Improvement of GaN-based light-emitting diode by indium-tin-oxide transparent electrode and vertical electrode

A sapphire-etched vertical-electrode nitride semiconductor (SEVENS) light-emitting diode (LED) is fabricated by means of a selective chemical wet-etching technique. The SEVENS-LED formed on sapphire substrate exhibits excellent device performance compared to a conventional NiAu lateral-electrode (LE) GaN-based LED formed on the same sapphire substrate. The integral light-output power of SEVENS-LED is /spl sim/7 mW, which is 1.75 times stronger than that of the conventional NiAu LE-LED (/spl sim/4 mW). The external quantum efficiency of SEVENS-LED is estimated to be approximately 13%.     

大功率激光二极管驱动电源研制

介绍了一种大功率激光二极管阵列驱动电源的设计方法。对电源的组成、工作原理和电流上升前沿影响因素进行了详细分析, 对输出线结构和反馈电路进行优化,有效地解决了大电流、长距离传输条件下电流脉冲前沿缓慢的问题。测试结果验证了设计思路的可行性,驱动电源实现了0~300 A连续可调、稳定度优于0.3%的输出,在300 A,40 m输出时脉冲前沿24.7 μs,为同类型的大功率激光二极管阵列驱动电源的工程化应用奠定了基础。     

大功率半导体激光驱动电源的研制

介绍了一种利用单片机控制的大功率半导体激光驱动电源。系统采用恒流源、光功率反馈、继电保护、慢启动、慢关闭等软保护措施,实现对半导体激光器输出光功率的软调整及有效保护。同时,采用半导体温度控制技术,对半导体激光器进行恒温控制,从而实现了半导体激光器光功率稳定、可靠、准确输出。经实验证明,在0℃-40℃的环境温度下,该驱动电源可使激光器的光功率稳定度优于0.5%;温度控制精度优于±0.3℃。     

GaAs CCD's with transparent (ITO) gates for imaging and optical signal processing

Sputtered indium tin oxide (ITO) film is used as the transparent Schottky gate material for GaAs CCD's. In addition the gigahertz clocking-rate capability of GaAs CCD's makes them attractive for high-speed optical signal processing applications. The operation of the GaAs CCD's with fixed-aperture mask over the transparent gates is reported here. Such structures are basic components of a GaAs CCD-based electrooptic processor (EOP).     

Performance characterization of InGaP Schottky contact with ITO transparent electrodes

We present the Schottky performance of transparent ITO on a wide bandgap InGaP semiconductor. For a transparent ITO Schottky electrode on InGaP, a transmittance of higher than 0.9, and a refractive index of 1.88 for a wavelength of 820 nm were obtained. We measured its associated resistivity as 1.94×10⁻³ Ω-cm after annealing at 300°C for 60 min under oxygen ambience. The effect of the thermal annealing temperature on the crystallization of ITO was examined by x-ray diffraction. As well an associated Schottky barrier height of 0.93 eV and an ideality factor of 1.07 were found using the Schottky diode configuration. The results indicate that ITO is a promising transparent Schottky material for electrooptical devices based on InGaP structures.     

Micro thermal management of high-power diode laser bars

Lifetime and reliability of high-power diode laser bars are sensitively related to operating temperature, mounting stress, and solder electromigration. These three factors have been taken into account for the development of a new packaging technology for 1 cm laser bars of gallium arsenide. We examine the use of chemical-vapor-deposited (CVD) diamond as heatspreaders in order to reduce thermal resistance of a microchannel cooler for liquid cooling. We show that it is possible to perform hard soldering on a CVD-diamond with a new technique. Additionally, we present a controlled water cooling system fit to the flow characteristics of the cooler. It permits one to adjust the emission wavelength of the diode lasers by changing the water flux     

Laser spectral envelope control using a double contact fabry-Perot laser diode for WDM-PON

We propose a double contact Fabry-Perot laser diode (F-P LD) as a temperature-independent wavelength-division-multiplexing source. By controlling injection currents of the double contact F-P LD, we achieve a fixed lasing envelope regardless of temperature variation. We also demonstrate error-free transmission using the double contact F-P LD as a wavelength-locking source within a 20 /spl deg/C operating temperature range.     

External cavity laser sensor using synchronously-pumped laser diode for position measurements of rough surfaces

A novel optical sensor for absolute position measurements of rough surfaces is presented. The technical surface acts as reflector of an external cavity for an antireflection-coated laser diode. Evaluation of the resulting mode spacing determines the laser cavity length, i.e. the distance to the rough surface. Modelocking by synchronous pumping of the laser diode allows highly-resolved measurements with position resolution of 5 /spl mu/m and temporal resolution of 200 /spl mu/s.     

Properties of diode laser pumps for high-power solid-state lasers

Diode lasers used to pump high average power solid-state lasers typically have broad spectral width so that most of the pump light is not at the peak of the gain medium's absorption feature. However, the long absorption length in these lasers enables even weakly absorbed light to pump efficiently. The result is that high absorption efficiency and improved pump distribution uniformity are possible when using realistic pump diodes. In addition, both quantities are nearly independent of the pump center wavelength.     

