Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Design of a plate type multi-DOF ultrasonic motor and its self-oscillation driving circuit

Multi-degrees-of-freedom (DOF) actuators have become more useful in the field of robotics, as a result of the increasing number of DOFs of systems. The general features of ultrasonic motors are suitable for constructing a direct-drive multi-DOF actuator. However, previously developed ultrasonic motors do not have advantages in volume and weight in contrast to multi-DOF motion units composed of plural electromagnetic motors. In the present study, authors developed a novel multi-DOF ultrasonic motor with a compact plate stator and spherical rotor. First, a new driving principle of the motor is proposed. Next, the stator geometry is designed in detail using the finite element method, and a prototype of the multi-DOF ultrasonic motor is produced. Then, vibration characteristics of the stator and driving characteristics of the motor have been measured, respectively. The results confirm that the motor successfully provides the desired multi-DOF motion of the rotor around orthogonal axes driven by a single plate stator. Finally, a novel self-oscillation driving circuit for the motor is proposed and driving tests using the circuit are conducted.     

All-epitaxial InAlGaAs-InP VCSELs in the 1.3-1.6-/spl mu/m wavelength range for CWDM band applications

All-epitaxial InAlGaAs-InP vertical-cavity surface-emitting lasers grown by metal-organic chemical vapor deposition were successfully demonstrated in the wavelength ranging from 1.3 to 1.6 /spl mu/m. The devices showed the high performances such as single-mode output power of higher than 1.1mW, sidemode suppression ratio of 37 dB, divergence angle of 9/spl deg/, and CW operation of temperature up to 80 /spl deg/C. We achieved the modulation bandwidth exceeding 2.5 Gb/s and power penalty free transmission over 30 km.     

Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation

We report continuous-wave (CW) operation of quantum-cascade lasers (/spl lambda/=6 /spl mu/m) up to a temperature of 313 K (40/spl deg/C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm/sup 2/, respectively, for a high-reflectivity-coated 12-/spl mu/m-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 /spl mu/m. A clear trend of improved performance is observed as the ridge narrows.     

High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.     

宏微压电驱动器的电源设计与试验

针对超声电机与压电微驱动器对驱动电源的要求,设计出一种既能驱动超声电机又能驱动压电微驱动器的驱动电源,该驱动电源由可调变压器、半桥模块及以高性能数字信号处理(DSP)芯片TMS320F28335为核心的控制器组成。该电源驱动超声电机时,电源输出相位差、频率均较大范围连续可调的二相超声频率交流电;驱动压电驱动器时,电源输出较大范围连续可调的直流电。对行波型旋转超声电机及钹型压电驱动器的系列驱动试验表明该电源能同时满足超声电机和压电驱动器的驱动要求。     

Analysis,measurement and control of a new disc-type ultrasonic motor system

This paper first presents an equivalent circuit model of a new disc-type ultrasonic motor and discusses its applications in evaluation of the stator’s frequency characteristics. The equivalent circuit analysis is based on the principle of ultrasonic motor operations and is conducted from the viewpoint of the mechanic vibration of the piezoelectric ceramic disk. Furthermore, because drift of the piezostator characteristics will cause variation of the motor speed, a controller is thus necessary in order to produce a constant output speed. In this research, the speed control scheme is implemented by using current modulation, so the revolutional speed will be kept constant. Meanwhile, the frequency behaviour of the proposed motor and its consequences on speed control scheme are discussed. Finally, a 3-D mechanical element with an extra electrical degree of freedom is employed to simulate the dynamic vibration modes of the linear piezoelectric, mechanical and piezoelectro-mechanic behaviours of a metal disc structure embedded with a piezoelectric actuator. In piezoelectric finite element formulation, a discretized equation of motion is developed and solved by using the integration scheme to explain why an adaptive boundary condition, a simple support condition with three non-equal-triangular (120°–90°–150°) fixed points near the edge for the mechanical design of a new disc-type piezoelectric ultrasonic stator, is defined so that a lateral elliptical motion of the contact point between stator and rotor can be realized for driving the rotor.     

