A5064242857- Spectroscopy and Laser Applications
- Laser Design and Applications
- Semiconductor Lasers and Optical Devices
- Atmospheric Ozone and Climate
- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
- Atmospheric and Environmental Gas Dynamics
- GaN-based semiconductor devices and materials
- Quantum Dots Synthesis And Properties
- Advanced Semiconductor Detectors and Materials
- Analytical Chemistry and Sensors
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Advanced Fiber Laser Technologies
- Advancements in Semiconductor Devices and Circuit Design
- Thermal properties of materials
- Optical properties and cooling technologies in crystalline materials
- Photonic Crystals and Applications
- Solid State Laser Technologies
- Advanced Materials Characterization Techniques
- Laser-induced spectroscopy and plasma
- ZnO doping and properties
- Integrated Circuits and Semiconductor Failure Analysis
- Magnetic confinement fusion research
- Water Quality Monitoring and Analysis
University of Wisconsin–Madison
2016-2025
University of Wisconsin System
2021
Intraband (United States)
2016
The mid-infrared spectral region, 2–20 μm, is of great interest for sensing and detection applications, in part because the vibrational transition energies numerous molecules fall that region. Silicon photonics a promising technology to address many these applications on single integrated, low-cost platform. Near-infrared light sources, heterogeneously integrated silicon, have existed more than decade, there been incorporations optical devices silicon platforms. However, no lasers fully onto...
The Wisconsin high-temperature superconductor axisymmetric mirror experiment (WHAM) will be a high-field platform for prototyping technologies, validating interchange stabilization techniques and benchmarking numerical code performance, enabling the next step up to reactor parameters. A detailed overview of experimental apparatus its various subsystems is presented. WHAM use electron cyclotron heating ionize build dense target plasma neutral beam injection fast ions, stabilized by...
By employing a graded-interfaces model based on generalized formalism for interface-roughness (IFR) scattering that was modified mid-infrared emitting quantum cascade lasers (QCLs), we have accurately reproduced the electro-optical characteristics of published record-performance 4.9 µm- and 8.3 µm-emitting QCLs. The IFR-scattering parameters at various interfaces were obtained from measured values trends found via atom-probe tomography analysis one our 4.6 μm-emitting QCL structures with...
The step-taper active-region (STA) design concept is implemented for ~5.0 μm-emitting quantum cascade lasers (QCLs) grown by metal-organic chemical vapor deposition (MOCVD). Carrier-leakage suppression yields high characteristic temperatures the threshold-current density Jth, T0, and slope efficiency ηsl, T1: 226 K 653 K. Resonant-tunneling extraction from lower level results in miniband-like extraction. In turn, internal ηi found, a variable mirror-loss study, to be ~77%; thus approaching...
Five, 8.36 μm-emitting quantum-cascade lasers (QCLs) have been monolithically phase-locked in the in-phase array mode via resonant leaky-wave coupling. The structure is fabricated by etch and regrowth which provides large index steps (Δn = 0.10) between antiguided-array elements interelement regions. Such high contrast photonic-crystal (PC) more than an order of magnitude higher PC-distributed feedback previously used for coherent beam combining QCLs. Absorption loss to metal layers inserted...
This study presents the growth and characterization of an 8.1 μm-emitting, InGaAs/AlInAs/InP-based quantum cascade laser (QCL) formed on InP-on-Si composite template by metalorganic chemical vapor deposition (MOCVD). First, for composite-template formation, a GaAs buffer layer was grown solid-source molecular-beam epitaxy commercial (001) GaP/Si substrate, thus forming GaAs/GaP/Si template. Next, InP metamorphic (MBL) structure atop MOCVD, followed MOCVD full QCL structure. The top-surface...
Quantum cascade lasers (QCLs) have emerged as promising candidate sources for free-space communications. High optical power densities, short photon lifetimes, and low internal capacitance are important factors influencing the transmission bandwidth. We report design fabrication of 4.7 μm emitting, 1.5 mm cavity length, single-mode distributed-feedback QCLs, with a CW front-facet output 165 mW calculated lifetime 11.6 ps, resulting in an electrically limited modulation 3 dB cutoff at 850 MHz.
Graded-interfaces modeling unveils key features of high-power, high-efficiency quantum-cascade lasers (QCLs): direct resonant-tunneling injection from a prior-stage, low-energy state into the upper-laser (ul) level, over wide (~50 nm) multiple-barrier region; and new type photon-induced carrier transport (PICT). Stage-level QCL operation primarily involves two steps: ul level photon-assisted diagonal transition. Furthermore, under certain conditions, prior-stage state, extending deep next...
By tailoring the active-region quantum wells and barriers of 4.5-5.0-μm-emitting cascade lasers (QCLs), device performances dramatically improve. Deep-well QCLs significantly suppress carrier leakage, as evidenced by high values for threshold-current characteristic temperature <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (253 K) slope-efficiency...
This paper explores the feasibility of a break-even-class mirror referred to as BEAM (break-even axisymmetric mirror): neutral-beam-heated simple capable thermonuclear-grade parameters and $Q\sim 1$ conditions. Compared with earlier experiments in 1980s, would have: higher-energy neutral beams, larger denser plasma at higher magnetic field, both an edge core capabilities address magnetohydrodynamic kinetic stability higher-temperature plasmas. Axisymmetry high-field magnets make this...
