基于AlN膜结构VCSEL热特性的研究

本文用ANSYS有限元热分析软件模拟了基于AlN膜钝化层和SiO2膜钝化层的高功率垂直腔面发射半导体激光器(VCSEL)器件内部的热场分布和热矢量分布.目的是证明AlN膜钝化层要比SiO2膜钝化层有具更好的特性,使器件能更稳定的工作,提高器件的特性,经模拟得到基于AlN膜钝化层的VCSEL热阻为3.12 ℃/W,而基于SiO2膜钝化层的VCSEL的热阻为4.77 ℃/W.经实验测得基于AlN膜钝化层的VCSEL热阻为3.59 ℃/W而基于SiO2膜钝化层的VCSEL的热阻为4.82 ℃/W,模拟结果和实验结果吻合较好.说明AlN膜钝化层要比SiO2膜钝化层具有更好的热特性.     

基于AlN膜结构VCSEL热特性的研究(英文)

本文用ANSYS有限元热分析软件模拟了基于AlN膜钝化层和Si O2膜钝化层的高功率垂直腔面发射半导体激光器(VCSEL)器件内部的热场分布和热矢量分布.目的是证明Al N膜钝化层要比SiO2膜钝化层有具更好的特性,使器件能更稳定的工作,提高器件的特性,经模拟得到基于Al N膜钝化层的VCSEL热阻为3.12℃/W,而基于SiO2膜钝化层的VCSEL的热阻为4.77℃/W.经实验测得基于Al N膜钝化层的VCSEL热阻为3.59℃/W而基于SiO2膜钝化层的VCSEL的热阻为4.82℃/W,模拟结果和实验结果吻合较好.说明AlN膜钝化层要比SiO2膜钝化层具有更好的热特性.     

Improved efficiency of GaAs-based VCSEL by utilizing fan-pad metallization and trench patterning

Emphasizing the Vertical-Cavity Surface-Emitting Laser (VCSEL) device packaging, fan-pad metallization and trench patterning are demonstrated for VCSEL operating at 850 nm of the electromagnetic spectrum. The fabricated devices are observed to exhibit low threshold current and series resistance, contributing thereby to higher VCSEL efficiency. It is also observed that the output spectral characteristics of the fabricated device show stable multimode operation. The results indicate that the proposed VCSEL packaging exhibits superior device performance as compared to the VCSEL device packaged with square-pad metal.     

分布反射面发射垂直微腔半导体激光器的微腔效应

从理论上分析了作为垂直腔面发射半导体激光器反馈面的异质多层结构对光腔中激光传输振荡过程的影响．指出其相位匹配和等效反射面位置对改善激光器性能的重要作用．说明目前这种被认为很有希望的微腔结构，实际上难以观察到微腔效应的物理根源，并指出其改进的途径． 关键词：     

N-DBR和双氧化限制层对VCSEL电、光、热特性的影响

根据增益波导垂直腔面发射激光器直接耦合的准三维理论模型,通过有限差分法对注入电流密度、载流子浓度、光场和热场分布方程求自洽解.研究了垂直腔面发射激光器的电、热和光波导特性,同时提出了一种具有双氧化限制层的增益波导垂直腔面发射激光器结构,并通过对比研究了N-型分布布喇格反射镜和双氧化限制层对增益波导垂直腔面发射激光器特性的影响.计算结果表明,如果忽略N-型分布布喇格反射镜的影响将与实际的垂直腔面发射激光器有较大偏差;双氧化限制层结构对激光器特性有较大的改善,它为增益波导垂直腔面发射激光器提供了一种降低阈值,抑制高阶横模的方法.     

Analysis of single-mode condition and high-order modes discrimination in photonic crystal VCSEL

A new technique for analyzing the single-mode condition and mode discrimination of high-order modes in photonic crystal VCSEL is proposed and reported in this paper. The technique proposed is a semi-empirical approach that uses analytical analysis based on experimental data. For that purpose, single- and multimode photonic crystal VCSEL devices are fabricated and characterized for comparison of device performance. The mode width for first- and second-order mode of PhC VCSEL is computed for analyzing the mode behavior. In order to verify the findings, the fabricated single- and multimode devices are analyzed using finite difference frequency domain technique for the purpose of showing the loss as a function of mode order for the PhC VCSEL. The results show close agreement between the computed and experiment findings, justifying the use of the proposed semi-empirical technique for analyzing single-mode condition and of high-order modes discrimination in photonic crystal VCSEL.     

