Review
Quantum Science & Technology
Miriam Serena Vitiello, Paolo De Natale
Summary: Quantum cascade lasers (QCLs) demonstrate the generation of artificial materials with tailor-made properties through quantum design, featuring intrinsic linewidths near the quantum limit and spontaneous phase-locking. Operating at terahertz frequencies, QCLs show important technological performances and have promising future prospects in the field of quantum technologies.
ADVANCED QUANTUM TECHNOLOGIES
(2022)
Article
Engineering, Electrical & Electronic
Jae Ha Ryu, Chris Sigler, Jeremy D. Kirch, Thomas Earles, Dan Botez, Luke J. Mawst
Summary: Grating-coupled, surface-emitting quantum-cascade lasers of linear geometry generally operate in an antisymmetric mode, which can be suppressed by designing gratings favoring symmetric-mode operation or having a central pi-phaseshift. Simulations and analysis show that the latter design has higher fabrication tolerance and can operate in a single-lobe beam pattern up to 0.63 W CW.
IEEE PHOTONICS TECHNOLOGY LETTERS
(2021)
Editorial Material
Nanoscience & Nanotechnology
Miriam S. Vitiello, Luigi Consolino, Massimo Inguscio, Paolo De Natale
Summary: QCL is the most powerful chip-scale source of optical frequency combs, allowing mode proliferation with large quantum efficiencies. THz QCL FCs have promising applications in various fields due to their high quantum efficiency and ease of integration.
Article
Chemistry, Multidisciplinary
Qi Yang, Jicheng Zhang, Xuemin Wang, Zhiqiang Zhan, Tao Jiang, Jia Li, Ruijiao Zou, Keyu Li, Fengwei Chen, Weidong Wu
Summary: This work presents a dual ridge terahertz quantum cascade laser lasing at 3.1 THz and analyzes its performance in detail. The experimental results provide a reference for realizing high-power terahertz quantum cascade lasers and offer guidance for the structural design of multiple ridges or laser arrays.
Article
Physics, Applied
Nathalie Lander Gower, Shiran Levy, Silvia Piperno, Sadhvikas J. Addamane, John L. Reno, Asaf Albo
Summary: We conducted an experimental study on a new design for a terahertz quantum cascade laser (THz QCL) that combines two-well injector and direct-phonon scattering schemes. This design improves the performance of the lasers by using a direct phonon scattering scheme for depopulating the lower laser level and reducing the overlap with the doped region. The design also achieves efficient isolation of active laser levels and shows potential for higher operating temperatures than the current records.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Luigi Consolino, Malik Nafa, Michele De Regis, Francesco Cappelli, Saverio Bartalini, Akio Ito, Masahiro Hitaka, Tatsuo Dougakiuchi, Tadataka Edamura, Paolo De Natale, Kazuue Fujita
Summary: This article presents the ultra-broadband THz emission obtained by intra-cavity mixing of different wavelengths, as well as the characterization and measurement methods of this emission. The new device can operate at low temperatures without the need for expensive liquid helium cooling, offering high stability and frequency accuracy.
APPLIED SCIENCES-BASEL
(2021)
Article
Multidisciplinary Sciences
Paolo Micheletti, Urban Senica, Andres Forrer, Sara Cibella, Guido Torrioli, Martin Frankie, Mattias Beck, Giacomo Scalari, J'rome Faist
Summary: Quantum cascade lasers (QCLs) offer an intriguing opportunity for generating on-chip optical dissipative Kerr solitons (DKS). Recent observations of DKS in mid-infrared ring QCLs have paved the way for achieving DKS at longer wavelengths. Terahertz ring QCLs with anomalous dispersion were realized using a waveguide planarization technology platform. A concentric coupled waveguide approach was implemented for dispersion compensation, while a passive broadband bullseye antenna improved power extraction and far field. The presence of solitons was confirmed through hysteric behavior, phase difference measurements, and intensity time profile reconstruction, which matched well with numerical simulations based on the Complex Ginzburg-Landau Equation (CGLE).
Article
Nanoscience & Nanotechnology
Kimberly S. Reichel, Eva Arianna Aurelia Pogna, Simone Biasco, Leonardo Viti, Alessandra Di Gaspare, Harvey E. Beere, David A. Ritchie, Miriam S. Vitiello
Summary: This study demonstrates the use of electrically pumped random laser resonators as sensitive photodetectors through the self-mixing effect, and shows the laser sensitivity to self-mixing under different feedback conditions. By utilizing two-dimensional cavities and reflecting emitted light back onto the surface, a near-field optical microscope with 120 nm spatial resolution is achieved, opening up possibilities for speckle-free nano-imaging and quantum sensing applications in the far-infrared region.
