Search

We present in water chemical spectroscopy by the use of a AgClBr fiber and a tunable mid-IR Quantum Cascade Laser source (QCL. We show detection of ppm concentration of ethanol in water.

We present a genetically optimized multi-wavelengths laser based on an aperiodic sampled grating. We show that the grating phases and amplitudes can be optimized to flatten the spectral signature allowing multi-wavelengths operation.

In the framework of the ANR project called COCASE, GSMA and III-V Lab develop a coherent quantum cascade laser array to obtain high power emission. This source will be combined to a photoacoustic spectrometer devoted to trace gas detection [1]. In such a spectrometer the sensitivity limit is directly proportional to the laser power.

We report on the realization of buried single ridge and μ-stripes quantum cascade lasers using HVPE and MOVPE regrowth steps of semi-insulating InP:Fe and Si doped layers. We present here the preliminary results obtained on these devices. The reduction of the thermal resistance achieved using semiinsulating InP:Fe for regrowth planarization and μ-stripe arrays approaches are shown and performance perspectives are addressed.

We demonstrate a monolithic Quantum Cascade Laser array. We show phase-locking and single-mode emission at λ=8.4μm. It consists of narrow ridges buried into InP:Fe. Phase-locking is provided by evanescent coupling between adjacent ridges. This μ-structuration is simultaneously an answer to the excessive heating and poor beam quality of broad area lasers. First, it increases the surface of exchange between the multi-layer active region and the InP:Fe, which presents a higher thermal conductivity. Secondly, by choosing carefully the width of emitters and the distance between them, we insure phase locking and control of the supermode emission. We have investigated 2μm wide emitters. In order to study the behavior of evanescent coupling, we have chosen spacing from 1 to 8 microns. The number of emitters ranges from 1 to 64. Technological feasibility was demonstrated up to 64 emitters, and lasing operation up to 32 emitters. We have obtained a pure dual-lobe far-field pattern as expected from an anti-symmetrical supermode. The width of each lobes narrows with an increasing array size as expected from the diffraction theory. The beam quality is insensitive to the injective current. The optical power scales linearly with the number of emitters.

We demonstrate high thermal dissipation of quantum cascade lasers (QCLs) using multi-stripes array technology. Buried QCL arrays offer both lateral dissipation enhancements while keeping beam quality control for large active region lasers. Experimental thermal resistances down to 2 K/W are reported. InP:Fe regrowth morphology has been optimized to limit current leakage. Thermal resistance decreasing with both number and width of emitters is demonstrated. Comparison with simulation shows excellent agreement, with a reduction factor of 3 when comparing to standard ridges QCL. These low thermal resistances project up to 40 W in continuous wave operation using state-of-the-art QCL design.

We present the optical analysis of spatial single-mode monolithic quantum cascade laser arrays in the mid-IR. Subwavelength parallel microstripe waveguides are buried into InP:Fe and phase locked by evanescent coupling. Lasing at room temperature is obtained at λ=8.4 μm. We describe the near- and far-field of stripe arrays comprising up to 32 emitters. One hundred percent coherent emission is shown experimentally and well accounted for by a standard optical simulation.

We have fabricated InP-based coherent quantum cascade laser micro-stripe arrays. Phase-locking is provided by evanescent coupling between adjacent stripes. Stripes are buried into semi-insulating iron doped InP. Lasing at room temperature is obtained at 8.4μm for stripe arrays comprising up to 16 emitters. Pure supermode emission is demonstrated via farfield measurements and simulations. The farfield pattern shows a dual-lobe emission, corroborating the predicted phase-locked antisymmetric supermode emission.