A5003411938- Spectroscopy and Laser Applications
- Semiconductor Lasers and Optical Devices
- Photonic and Optical Devices
- Particle Detector Development and Performance
- Particle physics theoretical and experimental studies
- Terahertz technology and applications
- Laser Design and Applications
- Radiation Detection and Scintillator Technologies
- Semiconductor Quantum Structures and Devices
- Atmospheric Ozone and Climate
- Particle Accelerators and Free-Electron Lasers
- CCD and CMOS Imaging Sensors
- Quantum Chromodynamics and Particle Interactions
- Advanced Fiber Laser Technologies
- High-Energy Particle Collisions Research
- Advanced Optical Sensing Technologies
- Medical Imaging Techniques and Applications
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Air Quality Monitoring and Forecasting
- Geophysics and Gravity Measurements
- Algorithms and Data Compression
- Advanced Fiber Optic Sensors
- Pulsars and Gravitational Waves Research
- Advanced Semiconductor Detectors and Materials
The University of Queensland
1988-2022
Queensland University of Technology
2014-2021
Sheffield Hallam University
2015
University of Leeds
2015
Brunel University of London
1987-1993
We present the first measurement of left-right cross section asymmetry (${\mathit{A}}_{\mathit{L}\mathit{R}}$) for Z boson production by ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ collisions. The was performed at a center-of-mass energy 91.55 GeV with SLD detector SLAC Linear Collider which utilized longitudinally polarized electron beam. average beam polarization (22.4\ifmmode\pm\else\textpm\fi{}0.6)%. Using sample 10 224 decays, we measure...
Terahertz-frequency quantum cascade lasers (THz QCLs) based on bound-to-continuum active regions are difficult to model owing their large number of states. We present a computationally efficient reduced rate equation (RE) that reproduces the experimentally observed variation THz power with respect drive current and heat-sink temperature. also dynamic (time-domain) simulations under range currents predict an increase in modulation bandwidth as approaches peak light–current curve, mid-infrared...
We provide an experimental evidence of transient instabilities (TIs) in a terahertz (THz) quantum cascade laser (QCL) under optical feedback, contrast to the widely accepted claim that THz QCLs are ultrastable against feedback. The TIs appear as periodic oscillations emitted power or terminal voltage with increasing oscillation frequency feedback increases. absence relaxation and low linewidth enhancement factor makes them platform uniquely suitable for exploring external-cavity-related...
In this paper, we demonstrate a simple square-wave electrical modulation scheme for imaging with laser feedback interferometry (LFI). Distinct advantages of include: 1) the straightforward creation modulating signal, even high-current lasers and 2) its natural suitability lock-in detection. We compare against two established modalities LFI: mechanical using an optical chopper swept-frequency approach. The proposed lends itself to high-frequency modulation, which paves way high frame-rate LFI...
Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor are operated using pulsed-mode excitation, their behavior under optical depends electronic and thermal characteristics laser, as well nature external cavity. Predicting a laser both pulsed operation therefore requires detailed model that includes laser-specific characteristics. In this paper we introduce such for an exemplar bound-to-continuum terahertz frequency quantum...
The typical modal characteristics arising during laser feedback interferometry (LFI) in multi-mode terahertz (THz) quantum cascade lasers (QCLs) are investigated this work. To end, a set of reduced rate equations with gain saturation for general Fabry-Pérot THz QCL under optical is developed. Depending on bandwidth the and level, three different operating regimes identified, namely single-mode regime, tuneable-mode regime. When operates regimes, self-mixing signal amplitude (peak to peak...
A vacuum balance that compares the weights of 10-kg stainless-steel masses suspended in evacuated tubes at different levels a hydroelectric reservoir is being used to measure gravitational attractions layers lake water up 10 m depth. The mean effective distance between interacting this experiment 22 m, making it largest-scale measurement G using precisely controlled moving masses. extends laboratory-type measurements into range previously explored only by geophysical methods. Assuming purely...
Single-mode frequency-tuneable semiconductor lasers based on monolithic integration of multiple cavity sections are important components, widely used in optical communications, photonic integrated circuits and other technologies. To date, investigations the ultrafast switching processes such lasers, essential to reduce frequency cross-talk, have been restricted observation intensity over nanosecond-timescales. Here, we report coherent measurements switch-on dynamics, mode competition...