Highly confined and continuous single-mode operation of self-align photonic crystal oxide VCSEL

In this letter, we report on single-mode operation of originally multi-mode oxide VCSEL by using etched photonic crystal air holes and unique trench structure. The device fabrication utilized conventional photolithography; with simplified lithography step of self-aligning the photonic crystal and trench structures to the laser aperture for efficient and vigorous device processing. The fabricated photonic crystal VCSEL with trench device exhibits a single-mode output power of 0.7 mW, threshold current of 3.5 mA, slope efficiency of 0.10 W/A, and continuous single-mode output spectra at wide operating current range. The results are compared with conventional multi-mode oxide VCSEL of similar device geometry. In addition, theoretical analysis is presented for developing further understanding of the photonic crystal VCSEL.     

Comprehensive uniformity analysis of GaAs-based VCSEL epiwafer by utilizing the on-wafer test capability

A comprehensive study of the uniformity of 850 nm VCSEL epiwafer grown by the MOCVD technique is presented. By utilizing the VCSEL planar structure, uniformity test is performed on-wafer directly, besides using the conventional photoluminescence technique. The VCSEL quantum wells are found to exhibit a peak emission wavelength of 839.5 nm. Also, the grown epiwafer is observed to exhibit a Fabry–Perot cavity resonance at 846.5 nm. Various VCSEL devices fabricated from the center to the edge of the VCSEL epiwafer show a similar trend towards the light–current and output spectral characteristics. However, the device existing near the epiwafer edge is observed to exhibit significantly different characteristics, which is attributed to the physical conditions of the device near the edge, and also the limitations of the epitaxial growth.     

Design and analysis of a GaAs-based 850-nm vertical-cavity surface-emitting laser with different doping in the reflection regions

The present paper deals with the analysis of a non-oxide type of vertical-cavity surface-emitting laser (VCSEL) for operation at 850 nm. The modeling and characterization of the VCSEL is presented in the context of design considerations. Efforts are made to emphasize the behavioral features of the proposed VCSEL, in view of the analytical investigation, which has been performed through a series of simulations for various relevant parameters that are vital for the determination of the VCSEL characteristics. Some of these parameters are the intensity and refractive-index distributions, gain response, spontaneous emission, material gain variations, etc. The results obtained are compared with the oxide-confined VCSEL. It is observed that the proposed model of the VCSEL is suitable at the operating wavelength of 850 nm.     

Simulation of exciton formation and transport in electrically driven polariton laser structures

A model for exciton formation, dissociation and transport is proposed for the simulation of an electrically pumped polariton laser with a geometry similar to that of a VCSEL and resonant cavity LEDs. We demonstrate how the strain effects and the geometry of the device influence the exciton distribution for a GaN/InGaN laser structure.     

Thermal analysis of high-index-contrast grating (HCG)-based VCSEL

A 3-D thermal analysis of 870 nm high-index-contrast grating (HCG)-based vertical cavity surface emitting laser (VCSEL) by using finite volume method (FVM) is presented in this paper. The HCG-based VCSEL is modeled by applying a steady-state 3-D heat dissipation model. Temperature distribution profile and thermal resistance (R_th) of the device are investigated by inserting the heat source value into the thermal simulation. Also, this analysis is performed for a conventional VCSEL operating at the same wavelength and under the same injected current as well as the same geometric sizes. The analysis shows that the maximum temperature inside the HCG-based VCSEL is lower than that inside the conventional VCSEL.     

