A5074026920- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Optical Network Technologies
- Semiconductor Quantum Structures and Devices
- Spectroscopy and Laser Applications
- Advanced Photonic Communication Systems
- Advanced Optical Network Technologies
- Functional Brain Connectivity Studies
- Laser Design and Applications
- Advanced Semiconductor Detectors and Materials
- Transcranial Magnetic Stimulation Studies
- EEG and Brain-Computer Interfaces
- Atmospheric Ozone and Climate
- Chalcogenide Semiconductor Thin Films
- Advanced Fiber Laser Technologies
- Solid State Laser Technologies
- Neural dynamics and brain function
- Optical Wireless Communication Technologies
- Advanced Chemical Sensor Technologies
- Analytical Chemistry and Sensors
- Advanced Optical Sensing Technologies
- Quantum Dots Synthesis And Properties
- Radiation Detection and Scintillator Technologies
- Atmospheric and Environmental Gas Dynamics
- Neuroscience and Neural Engineering
University of Maryland, Baltimore County
2015-2024
Marshall Space Flight Center
2016-2024
University of Maryland, Baltimore
2001-2022
Banaras Hindu University
2022
University of Maryland, College Park
2005-2017
Centeye (United States)
2017
AT&T (United States)
1989-2005
University of Baltimore
2002-2005
Nokia (United States)
1989-2005
Polytechnic University
1999
Chemical mapping at atomic-column resolution by energy-dispersive x-ray spectroscopy in a spherical aberration-corrected scanning transmission electron microscope (STEM) has been demonstrated for the 1.47-A dumbbell structure InGaAs. The structural imaging and chemical information two-dimensional map are directly correlated. Comparisons with other existing techniques of STEM conjunction energy-loss were discussed from aspects ionization interactions.
Room temperature spasing of surface plasmon polaritons at 1.46 μm wavelength has been demonstrated by sandwiching a gold-film plasmonic waveguide between optically pumped InGaAs quantum-well gain media. The spaser exhibits narrowing, the expected transverse-magnetic polarization, and mirror feedback provided cleaved facets in 1-mm long cavity fabricated with flip-chip approach. 1.06-μm pump-threshold ~60 kW/cm2 is good agreement calculations. architecture readily adaptable to all-electrical...
We report on room-temperature continuous-wave (CW) operation of /spl lambda//spl sim/8.2 μm quantum cascade lasers grown by metal-organic chemical vapor deposition without lateral regrowth. The have been processed as double-channel ridge waveguides with thick electroplated gold. CW output power 5.3 mW is measured at 300 K a threshold current density 2.63 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . gain room temperature close...
We describe the fabrication and performance of first integrated heterodyne receiver capable actual data reception. Integrating a continuously tunable 1.5 μm MQW-DBR laser with single-mode directional coupler/switch zero-bias MQW waveguide photodetectors, we have achieved error-free reception FSK-modulated pseudorandom digital code at 105 Mbit/s.
We report on a novel class of semiconductor metamaterials that employ strongly anisotropic dielectric function to achieve negative refraction in the midinfrared region spectrum, ∼8.5–13 μm. present two types metamaterials, layered highly doped/undoped heterostructures and quantum well superlattices are anisotropic. Contrary other optical these heterostructure systems optically thick (up 20 μm thick), planar, require no additional fabrication steps beyond initial growth. Using transmission...
In a multimode fiber (MMF) transmission system, the power penalty due to intersymbol interference (ISI) caused by differential mode delay (DMD) is one of main contributors total penalties in link budget. We demonstrated using equalization techniques overcome signal degradation modal conventional (62.5 μm) MMF. 10-Gb/s transmissions through 1.5-km-long MMF were realized. principle, this method can be applied achieve nearly any loss-limited distance.
Standoff detections of explosives using quantum cascade lasers (QCLs) and the photoacoustic (PA) technique were studied. In our experiment, a mid-infrared QCL with emission wavelength near 7.35 μm was used as laser source. Direct standoff PA detection trinitrotoluene (TNT) achieved an ultrasensitive microphone. The output light focused on explosive samples in powder form. signals generated detected directly by low-noise microphone 1 in. diameter. A distance up to 8 obtained alone. With...
