Graded-index Separate-confinement Heterostructure Single Quantum Well Research Articles

Self-consistent simulation on the modal gain of graded-index separate-confinement-heterostructure quantum-well lasers

The effective guide index directly causes the mutual influences in determining the complex refractive index of quantum well and the complex propagation constant of a guided mode. In this paper, self-consistent model (SCM) working on both density matrix theory and transfer matrix method is applied to investigate the modal gain of AlGaAs/GaAs graded-index separate-confinement-heterostructure single quantum-well (GRIN-SCH-SQW) lasers. Based on SCM, the simulated modal gain spectrum shows good agreement with the experimental result. Although varying with the thickness of SCH region or aluminum mole fraction, the percentage change of optical gain is much smaller than that of optical confinement factor. On the other hand, thin well width of QW results in a relative high optical gain but poor optical field confinement. Such opposing effects tend to balance each other and cause the modal gain almost insensitive to the well width change before 60 A. Further increase of well thickness, the percentage change of optical gain is obviously larger than that of optical confinement factor. Therefore the optical gain becomes the dominant parameter that directly decreases the magnitude of modal gain.

Deep centers inAlGaAs/GaAs GRIN-SCHSQW laser structures grown by MBE and MOCVD

The deep centers inAlGaAs/GaAs graded index-separate confinement heterostructure single quantum well (GRIN-SCHSQW) laser structures grown by MBE and MOCVD have been investigated using deep level transient spectroscopy (DLTS) technique. The majority and minority carrier DLTS spectra show that the deep (hole and electron) traps (H1 and E3), having large capture cross sections and concentrations, are observed in the gradedn-Al x Ga 1 − x As layer of laser structures in addition to the well-known DX centers. For laser structures grown by MBE, the deep hole trap H1 and the deep electron trap E3 may be spatially localized in the interface regions of discontinuous variation Al mole fraction of then-Al x Ga 1 − x As layer with x = 0.20−0.43. For laser structures grown by MOCVD, the deep electron trap E3 may be spatially localized in then-Al x Ga 1 − x As layer with x = 0.18−0.30, and the DX center may be spatially localized in the interface regions of discontinuous variation Al mole fraction of theAl x Ga 1 − x As layer with x = 0.22−0.30.

Design considerations for high-power GaInP/AlGaInP unstable-resonator semiconductor lasers

Simple expressions are derived to evaluate the lasing condition and power characteristics of unstableresonator semiconductor lasers (URSL's). The gain-loss characteristics of several quantum-well materials are summarized and found to be important for URSL design considerations. To optimize URSL performance, the cavity length needs to approach an optimum value, which varies from ~300 µm for an InGaAs/GaAs graded-index separate-confinement-heterostructure single-quantum-well (GRINSCHSQW) to ~1000 µm for GaInP/AlGaInP GRINSCH-SQW materials. A set of high-power (1-W, double-mirror, pulsed) 660-nm wavelength GaInP/AlGaInP URSL's with magnification of 2.5 were fabricated using focused-ion-beam micromachining technology. The brightness of a 300 µm × 1500 µm URSL approaches 320 MW cm(-2) Sr(-1) at a pump current of 3000 mA.

GaAs/AlGaAs first-order gratings fabricated with electron beam lithography and very-narrow-linewidth long-cavity DBR laser diodes

A technique for fabricating GaAs/AlGaAs first-order gratings using electron beam (EB) lithography and its application to long-cavity distributed-Bragg-reflector (DBR) laser diodes are presented. The field stitching error, which limits the application of EB lithography to optical devices, was reduced to 5 nm by deflection amplitude calibration using marks on the samples. A technique for controlling the coupling coefficient using partially corrugated gratings is also proposed. These techniques were applied to fabrication of GaAs/AlGaAs first-order gratings of graded-index, separate-confinement-heterostructure, single-quantum-well (GRIN-SCH-SQW) distributed-Bragg-reflector (DBR) laser diodes. The resulting stitching error did not influence the single-mode lasing characteristics, and a very narrow linewidth of 237 kHz was achieved. The results show that EB lithography using the above techniques is useful in the fabrication of various optical devices with gratings. >

High-speed photodetection in a reverse biased GaAs/AlGaAs GRINSCH SQW laser structure

The authors report extremely efficient ( approximately 100% internal quantum efficiency) and high-speed ( approximately 25-pS FWHM) photodetection in a reverse-biased GaAs/AlGaAs ridge waveguide single-quantum-well (SQW) graded-index separate confinement heterostructure (GRINSCH) laser structure near lambda =830 nm. The impulse response is limited by device parasitics to 25 pS at large reverse bias voltages, and by photogenerated electron escape closer to flatband conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Very low threshold single quantum well graded-index separate confinement heterostructure InGaAs/InGaAsP lasers grown by chemical beam epitaxy

We have succeeded in preparing 1.5 μm wavelength strained-layer graded-index separate confinement heterostructure (GRINSCH) InGaAs/InGaAsP single quantum well (SQW) injection lasers by chemical beam epitaxy (CBE). These lasers have extremely low threshold current density Jth of 170 A/cm2, internal quantum efficiency of 83%, and internal waveguide loss of 3.8 cm−1. To the best of our knowledge, these results represent the best values obtained thus far from long-wavelength InGaAs/InGaAsP quantum well injection lasers grown by any techniques. However, despite the recent rapid reduction in Jth, the threshold-temperature dependence remains poor (T0=45 K) even in these very low Jth GRINSCH SQW lasers.

22 W coherent GaAlAs amplifier array with 400 emitters

Greater than 22 W of optical power has been demonstrated from a multiple-emitter, traveling-wave semiconductor amplifier, with approximately 87% of the output at the frequency of the injection source. The device integrates, in AlGaAs graded-index separate-confinement heterostructure single quantum well (GRINSCH-SQW) epitaxy, 400 ridge waveguide amplifiers with a coherent optical signal distribution circuit on a 12*6 mm chip. >

A model for GRIN-SCH-SQW diode lasers

A comprehensive model for graded-index, separate-confinement-heterostructure, single-quantum-well (GRIN-SCH-SQW) Al/sub x/Ga/sub 1-x/As diode lasers is presented, and compared with experimental data. The model combines many individual features not heretofore included together, and gives good agreement with gain-vs.-current density data for different structure variations. In addition, the threshold temperature dependence agrees well with data for typical laser conditions, and the high-gain kink in T/sub 0/ versus temperature is qualitatively explained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>