A5070978505- Spectroscopy and Laser Applications
- Photonic and Optical Devices
- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Semiconductor Lasers and Optical Devices
- Advanced Fiber Laser Technologies
- Terahertz technology and applications
- ZnO doping and properties
- Laser Design and Applications
- Ga2O3 and related materials
- Photonic Crystals and Applications
- Semiconductor materials and devices
- Nanowire Synthesis and Applications
- Quantum Dots Synthesis And Properties
- Semiconductor materials and interfaces
- Atmospheric Ozone and Climate
- Random lasers and scattering media
- Acoustic Wave Resonator Technologies
- Laser-Matter Interactions and Applications
- Molecular Junctions and Nanostructures
- Chalcogenide Semiconductor Thin Films
- Metal and Thin Film Mechanics
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Plant and animal studies
Khalifa University of Science and Technology
2023-2024
King Abdullah University of Science and Technology
2017-2023
Philipps University of Marburg
2010-2022
Politecnico di Milano
2021
University of Bologna
2021
BAE Systems (United States)
2021
Photonics (United States)
2018
Technische Universität Braunschweig
2009-2010
Abstract High‐quality epitaxy consisting of Al 1− x Ga N/Al y N multiple quantum wells (MQWs) with sharp interfaces and emitting at ≈280 nm is successfully grown on sapphire a misorientation angle as large 4°. Wavy MQWs are observed due to step bunching formed the edges. A thicker QW width accompanied by greater accumulation gallium near macrostep edge than that flat‐terrace 4° misoriented sapphire, leading generation potential minima respect their neighboring QWs. Consequently,...
We present chemical kinetics and environmental monitoring applications in the long-wavelength mid-infrared (LW-MIR) region using a new diagnostic that exploits widely tunable light source emitting LW-MIR. The custom-designed laser is based on difference-frequency generation (DFG) process nonlinear orientation-patterned GaAs crystal. pump laser, an external-cavity quantum cascade tuned continuous-wave (cw) mode, while signal CO2 gas operated pulsed mode with kilohertz repetition rate. idler...
We report on a first experimental study of the molecular properties nematic liquid crystals in terahertz range. In beginning, we extract frequency and temperature dependent refractive index absorption coefficient cyanobiphenyls 5CB, 6CB 7CB from time domain spectroscopy measurements investigate impact alkyl chain length macroscopic crystal characteristics, focusing especially pronounced odd even effect. Next, deduce principle polarizabilities order parameter S by applying Vuks' approximation...
Spontaneously grown, self-aligned AlGaN nanowire ultraviolet light emitting diodes still suffer from low efficiency partially because of the strong surface recombination caused by states, i.e., oxidized and high-density states. Several passivation methods have been introduced to reduce nonradiative using complex toxic chemicals. Here, we present an effective method suppress such undesirable nanowires via diluted potassium hydroxide (KOH) solution, a commonly used chemical process in...
High-density dislocations in materials and poor electrical conductivity of p-type AlGaN layers constrain the performance ultraviolet light emitting diodes lasers at shorter wavelengths. To address those technical challenges, we design, grow, fabricate a novel nanowire structure adopting graded-index separate confinement heterostructure (GRINSCH) which active region is sandwiched between two compositionally graded layers, namely, GRINSCH diode. Calculated electronic band diagram carrier...
Group III-nitride semiconductor materials especially AlGaN are key-emerging candidates for the advancement of ultraviolet (UV) photonic devices. Numerous nanophotonics approaches using nanostructures (e.g., nanowires, nanorods, and quantum dots/disks) nanofabrication substrate patterning, crystals, nanogratings, surface-plasmons) have been demonstrated to address material growth challenges enhance device efficiencies devices operating at UV wavelengths. Here, we review progress...
The question whether nonionizing electromagnetic radiation of low intensity can cause functional effects in biological systems has been a subject debate for long time. Whereas the majority studies have not demonstrated these effects, some aspects still remain unclear, e.g., high-frequency terahertz range affects systems. In particular frequencies higher than 0.150 THz, investigations ability to genomic damage performed. present study, human skin cells were exposed vitro at two specific...
We present the first self-mode-locked optically pumped quantum-dot semiconductor disk laser. Our mode-locked device emits sub-picosecond pulses at a wavelength of 1040 nm and features record peak power 460 W repetition rate 1.5 GHz. In this work, we also investigate temperature dependence pulse duration as well time-bandwidth product for stable mode locking.