行波型超声电机速度控制技术的研究

当超声电机的驱动器处于开环工作时，超声电机的转速与驱动频率之间的关系表现为时变的非线性；同时其正向和反向的速度特性也常不一致，这给超声电机的应用造成了很大的障碍。该文首先推导出行波型超声电机定子上的孤极传感器反馈电压与其转速之间的关系。据此，作者设计和制造了速度控制器。其次，针对行波型超声电机的正向和反向速度特性不一致的情况，提出一种正、反向速度平衡补偿算法，并用硬件实现了平衡补偿控制器。实验结果表明：在驱动器中添加这个速度控制器和平衡补偿控制器后，不仅使行波型超声电机的速度特性对指令电压具有非时变的线性关系，而且使它的正、反向速度特性具有良好的一致性。这一研究成果为行波型超声电机在我国的实际应用扫除了技术障碍，也为其他类型超声电机速度控制技术的研究提供了有效的途径。     

A full-duplex dual-frequency self-steering array using phase detection and phase shifting

A full-duplex dual-frequency self-steering array using phase detection and phase shifting is presented. By RF decoupling the transmitter and receiver arrays, the proposed system promises greater system efficiency by ensuring a constant transmit power. This also allows for a separate low-frequency interrogating signal capable of various modulation schemes. A two-element prototype is demonstrated with interrogating and retrodirective frequencies of 1.425 and 2.85 GHz, respectively. Retrodirectivity is reported for angles of 0/spl deg/, -15/spl deg/, and +25/spl deg/. The power of the received signal is improved by up to 12 dB for -60/spl deg//spl les//spl theta//spl les/60/spl deg/ when compared to a conventional two-element array.     

Continuous-wave operation up to 36/spl deg/C of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers

We introduced ion-beam assisted deposition in order to improve the quality of Al/sub 2/O/sub 3/ and SiO/sub 2/, which were used as part of the mirrors of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers (VCSELs). The refractive index of Al/sub 2/O/sub 3/ was improved to 1.63 from 1.56 and the one of SiO/sub 2/ increased to 1.47 from 1.45. Low-threshold room-temperature continuous-wave (CW) operation of 1.3-/spl mu/m VCSEL with the improved mirrors was demonstrated. The threshold current was 2.4 mA at 20/spl deg/C. The CW operating temperature was raised to 36/spl deg/C, which is a record high temperature for 1.3-/spl mu/m VCSEL.     

Subharmonically pumped CMOS frequency conversion (up and down) circuits for 2-GHz WCDMA direct-conversion transceiver

Subharmonically pumped frequency down- and upconversion circuits are implemented in 0.18-/spl mu/m mixed-mode CMOS technology for 2-GHz direct-conversion WCDMA transceiver applications. These circuits operate in quadrature double-balanced mode and a required octet-phases (0/spl deg/, 45/spl deg/, 90/spl deg/, 135/spl deg/, 180/spl deg/, 225/spl deg/, 270/spl deg/, and 315/spl deg/) local oscillator (LO) signal comes from an active multiphases LO generator composed of a polyphase filter and active 45/spl deg/ phase shifting circuits. For linearity improvement, predistortion compensation and negative feedback schemes are used in the frequency down- and upconversion circuits, respectively. The downconverter achieves a conversion voltage gain of 20 dB (to 1-M/spl Omega/ load), 4-dBm IIP3 (18-dBm OIP3 to 50-/spl Omega/ load), 41-dBm IIP2 and 8.5-dB DSB NF at 1-MHz IF frequency, consuming 13.4 mA from 1.8-V supply, in the WCDMA Rx band (2110-2170 MHz). The upconverter, operating as two switched gain modes in the WCDMA Tx band (1920-1980 MHz), consumes 19.4 mA from 1.8-V supply and shows 14.5-dB conversion power gain, 15 -dBm OIP3 (0.5-dBm IIP3) and -11 dBm P/sub 1dB/ at maximum gain mode. At minimum gain mode, it realizes -0.3-dB conversion loss, 10.7-dBm OIP3 (11-dBm IIP3) and 0-dBm P/sub 1dB/, respectively. 3GPP WCDMA modulation tests are performed for both up- and downconversion circuits and the results are discussed in this paper.     

