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We observe for the first time up to nine transverse modes lasing in the individual elements of a two-dimensional vertical-cavity top surface-emitting laser array under pulsed operation. These modes consist of the TEM/sub 0,0/, TEM/sub 0,1/, TEM/sub 1,0/, TEM/sub 1,1/, TEM/sub 0,2/, TEM/sub 2,0/, TEM/sub 1,2/, TEM/sub 2,1/, and TEM/sub 2,2/ modes, Each of these modes couples coherently across the array to form very distinct supermodes. The transverse modes as well as the resulting supermodes are identified by examining the near-field and far-field profiles as well as the corresponding spectra. We also obtain a record 1.4 W (pulsed) of coherent output power from the array during multitransverse-mode operation. In addition, the polarization properties of the array are investigated, It is found that the TEM/sub 0,1/ mode is horizontally polarized along the [011] crystalline axis while all the other modes are dominantly vertically polarized along the [011~] axis.

We have performed an extensive series of measurements on symmetrical barrier bound‐to‐continuum and asymmetrical barrier bound‐to‐bound quantum well infrared photodetectors consisting of only a single well. We find that the behavior of the optical (e.g., responsivity) and transport properties (e.g., gain) as a function of bias is strikingly different from that of the usual multi‐quantum well detectors. The simplicity of the structure has allowed an accurate theoretical calculation of the potential drops across each barrier, the photoinduced carrier depletion in the quantum well and therefore a detailed understanding of the device physics.

An extensive series of measurements and theoretical analysis are presented on an undoped single‐quantum‐well infrared photodetector. The well is filled by electron tunneling through the thin emitter barrier resulting in several novel characteristics compared with the usual directly well‐doped detectors. These include a unity optical gain and a dramatic drop in the well carrier density (and responsivity) at high bias when the bound state in the well drops below the emitter conduction‐band edge.

We present a detailed and thorough study of a wide variety of quantum well infrared photodetectors (QWIPs), which were chosen to have large differences in their optical and transport properties. Both n- and p-doped QWIPs, as well as intersubband transitions based on photoexcitation from bound-to-bound, bound-to-quasi-continuum, and bound-to-continuum quantum well states were investigated. The measurements and theoretical analysis included optical absorption, responsivity, dark current, current noise, optical gain, hot carrier mean free path; net quantum efficiency, quantum well escape probability, quantum well escape time, as well as detectivity. These results allow a better understanding of the optical and transport physics and thus a better optimization of the QWIP performance.

The authors have demonstrated a smart pixel prototype field-effect-transistor-self-electrooptic-effect-device (FET-SEED) integrated optoelectronic amplifier utilizing process technology suitable for flexible design and fabrication of high-yield optoelectronic circuits. A single MBE growth sequence provides for quantum-well modulators, photodiodes, doped channel MIS-like field-effect transistors (DMTs), and resistors. The device dimensions are controlled in a planar technology using ion implantation and selective plasma etching for isolation and contacting. Results demonstrate optical amplification in a fully integrated circuit. This technology will enable increased functionality by providing digital electronic processing between optical input and output. >

We have investigated the stabilization of GexSn1-x on (001) InSb substrates, as well as InSb coated GaAs substrates. We find that alloys up to ≈1500A can be stabilized when 0 0.10, we observe partial phase separation into coherent α-Sn and α-GeSn. The films are stable in the temperature range of 125-130° C, depending on Ge concentration. We present a thermodynamic model which exhibits the trends observed in the growth and stability of epitaxially stabilized GexSn1-x alloys. Electrical and optical measurements show consistently high carrier concentrations (1021 cm-3) and low carrier mobility (

We demonstrate electrical switching and modulation between two orthogonal polarization modes of air‐post vertical‐cavity surface emitting lasers with cruciform transverse cavity geometry. The continuous‐wave lasing emission is switched from one polarization mode to the orthogonal mode at frequencies up to 50 MHz by a small signal modulation of the injection current. Furthermore, a polarized output signal at twice the input frequency is generated at frequencies up to 10 MHz by a large signal modulation of the injection current from below threshold to above the polarization switching transition.

We report over 130 °C continuous wave operation of unbonded vertical cavity top‐surface emitting lasers emitting more than 1.0 mW at 110 °C. Furthermore, we control threshold currents to within only ±1.35 mA (±12%) over a 150 °C temperature range. We are also able to control the threshold current to within a factor of 2 over a 50 nm wavelength range using the same epidesign.

Changes in cathodoluminescence (CL) intensity from a buried single AlGaAs/GaAs/AlGaAs quantum well (QW) as a result of exposure to electron cyclotron resonance (ECR) hydrogen or argon discharges are reported. For additional dc biases of 150 V on the sample during either H2 or Ar plasma exposure, we observe substantial decreases in CL intensity from the well. Ar+ ion bombardment creates damage more resistant to annealing than does H+ ion bombardment at the same energy. The ECR discharges alone with zero additional dc bias cause degradation in the well luminescence due possibly to defects created by energetic electron bombardment or ultraviolet illumination. At intermediate bias voltages (50 V) strong hydrogen passivation of nonradiative centers is observed, leading to 500% increases in CL intensity from the well. The initial characteristics of the QW under these conditions are restored by annealing at 400 °C.

