Enhancing the gain by quantum coherence in terahertz quantum cascade lasers

We propose and study GaAs/AlGaAs terahertz frequency quantum cascade lasers in which mid-infrared radiation is used as a coherent drive for enhancing the terahertz gain

High order optical sideband generation with Terahertz quantum cascade lasers

Optical sidebands are generated by difference frequency mixing between a resonant bandgap near-infrared beam and a terahertz (THz) wave. This is realized within the cavity of a THz quantum cascade laser using resonantly enhanced non-linearities. Multiple order optical sidebands and conversion efficiencies up to 0.1% are shown

Low temperature transport spectroscopy of defects using Schottky-barrier MOSFETs

International audienceArt overview of our technique to explore single defects in silicon using a novel transistor geometry, the Schottky barrier MOSFET, is described. In this device the doped source and drain regions of a conventional MOSFET are replaced with metallic contacts. At low temperatures electron transport is dominated by direct tunneling through the space charge region formed next to the metal/semiconductor interface. If single impurities or defects are present in this region, transport reveals resonant tunneling peaks that allow investigations of the magnetic field dependence and excited states. Here we discuss different experiments where we have on separate occasions observed defects that may be related to Pt, B and Tb. (C) 2009 Elsevier B.V. All rights reserved

Hybrid electronic-photonic subwavelength cavities operating at terahertz frequencies

International audienc

Hybrid electronic-photonic subwavelength cavities operating at terahertz frequencies

International audienc

Vertical subwavelength mode confinement in terahertz and mid-infrared quantum cascade lasers

We exploit the modal confinement properties of metal-metal ridge waveguides to investigate the effect of reducing the thickness of the active laser cores in both terahertz and mid-infrared quantum cascade lasers. Devices with active regions over 55 times thinner than the free-space emission wavelength are demonstrated. They show only a modest increase in threshold current density compared with conventional-thickness devices. The limited increase in threshold is possibly due to a parasitic current channel in addition to the radiative current channel. These structures could be useful for the development of ultra-low volume lasers

High order sideband generation in terahertz quantum cascade lasers

We demonstrate the generation of high order terahertz (THz) frequency sidebands (up to 3rd order) on a near infrared (NIR) optical carrier within a THz quantum cascade laser (QCL). The NIR carrier is resonant with the interband transition of the quantum wells composing the QCL, allowing the nonlinearity to be enhanced and leading to frequency mixing. A phonon depopulation based QCL with a double metal cavity was used to enhance the intracavity power density and to demonstrate the higher order sidebands. The 1st order sideband intensity shows a linear dependence with THz power corresponding to a single THz photon, while the second order sideband has a quadratic dependence implying a two THz photon interaction and hence a third order susceptibility. These measurements are compared to the photoluminescence and the QCL bandstructure to identify the states involved, with the lowest conduction band states contributing the most to the sideband intensity. We also show that the interaction for the second order sideband corresponds to an enhanced direct third order susceptibility χ( 3 ) of ∼7 × 10−16(m/V)2, two orders of magnitude greater than the bulk value

Vertical sub-wavelength mode confinement in THz quantum cascade lasers

We exploit the modal confinement properties of metal-metal ridge waveguides to reduce the thickness of the active laser cores in both terahertz and mid-infrared quantum cascade lasers. Devices with active regions over 60 times thinner than the free-space emission wavelength are demonstrated. The devices surprisingly show only a modest increase in threshold current density compared with conventional-thickness devices

Roadmap on optical sensors

Published 18 December 2023Optical sensors and sensing technologies are playing a more and more important role in our modern world. From micro-probes to large devices used in such diverse areas like medical diagnosis, defense, monitoring of industrial and environmental conditions, optics can be used in a variety of ways to achieve compact, low cost, stand-off sensing with extreme sensitivity and selectivity. Actually, the challenges to the design and functioning of an optical sensor for a particular application requires intimate knowledge of the optical, material, and environmental properties that can affect its performance. This roadmap on optical sensors addresses different technologies and application areas. It is constituted by twelve contributions authored by world-leading experts, providing insight into the current state-of-the-art and the challenges their respective fields face. Two articles address the area of optical fiber sensors, encompassing both conventional and specialty optical fibers. Several other articles are dedicated to laser-based sensors, micro- and nano-engineered sensors, whispering-gallery mode and plasmonic sensors. The use of optical sensors in chemical, biological and biomedical areas is discussed in some other papers. Different approaches required to satisfy applications at visible, infrared and THz spectral regions are also discussed.Mário F S Ferreira, Gilberto Brambilla, Luc Thévenaz, Xian Feng, Lei Zhang, Misha Sumetsky, Callum Jones, Srikanth Pedireddy, Frank Vollmer, Peter D Dragic, Ori Henderson-Sapir, David J Ottaway, Elodie Strupiechonski, Goretti G Hernandez-Cardoso, Arturo I Hernandez-Serrano, Francisco J González, Enrique Castro Camus, Alexis Méndez, Paola Saccomandi, Qimin Quan, Zhongcong Xie, Björn M Reinhard and Max Die