金属有机化学气相外延生长1310nm偏振无关混合应变量子阱半导体光放大器研究

采用低压金属有机化学气相外延设备进行了1.3μm压应变量子阱材料、张应变量子阱材料和混合应变量子阱材料的生长研究.通过x射线双晶衍射和光致发光谱对生长材料进行测试和分析.基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱（4CW3TW）结构有源区，并采用7°斜腔脊型波导结构以有效抑制腔面反射，经蒸镀减反膜后，半导体光放大器光纤光纤小信号增益达21.5dB，在1280—1340nm波长范围内偏振灵敏度小于0.6dB. 关键词： 偏振无关 应变量子阱 半导体光放大器 减反膜     

Optical gain and threshold properties of strained InGaAlAs/AlGaAs quantum wells for 850-nm vertical-cavity surface-emitting lasers

The valence subband structures, optical gain spectra, transparency carrier densities, and transparency radiative current densities of different compressively strained InGaAlAs quantum wells with Al_0.3Ga_0.7As barriers are systematically investigated using a 6 × 6 k · p Hamiltonian including the heavy hole, light hole, and spin-orbit splitting bands. The results of numerical calculations show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAlAs quantum wells can be enhanced by introducing more compressive strain in quantum wells. However, further improvement of the optical properties of InGaAlAs quantum wells becomes minimal when the compressive strain is higher than approximately 1.5%. The simulation results suggest that the compressively strained InGaAlAs quantum wells are of advantages for application in high-speed 850-nm vertical-cavity surface-emitting lasers.     

Numerical study on strained InGaAsP/InGaP quantum wells for 850-nm vertical-cavity surface-emitting lasers

The physical and optical properties of compressively strained InGaAsP/InGaP quantum wells for 850-nm vertical-cavity surface-emitting lasers are numerically studied. The simulation results show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAsP quantum wells can be efficiently improved by employing a compressive strain of approximately 1.24% in the InGaAsP quantum wells. The simulation results suggest that the 850-nm InGaAsP/InGaP vertical-cavity surface-emitting lasers have the best laser performance when the number of quantum wells is one, which is mainly attributed to the non-uniform hole distribution in multiple quantum wells due to high valence band offset. PACS 42.55.Px; 78.20.-e; 78.20.Bh; 78.30.Fs     

应变多量子阱激光器的阱数与腔长

本文从理论上分析计算并给出了应变多量子阱激光器阱数与腔长的优化设计结果.考虑到多生子阱阱区的注入不均匀性,提出了一种新的分析和计算方法.以1.55μmInGaAs(P)1.5%压缩应变多量子阱激光器为例,最佳的阱数为4个,最佳腔长为500μm左右.     

Exciton optical absorption in disordered,strained InGaAs/GaAs single quantum wells

The absorption coefficient spectrum of undoped, disordered InGaAs/GaAs single quantum wells is calculated within the parabolic band approximation in this compressively strained structure. Results are presented for light propagating normal to and along the plane of the quantum well, taking into consideration the 1S-like exciton and all bound states, including the 2D enhancement Sommerfeld factor. The results presented here show that the exciton peaks in TE polarization remain constant with disordering and exhibit a larger wavelength shift than in TM polarization. The absorption edge in disordered InGaAs/GaAs, which is a function of the strain and interdiffusion, can be tailored to the desired wavelength around 1.0 μm. These results can be of interest in the design of photonic devices on a single substrate.     

MOVPE Growth and Fabrication of 1.3μm High Power InGaAsP-InP Polarization-Insensitive Superluminescent Diodes with Complex Strained Quantum Wells

High power polarization-insensitive InGaAsP-InP multiple quantum well (MQW) superluminescent diodes (SLD's) emitting at 1.3μm were investigated. A combination of tensile strained and compressively strained quantum wells called complex strained MQW were used in a single active layer in order to obtain polarization insensitivity. Low-pressure metalorganic chemical vapor phase epitaxy was used for crystal growth. High resolution X-ray diffraction and photoluminescence spectra showed excellent crystal quality. The SLD's were fabricated to ridge waveguide structure with 7° tilted cavity, the two facets were coated with two layers anti-reflection TiO₂/SiO₂ films, residual facet reflectivity was found to be less than 0.04%. The SLD's exhibited a up to 18.8 mW optical output power and less than 1 dB polarization dependence of output power with a less than 0.5 dB optical spectra modulation at 250 mA.     

Compact,temperature-stable multi-gigahertz passively modelocked semiconductor disk laser

We present a compact passively mode-locked semiconductor disk laser at 1045 nm. The gain chip without any post processing consists of 16 compressively strained In Ga As symmetrical step quantum wells in the active region. 3-GHz repetition rate, 4.9-ps pulse duration, and 30-mW average output power are obtained with 1.4 W of 808-nm incident pump power. The temperature stability of the laser is demonstrated to have an ideal shift rate of 0.035 nm/K of the lasing wavelength.     

