C. Alibert

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.

Accurate refractive index measurements of doped and undoped InP by a grating coupling technique

Accurate measurements of InP refractive indices in the 1300–1600 nm wavelength range are reported. They are obtained using the grating coupling technique within an asymmetrical slab waveguide where an intrinsic InP guiding layer was grown on a doped InP substrate (N=2×1018 cm−3). Modal indices are obtained with an absolute precision of a few 10−4 from either guided or reflected waves. Bulk refractive indices of intrinsic and N‐doped InP are then deduced from the allowed modes propagating in the layered structure. With sample temperature maintained to within 0.01 K, InP bulk indices are obtained with a typical accuracy of 5×10−4. Furthermore, a (2.02±0.02) 10−4 K−1 refractive index temperature coefficient has been measured for bulk InP at room temperature.Accurate measurements of InP refractive indices in the 1300–1600 nm wavelength range are reported. They are obtained using the grating coupling technique within an asymmetrical slab waveguide where an intrinsic InP guiding layer was grown on a doped InP substrate (N=2×1018 cm−3). Modal indices are obtained with an absolute precision of a few 10−4 from either guided or reflected waves. Bulk refractive indices of intrinsic and N‐doped InP are then deduced from the allowed modes propagating in the layered structure. With sample temperature maintained to within 0.01 K, InP bulk indices are obtained with a typical accuracy of 5×10−4. Furthermore, a (2.02±0.02) 10−4 K−1 refractive index temperature coefficient has been measured for bulk InP at room temperature.

Observation of room-temperature laser emission from type III InAs/GaSb multiple quantum well structures

Multiple quantum well InAs/GaSb laser heterostructures with type III (type II broken gap) band alignment in the active region have been grown by molecular beam epitaxy. Intense electroluminescence was observed at room temperature (RT) with peak emission wavelengths in the range 1.95–3.4 μm. RT lasing has been achieved at 1.98 and 2.32 μm for the structures with 6 and 12 A thick InAs quantum wells, respectively.

Refractive indices of AlSb and GaSb‐lattice‐matched AlxGa1−xAsySb1−y in the transparent wavelength region

The refractive indices of AlSb grown by the solute diffusion method and GaSb‐lattice‐matched AlxGa1−xAsySb1−y alloy grown by liquid‐phase epitaxy have been determined at room temperature from accurate measurements of the reflectance of p‐polarized light as a function of the angle of incidence. The refractive index variations versus the photon energy were obtained in the spectral range 0.5–1.5 eV. Experimental data in the transparent wavelength region could be matched by calculated curves on the basis of a single‐oscillator model.

2.5 μm GaInAsSb lattice‐matched to GaSb by liquid phase epitaxy

GaSb lattice‐matched Ga1−xInxAsySb1−y has been grown by liquid phase epitaxy on (100) and (111)B oriented substrates using initial melt supersaturation ΔT varying from 10 to 30 °C, at growth temperatures >600 °C. It is shown that the band‐gap cutoff wavelength, measured at room temperature by the electroreflectance method, is ∼2.38 μm for (100) layers whatever ΔT, and increases from 2.38 μm up to 2.51 μm for (111)B oriented layers when ΔT is increased from 15 to 25 °C. Photoluminescence experiments at 2 K confirm the band‐gap reduction occurring at high ΔT with the (111)B orientation.

Low threshold high-power room-temperature continuous-wave operation diode laser emitting at 2.26 /spl mu/m

Diode lasers emitting at 2.26 /spl mu/m, based on the InGaAsSb-AlGaAsSb materials system, are reported. These devices exhibit high internal quantum efficiency of 78% and low threshold current density of 184.5 A/cm/sup 2/ for a 2-mm-long cavity. Output power up to 700 mW (/spl ap/550 mW) has been obtained at 280 K (300 K) in continuous-wave operation with 100 /spl mu/m/spl times/1 mm lasers. These devices have been coated with an antireflection on the output facet and are mounted epilayer down on a copper block. The working temperature was maintained by a thermoelectric Peltier cooling element.

Tunable diode laser absorption spectroscopy of carbon monoxide around 2.35 μm

Novel GaInSbAs/GaSb multiple-quantum-well lasers operating near room temperature have been successfully used for tunable diode laser absorption spectroscopy in the vicinity of 2.35 μm. Continuous current tuning over a more than 150-GHz frequency range has been realized. Direct absorption measurements have been carried out on the R9, R10, R11, and R12 lines of carbon monoxide. Traces of carbon monoxide at the level of 0.3 part in 106 in volume at 100 Torr could be detected by the low-frequency wavelength-modulation technique and an astigmatic multipass cell. These results show a potential use of these diode lasers in portable low-cost trace-pollutant sensors.

Photothermal investigations of thermal and optical properties of GaAlAsSb and AlAsSb thin layers

Investigation of the optical and thermal properties of GaAlAsSb/GaSb and AlAsSb/GaSb heterostructures by photothermal deflection spectroscopy (PDS) is presented. From a comparison of the amplitude and phase of the experimental PDS signal with the corresponding theoretical ones, we have determined the thermal conductivities and thickness, as well as the variations versus wavelength of the optical absorption coefficients and refractive indices of the GaAlAsSb and AlAsSb layers. The refractive indices measured in the transparency region and the small values of the thermal conductivity are in good agreement with theoretical interpolation reported in previous literature.

Measurement of the refractive index of GaInAs/InP quantum wells by a grating coupling technique

Effective indices of modes propagating in multiple GaInAs wells on InP barriers (MQW) waveguides are accurately measured in the 1.4–1.75 μm wavelength range using the grating coupling technique. Quantum size effects cause a selective polarization absorption and high birefringence, strongly depending on wavelength. The temperature dependence of refractive index and absorption originating from the temperature‐dependent band gap is also observed. In the transparency region the refractive indices of GaInAs wells in InP barriers are deduced for two well widths using a multilayer slab waveguide model and an exciton model based on Lorentzian oscillator.

Investigation of thermal and optical properties of distributed Bragg reflectors by photothermal deflection spectroscopy

We present the study of thermal and optical properties of 15.5 pair of GaAlAsSb/AlAsSb layers deposited upon a GaSb substrate by photothermal deflection spectroscopy. This stacking of layers constitutes a distributed Bragg mirror.