A5031498581- Spectroscopy and Laser Applications
- Photonic and Optical Devices
- Terahertz technology and applications
- Semiconductor Lasers and Optical Devices
- Advanced Fiber Laser Technologies
- Atmospheric Ozone and Climate
- Superconducting and THz Device Technology
- Thermal Radiation and Cooling Technologies
- Plasmonic and Surface Plasmon Research
- Semiconductor Quantum Structures and Devices
- Advanced Optical Sensing Technologies
- Laser Design and Applications
- Advanced Fiber Optic Sensors
- Spectroscopy and Quantum Chemical Studies
University of Leeds
2014-2019
High-resolution spectroscopy not only can identify atoms and molecules but also provide detailed information on their chemical physical environment relative motion. In the terahertz frequency region of electromagnetic spectrum, where many have fundamental vibrational modes, there is a lack powerful sources with narrow linewidths that be used for absorption measurements or as local oscillators in heterodyne detectors. The most promising solid-state source THz quantum cascade laser (QCL),...
The gain recovery time of a bound-to-continuum terahertz frequency quantum cascade laser, operating at 1.98 THz, has been measured using broadband terahertz-pump-terahertz-probe spectroscopy. is found to reduce as function current density, attaining value 18 ps the laser brought close threshold. We attribute this reduction improved coupling efficiency between injector state and upper lasing level active region aligns.
Abstract The effects of optical feedback (OF) in lasers have been observed since the early days laser development. While OF can result undesirable and unpredictable operation systems, it also cause measurable perturbations to operating parameters, which be harnessed for metrological purposes. In this work we exploit ‘self-mixing’ effect infer emission spectrum a semiconductor using laser-feedback interferometer, terminal voltage is used coherently sample reinjected field. We demonstrate...
In this work, we present a density-matrix model, which considers an infinite quantum cascade laser (QCL) and models transport via nearest neighbor approximation. We will discuss derivation of output parameters the model in detail show direct mathematical link to semiclassical rate equation approach. This can be extended arbitrary number states QCL period, without priori specification upper lower lasing level. Application various structures is possible, including bound-to-continuum...
Two-dimensional spectroscopy is performed on a terahertz (THz) frequency quantum cascade laser (QCL) with two broadband THz pulses. Gain switching used to amplify the first pulse and second probe system. Fourier transforms are taken respect delay time between pulses sampling of pulse. The two-dimensional spectrum consists three peaks at (ωτ = 0, ωt ω0), ω0, 2ω0, ω0) where ω0 denotes lasing frequency. peak ωτ 0 represents response zero-frequency (rectified) component instantaneous intensity...
We demonstrate the generation of continuous wave terahertz (THz) frequency radiation from photomixers fabricated on both Fe-doped InGaAs and InGaAsP, grown by metal-organic chemical vapor deposition. The were excited using a pair distributed Bragg reflector lasers with emission around 1550 nm, THz was emitted over bandwidth greater than 2.4 THz. Two four InGaAsP wafers different Fe doping concentrations investigated, material found to outperform in terms power. dependencies power photomixer...
A periodically poled lithium niobate (PPLN) crystal with multiple poling periods is used to generate tunable narrow-bandwidth THz pulses for injection seeding a quantum cascade laser (QCL). We demonstrate that longitudinal modes of the close gain maximum can be selected or suppressed according seed spectrum. The QCL emission spectra obtained by electro-optic sampling from laser, in most favorable case, shows high selectivity and amplification overlap frequency narrow-band seed. Proper...
The accuracy of high-resolution spectroscopy depends critically on the stability, frequency control, and traceability available from laser sources. In this work, we report exact tunable synthesis phase control a terahertz laser. is locked by injection lock loop for first time, with signal generated heterodyning selected lines an all-fiber infrared comb generator in ultrafast photodetector. line separation exactly determined Global Positioning System-locked microwave synthesizer, providing to...
We report the generation mechanism associated with nano-grating electrode photomixers fabricated on Fe-doped InGaAsP substrates. Two different emitter designs incorporating nano-gratings coupled to same broadband antenna were characterized in a continuous-wave terahertz (THz) frequency system employing telecommunications wavelength lasers for and coherent detection. The current-voltage characteristics THz emission bandwidth of emitters is compared bias polarities optical polarisations....
We report on the high-resolution frequency and phase control of a terahertz (THz) quantum cascade laser (QCL). The 2.0 THz QCL is locked to stable microwave reference via an all-fibre infrared comb. controlled by optical injection independently introducing phase-lock loop that provides electronic feedback QCL, forming (OIPLL). By implementing this, (1) instrument limited linewidth was $ {<; }1$ Hz (2) for fixed frequency, relative can be within range 0.3 π.
The gain recovery time of a bound-to-continuum terahertz frequency quantum cascade laser, operating at 1.98 THz, has been measured using broadband terahertz-pump-terahertz-probe spectroscopy. is found to reduce as function current density, reaching value 18 ps the laser brought close threshold. We attribute this reduction improved coupling efficiency between injector state and upper lasing level active region aligns.
We present a highly coherent tunable THz source based on an optical frequency comb generator with frequencies referenced to primary standards. The synthesizer is continuously from 122.5 GHz greater than 2.7 THz, spectral resolution of 10's Hz and accuracy 1 part in 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> . composite noise has been measured up record 300 GHz, -75 dBc/Hz at offset kHz, limited by the scaled phase reference...
The evolution of the gain terahertz quantum cascade laser during injection seeding is probed as a function time. Oscillations are commensurate with variations field envelope.
A terahertz quantum cascade laser is injection seeded with narrow-band seed pulses generated from a periodically poled lithium niobate crystal. The spectral emission of the controlled by spectra.
Narrowband THz pulses generated from a periodically poled lithium niobate crystal are used to injection seed terahertz quantum cascade laser. The phase locked spectral emission the laser is significantly influenced by spectrum of pulse.
We demonstrate the generation of continuous wave terahertz radiation from Fe-doped InGaAs and InGaAsP photomixers grown by Metal Organic Chemical Vapor Deposition (MOCVD), using a pair 1550 nm diode lasers. A bandwidth > 2.4 THz is obtained emitters effect doping on emitted power studied.
The dynamic response of a terahertz quantum cascade laser is probed as function time. gain the THz QCL saturated by injection seeding with an initial seed pulse. time-resolved seeded then second
The emission mechanism of continuous wave (CW) terahertz (THz) photomixers that make use nanostructured gratings (NSGs) is studied. Two different photomixer designs, based on a single-sided NSG and double-sided NSG, embedded in the same antenna design fabricated an Fe doped InGaAsP substrate, are characterized with ~1550 nm excitation. They shown to exhibit similar performance terms spectral bandwidth emitted power. mapped laser excitation position, from which assigned enhanced optical...