Disorder-induced buried-stripe optical waveguides in GaAs/AlGaAs MQW material

Buried-stripe optical waveguides have been fabricated in GaAs/AlGaAs multiquantum-well material by masked Si/sup +/ implantation followed by annealing at 750 degrees C to produce selective-area quantum well mixing. The waveguides were found to support both TE and TM modes with propagation losses of 33 and 56 dBcm/sup -1/, respectively, at a wavelength of 1.15 mu m.<>     

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.<>     

Planar, compatible OEIC's based on multiquantum well structures

An optoelectronic integrated-circuit (OEIC) structure, in which a variety of devices having different functions is built from a common multiquantum-well structure, is discussed. Basic operation of both a lateral-current-injection laser and a field-effect transistor is demonstrated using essentially the same AlGaAs/GaAs multiquantum-well structures.<>     

Lightwave-microwave unified analysis of electroabsorption modulators integrated with RF coplanar waveguides

We present a comprehensive analysis of the electrical-to-optical (E/O) response of multiquantum-well electroabsorption modulators integrated with microwave coplanar waveguides. The predicted small-signal E/O response is validated through comparison with measurement. A photocurrent effect on the dynamic extinction ratio is also demonstrated.     

离散谱折射率法优化设计深刻蚀、单模GaAs/GaAlAs脊形光波导

采用离散谱折射率法对深刻蚀GaAs/GaAlAs多层脊形光波导的特性作了详细的理论分析,并对所获得的较大截面、低损耗的单模脊形光波导的制作容差性作了进一步的分析．计算表明,用离散谱折射率法获得的单模脊形光波导具有较大的制作容差性．     

AlGaAs/GaAs multiquantum-well (MQW) laser applied to monolithic integration with FET driver

A ridge-waveguide AlGaAs/GaAs multiquantum-well (MQW) laser has been monolithically integrated with two MESFETs on a semi-insulating GaAs substrate. The laser was grown in an etched groove to realise a nearly planar horizontal arrangement with FETs. This MQW laser was found to successfully achieve a CW operation with a lowthreshold current of 20 mA at room temperature.     

Continuous-wave operation of lateral current injectionmultiquantum-well laser

Continuous-wave operation of an AlGaAs/GaAs lateral current injection multiquantum-well laser at room temperatures has been achieved by improving the structure and fabrication process. The laser has exhibited a threshold current of 47 mA and a differential quantum efficiency of 11%     

离散谱折射率法优化设计深刻蚀、单模GaAs/GaAlAs脊形光波导

采用离散谱折射率法对深刻蚀 Ga As/ Ga Al As多层脊形光波导的特性作了详细的理论分析 ,并对所获得的较大截面、低损耗的单模脊形光波导的制作容差性作了进一步的分析 .计算表明 ,用离散谱折射率法获得的单模脊形光波导具有较大的制作容差性 .     

Polarization splitting in lossy/gainy MQW directional couplers

We analyze polarization splitting of light in directional-coupler polarizers by using a transverse modal transmission-line representation. Because it is based on rigorous modal solutions, this approach provides very accurate results and can be applied to situations involving either lossy or gainy materials. By considering a polarizer in which multiquantum-well layers act as one of the two waveguides forming the coupling region, we find that maximum polarization discrimination is achieved at an optimal distance that is different from the polarization length predicted by conventional coupled-mode methods. We derive a novel criterion for determining that optimal length, examine the effect of material loss or gain, and obtain the far-field intensity of the light at the output of the coupler     

Pair-groove-substrate GaAs/AlGaAs multiquantum-well lasers with a self-aligned stripe geometry

GaAs/AlGaAs multiquantum-well (MQW) lasers with a self-aligned structure incorporating a waveguide and current confinement were fabricated on a substrate with a pair of etched grooves using two-step epitaxial growth. First, a current-blocking layer was grown selectively on the substrate by low-pressure organometallic vapour-phase epitaxy (OMVPE), and then the GaAs/AlGaAs MQW laser structure was constructed on the substrate with the OMVPE layer by molecular-beam epitaxy. The mesa-shaped part of the active layer above the current-confinement region provides a lateral refractive-index optical waveguide. The lasers show well controlled transverse-mode oscillations with low threshold currents.     

Electro-optic effects and electroabsorption in a GaAs/AlGaAs multiquantum-well heterostructure near the bandgap

We report phase difference measurements at 50 and 30 meV from the excitonic peak of a GaAs/AlGaAs multiquantum-well structure. We find pronounced dispersion of the quadratic effect; in contrast, we see no indication of dispersion in the linear effect even this close to the bandgap.     