894nm高温垂直腔面发射激光器及其芯片级铯原子钟系统的应用

报道了自行研制的894 nm高温垂直腔面发射激光器(VCSEL)以及基于此类器件的芯片级铯原子钟系统的应用实验结果.根据芯片级铯原子钟对VCSEL在特定高温环境下产生894.6 nm线偏振激光的要求,对器件的量子阱增益及腔模位置等材料结构参数进行了优化,确定增益-腔模失谐量为-15 nm,使器件的基本性能在高温环境下保持稳定.研制的VCSEL器件指标为:20—90?C温度范围内阈值电流保持在0.20—0.23 m A,0.5 m A工作电流下输出功率0.1 mW;85.6?C温度环境下激光波长894.6 nm,偏振选择比59.8:1;采用所研制的VCSEL与铯原子作用,获得了芯片级铯原子钟实施激光频率稳频的吸收谱线和实施微波频率稳频的相干布居囚禁谱线.     

Enhanced thermal stability of VCSEL array by thermoelectric analysis-based optimization of mesas distribution

The thermal stability of a vertical-cavity surface-emitting laser(VCSEL) array is enhanced by redesigning the mesa arrangement. Based on a thermoelectric coupling three-dimensional(3D) finite-element model, an optimized VCSEL array is designed. The effects of this optimization are studied experimentally. Power density characteristics of VCSEL arrays with different mesa configuration are obtained under different thermal stress in which the optimized device shows improved performance. Optimized device also shows better stability from measured spectra and calculated thermal resistances. The experimental results prove that our simulation model and optimization is instructive for VCSEL array design.     

用速率方程分析垂直腔面发射激光器的噪声

采用一种合理的噪声模拟方法，用速率方程对垂直腔面发射激光器的噪声特性进行了数值分析，在单模情况下计算了器件的自发辐射因子、输出功率、注入电流、阈值电流等参数与相对强度噪声、频率噪声以及线宽等特性的关系，计算结果与实验基本相符，对优化垂直腔面发射激光器的结构设计和应用条件有所裨益. 关键词：     

Investigation of the mode splitting induced by electro-optic birefringence in a vertical-cavity surface-emitting laser by polarized electroluminescence

The mode splitting induced by electro-optic birefringence in a P-I-N InGaAs/GaAs/A1GaAs vertical-cavity surface- emitting laser （VCSEL） has been studied by polarized electroluminescence （EL） at room temperature. The polarized EL spectra with E｜｜[110] and E ｜｜ [150] directions, are extracted for different injected currents. The mode splitting of the two orthogonal polarized modes for a VCSEL device is determined, and its value increases linearly with the increasing injected current due to electro-optic birefringence; This article demonstrates that the polarized EL is a powerful tool to study the mode splitting and polarization anisotropy of a VCSEL device.     

Current spreading modification to enhance single-fundamental-mode VCSEL operation at higher temperatures

Continuous-wave (CW) performance of modern oxide-confined (OC) vertical-cavity surface-emitting diode lasers (VCSELs) at room and elevated temperatures is investigated with the aid of the comprehensive fully self-consistent optical-electrical-thermal-gain model. A standard OC GaInNAs/GaAs double-quantum-well VCSEL emitting the 1.3-μm radiation is used as a typical modern VCSEL structure. The oxide aperture is placed at the anti-node position of an optical standing wave within a VCSEL cavity. The desired single-fundamental-mode (SFM) operation has been found to be expected only in VCSELs equipped with relatively small active regions of diameters equal or smaller than 10 μm. Therefore a proton implantation used as an radial additional confinement of the current spreading from the upper annular contact towards the centrally located active region is proposed and its impact on the VCSEL performance is investigated. The above structure modification has been found to enable a radical improvement in the VCSEL performance. In particular, in this case, the SFM VCSEL operation is possible even in VCSELs with quite large active regions and for much wider ambient-temperature range than in the standard OC VCSELs.     