Successful operation of long-wavelength InGaAsP low-threshold-current gain-coupled DFB lasers was demonstrated by using an quaternary grating that absorbs the (distributed feedback) emission. The amount gain (loss)-coupling is controlled composition (bandgap) and thickness InP-spacer layer between active layer. With optimally designed lasers, CW (continuous-wave) threshold currents were 10-15 mA (250- mu m cavity, as-cleaved), slope efficiency approximately 0.4 mW/mA (both facets) SMSR...
By invoking the slow-wave approximation, wave equation resumes form of Fresnel equation. Codes developed previously for paraxial beam propagation can be extended to simulate backward reflection and diffraction at any angle. Results planar waveguide gratings a beveled corner bend are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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 extremely low threshold current density Jth of 170 A/cm2, internal efficiency 83%, and waveguide loss 3.8 cm−1. To the best our knowledge, these results represent values obtained thus far from long-wavelength grown any techniques. However, despite recent rapid reduction Jth,...
The photoluminescence spectra of CdSx Se1−x doped glasses were found to be strongly dependent on the pumping laser intensity. Two spectral features corresponding two different recombination mechanisms identified. dynamic behavior can explained by competition between tunneling-mediated deeply trapped charges and direct excitons, free shallowly carriers, nonradiative recombination. Large (&gt;30 nm) blue shifts both peaks also observed as a function
Standoff chemical detection with a distance of more than 41 feet using photoacoustic effect and quantum cascade laser (QCL) operated at relatively low power, less 40 mW, is demonstrated for the first time. The option QCL provides advantages easy tuning modulation besides benefit compact size, light weight power consumption. standoff signal can be calibrated as function different parameters such pulse energy, gas vapor concentration distance. results yield good agreements theoretical model....
We report the chemical-beam epitaxial (CBE) growth of InP/InGaAsP Bragg mirrors around 1.55 μm wavelength region. Mirrors with nearly 100% reflectivity and more than 400 Å flat top region in band have been achieved by using 45 pairs InP (1348 Å) InGaAsP (1216 Å, λg=1.45 μm) quarter layers which a total thickness 11.5 μm. Excellent uniformity layer optical quality both horizontal vertical directions were obtained. This demonstrates unique capability CBE maintaining uniform reproducible during...
The IM (intensity modulation) and FM (frequency characteristics of vertical-cavity surface-emitting lasers are studied. laser has high efficiency broad bandwidth (near 8 GHz) at a very low bias (4.5 mA). Five Gb/s pseudorandom direct intensity modulation this with open eyes is demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
We report a tunable receiver based on MQW-DBR laser biased just below threshold. The device simultaneously integrates the functions of filter, optical amplifier, photodetectorand, if desired, an FSK discriminator. Using identical devices for both transmitter and receiver, we demonstrate transmission up to 250 Mbit/s with sensitivities in ˜- 30dBm range 10−9 BER. Speed is limited by FM response, independentspeed measurements indicate detection bandwidth at least 1.7 GHz.
Dense wavelength-division multiplexing (DWDM) technology offers tremendous transmission capacity in optical fiber communications. However, switching and routing lags behind the capacity, since most of today's packet switches routers are implemented using slower electronic components. Optical one potential candidates to improve be comparable with capacity. In this paper, we present an optically transparent asynchronous transfer mode (OPATM) switch that consists a photonic front-end processor...
We introduce a semiconductor distributed feedback (DFB) in which the grating is fabricated out of quantum well (QW) or superlattice multilayers. This approach provides very simple and effective scheme for achieving gain (loss)-coupled DFB lasers. The present idea was successfully demonstrated with 1.55-μm wavelength 6-QW In0.6Ga0.4As (5 nm)/InGaAsP (band-gap wavelength=1.25 μm, 18.6 nm) separate confinement heterostructure laser utilizing only 2-QW In0.62Ga0.38As (4 nm)/InP (9.3 as grating.
Inductively coupled plasma (ICP) operated in the reactive-ion etching mode is used for mesa of InP using Cl2/N2 chemistry with a Ni metal mask. Etch rates approximately 140 nm/min very smooth and vertical sidewalls are obtained at dc bias 120 V. The effects temperature, gas flow, chamber pressure, ICP source power, substrate power on etch rate studied; sidewall profile surface morphology will be discussed.