R. Teissier

Quantum cascade lasers emitting near 2.6 μm

Quantum cascade lasers (QCLs) emitting at wavelengths as short as 2.63–2.65 μm are demonstrated. The InAs/AlSb QCL design was optimized to weaken carrier leakage into the L-valley by reducing coupling between the active InAs quantum wells. The lasers with HR-coated facets operated up to 175 K.

Efficient light absorption in metal-semiconductor-metal nanostructures

A nanoscale metal–semiconductor grating is proposed for efficient and ultrafast photodetection. Theoretical and experimental results of efficient absorption in nanoscopic semiconductor wires are presented. The strong confinement of light in subwavelength metal–semiconductor gratings is achieved by Fabry–Perot resonances involving vertical transverse magnetic surface-plasmon waves and transverse electric guided waves. Photodetectors have been fabricated with 40×100nm cross sections of Ag and GaAs wires. The reflectivity and photocurrent mesurements are in good agreement with theoretical estimates.

Strong discontinuities in the complex photonic band structure of transmission metallic gratings

Complex photonic band structures (CPBS) of transmission metallic gratings with rectangular slits are shown to exhibit strong discontinuities that are not evidenced in the usual energetic band structures. These discontinuities are located on Wood-Rayleighs anomalies and reveal unambiguously two different types of resonances, which are identified as horizontal and vertical surface-plasmon resonances. Spectral position and width of peaks in the transmission spectrum can be directly extracted from CPBS for both kinds of resonances.

Room temperature operation of InAs∕AlSb quantum cascade lasers

The room temperature operation of InAs∕AlSb quantum cascade lasers is reported. The structure, grown by molecular beam epitaxy on an InAs substrate, is based on a vertical transition design and a low loss n+-InAs plasmon enhanced waveguide. The lasers emitting near 4.5μm operate in pulse regime up to 300K. The threshold current density of 3.18-mm-long lasers is 1.5kA∕cm2 at 83K and 9kA∕cm2 at 300K.

InAs∕AlSb quantum cascade lasers emitting below 3μm

Quantum cascade lasers emitting below 3μm are demonstrated. The lasers based on the InAs∕AlSb material system emit at 2.95–2.97μm in pulsed mode with threshold current densities near 3kA∕cm2 at 84K and operate up to room temperature. No degradation has been observed in laser performances compared with InAs∕AlSb quantum cascade lasers emitting at 3.14–3.35μm. The obtained results show no influence of the L valley in InAs on operation of these short wavelength quantum cascade lasers.

InAs∕AlSb quantum cascade lasers emitting at 2.75–2.97μm

Quantum cascade lasers emitting at wavelengths as short as 2.75μm at 80K and 2.97μm near room temperature are demonstrated. Despite the small band gap of InAs, the laser performances are not affected by interband absorption. No effect of the L valley in InAs on quantum cascade laser performances is observed at 80K in these devices.

High temperature operation of λ≈3.3μm quantum cascade lasers

We report quantum cascade lasers emitting at a wavelength near 3.3μm up to a temperature of 400K in pulsed mode. A fine tuning of the InAs∕AlSb active region design allowed to maintain efficient electron injection and to reduce thermal backfilling at high temperatures. The threshold current density is 3kA∕cm2 at 300K with characteristic temperature T0 of 175K. The lasers emitted up to 1W peak power in a single lateral mode at room temperature.

Very short wavelength (λ=3.1–3.3μm) quantum cascade lasers

Quantum cascade lasers emitting at wavelengths as short as 3.1–3.3 m are reported. Such high intersubband emission energies up to 400 meV have been obtained thanks to the high conduction band offset of the InAs/AlSb material system. The structures, grown by molecular beam epitaxy on InAs substrates, are based on the bound-to-continuum design and use a low loss plasmon enhanced waveguide consisting of n+-InAs cladding layers with InAs/AlSb superlattice spacers surrounding the active zone. The lasers exhibit threshold current densities close to 3 kA/cm2 at 83 K and operate in pulsed mode up to 240 K.

Influence of the material parameters on quantum cascade devices

An experimental investigation on the influence of the material systems on the optical properties of quantum cascade structures is presented. Three electroluminescent quantum cascade devices have been grown using GaAs∕AlGaAs, GaInAs∕AlInAs, and InAs∕AlSb heterostructures. The devices emit at 10μm and are based on a similar bandstructure design. Our results verify that the optical quantum efficiency has the predicted dependence on the electron effective mass. We also demonstrate that the shape of the electroluminescence spectra is independent from the particular material parameters and mainly depends on the tunnel coupling between the injector state and the upper state of the radiative transition.

LO-phonon scattering of cavity polaritons in an electroluminescent device

Emission of longitudinal optical phonons between the upper and the lower polariton branches has been observed in an intersubband electroluminescent device, operating in the strong coupling regime.