Roland Teissier

We report InAs-based quantum cascade lasers (QCLs) operating near 14 µm with a threshold current density J_th as low as 0.6 kA/cm² at room temperature. The threshold obtained is lower than the J_th of the best reported InP-based QCLs to date without facet treatment. The achieved performance improvement is partially due to an increased separation between the upper transition level and the next one in the active quantum wells of the employed QCL design.

A study of transport in a quantum hot electron transistor made of an InAs/AlSb heterostructure is reported. It exhibited that the quantum hot electron transistors with a thick emitter efficiently prevented the parasitic base currents compared with transistors with a thin emitter. The static characteristics of the fabricated devices demonstrated an enhancement of the current gain of 9 and a collector breakdown voltage of 1.5 V with thick-emitter designed transistors. In optimized devices, the current is dominated by fast resonant tunneling that is promising for their future development of as high frequency transistors.

We present InAs/AlSb quantum cascade lasers (QCLs) monolithically integrated on an on-axis (001) Si substrate. The lasers emit near 8 μm with threshold current densities of 0.92–0.95 kA/cm² at 300 K for 3.6-mm-long devices and operate in pulsed mode up to 410 K. QCLs of the same design grown for comparison on a native InAs substrate demonstrated a threshold current density of 0.75 kA/cm² and the same maximum operating temperature. The low threshold current density of the QCLs grown on Si makes them suitable for photonic integrated sensor implementation.

—The tunneling electron transport in GaAs/AlAs and InAs/AlSb superlattices with electric domains at room temperature is studied. At voltages above the threshold for the formation of domains,...

We report low threshold continuous wave (CW) operation of InAs/AlSb quantum cascade lasers emitting around 20 μm. The laser cavity was made of a plasmon-enhanced dielectric waveguide with cladding layers made of n-InAs. The devices exhibited a threshold current density of 1.38 kA/cm² at the maximum temperature of CW operation of 240 K and an output power of 14 mW/facet at T = 80 K. In pulsed mode, the lasers operated up to 380 K with a threshold current density of 1.15 kA/cm² at room temperature.

Terahertz range photoluminescence from specially designed structures with tunnel coupled double quantum wells under interband optical excitation has been investigated. A series of narrow emission lines were observed and interpreted as intersubband radiative transitions between electron quantum confinement levels.

In order to improve the maximum operating temperature of THz quantum cascade lasers (QCLs) we propose to modify the three well resonant phonon design by increasing the energy of the separation between the bottom transition levels and the ground states, which is usually adjusted to the LO-phonon energy in GaAs. The fabricated devices based on this design with non-resonant depopulation of the bottom transition level operated in pulsed mode up to 190K, which is the best-reported performance for THz QCLs with Al_0.15Ga_0.85As barriers based on an Au-Au double-metal waveguide. The performed analysis showed that the achieved improvement could be explained by the proposed design modification.

An off-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor was designed for ethylene detection using a distributed-feedback quantum cascade laser (QCL) operating in the mid-infrared around 11 μm. The acoustic microresonator configuration was experimentally optimized using an original open-cell photoacoustic setup with a MEMS microphone. Correction factors based on theoretical acoustic models were introduced in order to accurately describe the response of millimeter-sized acoustic resonators. The optimized QEPAS sensor exhibited a limit of detection of 60 ppb for 60 s integration, giving a NNEA of 4.8 × 10⁻⁸ W·cm⁻¹·Hz^-0.5.

Indium arsenide (InAs)‐based quantum cascade lasers (QCLs) operating close to 25 µm are reported. Thick n‐doped InAs cladding layers were used for optical confinement. Fabry–Perot lasers exhibited a threshold current density as low as 1.1 kA/cm ² in pulsed mode at 80 K. The lasers operated in this regime up to 240 K, where the threshold current density increased up to 1.7 kA/cm ² . These are the lowest threshold current densities for QCLs operating above 20 µm.