discussed and analyzed in detail. The processing of a thin LiTaO₃ wafer, the characterization of an IR filter window, and the assembly of the wafer and filter are explained. A LiTaO₃ sensor element, a CMOS amplifier, a narrow-band filter (which can be selected to operate within the appropriate spectral region), and the read-out circuits are set into a TO-18 vessel. Each TO-18-type detector offers a single channel (a single detection wavelength). Two TO-18 detectors with different filters, one acting as a detection channel and the other as a reference, a broadband light source, a circuit board and a flake of wire gauze are assembled and integrated into a gilded gas cell for the purpose of detecting ethene gas.     

Integrated CMOS system and thermally actuated optical switch for wavelength modulation/lock in communication network

The advancement of communication technology and growth of internet traffic have continuously driven the fast evolution of networks. Compared to the traditional optoelectronic switch, all-optical switch provides high throughput, rich routing functionalities, and excellent flexibility for rapid signal exchange in fiber optical network. Among various all-optical switches, thermal actuated ring switch provides the advantages of high accuracy, easy actuation, and reasonable switching speed. However, when scale up, thermal ring switch may encounter issues related to fabrication error, non-accurate wavelength response, and large terminal numbers in the control circuit. In this research, we propose the employment of an integrated CMOS control circuit to compensate the fabrication error and tune as well as lock the wavelength in a thermal-actuated ring-type optical switch through a frequency modulation scheme. Additional functionalities can also be added in this circuit by tailoring externally the roundtrip loss or coupling constants of the ring. The design concept can be easily scaled up for large array optical switch system without much change in the terminal numbers thanks to the three-dimensional hierarchy of control circuit design, which effectively reduces the terminal numbers into the cubic root of the total control unit numbers. The integrated circuit has been designed, simulated, as well as fabricated, and demonstrated a decent performance with free spectral range (FSR) equal to 1.5 nm at 1534 nm and very accurate wavelength modulation to 0.3 nm within 0.01 nm fluctuation for thermal actuated ring type optical switch.     

1 pF的数显电容计

用CMOS门电路、1 0 0kHz石英晶体、单稳态电路及计数 /译码器 ,制作了测量精度可达 1 pF的数显电容计