Design and control of an ultrasonic motor capable of generatingmulti-DOF motion

A multi-degree-of-freedom (DOF) ultrasonic motor consisting of a bar-shaped stator and a spherical rotor was developed. It can generate 3-DOF rotation of the rotor around perpendicular axes using the bending vibration and longitudinal vibration of the stator, which is designed using the finite element analysis. From the simulated driving characteristics, a control method for the ultrasonic motor is proposed. Following this, the driving characteristics of the motor under both open-loop and closed-loop controls were measured experimentally. The multi-DOF position control of the rotor was achieved successfully using the proposed control method     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

Vertical-cavity surface-emitting lasers in the 8-/spl mu/m midinfrared spectral range with continuous-wave and pulsed emission

Continuous-wave (CW) as well as pulsed-laser emission from a midinfrared (/spl lambda/=7.92 /spl mu/m) IV-VI vertical-cavity surface-emitting laser at 1.8 K is presented. The high-finesse microcavity, containing PbSe as an active medium, was optically pumped with a carbon monoxide laser at a wavelength of 5.28 /spl mu/m (1894 cm/sup -1/) in either CW or Q-switched mode. The maximum achieved CW power was 4.8 mW and pulsed peak powers were up to 23 W. Linewidths are considerably narrower than 0.10 cm/sup -1/, corresponding to 0.6 nm.     

Continuous-wave operation of GaInAs-AlGaAsSb quantum cascade lasers

We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-/spl mu/m-thick gold layer on both sides of the laser ridge to extract heat from the active region in the lateral direction, together with mounting the device epilayer down, we have achieved CW operation of GaInAs-AlGaAsSb QC lasers composed of 25 stages of active/injection regions. The maximum CW operating temperature of the lasers is 94 K, and the emission wavelength is around /spl lambda//spl sim/4.65 /spl mu/m. For a device with the size of 10/spl times/2000 /spl mu/m/sup 2/, the CW optical output power per facet is 13 mW at 42 K and 4 mW at 94 K. The CW threshold current density is 1.99 kA/cm/sup 2/ at 42 K, and 2.08 kA/cm/sup 2/ at 94 K, respectively.     

A 1.2-V 1.5-Gb/s 72-Mb DDR3 SRAM

A 1.2-V 72-Mb double data rate 3 (DDR3) SRAM achieves a data rate of 1.5 Gb/s using dynamic self-resetting circuits. Single-ended main data lines halve the data line precharging power dissipation and the number of data lines. Clocks phase shifted by 0/spl deg/, 90/spl deg/, and 270/spl deg/ are generated through the proposed clock adjustment circuits. The latter circuits make input data sampled with an optimized setup/hold window. On-chip input termination with a linearity error of /spl plusmn/4.1% is developed to improve signal integrity at higher data rates. A 1.2-V 1.5-Gb/s 72-Mb DDR3 SRAM is fabricated in a 0.10-/spl mu/m CMOS process with five metals. The cell size and the chip size are 0.845 /spl mu/m/sup 2/ and 151.1 mm/sup 2/, respectively.     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.     

基于LPC2124的超声波电机驱动控制系统

针对行波型超声波电机的驱动控制特性,为方便电机调试,实现电机的转速或位置信号检测,检测电机首次启动时的环境温度,设计了一款基于LPC2124的驱动控制系统。采用传统的推挽电路实现功率放大,串联电感进行谐振匹配。运用LPC2124内置的脉宽调制器和A/D转换器,外加微调电阻,可实时调节PWM频率,从而方便电机的调试。霍尔传感器ATS642LSH结合固定在电机转子上的环形齿轮,检测电机转速或位置。采用LM75温度传感器,检测环境温度,给电机的首次启动提供一个参考温度。试验表明,系统能顺利检测环境温度,能稳定、可靠地驱动电机工作,同时检测电机的转速或位置信号。     

Electrically pumped room temperature CW VCSELs with 2.3 /spl mu/m emission wavelength

Continuous wave (CW) operation at room temperature of electrically pumped InGaAlAs/InP vertical-cavity surface-emitting lasers (VCSELs) at emission wavelengths as high as 2.3 /spl mu/m is demonstrated for the first time. Devices with 15 /spl mu/m active region diameter show a maximum output power of 0.75 mW at 20/spl deg/C and a maximum CW operating temperature of 45/spl deg/C.     

Two-step laterally tapered spot-size converter 1.55-/spl mu/m DFB laser diode having a high slope efficiency

We demonstrate a two-step lateral tapered 1.55-/spl mu/m spot-size converter distributed feedback laser diode (SSC DFB LD) having slope efficiencies as high as 0.457 and 0.319 mW/mA measured at 25 /spl deg/C and 85 /spl deg/C, respectively. The SSC DFB LD fabricated by using a nonselective grating process has a double core waveguide structure including a planar buried heterostructure type active waveguide and a ridge type passive waveguide. The fabricated SSC DFB LD operates at 1.553-/spl mu/m wavelength and shows a far-field pattern in horizontal and vertical directions of 7.3/spl deg/ and 11.6/spl deg/, respectively.