Approximate Well Width Formulas of 1.55 μm Possible Compositional In1-x-yGayAlxAs Strained Quantum-well Laser

We have used Harrison′s model and anisotropic parabolic approximation to calculate band structure of In1-x-yGayAlxAs compressively strained quantum well. For design of 1.55 μm wavelength lasers, well widths for the possible compositions are presented. A useful empirical formula is given.     

Approximate Well Width Formulas of 1.55 μm Possible Compositional In_(1-x-y) Ga_yAl_xAs Strained Quantum-well Laser

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Numerical study of strained InGaAs quantum well lasers emitting at 2.33 μm using the eight-band model

We investigate the band structure of a compressively strained In(Ga)As/In 0.53 Ga 0.47 As quantum well (QW) on an InP substrate using the eight-band k · p theory.Aiming at the emission wavelength around 2.33 μm,we discuss the influences of temperature,strain and well width on the band structure and on the emission wavelength of the QW.The wavelength increases with the increase of temperature,strain and well width.Furthermore,we design an InAs /In 0.53 Ga 0.47 As QW with a well width of 4.1 nm emitting at 2.33 μm by optimizing the strain and the well width.     

长波长大应变InGaAs/InGaAsP分布反馈激光器的材料生长与器件制备

采用低压金属有机化合物气相沉积法(LP-MOCVD)生长并制作了1.6—1.7μm大应变InGaAs/InGaAsP分布反馈激光器.采用应变缓冲层技术，得到质量良好的大应变InGaAs/InP体材料.器件采用了4个大应变的量子阱，加入了载流子阻挡层改善器件的温度特性.1.66μm和1.74μm未镀膜的3μm脊型波导器件阈值电流低(小于15mA)，输出功率高(100mA时大于14mW).从10—40℃，1.74μm激光器的特征温度T₀=57K，和1.55μm InGaAsP分布反馈激光器的特征温度相当. 关键词： MOCVD InGaAs/InGaAsP 应变量子阱 分布反馈激光器     

InP-based InGaAs/InAlGaAs digital alloy quantum well laser structure at 2 μm

The structural and optical characteristics of InP-based compressively strained InGaAs quantum wells have been significantly improved by using gas source molecular beam epitaxy grown InAs/In 0.53 Ga 0.47 As digital alloy triangular well layers and tensile In 0.53 Ga 0.47 As/InAlGaAs digital alloy barrier layers.The x-ray diffraction and transmission electron microscope characterisations indicate that the digital alloy structures present favourable lattice quality.Photoluminescence (PL) and electroluminescence (EL) measurements show that the use of digital alloy barriers offers better optical characteristics than that of conventional random alloy barriers.A significantly improved PL signal of around 2.1 μm at 300 K and an EL signal of around 1.95 μm at 100 K have been obtained.     

High power AlGaInP laser diodes with zinc-diffused window mirror structure

The technology of zinc-diffusion to improve catastrophic optical damage (COD) threshold of compressively strained GaInP/A1GaInP quantum well laser diodes has been introduced. After zinc-diffusion, about 20-μm-long region at each facet of laser diode has been formed to serve as the window of the lasing light. As a result, the COD threshold has been significantly improved due to the enlargement of bandgap by the zinc-diffusion induced quantum well intermixing, compared with that of the conventional non-window structure. 40-mW continuous wave output power with the fundamental transverse mode has been realized under room temperature for the 3.5-μm-wide ridge waveguide diode. The operation current is 84 mA and the slope efficiency is 0.74 W/A at 40 mW. The lasing wavelength is 656 nm.     

Carrier transport and its effect on the turn-on delay time in strained GalnAsP/InP multiple quantum well lasers

The effects of carrier transport on turn-on delay time in multiple quantum well lasers were investigated both theoretically and experimentally. By using rate equation analysis with two components of the carrier density inside and outside of the quantum wells, we found that carrier transport caused two important effects: one is the stationary effect of a significant reduction in carrier density in quantum wells; the other is an increase in differential carrier lifetime.As an experimental investigation, compressively strained 1.3 m GalnAsP/InP multiple quantum well (MQW) lasers were fabricated and their turn-on delay times were measured and investigated. The short-cavity buried-heterostructure lasers showed low-threshold current (2 to 3 mA) and small turn-on delay time (<200 ps) at biasless 30 mA pulse current. Although these performances are suitable for high-speed digital transmission, it was found that the carrier lifetimes derived from the turn-on delay measurement were larger for strained quantum well lasers than for conventional quantum well lasers and double heterostructure lasers. These phenomena are explained using the carrier transport model and are discussed. The solutions for further reduction in carrier lifetime and turn-on delay are discussed.     