4.8 μ m emitting, quantum cascade (QC) lasers that suppress carrier leakage out of their active regions to the continuum have been realized by using deep (in energy) wells in regions, tall barriers and around tapered conduction-band-edge relaxation regions. The characteristic temperature coefficients T0 T1 for threshold current density Jth slope efficiency, respectively, reach values 238 K over 20–60 °C range, which means efficiency vary with half as fast those conventional QC lasers. In...
Grating-coupled surface-emitting (GCSE) lasers generally operate with a double-lobed far-field beam pattern along the cavity-length direction, which is result of lasing being favored in antisymmetric grating mode. We experimentally demonstrate GCSE quantum-cascade laser design allowing high-power, nearly single-lobed surface emission parallel to longitudinal cavity. A 2nd-order Au-semiconductor distributed-feedback (DFB)/distributed-Bragg-reflector (DBR) used for feedback and out-coupling....
Silicon integration of mid-infrared (MIR) photonic devices promises to enable low-cost, compact sensing and detection capabilities that are compatible with existing silicon electronic technologies. Heterogeneous by bonding III-V wafers waveguides has been employed previously build integrated diode lasers for wavelengths from 1310 2010 nm. Recently, Fabry-Pérot Quantum Cascade Lasers on provided a 4800 nm light source applications. Distributed feedback (DFB) appealing many high-sensitivity...
Resonant coupling of the transverse-magnetic polarized (guided) optical mode a quantum-cascade laser (QCL) to antisymmetric surface-plasmon modes 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antisymmetric-mode absorption. In turn, lasing symmetric mode, that is, surface emission single-lobe far-field beam pattern, is strongly favored over controllable ranges grating duty cycle and tooth height. By using core-region characteristics published 4.6...
8.4 μm-emitting quantum cascade lasers (QCLs) have been designed to have, right from threshold, both carrier-leakage suppression and miniband-like carrier extraction. The slope-efficiency characteristic temperature T1, the signature of suppression, is found be 665 K. Resonant-tunneling extraction lower laser level (ll) below it, coupled with highly effective ll-depopulation provide a very short ll lifetime (~0.12 ps). As result laser-transition differential efficiency reaches 89%, internal...
Five-element phase-locked arrays of 4.7 μm-emitting quantum cascade lasers are demonstrated which operate either in a near-diffraction-limited (D.L.) beam to 3.6 W peak pulsed power or narrow (<; 3.5 × D.L.) up 6.1 power. Devices fabricated by two-step MOCVD process and predominantly an in-phase array mode, agreement with design-simulation studies. Analysis based on the actual device dimensions indicate that near-resonant leaky-wave coupling occurs. Scaling larger number elements...
Thermal management efforts in nanoscale devices must consider both the thermal properties of constituent materials and interfaces connecting them. It is currently unclear whether alloy/alloy semiconductor superlattices such as InAlAs/InGaAs have lower conductivities than their alloys. We report measurements crossplane resistivity at room temperature, showing that superlattice resistivities are larger by a factor 1.2-1.6 bulk materials, depending on strain state composition. show additional...
A new deep-well quantum-cascade laser (QCL) design, for which the barrier layers in active region are tapered such that their conduction band edges increase energy from injection to exit barrier, results significant suppression of carrier leakage 4.8 µm-emitting devices. For heatsink temperatures 20–60°C range, characteristic temperature coefficients threshold, T0, and slope efficiency, T1, reach values as high 231 K 797 K, respectively. The T1 more than a factor two higher best reported...
We demonstrate coupling of the laser mode into a passive waveguide by transfer-printing fully processed mid-infrared quantum cascade lasers onto silicon-on-sapphire platform. The is coupled silicon via an adiabatic taper. experimentally achieved efficiency taper estimated to be ∼10%, and theoretical calculations show that over 75% achievable reducing adhesive layer thickness below 100 nm. Light waveguides confirmed images taken at output facet 3-mm-long Si with camera. Our technique enables...
When conventionally calculating carrier leakage for state-of-the-art quantum cascade lasers (QCLs), that is, LO-phonon-assisted from the upper laser level via electron thermal excitation to high-energy active-region (AR) states, followed by relaxation low-energy AR ∼18%-wide gaps were recently found between calculated and experimentally measured internal efficiency values. We incorporate elastic scattering [i.e., interface-roughness (IFR) alloy-disorder scattering] into carrier-leakage...
A III-V thin-film single-quantum-well edge-emitting laser is patterned on both sides of the epitaxial layer and bonded to silicon. Injected threshold current densities 420 A/cm(2) for gain-guided lasers with bottom p-stripes top n-stripes 244 index-guided p-ridge n-stripe are measured a lasing wavelength approximately 995 nm. These densities, among lowest silicon reported date (to our knowledge), enable implementation integrated applications such as power-efficient portable chip-scale...
The equations for the threshold-current density J<sub>th</sub>, differential quantum efficiency η<sub>d</sub> and maximum wallplug η<sub>wp,max</sub> quantum-cascade lasers (QCLs) have been modified electron leakage backfilling. We used a thermalexcitation model of "hot" injected electrons from upper laser state to active-region energy states calculate currents. Then calculated characteristic temperature T<sub>0</sub> J<sub>th</sub> was found agree well with experiment both...