Article
Optics
Yuan-Yuan Li, Fang-Yuan Zhao, Yu Ma, Wei-Jiang Li, Jun-Qi Liu, Feng-Qi Liu, Jun-Wei Luo, Jin-Chuan Zhang, Shen-Qiang Zhai, Ning Zhuo, Li-Jun Wang, Shu-Man Liu
Summary: By integrating a suitable lens with a well-designed QCL array, multiple spatially-separated beams with controlled divergence angles and focusing efficiency are achieved. This method demonstrates excellent emission characteristics and multi-wavelength spectra at 77 K temperature.
OPTICS AND LASER TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Yuyang Wu, Jinchuan Zhang, Yunhao Zhao, Chongyun Liang, Fengqi Liu, Yi Shi, Renchao Che
Summary: This study investigates the mechanism of the temperature degradation of population inversion in terahertz quantum cascade lasers. It is found that the limited extraction efficiency of the extraction system is the main cause for the decrease in population inversion at elevated temperatures. Additionally, the temperature-induced electron-phonon scattering and electron-ionized donor separation also contribute to the degradation of population inversion.
Article
Physics, Applied
Viktor Rindert, Ekin Onder, Andreas Wacker
Summary: This paper presents detailed simulations of terahertz quantum cascade lasers based on two-well designs, analyzing the factors affecting the maximal operation temperatures and proposing methods to improve the current injection.
PHYSICAL REVIEW APPLIED
(2022)
Article
Physics, Applied
Ali Khalatpour, Man Chun Tam, Sadhvikas J. Addamane, John Reno, Zbignew Wasilewski, Qing Hu
Summary: In this paper, the maximum operating temperature of THz QCLs has been improved to approximately 261K, as a step toward the realization of compact semiconductor THz sources.
APPLIED PHYSICS LETTERS
(2023)
Article
Physics, Applied
Yu Wu, Sadhvikas Addamane, John L. Reno, Benjamin S. Williams
Summary: A new VECSEL external cavity design is demonstrated to transition from single/double-mode lasing to multi-mode lasing, with up to nine modes lasing simultaneously, paving the way for eventual frequency comb operation.
APPLIED PHYSICS LETTERS
(2021)
Article
Physics, Applied
Benjamin Roben, Xiang Lu, Klaus Biermann, Lutz Schrottke, Holger T. Grahn
Summary: Terahertz quantum-cascade lasers are based on complex semiconductor heterostructures, with optical gain generated by intersubband transitions. The effective group refractive index ng,eff can be determined by the spacing of laser modes in the emission spectra.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Optics
Muhammad Anisuzzaman Talukder, Paul Dean, Edmund H. Linfield, A. Giles Davies
Summary: This study introduces a THz QCL heterostructure designed to emit two resonant photons from each electronic relaxation between two same-parity states, predicting a significant enhancement of light intensity compared to conventional THz QCL structures through simulations.
Article
Chemistry, Multidisciplinary
Yonatan Ashlea Alava, Daisy Q. Wang, Chong Chen, David A. Ritchie, Arne Ludwig, Julian Ritzmann, Andreas D. Wieck, Oleh Klochan, Alexander R. Hamilton
Summary: The use of in situ epitaxial aluminum gates in GaAs/AlxGa1-xAs heterostructures effectively eliminates surface charge scattering, improving electron mobility. The electron mobility is strongly influenced by the thickness of aluminum, and the type of semiconductor wetting layer used at the semiconductor-aluminum interface. For 8 nm thick aluminum, the choice of wetting layer also impacts electron mobility, with aluminum on GaAs resulting in higher mobility compared to other wetting layers.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Luke W. Smith, Jack O. Batey, Jack A. Alexander-Webber, Yu-Chiang Hsieh, Shin- Fung, Tom Albrow-Owen, Harvey E. Beere, Oliver J. Burton, Stephan Hofmann, David A. Ritchie, Michael Kelly, Tse-Ming Chen, Hannah J. Joyce, Charles G. Smith
Summary: This study investigates the insulating states in monolayer graphene grown by chemical vapor deposition (CVD) and wet transferred on Al2O3 without specialized fabrication techniques. The results show the existence of insulating properties and the opening of an energy gap induced by the magnetic field in a graphene device with a bottleneck. A locally high-quality region within the bottleneck dominates transport and causes the device to behave as an insulating tunnel junction. The use of wet transfer fabrication techniques and multiplexing demonstrates the convenience of these scalable and reasonably simple methods for finding high-quality devices for fundamental physics research and functional properties.