We report the occurrence of higher-order transverse modes lasing in the individual elements of a two dimensional VCSEL array. Each of these modes couples coherently to form very distinct supermodes. In addition, very interesting polarization properties are observed. The TEM 0,1 mode is horizontally polarized along the [Oll] crystalline axis while all other modes are dominantly vertically polarized along the [011] axis.

Although there has been extensive research1–8 on multi-quantum well infrared photodetectors (QWIPs), which typically contain many (~50) periods, there has been relatively limited experimental work9–11 (using a fixed frequency CO2 laser) done on QWIPs containing only a single quantum well. Recently, we have performed a complete series of experiments12–14 on single quantum well structures with n-type doped well, p-type doped well and un-doped well. These doped-single well detectors are, in fact, particularly interesting since they have exceptionally high optical gain compared to multi well detectors. The optical response of the undoped single quantum well detector is strongly dependent on the bias voltage because the well is filled by tunneling through a thin emitter barrier. In addition, their simple band structures allow accurate calculations of the bias voltage dependence of the potential profiles of each of the two barriers, band bending effects in the contacts, as well as charge accumulation (or depletion) in the quantum well. Therefore by comparing theory with experiment, one can achieve a better overall understanding of the optical and transport physics in these quantum well infrared photodetectors.

Heavily implanted MQW structures have not been examined as a function of applied bias in a pin geometry. Such studies address the interesting physical question of whether phenomena such as sharp excitons and quantum confined stark effect (QCSE), normally associated with ultra-clean material can persist amid the controlled introduction of defects.[1] We have studied several such MQW pin samples, each of which was grown on a quarter-wave dielectric reflecting stack mirror consisting of Al0.11Ga0.89As and AlAs layers. Devices contained 60 periods of GaAs quantum wells 100 Å thick with 60 Å Al x Ga1- x As barriers having mole fractions of x=0.3, 0.45, and 1.0. Devices were implanted with roughly 130 keV protons, focusing the damage into the intrinsic regions, to dose levels of 1 × 1012cm−2, 1 × 1013cm−2, and 1 × 1014cm−2. Large-area mesa devices were then fabricated from these structures via standard lithographic techniques. We have previously reported the behavior of x=0.3 barrier samples.[2]

Electronic chips have tremendous data processing capabilities but they also have a communications bottleneck. The amount of data that can be processed on electronic chips far exceeds the amount of data that can be brought in and out of these chips.

Absorption-based light modulators are attractive because they can be made compact and in high densities, operating with light normal to the plane of the device. The intrinsic power dissipation of such a modulator is simply the absorbed optical power, which (neglecting radiative recombination) must be dissipated in the device. However, most of the total dissipation in electrically-driven multiple quantum well (MQW) modulators operating with light incident normal to the device plane is non-intrinsic, resulting from motion of photo-generated carriers in externally applied electric fields. For example, in a pin MQW device biased to 5 V, motion of photo-generated electron-hole pairs through the total potential= V + V bi deposits about 6.3 eV of energy, 5 eV of which is non-intrinsic. Minimizing the overall dissipation in these devices is important, because it ultimately determines the packing density and the maximum optical input power.

Solid-state lasers with small gain cross sections require a fast and low-loss saturable absorber for passive modelocking. Intracavity semiconductors introduce too much loss, have too small a saturation intensity and have problems withstanding the high intracavity peak intensities. One solution is to put the semiconductor inside a low-Q coupled cavity (RPM) [1,2]. An intracavity reactive nonlinearity, such as self-focusing, has been used to produce fast saturable-absorber-like modelocking that is, however, not self-starting [3,4,5,6]

Efficiency and maximum power obtainable from vertical cavity lasers (VCL) are low at present due to high series resistance. It is possible to circumvent this and maintain high cavity quality by using a highly conductive, extremely thin metallic layer located in a node (null) of the standing waves just above the active layer. The fabrication was as follows: Bottom mirror and active region were essentially the same as in previous VCLs, and n-doped Al x Ga1- x As/AlAs mirror with an active region about a quarterwave thick. After ~1000 Å of p-doped AlGaAs on top of the active region the epitaxial growth stopped. An ~50-Å Au layer was evaporated on top of this and a conventional dielectric mirror (TiO2/SiO2) completed the structure. Current is injected from thicker Au contacts just to the side of the cavity into the thin layer, then directly into the p-doped layer just above (~1000 Å) the active region. Optically pumped lasing occurred at 240-pj input to such a device. The l–V response of a separate similar device, 10 μm in diameter, showed a nearly constant ~100 ohm resistance. More precise fabrication should yield better performance, both optically and electrically and electrically, in a single device.

We report for the first time the growth of high quality films of metastable α‐Sn. The structural properties of the molecular beam epitaxy grown metastable α‐Sn are investigated by means of in situ reflection high‐energy electron diffraction (RHEED) analysis, scanning electron microscopy including electron channeling patterns, and high‐resolution x‐ray scattering techniques. Scanning electron microscopy reveals a growth morphology of smooth and uniform surfaces. RHEED patterns yield a highly streaked (2×1) surface reconstruction suggesting a layer‐by‐layer growth mechanism. Triple‐axis x‐ray diffractometry was employed to determine structural parameters and the strain distribution. In‐plane rocking scans of the (400) reflection indicate a half width of 3 arcsec for the heterostructure α‐Sn/InSb. Out‐of‐plane scans reveal a tetragonal distortion perpendicular to the film plane, contributing a net strain of ∼0.28%. These results are in quantitative agreement with values calculated using simple elastic theory.