D.B. Young

Bio: D.B. Young is an academic researcher from University of California, Santa Barbara. The author has contributed to research in topics: Semiconductor laser theory & Laser. The author has an hindex of 22, co-authored 45 publications receiving 1394 citations.

Low threshold planarized vertical-cavity surface-emitting lasers

Abstract: Vertical-cavity surface-emitting lasers fabricated utilizing a self-aligned process to provide planarized contacts are discussed. A single 80-AA In/sub 0.2/Ga/sub 0.8/As strained quantum well was used in the active region. Emission was at 963 nm. Threshold currents under continuous-wave room temperature operation of 1.1 mA, at 4.0-V bias, were measured for numerous 12- mu m*12- mu m devices. Corresponding threshold current densities were 800 A/cm/sup 2/ (600 A/cm/sup 2/ for broad area devices). These are the lowest figures yet reported for this type of device. It was found that grading of the mirror had a marked effect on mirror resistance. >

Enhanced performance of offset-gain high-barrier vertical-cavity surface-emitting lasers

Abstract: The temperature dependence and power output of vertical-cavity surface-emitting lasers (VCSELs) are addressed. The peak wavelength of the quantum well has been offset from the wavelength of the device cavity mode so that they are aligned at elevated temperatures. The result of this design change is to produce an 8- mu m-diameter VCSEL capable of operation to 145 degrees C, as well as CW operation of broad-area (70- mu m diameter) heat-sunk devices to record power levels. Fiber coupling experiments were also carried out, and a record 33-mW CW power was coupled to a multimode fiber. >

Band‐gap engineered digital alloy interfaces for lower resistance vertical‐cavity surface‐emitting lasers

Abstract: We report on a technique of grading the heterobarrier interfaces of a p‐type distributed Bragg reflector mirror to reduce the operating voltages of vertical‐cavity surface‐emitting lasers (VCSELs). We report VCSELs with lower operating voltages (2–3 V) and record continuous‐wave room‐temperature power‐conversion efficiencies (17.3%). We experimentally demonstrate that by using a parabolic grading and modulating the doping correctly, a flat valence band is generated that provides low voltage hole transport. The low resistance mirrors are achieved using low Be doping, digital‐alloy grading and 600 °C growth temperatures.

High efficiency submilliamp vertical cavity lasers with intracavity contacts

Abstract: Contacts have been made to p- and n-type layers on opposite sides of the active region within the cavity of an InGaAs vertical cavity surface emitting laser. The two concentric ring contacts allow all electrical connections on and emission from the top surface of a semi-insulating GaAs substrate. The design includes a novel current leveling layer to minimize current crowding effects. A high external quantum efficiency of 46% has been measured with maximum output powers up to 6 mW for a 15 /spl mu/m diameter device and threshold currents of 0.72 mA for a 7 /spl mu/m diameter laser. >

Lateral carrier diffusion and surface recombination in InGaAs/AlGaAs quantum‐well ridge‐waveguide lasers

Abstract: We measured the increase in threshold currents due to lateral carrier diffusion in InGaAs/AlGaAs quantum‐well ridge‐waveguide laser diodes. The ridge stripes were fabricated by using both in situ monitored pure Cl2 reactive ion etching and selective wet etching to completely eliminate the spreading current in the conductive upper cladding layer while keeping the ridge sidewalls straight. After comparing the threshold data with a theoretical model, the ambipolar diffusion coefficient is found to be 22 cm2/s in the population‐inverted InGaAs layer. This model is based on the calculated optical gain curve and the ambipolar carrier transport in the quantum‐well and waveguiding layers. The dependence of carrier lifetime on the local carrier concentration is included in the calculation. Moreover, from another set of devices with the portions of the active layer outside the ridge stripes etched away, the surface recombination velocity is found to be around 1–2×105 cm/s.

Diode Lasers and Photonic Integrated Circuits

Abstract: Ingredients. A Phenomenological Approach to Diode Lasers. Mirrors and Resonators for Diode Lasers. Gain and Current Relations. Dynamic Effects. Perturbation and Coupled--Mode Theory. Dielectric Waveguides. Photonic Integrated Circuits. Appendices. Index.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

Abstract: We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

Resonant cavity enhanced photonic devices

Abstract: We review the family of optoelectronic devices whose performance is enhanced by placing the active device structure inside a Fabry‐Perot resonantmicrocavity. Such resonantcavity enhanced (RCE) devices benefit from the wavelength selectivity and the large increase of the resonant optical field introduced by the cavity. The increased optical field allows RCE photodetector structures to be thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. Off‐resonance wavelengths are rejected by the cavity making RCE photodetectors promising for low crosstalk wavelength division multiplexing(WDM) applications. RCE optical modulators require fewer quantum wells so are capable of reduced voltage operation. The spontaneous emission spectrum of RCE light emitting diodes(LED) is drastically altered, improving the spectral purity and directivity. RCE devices are also highly suitable for integrated detectors and emitters with applications as in optical logic and in communication networks. This review attempts an encyclopedic overview of RCE photonicdevices and systems. Considerable attention is devoted to the theoretical formulation and calculation of important RCE device parameters. Materials criteria are outlined and the suitability of common heteroepitaxial systems for RCE devices is examined. Arguments for the improved bandwidth in RCE detectors are presented intuitively, and results from advanced numerical simulations confirming the simple model are provided. An overview of experimental results on discrete RCE photodiodes, phototransistors, modulators, and LEDs is given. Work aimed at integrated RCE devices,optical logic and WDM systems is also covered. We conclude by speculating what remains to be accomplished to implement a practical RCE WDM system.

Surface-emitting laser-its birth and generation of new optoelectronics field

Abstract: The surface-emitting laser (SEL) is considered one of the most important devices for optical interconnects and LANs, enabling ultra parallel information transmission in lightwave and computer systems. We introduce its history, fabrication technology, and discuss the advantages. Then, we review the progress of the surface emitting laser and the vertical-cavity surface-emitting laser (VCSEL), covering the spectral band from infrared to ultraviolet by featuring its physics, materials, fabrication technology, and performances, such as threshold, output powers, polarizations, line-width, modulation, reliability, and so on.

Nanoscale wires and related devices

Abstract: The present invention relates generally to sub-microelectronic circuitry, and more particularly to nanometer-scale articles, including nanoscale wires which can be selectively doped at various locations and at various levels. In some cases, the articles may be single crystals. The nanoscale wires can be doped, for example, differentially along their length, or radially, and either in terms of identity of dopant, concentration of dopant, or both. This may be used to provide both n-type and p-type conductivity in a single item, or in different items in close proximity to each other, such as in a crossbar array. The fabrication and growth of such articles is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components. For example, semiconductor materials can be doped to form n-type and p-type semiconductor regions for making a variety of devices such as field effect transistors, bipolar transistors, complementary inverters, tunnel diodes, light emitting diodes, sensors, and the like.