Article
Physics, Multidisciplinary
Luke W. Smith, Hong-Bin Chen, Che-Wei Chang, Chien-Wei Wu, Shun-Tsung Lo, Shih-Hsiang Chao, I Farrer, H. E. Beere, J. P. Griffiths, G. A. C. Jones, D. A. Ritchie, Yueh-Nan Chen, Tse-Ming Chen
Summary: By integrating the Kondo correlation and spin-orbit interactions, researchers have demonstrated electrical control of the Kondo correlation using spin-orbit interactions in semiconductor quantum point contacts. The transition from single to double peak zero-bias anomalies in nonequilibrium transport indicates controlled Kondo spin reversal. Universal scaling of the Kondo conductance suggests that spin-orbit interactions can enhance the Kondo temperature.
PHYSICAL REVIEW LETTERS
(2022)
Article
Multidisciplinary Sciences
Lev Levitin, Harriet van der Vliet, Terje Theisen, Stefanos Dimitriadis, Marijn Lucas, Antonio D. Corcoles, Jan Nyeki, Andrew J. Casey, Graham Creeth, Ian Farrer, David A. Ritchie, James T. Nicholls, John Saunders
Summary: In this study, the authors cool a two-dimensional electron gas to sub-millikelvin temperatures by immersing it in liquid He-3 and utilizing nuclear adiabatic demagnetization.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Alessandra Di Gaspare, Valentino Pistore, Elisa Riccardi, Eva A. A. Pogna, Harvey E. Beere, David A. Ritchie, Lianhe Li, Alexander Giles Davies, Edmund H. Linfield, Andrea C. Ferrari, Miriam S. Vitiello
Summary: This study demonstrates mode-locking in surface-emitting electrically pumped random quantum cascade lasers at terahertz frequencies by exploiting the giant third-order nonlinearity of semiconductor heterostructure lasers and the nonlinear properties of graphene. Self-induced phase-coherence between naturally incoherent random modes and phase-locked random modes are achieved using lithographically patterning a multilayer graphene film or coupling a saturable absorber graphene reflector. This milestone in the physics of disordered systems paves the way for miniaturized, electrically pumped mode-locked light sources for various applications.
Article
Chemistry, Multidisciplinary
Leonardo Viti, Elisa Riccardi, Harvey E. Beere, David A. Ritchie, Miriam S. Vitiello
Summary: The on-chip integration of two-dimensional nanomaterials with terahertz quantum cascade lasers has led to wide spectral tuning, nonlinear high-harmonic generation, and pulse generation. In this study, a large area multilayer graphene (MLG) was transferred to a THz QCL to monitor its local lattice temperature during operation. The MLG's temperature dependence of electrical resistance was used to measure the local heating of the QCL chip. The results were validated through photoluminescence experiments. This integrated system provides a fast temperature sensor for THz QCLs and enables full electrical and thermal control on laser operation.
Letter
Chemistry, Multidisciplinary
Daisy Q. Wang, Zeb Krix, Oleg P. Sushkov, Ian Farrer, David A. . Ritchie, Alexander R. . Hamilton, Oleh Klochan
Summary: By imposing an external periodic electrostatic potential, the electronic properties of the confined electrons in a quantum well can be different from those in the host semiconductor. In this study, we fabricated and investigated a tunable triangular artificial lattice on a GaAs/AlGaAs heterostructure, where the band structure and Fermi surface can be transformed by altering a gate bias. Magnetotransport measurements revealed multiple quantum oscillations and commensurability oscillations due to electron scattering from the artificial lattice. Increasing the modulation strength revealed new commensurability oscillations caused by electron scattering from the artificial Fermi surface and triangular lattice. These results demonstrate the ability to form artificial two-dimensional crystals with designer electronic properties using low disorder gate-tunable lateral superlattices.
Article
Nanoscience & Nanotechnology
J. D. Fletcher, W. Park, S. Ryu, P. See, J. P. Griffiths, G. A. C. Jones, I. Farrer, D. A. Ritchie, H. -s. Sim, M. Kataoka
Summary: Coulomb forces between high-energy electrons in unscreened regime are detected and analysed using a mesoscopic electron collider. The ability to control Coulomb interactions on picosecond time scales is crucial for quantum logic devices with flying electrons. Despite previous findings, our study reveals Coulomb-dominated collisions of high-energy single electrons in counter-propagating ballistic edge states, indicating new ways to utilize Coulomb interactions for high-speed sensing or gate operations on flying electron qubits.