Wavelength Filter and Converter by NDFWM in Strained Quantum Wells

A novel kind of wavelength filter and converter using nondegenerate four-wave mixing (NDFWM) in an optical amplifier with tensile and compressively strained quantum wells (T/C SQW) is reported in this paper. The configuration of the T/C SQW converting filter is designed first, followed by the establishment of the coupling model of the device. The influences of the property parameters of the optical amplifier with T/C SQW on the output efficiency, 3dB bandwidth, and the frequency shift are mainly discussed. The device can serve as both filter and wavelength converter with high conversion efficiency and narrow bandwidth on the order of 0.01 nm. Meanwhile, the frequency conversion range, which is decided by the gain bandwidth of the semiconductor media, is up to 5000 Ghz in the considered case.     

Design of strain compensated InGaAs/GaAsSb type-II quantum well structures for mid-infrared photodiodes

In this paper, the transition wavelength and wave function overlap of type-II In_xGa_1-xAs/GaAs_1-ySb_y quantum wells are numerically calculated using a 4-band k · p Hamiltonian model. The simulation results indicate that absorption wavelength from 2 to 4?μm can be achieved with a strain compensated quantum well structure. The transition wavelength and wave function overlap can be optimized by properly selecting the thicknesses and composition of the quantum well layers.     

GaInAsSb/AlGaAsSb lasers in the wavelength range between 2.73 μm and 2.93 μm

Compressively strained multiple quantum well lasers in the GaInAsSb/AlGaAsSb material system are reported. Indium concentrations between 40% and 47.5% were chosen for the GaInAsSb quantum wells. Compressive strains varied between 1.16% and 1.43%. The lasers worked continuous wave at room temperature up to a wavelength of 2.81 μm. For a laser with 2.93 μm wavelength continuous wave operation was found up to a temperature of −23°C. This laser worked in pulsed operation at 15°C.     

Stokes shift in one-side modulation-n-doped-strained GaxIn1 − xAs/InP asymmetric quantum well

The effects of strain on the Stokes shift in one-side modulation-dopedGa_xIn_1 − xAs /InP asymmetric quantum wells (AQWs) are systematically investigated. By making use of a self-consistent Poisson–Schrödinger solver in the frame of a finite difference method, the quasi-Fermi levels and the band bending are determined under the effective mass approximation. The central-zone valence-band structures for compressively strained and tensile strained AQWs were calculated by making use of a four-band Luttinger–Kohn Hamiltonian. It was found that the strain influences the relative positions of the heavy-hole HH₁and the light-hole LH₁subbands and that the Stokes shifts are greatly reduced by tensile strain in the case of a Ga_0.6In_0.4As /InP AQW. Moreover, it was found that due to the presence of the two-dimensional electron gas the Stokes shifts in AQWs are much larger than the corresponding ones for a square quantum well. Also, the variation of the Stokes shift with spacer layer width for compressively strained AQWs was found to be more rapid than that for tensile strained AQWs.     

Strain and optical transitions in InAs quantum dots on (001) GaAs

To investigate the strain characteristics of InAs quantum dots grown on (001) GaAs by solid source molecular beam epitaxy we have compared calculated transition energies with those obtained from photoluminescence measurements. Atomic force microscopy shows the typical lateral size of the quantum dots as 20–22 nm with a height of 10–12 nm, and photoluminescence spectra show strong emission at 1.26 μ m when the sample is capped with a GaAs layer. The luminescence peak wavelength is red-shifted to 1.33 μ m when the dots are capped by an In_0.4Ga_0.6As layer. Excluding the strain it is shown that the theoretical expectation of the ground-state optical transition energy is only 0.566 eV (2.19 μ m), whereas a model with three-dimensionally-distributed strain results in a transition energy of 0.989 eV (1.25 μ m). It has thus been concluded that the InAs quantum dot is spatially strained. The InGaAs capping layer reduces the effective barrier height so that the transition energy becomes red-shifted.     

固定波长应变量子阱的设计与比较

针对ｌｎＧａＡｓＰ材料，我们比较了不同应变与阱宽组合的固定波长应变量子阱特性压应变下量子阱的应变量越大，阱宽越窄，其能带结构越理想张应变下主要由于电子与轻空穴的偶极矩阵元比电子与重空穴的大，以及其较大的态密度，使得张应变量子阱的微分增益比压应变和匹配量子阱的大得多如果固定的张应变量只能使第一子带为ＬＨ，第二子带为ＨＨ，则存在一个最优的阱宽，阱宽太小不能消除ＬＨＩ与ＨＨ２的耦合，阱宽太大又会带来ＬＨ３与ＨＨ２的耦合，同样会有不利影响