Comparative analysis of quantum cascade laser modeling based on density matrices and non-equilibrium Green's functions

We study the operation of an 8.5 mu m quantum cascade laser based on GaInAs/AlInAs lattice matched to InP using three different simulation models based on density matrix (DM) and non-equilibrium Green's function (NEGF) formulations. The latter advanced scheme serves as a validation for the simpler DM schemes and, at the same time, provides additional insight, such as the temperatures of the sub-band carrier distributions. We find that for the particular quantum cascade laser studied here, the behavior is well described by simple quantum mechanical estimates based on Fermi's golden rule. As a consequence, the DM model, which includes second order currents, agrees well with the NEGF results. Both these simulations are in accordance with previously reported data and a second regrown device. (C) 2014 AIP Publishing LLC

Laser spectroscopy for breath analysis : towards clinical implementation

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.Peer reviewe

Optical-feedback cavity-enhanced absorption spectroscopy with a quantum cascade laser

International audienceNot Availabl

High frequency dynamics in quantum cascade lasers : a roadmap to free-space communications in the mid-infrared

International audienceQuantum cascade lasers, which can emit deterministic chaotic patterns, are found to exhibit improved chaos properties when using optical injection instead of feedback. These findings pave a way for high-speed secure communications in the mid-infrare

Optical-Feedback Cavity-Enhanced Absorption Spectroscopy with a quantum-cascade laser yields the lowest formaldehyde detection limit

We report on the first application of Optical Feedback-Cavity Enhanced Absorption Spectroscopy to formaldehyde trace gas analysis at mid-infrared wavelengths. A continuous-wave room-temperature, distributed-feedback quantum cascade laser emitting around 1,769 cm-1 has been successfully coupled to an optical cavity with finesse 10,000 in an OF-CEAS spectrometer operating on the v2 fundamental absorption band of formaldehyde. This compact setup (easily transportable) is able to monitor H2CO at ambient concentrations within few seconds, presently limited by the sample exchange rate. The minimum detectable absorption is 1.6×10-9 cm-1 for a single laser scan (100 ms, 100 data points), with a detectable H2CO mixing ratio of 60 pptv at 10 Hz. The corresponding detection limit at 1 Hz is 5 × 10-10 cm-1, with a normalized figure of merit of 5 × 10-11cm-1= √Hz (100 data points recorded in each spectrum taken at 10 Hz rate). A preliminary Allan variance analysis shows white noise averaging down to a minimum detection limit of 5 pptv at an optimal integration time of 10 s, which is significantly better than previous results based on multi-pass or cavity-enhanced tunable QCL absorption spectroscopy. © 2013 Springer-Verlag Berlin Heidelberg

High frequency dynamics in quantum cascade lasers : a roadmap to free-space communications in the mid-infrared

International audienceQuantum cascade lasers, which can emit deterministic chaotic patterns, are found to exhibit improved chaos properties when using optical injection instead of feedback. These findings pave a way for high-speed secure communications in the mid-infrare

An Indirect Determination of the Polarization Anisotropy in a Quantum Cascade Laser Under Strong Cross-Polarization Feedback

International audienceThis work demonstrates that a non TM-polarized wave can be generated by a quantum cascade laser subjected to strong cross-polarization optical feedback. This finding is used to determine the anisotropy between the two existing polarizations Acknowledgments: this work is supported by the French Defense Agency (DGA), the French ANR program under grant ANR-17-ASMA-000