NATURE NANOTECHNOLOGY
(2023)
Article
Engineering, Electrical & Electronic
C. P. Dobney, A. Nasir, P. See, C. J. B. Ford, J. P. Griffiths, C. Chen, D. A. Ritchie, M. Kataoka
Summary: We have fabricated a device with two lateral p-n junctions on an n-type GaAs/Al0.33Ga0.67As heterostructure. The n-type material was converted to p-type by removing dopants and applying a voltage to a gate in this region. Controlled electroluminescence from both p-n junctions was demonstrated by varying the applied bias voltages. The emitted spectrum peak width was approximately 8 units.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Optics
Davide Baiocco, Ignacio Lopez-Quintas, Javier R. Vazquez de Aldana, Mauro Tonelli, Alessandro Tredicucci
Summary: This work presents the operation of a femtosecond-laser-written diode-pumped visible waveguide laser based on praseodymium-doped lithium lutetium fluoride. Different types of waveguides, including single-track structures, stress-induced waveguides, and depressed cladding structures, were fabricated using the femtosecond laser-induced refractive index modification in the crystal. The waveguide design was optimized to achieve extremely low propagation losses, and lasing at various wavelengths, including 604 nm, 721 nm, and 698 nm, was achieved from different waveguides.
Article
Physics, Applied
L. Liu, Y. Gul, S. N. Holmes, C. Chen, I. Farrer, D. A. Ritchie, M. Pepper
Summary: In this study, we systematically investigate a structure found in In0.75Ga0.25As heterostructures, and observe its stability and anisotropy in high magnetic fields. This research is important for understanding low-dimensional electronic systems with strong spin-orbit coupling.
APPLIED PHYSICS LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Abdullah M. Zaman, Yuezhen Lu, Nikita W. Almond, Oliver J. Burton, Jack Alexander-Webber, Stephan Hofmann, Thomas Mitchell, Jonathan D. P. Griffiths, Harvey E. Beere, David A. Ritchie, Riccardo Degl'Innocenti
Summary: The study investigates the polarization modulation performance of an integrated metamaterial/graphene device in the THz band. By modifying the graphene's Fermi level, the device's optical response can be modified, enabling active tuning of ellipticity and continuous modification of optical activity. Active circular dichroism and optical activity can be independently exploited by carefully selecting the transmitted frequency and relative angle between the incoming linear polarization and the device's symmetry axis. This all-electronically tuneable versatile polarization device has potential applications in polarization spectroscopy, imaging, and THz wireless generation.
FRONTIERS IN NANOTECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
P. M. T. Vianez, Y. Jin, W. K. Tan, Q. Liu, J. P. Griffiths, I. Farrer, D. A. Ritchie, O. Tsyplyatyev, C. J. B. Ford
Summary: Determining the bare electron mass (m0) in crystals is challenging due to many-body effects. By using a one-dimensional geometry, the interaction effects can be separated from m0, and the measured value is (0.0525 +/- 0.0015)me in GaAs. The value of m0 remains constant with varying density, and it is approximately 22% lighter than observed in higher-dimensional GaAs structures, consistent with the quasiparticle picture of a Fermi liquid.
Article
Materials Science, Multidisciplinary
M. J. Rendell, S. D. Liles, A. Srinivasan, O. Klochan, I. Farrer, D. A. Ritchie, A. R. Hamilton
Summary: In two-dimensional systems with a spin-orbit interaction, magnetic focusing is utilized to separate particles with different spins spatially. We conducted measurements on hole magnetic focusing under two different magnitudes of the Rashba spin-orbit interaction. We discovered that the attenuation of a focusing peak, conventionally linked to a change in spin polarization, is actually caused by a change in the scattering of a spin state in hole systems with a k3 spin-orbit interaction. Additionally, we found that the change in scattering length determined through magnetic focusing is consistent with the results obtained from Shubnikov-de Haas oscillations measurements.
Article
Materials Science, Multidisciplinary
A. Shetty, F. Sfigakis, W. Y. Mak, K. Das Gupta, B. Buonacorsi, M. C. Tam, H. S. Kim, I Farrer, A. F. Croxall, H. E. Beere, A. R. Hamilton, M. Pepper, D. G. Austing, S. A. Studenikin, A. Sachrajda, M. E. Reimer, Z. R. Wasilewski, D. A. Ritchie, J. Baugh
Summary: The effects of illumination on undoped two-dimensional electron gases (2DEGs) of varying depths at low temperature are investigated. Unbiased illuminations result in a gain in mobility at a certain electron density for 2DEGs located farther away from the surface, while for 2DEGs closer to the surface, a loss in mobility is observed. Biased illuminations with positive gate voltages lead to a mobility gain, whereas those with negative gate voltages result in a mobility loss. The magnitude of the mobility gain/loss weakens with increasing depth of the 2DEG. These changes in mobility are reversible through another biased illumination with the appropriate gate voltage, provided both n-type and p-type Ohmic contacts are present. Experimental results are modeled using Boltzmann transport theory, and possible mechanisms are discussed.