大功率半导体激光器调制特性的实验研究

设计了一种带有调制输入接口及恒电流、恒功率、恒温控制的光源系统,着重对其低频调制特性进行了实验研究.通过引入负反馈及自动温度控制技术,从外部电路角度改善了半导体激光器的调制输出特性,有效抑制了驰豫振荡,优化了激光二极管(LD)的调制输出参数.     

Local beam deflector interated in a diode laser cavity

Deflection of a diode laser beam using a local deflector monolithically integrated in the cavity near an output facet is demonstrated. The index distribution in the deflector is adjusted by controlling the injection currents, and the laser beam is scanned over 9° by the prism effect of the deflector.     

大功率半导体激光加工光致等离子体折射效应

为了研究大功率半导体激光加工过程中,光致等离子体对激光光束显著的屏蔽作用,以波长为976nm、光斑尺寸为0.5mm1mm、最大功率为4kW的半导体激光加工系统为实验基础,采用了与实际相符的光致等离子体电子密度数学模型和几何光学ABCD矩阵算法,从吸收和折射两方面对光致等离子体的屏蔽作用进行了理论分析和实验研究,得到了在光致等离子体电子密度ne1.01018/cm3的条件下,光致等离子体的折射效应才是引起半导体激光光束屏蔽的主要原因这一结果。结果表明,光致等离子体改变了聚焦光束的形态,使其焦点下移、光斑变大、能量密度变小,其效果类似于一个非线性梯度折射率的负透镜。     

Model constitution of work modes based on high-power laser diode

This paper describes the model constitution and drive circuit design of high-power laser diode (LD), which works in constant current mode, constant power mode and constant voltage mode, based on the electrical characteristics of high power LD. By model constitution and analysis, the relations between the control voltage and the output current are set up, respectively. After an analysis of factors affecting the stability of output current, safety circuits are provided to protect the use of LD.     

Microwave self-modulation of a diode laser coupled to an external cavity

An external cavity coupled to a conventional Fabry-Perot GaAs diode laser operating continuously has been found to cause modulation of the light output at a frequency within the range 0.5 to several GHz. The modulation depth is close to 100 percent and the linewidth can be made as narrow as 180 kHz. The modulation is thought to be stimulated by the intensity noise fluctuations, which peak at the well-known spiking frequency fr. The oscillations are strongly enhanced by a frequency locking action of the external cavity, being efficient when the external cavity round-trip time2L/c, or a multiple thereof, corresponds to the inverse of the spiking frequency. Since the latter is dependent on both pump current and temperature, the system can simply be tuned by adjusting the pump current. For a fixed resonator length, the narrow-band oscillations occur in a small current range, in which an increase in frequency with increasing current at a rate of 400 kHz/mA is observed. A small-signal analysis based on simple rate equations shows the influence of the external cavity on the intrinsic resonance frequency fr. It demonstrates that self-modulation can only occur for small values of the coupling coefficient ε between the laser diode and the external cavity.     

Multiwavelength picosecond pulses generated from a self-seededFabry-Perot laser diode with a fiber external cavity using fiber Bragggratings

A novel scheme for generating multiwavelength short pulses using fiber Bragg gratings (FBGs) was demonstrated. In this scheme the external cavity length for all wavelengths selected by the gratings is intrinsically identical and the FBGs can be cascaded into the external cavity. Simultaneous generation of 1-GHz dual-wavelength short pulses with a wavelength separation of 1.6 or 18 nm was demonstrated. A sidemode suppression ratio (SMSR) better than 30 or 25 dB was achieved at both wavelengths in the former and latter cases respectively. Three-wavelength 1-GHz ps pulses with a SMSR better than 25 dB at all three wavelengths were also successfully generated     

Remote displacement measurements using a laser diode

A technique for measuring displacements remotely to minimum distances of 8 mm with a resolution of 2 ?m is described. A dynamic interferometer method is employed using a frequency-ramped laser diode. A direct measurement of the period of the resulting beat signal is used to determine the displacement.     

光杠杆实现外腔半导体激光器波长调谐的理论研究

提出利用"光杠杆"的方法来精密调节光栅外腔半导体激光器的输出波长.光杠杆由光楔构成,采用旋转光楔的方法,实现激光输出波长的精密调谐,同时降低了调谐的机械要求.     

Direct supermode analysis of phase-locked diode laser arrays

Supermode structures of phase-locked diode laser arrays are predicted using the finite-element technique. In this approach, modal information such as effective refractive index, modal gain and near-field pattern can be obtained straightforwardly by solving a standard matrix eigenvalue problem. Application to an eight-element array successfully demonstrates the power of the method.     

Measurement of photothermally induced distortion of thin films using an external cavity laser diode sensor

The thermal distortion of a 2.5 mu m thick gold film on a glass plate, produced by a modulated Ar ion laser beam, was measured using a simple external cavity laser diode configuration. Experimental results agree well with calculations. The results of these measurements will help elucidate the photoinductive effect, the photothermally induced change in the inductance of a coil placed over the gold film.<>