1,671 research outputs found
Terahertz Quantum Cascade Lasers - The Past, Present, and Potential Future
Since their first demonstration in 2002, the development of terahertz frequency quantum cascade lasers has been extremely rapid. We overview some of the advances that have taken place and which have made the terahertz quantum cascade laser such a ubiquitous source. We also consider potential future directions for terahertz quantum cascade laser technology, including its use in satellite-borne instrumentation for future Earth observation and planetary science missions
High-power GaAs/AlGaAs quantum cascade lasers with emission in the frequency range 4.7–5.6 THz
Terahertz emission and detection using Fe-doped InGaAs and low-temperature-grown-GaAs photoconductive switches
Wideband Electrically Controlled Vernier Frequency Tunable Terahertz Quantum Cascade Laser
Frequency tuning in terahertz frequency quantum cascade lasers is challenging because of low thermal and current tuning coefficients. Moreover, photonic designs like Vernier selection based sampled gratings, used in telecom lasers to tune emission frequency, are unsuitable due to the long terahertz wavelengths and will require impractically long cavities (>15 mm). Here, we report the first wideband frequency tuning from a monolithic device exploiting Vernier selection rules using a coupled-cavity laser with a defect engineered photonic lattice. A precisely positioned defect lattice allows us to engineer the free spectral range and finesse of one of the cavities, similar to a sampled grating but using shorter cavity lengths (<4 mm). A coupled-cavity was used to tune the emission frequency. We achieve frequency tuning over 209 GHz, including mode hop-free continuous tuning of ∼6–21 GHz across six frequency bands, controlled through Stark shift, cavity-pulling, localized Joule heating, and thermal effects
Ultra-fast sampling of terahertz pulses from a quantum cascade laser using superconducting antenna-coupled NbN and YBCO detectors
We demonstrate the ultra-fast detection of terahertz pulses from a quantum cascade laser (QCL) using superconducting NbN and YBCO detectors. This has enabled both the intrapulse and interpulse dynamics of a THz QCL to be measured directly, including interpulse heating effects on sub-μs timescales
Terahertz near-field microscopy using the self-mixing effect in a quantum cascade laser
We demonstrate terahertz (THz) apertureless near-field microscopy exploiting the self-mixing effect in a quantum cascade laser (QCL). A THz wave is scattered by a sharp needle positioned above an object and coupled back into the QCL cavity resulting in detection of the THz near-field signal through the self-mixing effect. Using this technique we demonstrate two-dimensional imaging at 2.53 THz with a spatial resolution of 1 μm - the highest image resolution achieved with a THz frequency QCL to date. This method offers an experimentally simple approach to coherent, high-resolution THz imaging
Electrically-controlled frequency tuning of terahertz quantum cascade lasers over 190 GHz using a coupled cavity with integrated photonic lattice
Quasi-continuous tuning in coupled cavity terahertz quantum cascade lasers with an integrated photonic lattice
Pump-probe measurements of gain in a terahertz quantum cascade laser
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. The recovery time is found to reduce as a function of current density, reaching a value of 18 ps as the laser is brought close to threshold. We attribute this reduction to improved coupling efficiency between the injector state and the upper lasing level as the active region aligns
Terahertz near-field microscopy using the self-mixing effect in a quantum cascade laser
We demonstrate terahertz (THz) apertureless nearfield microscopy exploiting the self-mixing effect in a quantum
cascade laser (QCL). A THz wave is scattered by a sharp needle
positioned above an object and coupled back into the QCL cavity
resulting in detection of the THz near-field signal through the
self-mixing effect. Using this technique we demonstrate twodimensional imaging at 2.53 THz with a spatial resolution of ︎
1 µm – the highest image resolution achieved with a THz
frequency QCL to date. This method offers an experimentally
simple approach to coherent, high-resolution THz imaging
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