Analytical model of a superluminescent diode

Using a set of traveling wave rate equations ,a superluminescent diode with a low facet reflectivity is studied .Analytical expressions of the distribu-tions of carrier density ,forward-and backward-propagation photon densities,and gain are obtained at different facet reflectivities.It is shown that the high nonuni-form carrier distribution is evident in the case of low facet reflectivity.The results can serve as useful guides in understanding emission mechanism of superlumi-nescent diodes.     

Analytical model of a superluminescent diode

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Lateral confinement InGaAsP superluminescent diode at 1.3 µm

A superluminescent diode (SLD) has properties, based on the degree of coherence, that are bounded by those of the light emitting diode and the laser diode. The SLD can be designed to meet a wide range of optical system needs. By introducing ridge-waveguide lateral confinement, a good anti-reflection coating at one end and a high reflectivity mirror at the other, we have demonstrated an SLD that allows 30 percent coupling efficiency into a lensed 0.23 NA, 50 μm diameter graded index core fiber. The power in the fiber is 550 μW at 250 mA and 20°C. It is possible to maintain a constant power level in the fiber greater than 250 μW over the temperature range 0 to 35°C by adjusting the current. The spectral width is 300 Å and the modulation bandwidth 350 MHz. PCM with 400 Mbit/s rate has been observed. These devices are relatively easy to fabricate from ridge-waveguide lasers or any other lateral confinement laser.     

Vertical-cavity surface-emitting lasers with lateral carrier confinement

A novel method to reduce threshold currents in vertical-cavity surface-emitting lasers (VCSELs) is proposed. By using selective quantum well intermixing, lateral heterobarriers are created that prevent carriers from diffusing away from the optical modes. Our devices show 40% reduction of threshold currents with the implementation of lateral carrier confinement     

超辐射发光二极管数值仿真模型

采用谱分割方法和分段模型对1.5 μm 波段的超辐射发光二极管(SLD)进行了仿真.为减小分段模型的分段数目和计算时间,对文献中常采用的计算每小段平均光功率(平均光子数密度)的3种主要方法进行了对比分析,结果表明:积分平均的方法具有显著的优势.与商用器件的测试结果相比,数值计算的输出光谱和电流-输出功率曲线基本相符.对高功率SLD的数值仿真表明:在有源区长度大于1mm后,输出功率的增长出现明显的饱和现象,纵向空间烧孔(LSHB)效应限制了增加有源区长度对输出功率增长的贡献.此外,对高功率SLD,使用忽略LSHB效应的单段模型计算输出功率可产生数倍的误差,因此,采用分段模型计入LSHB效应是必要的.     

Broadband quantum dot superluminescent LED with angled facet formed by focused ion beam etching

Broadband quantum dot superluminescent light emitting diodes (LEDs) are realised by focused ion beam etching an angled facet in an edge emitting dot-in-well laser diode structure. The device exhibits a large and flat emission spectral width up to 142 nm at 0.3 mW, maximum CW output power as high as 3 mW, and effective facet reflectivity <1times10^-6     

Radial confinement in lateral power devices

The aim of this paper is to demonstrate a novel, radial confinement approach to improve the breakdown performance of a lateral power device. The key feature is that the drift region width decreases gradually from the anode to the cathode to achieve charge confinement in the radial direction. As a result, the n⁻ drift region concentration can be increased by a factor of 7 in comparison to a conventional counterpart leading to a lower specific on-state resistance. This technique is applicable to silicon-on-insulator technologies, such as the SOI or SOS, and to high-voltage thin-film transistor technologies on glass. Experimental results from radial diodes fabricated in SOS technology show a blocking capability higher than from those of their conventional counterparts.     

具有侧面柱状结构的高压LED芯片制备

设计制作了一种具有侧面柱状结构的高压发光二极 管(HV-LED)芯片,与未作侧面柱状结构的HV-LED芯片相比, 在正向电流20mA下,其光功率提高了7.6%,而正向电压和波长基 本维持不变。对这两种HV-LED 芯片的电流和电压以及电流和光功率的关系进行研究。封装白光后的测试结果表明,在色温 4500K、 驱动 电流20mA下, 具有侧面柱状结构的HV-LED芯片光效达 125. 6lm/W。在标准测试温度为20℃、正向电流为20mA驱动下,具有侧面柱状结构的HV-LED芯片封装老化测试1000h后,光衰仅为2%。     

The monolithic integration of a superluminescent diode with a poweramplifier

Monolithic integration of a superluminescent diode with a tapered semiconductor power amplifier is proposed. The basic operation of the integrated optical source is demonstrated under pulse conditions. Output power obtained by the integrated device is one to two orders of magnitude higher than the conventional superluminescent diode (SLD) devices     

A novel separate lateral confinement quantum-well heterostructurelaser

Utilizing separate structures for the lateral confinement of the optical mode and injected carriers, we optimize the overlap of the optical mode with the gain to demonstrate lasers with lower threshold currents than standard ridge waveguide lasers     

Submilliampere-threshold InGaAs-GaAs quantum-well ridge-waveguidelasers with lateral confinement provided by impurity-induced disordering