Localization effects on the optical properties of GaAs1−xBix/GaAs single quantum wells (SQWs), with Bi contents ranging from x = 1.1% to 6.0%, are investigated using continuous-wave and time-resolved photoluminescence. The temperature- excitation density dependence PL spectra systematically studied, carrier recombination mechanisms analyzed. At low temperatures, time-integrated emission is dominated by localized electron-hole pairs due varying content clustering in alloy. extracted energy...
The valence and conduction band offsets (VBO CBO) at the semiconductor heterojunction are crucial parameters to design active region of contemporary electronic optoelectronic devices. In this report, study alignment In0.15Al0.85N/MoS2 lattice matched heterointerface, large area MoS2 single layers chemical vapor deposited on molecular beam epitaxial grown In0.15Al0.85N films vice versa. We grew InAlN having an in-plane parameter closely matching with that MoS2. confirm is a layer from optical...
Terahertz time-domain spectroscopy (THz TDS) holds high potential as a non-destructive, non-contact testing tool. We have identified plethora of emerging industrial applications such quality control processes and products in the plastics industry. Polymers are transparent to THz waves while additives show significantly higher permittivity. This dielectric contrast allows for detecting additive concentration degree dispersion. present first inline configuration TDS spectrometer monitoring...
The longitudinal multi-mode emission in a vertical-external-cavity surface-emitting laser is investigated using both single shot streak camera measurements and interferometric measurement techniques. For this, the operated single- two-color regime an etalon free-running configuration without etalon, respectively. analyzed with respect to pump power output coupling losses for long short resonator. We observe steep increase of bandwidth close threshold monitor transition between operation....
Group-III nitride nano-dimensional materials with noncentrosymmetric crystal structure offer an exciting area of piezotronics for energy conversion applications. We experimentally report the piezotronic and piezo-phototronic effects n-InGaN nanowires (NWs) having emission wavelength in visible region (≈510 nm). The n-type InGaN NWs, exhibiting high structural optical quality, were grown by plasma-assisted molecular beam epitaxy (PAMBE) on Ti/TaN/Si substrates to facilitate direct bottom...
We present a multimodal diode-laser-based terahertz (THz) spectroscopy system. In contrast to other laser-based THz setups that provide either cw or broadband generation, our configuration combines the advantages of both approaches. Our low complexity setup enables fast switching from difference frequency generation emission, enabling sophisticated data analysis like much more complex time domain systems.
Photoelectrochemical methods are implemented to quantify the hole concentration in AlGaN nanowires, calibrate doping conditions, and design ultraviolet light-emitting diodes.
Frequency combs have triggered an impressive evolution of optical metrology across diverse regions the electromagnetic spectrum, from ultraviolet to terahertz frequencies. An unexplored territory, however, remains in region vibrational bending modes, mostly due lack single-mode lasers long-wavelength (LW) part mid-infrared (MIR) spectrum. We fill this gap through a purely MIR-based nonlinear laser source with tunability 12.1 14.8 $\mu$m, power up 110 $\mu$W, MHz-level linewidth and comb...
The temporal stability of a two-color vertical-external-cavity surface-emitting laser is studied using single-shot streak-camera measurements. collected data evaluated via quantitative statistical analysis schemes. Dynamically stable and unstable regions for the operation are identified dependence on pump conditions analyzed.
We report on a comparative experimental and theoretical study of the thermal quenching photoluminescence (PL) intensity in Ga(AsBi)/GaAs heterostructures. An anomalous plateau PL is observed at intermediate temperatures under relatively low excitation intensities. Theoretical analysis based well-approved approach shows that this peculiar behavior points non-monotonous density states (DOS) disorder-induced band tails with least two-energy-scales. While previous studies carried out high...
Highly stabile single mode and multi-mode random lasing emissions were observed from ZnO nanorods array prepared on glass substrates using chemical deposition technique. By varying the post-growth-annealing time, nanorod diameters between 54 78 nm with population densities 75 95 nanorods/µm2 obtained. Depending density diameter of nanorods, single, double triple lowest threshold 209 mJ/cm2. Furthermore, showed an obvious dependency density. The emission maintained its wavelength increasing...