Low threshold CW operation of circular-grating surface-emitting DBRlasers using MQW and a self-aligned process

In this letter, we present the first room temperature continuous wave operation of circular-grating surface-emitting DBR lasers. The structure is an InGaAs/GaAs strained multiquantum-well. A modified fabrication process with a better control on the steps is used. A CW threshold current as low as 26 mA at a lasing wavelength of about 977 mm are reported. This is the first demonstration of CW operation for these lasers in any material system     

Monolithic integration of curved waveguides and channeled-substrate DH lasers by wet chemical etching

Integration of AlGaAs/GaAs curved waveguides and other two-dimensional waveguides with DH lasers and detectors is demonstrated. Devices are fabricated from LPE AlGaAs/GaAs layers by wet chemical etching processes. Differential transfer efficiencies ofeta_{t}= 5percent are routinely achieved in a structure consisting of an integrated laser, a 90° curved waveguide with 150μm radius, and a detector, for the case where one laser mirror is etched and one cleaved. This value iseta_{t}= 4percent if both mirrors are etched. A comparison of waveguide attenuation between straight and curved rib waveguides is given, along with the transfer characteristics of curved waveguides. The loss coefficient of curved rib waveguides with 150-μm radius is about two times that of a straight waveguide of the same length. The fabrication and properties of channeled-substrate crescent (CSC) lasers and detectors with transverse single-mode confinement, monolithically integrated by means of passive CSC interconnecting waveguides, is also described.     

Reduced spontaneous emission factor in quantum-well lasers

Spatial and spectral mode measurements on gain-guided GaAs multiquantum-well lasers yield greatly reduced spontaneous emission K-factors in lasing modes as compared to conventional lasers. Small K-factors lead to narrow far fields and to nearly single longitudinal mode operation in gain-guided quantum-well lasers     

金属覆盖型光波导极化器的分析和设计

本文通过精确求解波导的本征方程，针对光波导极化器，分析了金属覆盖四层光波导中ＴＭ模随缓冲层参数变化的特性，指出了存在于其中的模式共振点，根据模式共振点的特点给出了金属覆盖型光波导化器的优化设计原则，最后讨论了使用ＣａＡｓ／ＧａＡｌＡｓ材料制作光波导极化器的意义。     

Field and spatial geometry dependencies of the electron and holeionization rates in GaAs/AlGaAs multiquantum well APD's

Numerical calculations are presented of the electron and hole ionization rates in GaAs/AlGaAs multiquantum-well APDs (avalanche photodiodes) as a function of the applied electric field and the spatial geometries, i.e., the barrier- and well-layer widths, respectively. The model is calibrated to existing experimental data on bulk GaAs materials and then extrapolated to the multiquantum well structure. It is found that at high electric field strengths the net ionization rate approaches the weighted average of the constituent bulk rates; the potential discontinuity is relatively insignificant. The potential discontinuity most greatly affects the electron ionization rate at low applied electric field strengths within a spatially symmetric structure. It is further determined that the electron-to-hole ionization rate ratio is greatest at low applied electric fields with a spatially symmetric structure with equal well and barrier widths     

Grafted GaAs detectors on lithium niobate and glass opticalwaveguides

The integration of a GaAs MSM (metal-semiconductor-metal) detector with LiNbO₃ and glass optical waveguides is discussed. A 250-nm thick GaAs detector layer was fabricated using a recently reported liftoff technique and subsequently grafted onto the waveguide chip. Proof of the optical interaction between the waveguide and its grafted detector was provided by the total absorption of 633 nm of guided light within a distance of ~1 mm from the leading edge of the GaAs layer and by the presence of a photocurrent at the detector terminals. It is suggested that the grafting technique will prove useful in the design of new and cost-effective optoelectronic devices     

Experimental study of switching in a p-i(MQW)-n vertical coupler

Electrically controlled switching in a vertically arranged p-i(MQW)-n directional coupler with GaAs/GaAlAs multiple-quantum-well (MQW) waveguides is discussed. Coupling lengths and extinction parameters are determined by using a sample processed in such a way that injection conditions are well defined and that the coupler length can be varied continuously     

Effect of residual doping on optimum structure of multiquantum-well optical modulators

Using a variational method we have calculated the effect of residual doping on the optimum structure of multiquantum-well (MQW) optical modulators which utilise the quantum confined Stark effect. Residual doping gives a nonuniform electric field and a degraded modulation depth. For example, for a structure consisting of 100 ? GaAs wells and 100 ? Ga0.7A10.3As barriers, we calculate the optimum number of wells to be 20 for a doping of 5 × 1015 cm?3.