We propose a laser feedback interferometer operating at multiple terahertz (THz) frequency bands by using pulsed coupled-cavity THz quantum cascade (QCL) under optical feedback. A theoretical model that contains multi-mode reduced rate equations and thermal is presented, which captures the interplay between electro-optical, thermal, effects. By self-heating effect in both active passive cavities, self-mixing signal responses three different are predicted. multi-spectral interferometry system...
We present a model for longitudinal mode competition in coupled-cavity (CC) terahertz (THz) quantum cascade lasers (QCLs) by using scattering matrix method and multi-mode reduced rate equations (RREs). The dependence of the selection tuning characteristics on various device parameters is systematically investigated, including net waveguide loss, optical length passive cavity, heat-sink temperature different relationship between active cavity lengths. changes eigenmode frequencies due to...
Terahertz frequency quantum cascade lasers offer a potentially vast number of new applications. To better understand and apply these lasers, device-specific modeling method was developed that realistically predicts optical output power under changing current drive chip temperature. Model parameters are deduced from the self-consistent solution full set rate equations, obtained energy-balance Schrödinger-Poisson scattering transport calculations. The model is, thus, derived first principles,...
Terahertz quantum cascade-lasers (QCLs) are able to produce higher optical output power at temperatures when operated in pulsed mode. Predicting a laser's behavior under operation order achieve performance requirements is, however, nontrivial exercise: the complex and nonlinear interplay between current, electric field, thermal transients gives rise responses both emission frequency. In applications where it is important predict control these behaviors, establishing link current drive,...
We explain the origin of voltage variations due to self-mixing in a terahertz (THz) frequency quantum cascade laser (QCL) using an extended density matrix (DM) approach. Our DM model allows calculation both current-voltage (I-V) and optical power characteristics QCL under feedback by changing cavity loss, which gain active region is clamped. The variation intra-cavity field strength necessary achieve clamping, corresponding change bias required maintain constant current through...
We have determined the strong coupling ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$ from measurements of jet rates in hadronic decays ${\mathit{Z}}^{0}$ bosons collected by SLD experiment at SLAC. Using six collinear and infrared safe algorithms we compared our data with predictions QCD calculated up to second order perturbation theory, also resummed calculations. find...
In this article, we explore the interplay between self-pulsations (SPs) and self-mixing (SM) signals generated in terahertz (THz) quantum cascade lasers (QCLs) under optical feedback. We find that feedback dynamics a THz QCL, namely, SPs, modulate conventional SM interference fringes laser interferometry system. The phenomenon of fringe loss signal - well known interband diode was also observed along with pronounced SPs. With an increasing strength, transition from regular at weak (C ≤ 1) to...
Terahertz (THz) quantum cascade lasers (QCLs) are compact sources of radiation in the 1–5 THz range with significant potential for applications sensing and imaging. Laser feedback interferometry (LFI) QCLs is a technique utilizing sensitivity QCL to reflected back into laser cavity from an external target. We will discuss modelling techniques explore LFI biological tissue imaging show that confocal nature systems, their innate capacity depth sectioning, makes them suitable skin diagnostics...
This paper describes the design, construction, and initial operation of SLD Vertex Detector, first device to employ charge coupled devices (CCDs) on a large scale in high energy physics experiment. The Detector comprises 480 CCDs, with total 120 Mpixels. Each pixel functions as an independent particle detecting element, providing space point measurements charged tracks typical precision 5 μm each co‐ordinate. CCDs are arranged four concentric cylinders just outside beam pipe which surrounds...
Ultrashort terahertz pulse generation is essential for a range of proven applications, from time-resolved spectroscopy fundamental excitations to nondestructive testing and imaging. Recently, it has been shown that semiconductor-based quantum cascade lasers (QCLs) can be used generate pulses as short few picoseconds through active mode locking. However, further progress subpicosecond high peak power hampered by poor knowledge on how the electric field actually forms in these lasers. Here, we...
Remarkable progress in terahertz (THz) technology over the past decade has been driven by potential applications of THz waves areas such as biomedical imaging, long-range screening, and organic materials identification [1]. This growth is no small measure related to success quantum cascade laser (QCL) which established itself one most promising radiation sources at frequencies [2]. The appeal these novel semiconductor lasers stems from their compact size, broad spectral coverage (∼ 1–5 THz),...