A. Vicet

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.

Trace gas detection with antimonide-based quantum-well diode lasers

Widely tunable GaInAsSb/AlGaAsSb quantum well (QW) lasers have been grown by molecular beam epitaxy on GaSb substrates. Their emission wavelength, from 2.0 to 2.5 microm, make them suitable for the detection of many gas species in the wavelength range which corresponds to an atmospheric transmission window. Using these devices an experimental setup for open path gas detection has been developed.

Measurements of optical losses in mid-infrared semiconductor lasers using Fabry–Pérot transmission oscillations

We present a Fabry–Perot resonator technique for room temperature optical loss measurements on mid-infrared (λ∼2–4 μm) lasers. The quality of optical waveguides for λ≈2.3 μm InGaAsSb/AlGaAsSb/GaSb interband lasers and a λ≈3.7 μm strain-compensated InGaAs/InAlAs/InP quantum cascade laser have been estimated using this method. The optical losses for these lasers lie in the range 15–25 cm−1 for interband lasers and 4–5 cm−1 (transverse electric polarization) and 21–23 cm−1 [transverse magnetic (TM) polarization] for the quantum cascade laser. The considerably higher losses for TM polarization in the case of quantum cascade laser are explained by intersubband absorption in the active layers. The method may be applied to structures with only a minimum amount of device processing, facilitating rapid progress in development of mid infrared laser designs in new materials systems.

Quartz enhanced photoacoustic spectroscopy with a 3.38 μm antimonide distributed feedback laser

A system for gas sensing based on the quartz-enhanced photoacoustic spectroscopy technique has been developed. It makes use of a quantum well distributed feedback (DFB) laser diode emitting at 3.38 μm. This laser emits near room temperature in the continuous wave regime. A spectrophone, consisting of a quartz tuning fork and two steel microresonators were used. Second derivative wavelength modulation detection is used to perform low concentration measurements. The sensitivity and the linearity of the Quartz enhanced photoacoustic spectroscopy (QEPAS) sensor were studied. A normalized noise equivalent absorption coefficient of 4.06×10(-9) cm(-1)·W/Hz(1/2) was achieved.

Mid-Infrared 2—5 μm Heterojunction Laser Diodes

High performance mid-infrared (2–5 μm) laser diodes are needed for applications such as high resolution and high sensitivity chemical gas analysis and atmospheric pollution monitoring. The goal is to obtain continuous wave laser emission at room temperature, with output power > 1 mW. Different technologies are under investigation to reach this objective. The GaInAsSb/AlGaAsSb strained multi-quantum-well laser showed striking results in CW operation at and above room temperature and appears as a well established technology for laser emission in the 2.0–2.7 μm wavelength range. Beyond 2.7 μm, the IV–VI lasers based on the PbSe/PbSrSe system, type-II “W” quantum well lasers based on the InAs/GaInSb system, and type-II interband and intersubband III–V cascade lasers, are competitive technologies. They could all operate at room temperature or near room temperature, but only in the pulsed regime. This paper presents an overview of the state of the art of these different mid-infrared systems emitting in the 2–5 μm wavelength range. Two heterojunction laser technologies are detailed: the 2–3 μm GaInAsSb multi-quantum-well laser, and the 3–5 μm type-II and type-II “W” laser diodes.

Laser Diodes for Gas Sensing Emitting at 3.06

Type-I quantum-well laser diodes with an active region constituted of GaInAsSb-AlGaInAsSb are reported. Broad-area lasers have demonstrated a threshold current density of 255 A/cm2 at room temperature. Distributed-feedback lasers have been operated in the continuous-wave regime at 20°C with a wavelength of 3.06 μm, a threshold current of 54 mA, and an output power of 6 mW.

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We report on the growth, fabrication, and experimental study of distributed feed-back antimonide diode lasers with buried grating. A second order index-coupled grating was defined by interferometric lithography on the top of the laser waveguide and dry etched by reactive ion etching. The grating was then buried thanks to an overgrowth of the top cladding layer using molecular beam epitaxy. The wafer was then processed using standard photolithography and wet etching into 15 μm-wide laser ridges. Single frequency laser emission at a wavelength of 2.2 μm was measured with a side mode suppression ratio of 34 dB, a maximum output power of 30 mW, and a total continuous tuning range of 6.5 nm.

m at Room Temperature

We report on the growth, fabrication, experimental study and application in an absorption gas setup of distributed feed-back antimonide diode lasers with buried grating. First, half laser structures were grown by molecular beam epitaxy on GaSb substrates and stopped at the top of the waveguide. A second order Bragg grating was then defined by interferometric lithography on the top of the structure and dry etched by Reactive Ion Etching. The grating was, afterwards, buried thanks to an epitaxial regrowth of the top cladding layer. Finally, the wafer was processed using standard photolithography and wet etched into 10 µm-wide laser ridges. A single frequency laser emission around 2.3 µm was recorded, a maximum output power of 25 mW and a total continuous tuning range reaching 4.2 nm at fixed temperature. A device has been used to detect methane gas and shows strong potential for gas spectroscopy. This process was also replicated for a target of 3 µm laser emission. These devices showed an output power of 2.5 mW and a SMSR of at least 23 dB, with a 2.5 nm continuous tuning range at fixed temperature.

Distributed feedback GaSb based laser diodes with buried grating

The quantum cascade laser is a semiconductor light source based on resonant tunnelling and optical transitions between quantised conduction band states. In these devices the principles of operation are not based on the physical properties of the constituent materials, but arise from the layer sequence forming the heterostructure. The quantum design and the control of the layer thickness, down to an atomic mono-layer, allows one to ascribe into a semiconductor crystal, artificial potentials with the desired electronic energy levels and wavefunctions. In recent years the performance of quantum cascade lasers has improved markedly and this semiconductor technology is now an attractive choice for the fabrication of mid-far infrared lasers in a very wide spectral range (3.5-160 μm). At present, the best performances are reached at wavelength between 5-10 μm, but recent results on new material systems with deeper quantum wells are indicating that this technology will be soon available also in the 3-5 μm spectral region.

Distributed feedback GaSb based laser diodes with buried grating: a new field of single-frequency sources from 2 to 3 µm for gas sensing applications.

Summary form only. The wavelength range between 2.2 and 2.4 /spl mu/m are of great interest for molecular spectroscopy and environmental monitoring. Tunable diode laser absorption spectroscopy is one of the most accurate techniques for gas analysis and to reduce the cost of the equipment diode lasers operating in continuous wave (cw) regime above room temperature (RT) are required. In this contribution we present single mode GaInSbAs-GaAlSbAs QW lasers operating in cw regime up to 130/spl deg/C.