Infrared and terahertz quantum technologies
THz quantum gap: exploring potential approaches for generating and detecting non-classical states of THz light
Over the past few decades, THz technology has made considerable progress, evidenced by the performance of current THz sources and detectors, as well as the emergence of several THz applications. However, in the realm of quantum technologies, the THz spectral …
Strong coupling in metal-semiconductor microcavities featuring Ge quantum wells: a perspective study
In this work we theoretically investigate the possibility of observing strong coupling at mid-infrared frequencies within the group-IV semiconductor material platform. Our results show that the strong coupling condition is attainable in Ge/SiGe quantum wells …
Metrology of frequency comb sources: assessing the coherence, from multimode to mode-locked operation
Since the beginning of this millennium, frequency comb generators have reshaped frequency metrology and related areas. After more than two decades since their first realization, several other ways to generate frequency combs, in any spectral region, have been …
Probing THz intersubband absorption using Johnson noise thermometry
We investigate the THz intersubband absorption behavior of a single 40-nm wide GaAs/AlGaAs square quantum well (QW) using Johnson noise thermometry. In our measurements, the Johnson noise associated with intersubband absorption is measured from the in-plane …
Extraction of the electron excess temperature in terahertz quantum cascade lasers from laser characteristics
We propose a method to extract the upper laser level’s (ULL’s) excess electronic temperature from the analysis of the maximum light output power (P max) and current dynamic range ?J d = (J max ? J th) of terahertz quantum cascade lasers (THz QCLs). We …
Continuous-wave GaAs/AlGaAs quantum cascade laser at 5.7?THz
Design strategies for improving terahertz (THz) quantum cascade lasers (QCLs) in the 5–6?THz range are investigated numerically and experimentally, with the goal of overcoming the degradation in performance that occurs as the laser frequency approaches the …
Modeling with graded interfaces: Tool for understanding and designing record-high power and efficiency mid-infrared quantum cascade lasers
By employing a graded-interfaces model based on a generalized formalism for interface-roughness (IFR) scattering that was modified for mid-infrared emitting quantum cascade lasers (QCLs), we have accurately reproduced the electro-optical characteristics of …
An interband cascade laser based heterodyne detector with integrated optical amplifier and local oscillator
Heterodyne detection based on interband cascade lasers (ICL) has been demonstrated in a wide range of different applications. However, it is still often limited to bulky tabletop systems using individual components such as dual laser setups, beam shaping …
Ultra-sensitive heterodyne detection at room temperature in the atmospheric windows
We report room temperature heterodyne detection of a quantum cascade laser beaten with a local oscillator on a unipolar quantum photodetector in two different atmospheric windows, at 4.8?µm and 9?µm. A noise equivalent power of few pW is measured by …
Design and performance of GaSb-based quantum cascade detectors
InAs/AlSb quantum cascade detectors (QCDs) grown strain-balanced on GaSb substrates are presented. This material system offers intrinsic performance-improving properties, like a low effective electron mass of the well material of 0.026 m 0, enhancing the …
Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study
We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the …
High-quality CMOS compatible n-type SiGe parabolic quantum wells for intersubband photonics at 2.5–5 THz
A parabolic potential that confines charge carriers along the growth direction of quantum wells semiconductor systems is characterized by a single resonance frequency, associated to intersubband transitions. Motivated by fascinating quantum optics …
Integrated PIN modulator and photodetector operating in the mid-infrared range from 5.5 um to 10 um
This study reports the experimental demonstration of the first waveguide-integrated SiGe modulator using a PIN diode operating in a wide spectral range of the mid-infrared region. At the wavelength of 10?µm, an extinction ratio up to 10?dB is obtained in …
Low-loss hybrid germanium-on-zinc selenide waveguides in the longwave infrared
The longwave infrared (LWIR) range, which spans from 6?µm to 14?µm, is appealing for sensing due to strong molecular fingerprints in this range. However, the limited availability of low-loss materials that can provide higher-index waveguiding and …
Theoretical model of passive mode-locking in terahertz quantum cascade lasers with distributed saturable absorbers
In research and engineering, short laser pulses are fundamental for metrology and communication. The generation of pulses by passive mode-locking is especially desirable due to the compact setup dimensions, without the need for active modulation requiring …
Harmonic quantum cascade laser terahertz frequency combs enabled by multilayer graphene top-cavity scatters
Optical frequency comb synthesizers, operating in the harmonic regime, are metrological sources in which the emitted optical power is concentrated in a few modes, spaced by several multiples of the cavity free spectral range (FSR). This behavior reflects in a …
Optical conductivity of a Bi_2Se_3 topological insulator with a THz transparent top gate
We have performed an investigation into the optical conductivity and magnetotransport properties of top-gated devices patterned on the topological insulator Bi2Se3 in order to determine the relative effects of the different carrier species that exist within …
Engineering the plasmon modes of a confined electron gas
The volume plasmon modes of a confined electron gas are engineered in a step-like semiconductor potential, which induces the formation of adjacent regions of different charge density. Each region supports spatially localized collective modes. Adjacent modes …
Photon-assisted ultrafast electron–hole plasma expansion in direct band semiconductors
Time-resolved terahertz spectroscopy is used to investigate formation and ultrafast long-distance propagation of electron–hole plasma in strongly photoexcited GaAs and InP. The observed phenomena involve fundamental interactions of electron–hole system …
Magnetospectroscopy of shallow donors in two dimensions in the presence of fluctuations of the electrostatic potential
Spectroscopy of shallow donors is a tool to test theoretical models and to reveal properties of semiconductors. In this work we consider intra-shallow impurity transitions by studying a CdTe/(Cd, Mg)Te structure grown by a molecular beam epitaxy in which both …
Electronic transparency of internal interfaces in metallic nanostructures comprising light, heavy and ferromagnetic metals measured by terahertz spectroscopy
We investigate the electronic transport at the internal interface within a selection of metallic bilayer nanostructures using the contact-free, all-optical method of THz time-domain spectroscopy. The Ru/Co, Ru/Pt, and Ru/Al bilayer nanostructures and their …
Terahertz metamaterials for light-driven magnetism
We describe the design of two types of metamaterials aimed at enhancing terahertz field pulses that can be used to control the magnetic state in condensed matter systems. The first structure is a so-called “dragonfly” antenna, able to realize a five-fold …
Spintronic terahertz emitters with integrated metallic terahertz cavities
Spintronic terahertz emitters (STEs), based on optical excitation of nanometer thick ferromagnetic/heavy metal (FM/HM) heterojunctions, have become important sources for the generation of terahertz (THz) pulses. However, the efficiency of the optical-to-THz …
Sculpting ultrastrong light–matter coupling through spatial matter structuring
The central theme of cavity quantum electrodynamics is the coupling of a single optical mode with a single matter excitation, leading to a doublet of cavity polaritons which govern the optical properties of the coupled structure. Especially in the ultrastrong …
Photoelectric tunable-step terahertz detectors: a study on optimal antenna parameters, speed, and temperature performance
Field effect transistors have shown promising performance as terahertz (THz) detectors over the past few decades. Recently, a quantum phenomenon, the in-plane photoelectric effect, was discovered as a novel detection mechanism in gated two-dimensional …
Engineering topological interface states in metal-wire waveguides for broadband terahertz signal processing
Innovative terahertz waveguides are in high demand to serve as a versatile platform for transporting and manipulating terahertz signals for the full deployment of future six-generation (6G) communication systems. Metal-wire waveguides have emerged as …