Sensitivity of a VCSEL threshold performance to inaccuracies in its manufacturing

The paper describes an impact of various possible inaccuracies in manufacturing of verticalcavity surface-emitting diode lasers (VCSELs), like thicknesses and compositions of their layers different from assumed ones, on VCSEL room-temperature (RT) continuous-wave (CW) threshold performance. To this end, the fully self-consistent comprehensive optical-electrical-thermal-recombination VCSEL model has been applied. While the analysis has been carried out for the 1.3-μm oxide-confined intra-cavity contacted GaInNAs/GaAs VCSEL, its conclusions are believed to be more general and concern most of modern VCSEL designs. As expected, the VCSEL active region has been found to require the most scrupulous care in its fabrication, any uncontrolled variation in compositions and/or thicknesses of its layers is followed by unaccepted RT CW lasing threshold increase. Also spacer thicknesses should be manufactured with care to ensure a proper overlapping of the optical standing wave and both the gain and lossy areas within the cavity. On the contrary, less than 5% thickness changes in distributed-Bragg-reflectors are followed by nearly insignificant changes in VCSEL RT CW threshold. However, exceeding the above limit causes a rapid increase in lasing thresholds. As expected, in all the above cases, VCSELs equipped with larger active regions have been confirmed to require more careful technology. The above results should enable easier organization of VCSEL manufacturing.     

Design of Long-Wavelength Vertical-Cavity Surface-Emitting Lasers with Resonant Optical Pumping

An optically pumped long-wavelength vertical-cavity surface-emitting laser (VCSEL) with resonant optical pumping has been proposed. The proposed structure enables the dual-resonance of pump light (1300 nm band) and output light (1550 nm band) at the same time. It is shown that high pumping efficiency of ∼99% can be obtained by adjusting the top mirror reflectivity and the cavity length. This dual-resonance VCSEL (DR-VCSEL) may have great advantages of high efficiency pumping, low power consumption and can be fabricated by using conventional VCSEL fabrication techniques with reasonable fabrication tolerances.     

Designing strategy to enhance mode selectivity of higher-output oxide-confined vertical-cavity surface-emitting lasers

Performance of modern oxide-confined (OC) vertical-cavity surface-emitting diode lasers (VCSEL s) is more sensitive to the construction details than in the case of other VCSEL s. In particular, a stable single-fundamental-mode operation is difficult to be achieved in these VCSEL s especially in higher-output large-size continuous-wave (cw) operating devices at higher temperatures. In the present paper, an operation of OC VCSEL s has been investigated with the aid of the comprehensive fully self-consistent model using the (GaIn)(NAs)/GaAs quantum-well VCSEL with two oxide apertures as a typical example. A new approach is proposed to enhance cw RT single-fundamental-mode low-threshold operation in higher-output OC VCSEL s. One of their oxide apertures should be shifted to the node position of the resonator standing wave where it is working as the electrical aperture only. Then diameters of both apertures may be changed independently giving an additional degree of freedom for VCSEL designing, which enables their optimisation. While the larger-diameter optical aperture placed in the anti-node position creates an efficient radial waveguiding effect, the smaller-diameter electrical aperture enhances a more uniform current injection into the VCSEL active region. Due to combining influence of both the apertures, the single-fundamental-mode operation is predicted in a large device with the 10-m-diameter active region even for 80 K active-region temperature increase over RT of the ambient. An impact of intentional detuning at room-temperature (RT) of VCSEL active-region gain spectrum towards shorter wavelengths with respect to the resonator mode improves mode selectivity is also analysed. PACS  42.55.Px; 02.60.Cb; 85.60.Bt     

Optimization of electro-optical characteristics of GaAs-based oxide confinement VCSEL

An experimental study has been presented of the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) operating in the 850 nm region of the electromagnetic spectrum. In this regard, various relevant VCSEL samples with numerous oxide aperture sizes have been fabricated and characterized. Thorough investigations of the electrical as well as optical characteristics of the fabricated samples have been performed which includes the overall device performance as a function of the oxidize aperture sizes. It is reported that the VCSEL with oxide aperture size <10 μm require low threshold currents (<1 mA). Further, the differential quantum efficiencies up to 28% were measured for a number of these devices. It is found that devices employing oxide aperture of 10 to 15 μm shows promising electro-optical characteristics for 850 nm oxide VCSEL optimization.