Multiplexed infrared diodes for absorption spectroscopy – MIDAS

This project aims to demonstrate high sensitivity gas sensing with gas discrimination capacity, using nanophotonic integrated laser diodes. It is based on an existing collaboration between LAAS-CNRS and IES, following a first project in the ANR blanc framework CRISPI CRISPI. In this new project; we aim to demonstrate state of the art gas analysis capacities with designs robust enough to be incorporated in embedded systems, thus enabling the use in the field of high performance gas monitoring systems. The project thus inscribes in the field of the ANR P2N call for “nanophotonics and photonic crystal based functions, new sensors, for mid infrared spectroscopy applications”.
As a summary, we propose to implement for the first time all photonic crystal DFB laser design in electrically pumped GaSb laser diodes, to demonstrate laser arrays optimized for gas sensing. Several lasers with discrete emission lines will allow to combine smooth analog tuning by current injection of the emission wavelength with discrete digital multiplexing by sweeping from laser to laser, giving an unprecedented flexibility in gas sensing in the mid-IR range. Such a feature should allow in the near future to implement various multiplexed acquisition schemes to improve signal-to-noise ratio, resolution and robustness towards slow perturbations like thermal drifts.The heart of this project is to develop a new kind of single-mode laser array for spectroscopy in the mid-IR, based on recent advances in nanophotonics, namely all photonic crystal second order DFB lasers. This new approach will simultaneously overcome the current limitations in terms of performances of existing devices in terms of wavelength range and resolution and loosen constraints on temperature and current control.
Achieving such an ambitious goal will require taking up several challenges:
- Optimized single-mode DFB laser based on PhC defect waveguide will have to be demonstrated on GaSb. This requires transferring the designs actually optimized on GaAs membranes at 980 nm emission wavelength to a “bulk” approach at 2.3 µm. It also requires to further optimize the technology successfully applied during the CRISPI project to achieve etchings with aspects ratios as high as those reached on GaAs at LAAS-CNRS.
- Growths of laser structures for emission at 3.3 µm are also challenging. Today, only two laboratories master the realization of such structures and regularly publish results in this field: the State University of New York and the IES laboratory. Moreover specifically optimized vertical structures will have to be designed and grown to accommodate for the requirements of deep etching in GaSb.
- A last challenge is the use of such devices on gas demonstrators. First results of gas detection with antimonide based PhC lasers were shown at the end of the CRISPI project. Lasers fabricated in within the MIDAS project should exhibit more flexibility: a larger tuning range will lead to more gas selectivity and a higher sensitivity. The multiplexed approach is very innovative; it doesn’t need to tune the emitted wavelength: thus detection will gain in acquisition time.