A5071754533- Spectroscopy and Laser Applications
- Terahertz technology and applications
- Photonic and Optical Devices
- Semiconductor Quantum Structures and Devices
- Semiconductor Lasers and Optical Devices
- Atmospheric Ozone and Climate
- Advanced Semiconductor Detectors and Materials
- Advanced Fiber Laser Technologies
- Laser Design and Applications
- Ga2O3 and related materials
- Nanowire Synthesis and Applications
- ZnO doping and properties
- Quantum and electron transport phenomena
- GaN-based semiconductor devices and materials
- Superconducting and THz Device Technology
- Photonic Crystals and Applications
- 2D Materials and Applications
- Air Quality Monitoring and Forecasting
- Spectroscopy and Quantum Chemical Studies
- Strong Light-Matter Interactions
- Advanced Chemical Sensor Technologies
- Advanced Chemical Physics Studies
- Quantum Dots Synthesis And Properties
- Gas Sensing Nanomaterials and Sensors
- MXene and MAX Phase Materials
CSIR National Physical Laboratory of India
2012-2024
Academy of Scientific and Innovative Research
2016-2024
Council of Scientific and Industrial Research
2016-2023
University of Leeds
2010-2019
Vellore Institute of Technology University
2018
Bose Institute
2017
Saha Institute of Nuclear Physics
2017
Queensland University of Technology
2015
The University of Queensland
2015
Sheffield Hallam University
2015
We report terahertz quantum cascade lasers operating in pulsed mode at an emission frequency of 3 THz and up to a maximum temperature 178 K. The improvement the is achieved by using three-quantum-well active region design with resonant-phonon depopulation utilizing copper, instead gold, for cladding material metal-metal waveguides.
The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of THz radiation offering high power, spectral purity and moderate tunability. As such, these sources are particularly suited to the application imaging across range disciplines, have motivated significant research interest in this area over past decade. In paper we review technological approaches QCL-based key advancements within field. We discuss detail number targeted areas including multiple-frequency...
We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect self-mixing in QCL, and, specifically, monitoring perturbations to voltage across induced light reflected from an external object back into cavity. Self-mixing offers high sensitivity, potentially fast response, simple, compact optical design, we show that it can be used obtain high-resolution...
A simplistic design of a self-powered UV-photodetector device based on hybrid reduced-graphene-oxide (r-GO)/gallium nitride (GaN) is demonstrated. Under zero bias, the fabricated photodetector shows photosensivity ∼85% while ohmic contact GaN with an identical structure exhibits only ∼5.3% at 350 nm illumination (18 μW/cm2). The responsivity and detectivity were found to be 1.54 mA/W 1.45 × 1010 Jones (cm Hz½ W−1), respectively, bias fast response (60 ms), recovery time (267 excellent...
Terahertz (THz) quantum cascade lasers (QCLs) are currently the most advanced electrically pumped semiconductor in spectral range 1-5 THz. However, their operation at room temperature is still an unresolved challenge. In this paper, we discuss our efforts to improve performance of these devices. particular, present THz QCLs that approach thermoelectric cooled and factors limit high-temperature performance. We also a different type QCL source produces coherent radiation without population...
We demonstrate that the cavity resonance frequency - round-trip of Terahertz quantum cascade lasers can be injection-locked by direct modulation bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, show locking ranges above 200MHz. Inside this range laser is phase-locked, a phase noise determined RF-synthesizer. find square-root dependence RF-power in agreement classical injection-locking theory. These...
We investigate the implementation of surface emission via a second order grating in terahertz quantum cascade lasers with double-metal waveguides. Absorbing edge structures are designed to enforce anti-reflecting boundary conditions, which ensure distributed feedback cavity. The duty cycle is chosen maximize slope efficiency. Fabricated devices demonstrate output powers that comparable those measured from edge-emitting double metal waveguide without gratings. efficiency emitting twice...
The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of high-power radiation with narrow intrinsic linewidth. As such, THz QCLs are extremely promising sources for applications including high-resolution spectroscopy, heterodyne detection, and coherent imaging. We exploit the remarkable phase-stability to create swept-frequency delayed self-homodyning method both imaging materials analysis, using feedback interferometry. Using our scheme we obtain amplitude-like...
There has been growing interest in the use of terahertz (THz) quantum cascade lasers (QCLs) for sensing applications. However, lack compact and sensitive THz detectors limited potential commercial exploitation sensors based on these devices. We have developed a self-mixing technique which QCLs are used both generation interferometric radiation, eliminating need separate detector. Using this technique, we measured displacement remote target, with without opaque (in visible spectrum) materials...
We report the heterodyne detection and phase locking of a 2.5 THz quantum cascade laser (QCL) using terahertz frequency comb generated in GaAs photomixer femtosecond fiber laser. With 10 mW emitted by QCL, phase-locked signal at intermediate yields 80 dB signal-to-noise ratio bandwidth 1 Hz.
We analyze the temperature performance of five terahertz (THz)-frequency quantum cascade lasers based on a three-quantum-well resonant-phonon depopulation design as function operating frequency in 2.3-3.8-THz range. find evidence that device is limited by interplay between two factors: 1) optical phonon scattering thermal electrons, which dominates at shorter wavelengths, and 2) parasitic current, longer wavelengths. present simple model provides an accurate estimate current these devices...
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Abstract Compact optical detectors with fast binary photoswitching over a broad range of wavelength are essential as an interconnect for any light‐based parallel, real‐time computing. Despite the tremendous technological advancements yet there is no such single device available that meets specifications. Here multifunctional self‐powered high‐speed ultrabroadband (250–1650 nm) photodetector reported based on graphitic carbon‐nitride (g‐C 3 N 4 )/Si hybrid 2D/3D structure. The shows novel...
Terahertz frequency quantum cascade lasers (THz QCLs) are compact sources of coherent THz radiation with potential applications that include astronomy, trace-gas sensing, and security imaging. However, the reliance on slow incoherent thermal detectors has limited their practical use in systems. We demonstrate sensing using self-mixing (SM) interferometry, which is reflected from an object back into QCL cavity, causing changes laser properties; thus acts simultaneously as both a source...
There is considerable interest in the interrogation of biological tissue at terahertz (THz) frequencies, largely due to contrast optical properties different tissues which occur this electro-magnetic radiation band. Of particular are THz biomedical images, have potential highlight information than those acquired other frequency bands, thereby providing an augmented picture structures. In work, we demonstrate feasibility interferometric imaging technique using a quantum cascade laser (QCL)...
Terahertz quantum cascade lasers with wide-ridge metal-metal waveguides are prone to lasing in high-order lateral modes, which reduce the maximum light output power from these devices. We have demonstrated, theoretically and experimentally, that can be improved severalfold by introducing “side absorbers” into waveguide structure, enforce TM00 mode minor temperature performance deterioration. Lasers without side absorbers operate up 168K, a current record for devices processed using...
The use of integrated photonic structures to tailor the behavior light is extremely promising for optimizing performance and introducing advanced functionalities into optoelectronic devices. We demonstrate a powerful method based on photonic-band engineering which allows optimization resonator quality factors devices operating band-edge photonic-crystal states. also show that carefully designed π-shifts in two-dimensional photonic-resonators give enhanced beam properties. application these...