Characteristics of short-wavelength (617<λ<640 nm) Ga0.4In0.6P/(AlxGa1-x)0.5In0.5P strained, thin multiple-quantum-well lasers

The authors examine the operating characteristics of short wavelength (617<λ<640 nm) AlGaInP lasers containing three thin (~20 Å) compressively strained Ga_0.4In_0.6 P/(Al_0.6Ga_0.4)_0.5In_0.5 P quantum wells and Al_0.5In_0.5P cladding layers, grown by low pressure organometallic vapor phase epitaxy. At room temperature, wavelengths as short as 617 nm have been achieved, with pulsed threshold current density of 2.5 kA/cm². As a result of greater electron confinement at longer wavelengths, the threshold, and its temperature sensitivity, are improved     

High power, low threshold, singlemode 630 nm laser diodes

Output powers exceeding 45 mW under room temperature, continuous wave operation and threshold currents as low as 30 mA are demonstrated in singlemode AlGaInP visible laser diodes emitting at 636 nm. Singlemode operation is maintained at output powers exceeding 40 mW.<>     

High-speed single-quantum-well InGaAs/GaAs laser design andexperiment

Summary form only given. The authors report damping factors an order of magnitude lower than previously reported for SQW lasers. They also report bandwidths of 15 GHz obtained in SQW (single quantum well) lasers as a result of proper design of the quantum-well structure. The laser samples were grown on (100) n-type GaAs by molecular beam epitaxy (MBE). The SQW lasers had a minimum broad area threshold of 125 A/cm². A self-aligned technique was used to fabricate the narrow-ridge waveguide lasers. The ridges were dry-etched using Cl₂ . A model was developed that quantitatively explains the large enhancement in the dynamic response in the SQW lasers compared to those reported previously. This leads to an optimal design of quantum-well lasers for large-modulation bandwidths     

Transport limits in high-speed quantum-well lasers: experiment andtheory

It is shown experimentally that the modulation bandwidth of quantum well lasers can be reduced by a factor of six due to carrier transport across undoped layers of the laser as in the separate confinement heterostructure (SCH). Analytical expressions are given for the modulation response function, resonance frequency, damping rate and K factor to include carrier transport, and it is shown that carrier transport is responsible for a low-frequency rolloff which limits the modulation response of quantum-well lasers. It also shown that carrier transport leads to a reduction in the effective differential gain, while the gain compression factor remains largely unaffected by it     

Single quantum well strained InGaAs/GaAs lasers with large modulation bandwidth and lower damping

Strained In/sub 0.2/Ga/sub 0.8/As/GaAs single quantum well polyimide buried ridge waveguide lasers with 3 dB modulation bandwidths of 15 GHz and gain compression factors in as small as 9.98*10/sup -18/cm/sup -3/ have been fabricated. The authors have also observed that the gain compression factor is not larger than in lasers with bulk active areas, and is lower for structures with a smaller number of wells and shorter cavity lengths.<>     

610-nm band AlGaInP single quantum well laser diode

The short-wavelength limits of AlGaInP visible laser diodes with Al_0.5In_0.5P cladding layers, and Ga_xIn _1-xP single quantum well (QW) active regions are investigated. Good performance is maintained throughout the 620 nm band, but the characteristics rapidly degrade in the 610 nm band. Biaxial-compression and -tension were compared, with the case of tension yielding slightly better performance. Using a 25 Å Ga_0.45 In_0.55P QW, a wavelength of 614 nm was obtained, while a 50 Å Ga_0.6In_0.4P QW emitted at 620 nm with a threshold current density of 0.8 kA/cm². These results with thin single QWs indicate the effectiveness of using an Al_0.5In_0.5P cladding layer to reduce electron leakage     

InGaAs vertical-cavity surface-emitting lasers

The authors give theoretical and experimental results for vertical-cavity surface-emitting lasers (VCSELs). The modeling is applied to the design of InGaAs VCSELs. A simple method to calculate the reflectivity of semiconductor stack mirrors with graded interfaces and compound metal/semiconductor stack mirrors is introduced. The theoretical predictions are compared to results from actual device measurements. A novel technique is introduced to determine material parameters: fabrication of in-plane lasers from VCSEL material. The procedure used to determine the optical mode in such an in-plane laser is described. Using the insight gained from modeling, the external efficiency was increased to >30% with a threshold current density of 1 kA/cm²     

High speed quantum-well lasers and carrier transport effects

Carrier transport can significantly affect the high-speed properties of quantum-well lasers. The authors have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. They show theoretically and experimentally that carrier transport can lead to significant low-frequency parasitic-like rolloff that reduces the modulation response by as much as a factor of six in quantum-well lasers. They also show that, in addition, it leads to a reduction in the effective differential gain and thus the resonance frequency, while the nonlinear gain compression factor remains largely unaffected by it. The authors present the temperature dependence data for the K factor as further evidence for the effects of carrier transport     

Design and characterization of In0.2Ga0.8AsMQW vertical-cavity surface-emitting lasers

The device design, material characterization, and performance of optimized vertical-cavity surface-emitting lasers (VCSELs) are presented. The basic design goal was to increase the output power of the lasers without greatly increasing the low threshold current reported in earlier devices. The material characterization was performed by measuring in-plane lasers and broad-area VCSELs made from the same material as the small VCSELs. For 10-μm-square devices, outputs over 3 mW, device operation over 100°C, 6% wall-plug efficiency, threshold voltages under 3 V, and threshold currents under mA are reported     

Modeling temperature effects and spatial hole burning to optimizevertical-cavity surface-emitting laser performance

Two-dimensional physical models for single-mode index guided vertical cavity surface emitting lasers (VCSELs) are developed and compared with experimental measurements on state-of-the-art devices. Starting with the steady-state electron and photon rate equations, the model calculates the above threshold light-current (LI) characteristics. Included are temperature effects, spatial hole burning effects, carrier diffusion, surface recombination, and an estimation of optical losses. The model shows that the saturation of output power in the experimental devices is due to carrier leakage over the heterojunction and not simply the shifting of the gain peak relative to the cavity mode. Using the verified model new designs are analyzed, showing that output powers greater than 15 mW and power efficiencies above 20% should be achievable with existing processing technology