Significant reduction of threshold currents in InGaAs-GaAs quantum-well ridge-waveguide lasers has been achieved by using silicon-induced disordering to provide lateral confinement. Room-temperature threshold currents as low as 0.7 mA for pulsed operation and 0.9 mA for cw operation have been obtained from an uncoated 137-μm-long and 0.3-μm-wide device. In addition, the effects of high-temperature annealing on the various device characteristics, such as the gain curve, internal loss, and quantum efficiency, have been investigated     

Influence of separate confinement heterostructure on emission bandwidth of InGaAsP superluminescent diodes/semiconductor optical amplifiers with nonidentical multiple quantum wells

Experiments show that the layer of separate confinement heterostructure (SCH) has a significant influence on the emission spectrum of superluminescent diodes (SLDs)/semiconductor optical amplifiers (SOAs). Reducing the thickness of SCH layer at the p-side could improve the uniformity of carrier distribution among multiple quantum wells (MQWs). With three In/sub 0.67/Ga/sub 0.33/As/sub 0.72/P/sub 0.28/ QWs near the p-side and two In/sub 0.53/Ga/sub 0.47/As QWs near the n-side, when the thickness of the SCH layer changes from 120 to 30 nm, the operation current for SLDs/SOAs to exhibit the full-width at half-maximum spectral width of above 270 nm could be reduced from 500 to 160 mA.     

Single-mode AlGaAs-GaAs lasers using lateral confinement bynative-oxide layers

We report on results of wet oxidized narrow-stripe QW laser diodes operating in single lateral and longitudinal mode around an emission wavelength of 850 nm. Devices with an active width of 4-10 μm achieved output powers of up to 240 mW in continuous-wave (CW) operation at room temperature     

Two-dimensional quantum-mechanical confinement of electrons in LED by strong magnetic fields

Two-dimensional quantum-mechanical confinement of electrons in a GaAlAs light emitting diode (LED) is realized by applying strong magnetic fields, in which electrons can move freely only in the direction of magnetic fields, and the dimensionality of the free carrier motion is reduced from three to one. With this confinement of electrons, considerable suppression of half-value width of the spectrum broadening from 80 to 60 Å at 80 K in the LED is observed. The systematic shift of the emission peak toward shorter wavelength is also observed in accordance with the theory, which takes into account the Landau level broadening due to finite electron mobility.     

Optical properties of a GaAlAs superluminescent diode

The optical properties of a GaAlAs superluminescent diode (SLD) are described. The spectra of this device exhibit a large number of longitudinal modes. The coupling efficiency into a 0.23 NA 50 μm diameter graded index fiber is ∼ 30 percent. The current required for constant light output at a temperatureTcan be written asI(T) sim I_{0} cdot exp (T/T_{2})whereT_{2} sim 120K. A model of the SLD is described.     

Application of perturbation theory to the analysis of diode lasers with lateral optical confinement

Perturbation theory is used in order to calculate the effective-index distribution in dielectric waveguides that exhibit slow lateral variations. As an example, the method is employed to find the optical modes in diode lasers with lateral spatial variations in thickness. Very good agreement with experiment is obtained for the case of GaAlAs double heterostructure lasers with a crescent-shaped waveguide.     

(Al)GaInP laser with lateral confinement by epitaxial growth onnonplanar substrates

The authors present an AlGaInP/GaInP strained QW laser with AlGaAs cladding layers grown over nonplanar substrates. Excellent device quality and performance is obtained on substrates patterned with ridges prior to epitaxial growth. The lateral current and carrier confinement achieved by exploiting the disordering of the neutral superlattice at ridge sidewalls with shallow angles results in a threshold current density for 5-μm-wide stripes that is one-half that of conventional devices. The potential of this device for high electrical-to-optical conversion makes it well suited for applications to dense addressable laser arrays     

Mode analysis of semiconductor lasers using lateral confinement bynative-oxide layers

We have analyzed the lateral mode behavior of 980 nm InGaAs-AlGaAs lasers, where the waveguiding is carried out by oxidized AlAs layers beside a current aperture. The effective refractive-index step between the active and oxidized region has been calculated. We have found that the effective refractive-index step can be adjusted exactly by the thickness of the AlAs layer and its distance to the graded-index separate-confinement heterostructure region. We have compared this native-oxide-confined laser to a standard ridge-waveguide laser with respect to the lateral index step. Furthermore, we suggest a structure for a lateral separate confinement of carriers and optical waves. Experimental results are presented which are in good agreement with the numerical simulations     

用单片机串行口实现动态扫描LED显示

LED(发光二极管)显示通常要占用单片机的并行口,往往在控制系统中有一定的局限性。为此,采用80C51单片机串行口和I/O扩展芯片扩展并行口,设计了一个8位LED显示驱动电路,通过对串行口动态扫描,把要显示的数据从单片机的串行口送到LED显示器的字段和字位,从而实现用单片机最少的外部资源达到最佳的显示效果。     

Low-drift fibre gyro using a superluminescent diode

By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained.