Carrier-induced index change in AlGaAs double-heterostructure lasers

A large carrier-induced index change is reported for conventional 8 ?m-stripe oxide-isolated AlGaAs double-heterostructure lasers. At threshold, the index change of the active layer is ?0.05 to ?0.07, which is a factor of 5 to 10 larger than previously reported. It is accompanied by an even greater change in dispersion. These effects cannot be explained by a free-carrier effect, and are most likely caused by a carrier-induced shift of the absorption edge.     

Carrier-induced differential refractive index in GaInAsP-GaInAsseparate confinement multiquantum well lasers

Measurements of subthreshold spectra on SCMQW (separate-confinement multiquantum-well) lasers with the number of wells varying from three to nine have led to the determination of the carrier-induced differential refractive index dμ/dN~-3.6×10^-20. This value is 1.8 greater than in the case of conventional bulk lasers. This study allows for a better understanding of quantum well laser parameters such as the spectral linewidth enhancement factor. It is also useful for the design of tunable lasers     

Gain, refractive index change, and linewidth enhancement factor inbroad-area GaAs and InGaAs quantum-well lasers

We report experimental and theoretical results for the injection-level dependence of the gain, refractive index variation, and linewidth enhancement factor (α) for four different quantum-well (QW) laser structures. Two of the lasers have GaAs QW layers that vary in width while the other two have InGaAs active layers that vary in QW depth. Experimental Hakki-Paoli data are used to compare gain, index change, and α-parameter between these pairs of devices. The results of two simulations are compared to the experimental data. The first is based on the approximation of parabolic bands for both the conduction and valence bands while the second employs the k·p method to refine the calculation of the valence bands. Our findings include: (1) narrower and deeper QWs yield lower α values; (2) modeling results from the k·p method are only slightly improved over those from the parabolic band model; (3) at high injection levels, stimulated emission below threshold is a prominent effect in these devices; and (4) at high injection levels, carriers in the barrier energy states above the well are shown to be responsible for increasing α values     

InGaAsP quaternary alloys: Composition,refractive index and lattice mismatch

Extrapolation schemes for the calculation of InGaAsP material parameters are described. Experimental data on alloy composition, bandgap, lattice parameter and refractive index are presented and compared with calculated values. Refractive index steps between InGaAsP and InP were found to vary significantly with lattice mismatch. Errors in alloy composition of mismatched epitaxial layers, deduced from bandgap and lattice parameter measurements, can be caused by a tetragonal distortion of the crystal lattice.     

GaAs、GaP、InP、InGaAsP、AlGaAs、InAlGaAs的化学腐蚀研究

为研制全集成光开关、微片式激光器等，对ＧａＡｓ、ＧａＰ、ＩｎＧａＡｓＰ、ＩｎＡＩＧａＡｓ、ＡｌＧａＡｓ等材料的化学腐蚀进行了实验研究。为了研制ＩｎＡｌＧａＡｓ／ＩｎＡｌＡｓ／ＩｎＡｌＧａＡｓ微片式激光器，开发了Ｈ３ＰＯ４／Ｈ２Ｏ２／Ｈ２Ｏ薄层腐蚀液和ＨＣｌ／Ｈ２Ｏ选择性腐蚀液；为了研制ＩｎＧａＡｓＰ／ＩｎＰ／ＩｎＧａＡｓＰＴｂａｒ型光波导，开发了ＨＣｌ／Ｈ３ＰＯ４／Ｈ２Ｏ２薄层腐蚀液和ＨＣｌ／Ｈ２Ｏ２选择性腐蚀液；为了研制ＧａＰ、ＩｎＧａＰ光波导，开发了ＨＣｌ／ＨＮＯ３／Ｈ２Ｏ薄层腐蚀液。它们都具有稳定、重复性好、速率可控、腐蚀后表面形貌好等特点。除此之外，蚀刻成的ＧａＰ光波导侧壁平滑无波纹起伏。此种结果尚未见报导。     

Monolithic integration of GaAs MESFET and InP/InGaAsP 2*2 optical switch

An optical switching OEIC (optoelectronic integrated circuit), consisting of a GaAs MESFET and an InP/InGaAsP 2*2 buried waveguide optical switch, is reported for the first time. Fully monolithic integration is obtained by heteroepitaxial GaAs-on-InP growth and photolithographical interconnection. The combined OEIC allows switching voltages of about 1 V with an extinction ratio of -6 dB.<>     

The change in refractive index of AlGaAs/GaAs single quantum wells due to impurity-induced mixing

The authors report the results of some calculations of the effect of the width and shape of the quantum well on the change of the refractive index of a single 100 AA thick square GaAs quantum well with thick A1/sub 0.30/Ga/sub 0.70/As barriers. The refractive-index difference between implanted and unimplanted layers after impurity-induced mixing has been calculated for a variety of structures. The results show that a large refractive-index difference can be achieved for heavily mixed wide wells for use at longer wavelengths, while negative refractive-index changes can be predicted for the moderate mixing case. The application of these results to multiquantum-well waveguides also predicts the conditions for the transition between guiding and antiguiding in waveguides.<>     

Facet oxidation of InGaAsP/InP and InGaAs/InP lasers

The facet oxidation of InGaAsP/InP and InGaAs/InP lasers is investigated after aging under high constant optical output power or high current stress. Facet oxidation in InGaAsP/InP lasers is negligibly small under several thousand hours of practical operation. The thickness of oxide film increases in proportion to optical output power and logarithm of aging time. The growth rate of facet oxide film weakly depends on the junction temperature and the activation energy is estimated to be 0.07 eV within a experimental range between 25 and 150°C. The facet of InGaAs/InP lasers are oxidized more easily than that of InGaAsP/InP lasers but are about two orders of magnitude more stable against oxidation than that of AlGaAs/GaAs lasers.     

Effect of GaAs/AlGaAs quantum-well structure on refractive index

We investigate the refractive index difference between the GaAs/AlGaAs quantum wells (QWs) and bulk AlGaAs. We find the refractive index difference is smaller when the electric field in the nominally intrinsic MQW region is larger, or when the well (GaAs) thickness of the QW's is larger, or when the Al fraction of the QWs is smaller. The maximum refractive index difference between the 100 Å GaAs/100 Å Al_0.2Ga_0.8As QWs at zero electric filed and bulk Al_0.1Ga_0.9As is about 0.044. Even with a small refractive index difference of 0.0132, the OFF-state reflectance of a normally-off MQW modulator at the designed photon wavelength will increase from the desired value of 0% to 90% when the reflectivity of the bottom mirror is 0.99     

InP和InGaAsP晶体上衍射光栅的刻制技术

采用全息光刻的技术,在InP 和InGaAsP晶体上刻制亚微米衍射光栅,获得较好的重复性和均匀性,并已应用于研制长波长分布反馈激光器.     

Modal refractive index of 1.3 μm InGaAsP, AlGaInAs and GaInNAssemiconductor lasers under high hydrostatic pressure

The accurate experimental determination of the modal refractive index of 1.3 μm InGaAsP, AlGaInAs and GaInNAs multiple quantum-well lasers by measuring the longitudinal mode separation up to a pressure of 15 kbar is reported for the first time. A small increase of the indices is observed for the three materials with increasing pressure, which causes a decrease of lasing wavelength     

Carrier-induced energy shift in GaAs/AlGaAs multiple quantum welllaser diodes

Emission energy shift due to high carrier density at threshold in multiple quantum well (MQW) laser diodes is investigated theoretically. This energy shift is evaluated through the Schrodinger and the Poisson equations self-consistently as well as the calculation of the gain spectra with carrier-dependent lifetime broadening. The band filling and the gain broadening effects show a blue shift on the emission energy. Larger number of wells, lower barrier height, or wider well thickness, reduces the blue shift dependence on the carrier density. At high injections, this blue shift is offset by the bandgap shrinkage effect, which displays smaller influence on MQW's. While the carrier density is further increased, the transition due to the second quantized state is found in single quantum wells, however it is difficult to be observed in MQW's     

Effective refractive index and first-order-mode cutoff conditions in InGaAsP/InP DH laser structures (λ = 1.2-1.6 µm)

The virtual wavelength-invariance of the ratio between bandgap wavelength and the square root of the dielectric-constant step in InGaAsP/InP DH structures [i.e., (lambda_{g}/sqrt{Deltaepsilon}) = 0.95 pm 0.03for 1.2 μm< lambda_{g} < 1.6 mum] and an analytical approximation for the transverse propagation constantb, allow the derivation of an accurate, closed-form expression for the effective refractive index Neffof InGaAsP/InP planar DH lasers emitting in the1.2-1.6 mum range. Then, Neffis only a function of two readily measurable parameters: emission wavelength and active-layer thickness. Furthermore, the mode cutoff conditions for various lateral waveguides: buried-rectangular, buried-crescent, and ridge-guide, become wavelength-independent analytical expressions. First-order-mode cutoff conditions for these lateral waveguides are derived, plotted and compared to experimental data from mode-stabilized 1.3 and 1.55 μm DH lasers.     

Properties of wide-mesastripe InGaAsP/InP lasers

Wide-mesastripe InGaAsP/InP heterostructure lasers emitting at 1.3–1.5 µm were grown by metal-organic chemical vapor deposition (MOCVD). Radiation-power-current and spectral characteristics of the lasers have been studied in pulsed and continuous wave (cw) operation in the temperature range of 10–60°C. The temperature of the active region of the diode laser is higher by 30–60°C than that of the copper heatsink upon saturation of the cw output power. The temperature dependence of the differential quantum efficiency strongly affects the cw output power. Output powers of 3 and 2.6 W are achieved in mesastripe lasers in cw operation, and 9 and 6.5 W in pulsed operation, at wavelengths of 1.3 and 1.5 µm, respectively.     

Dispersion of the group velocity refractive index in GaAs double heterostructure lasers

The dispersion of the refractive index corresponding to the group velocityn*_{1}has been measured as a function of wavelength. It is obtained from the longitudinal mode spacing of GaAs buried heterostructure lasers at threshold. The dependence ofn*_{1}on wavelength contains an approximately constant term due to the refractive index n1and a strongly dispersive component due to-lambda (partialn_{1}/ partiallambda). For a given spectral bandwidth, the dispersion ofn*_{1}causes a temporal broadening of a pulse as it passes through the medium. This dispersive effect is shown to contribute to the width of 0.65 ps long pulses obtained recently from mode locked semiconductor lasers. By reducing the length of the laser, the dispersive effect is reduced and it is suggested that pulses as short as 10^-13s should be obtainable from such mode locked semiconductor lasers.     

High field transport in GaAs,InP and InAs

Calculations of the steady state and transient electron drift velocities and impact ionization rate are presented for GaAs, InP and InAs based on a Monte Carlo simulation using a realistic band structure derived from an empirical pseudopotential. The impact ionization results are obtained using collision broadening of the initial state and are found to fit the experimental data well through a wide range of applied fields. In InP the impact ionization rate is much lower than in GaAs and no appreciable anisotropy has been observed. This is due in part to the larger density of states in InP and the corresponding higher electron-phonon scattering rate. The transient drift velocities are calculated under the condition of high energy injection. The results for InP show that higher velocities can be obtained over 1000–1500 Å device lengths for a much larger range of launching energies and applied electric fields than in GaAs. For the case of InAs, due to the large impact ionization rate, high drift velocities can be obtained since the ionization acts to limit the transfer of electrons to the satellite minima. In the absence of impact ionization, the electrons show the usual runaway effect and transfer readily occurs, thus lowering the drift velocity substantially.     

高频大功率InGaAsP/InP SPB-BC激光器

在普通掩埋新月型激光器的基础上,提出了一种高频大功率的InGaAsP/InP激光器结构——选择性质子轰击掩埋新月型(SPB-BC),并对激光器结构模型进行了理论分析。采用p-InP衬底,最大输出功率为80mW。500μm腔长激光器,它的调制带宽可以达到6.0GHz。     

Transferred-electron effect in InGaAsP alloys lattice-matched to InP

Measurements of the transferred-electron effect in InP, In_0.73Ga_0.27As_0.64P_0.36, and in In_0.53Ga_0.47As are presented. The results show that especially InGaAs promises superior performance for high-efficiency Gunn devices. Important properties affecting the electron transfer have been investigated. The peak velocity v_p and its temperature dependence, the accompanying threshold field F_p, and the dependence of the current drop on the dimensions of the devices (nl and nd product) are reported. To demonstrate the potential of InGaAs first results with Gunn oscillators using devices of this alloy are mentioned.