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Reference : UPR8001-VERBAR-003
Workplace : TOULOUSE
Date of publication : Monday, May 03, 2021
Scientific Responsible name : V. Bardinal
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Our digital society relies more and more on remote communications. In this context, efficient and low cost high speed optical interconnects are crucial. VCSELs (vertical cavity surface emitting lasers) operating in the near-infrared (NIR) range are key photonic components for these systems. This is due to their low power consumption, their parallel operation and their high modulation rate properties. However, their coupling with an optical fiber remains long and costly, due to low tolerances to misalignments (~1µm for single mode devices). Moreover, there is no simple and collective method to fabricate a "bent" optical link, in which the vertically-emitted VCSEL beam could be redirected in the horizontal plane of the optical fibers.
The 3D-BEAM-FLEX national research project aims at demonstrating the fabrication of continuous and flexible single-mode waveguides between VCSEL arrays and single-mode optical fibers by exploiting a new patented method of self-writing in NIR photosensitive materials. Our innovative process is based on a two-step photo-fabrication and on specific mechanical properties of the used photopolymer materials. Preliminary results of coupling in the visible range between two standard optical fibers have already been obtained. The objective of the thesis will be to demonstrate experimentally and theoretically the interest of this new method for the coupling between a VCSEL and a single mode fiber. The first step will be to participate in the development of a multi-axis alignment bench to implement the method. The best photochemical conditions will be then determined , first for a standard wavelength of 850nm (data center applications), then at 1.31µm and 1.55µm (telecom applications). The experimental results will be compared to the ones given by the modeling of the waveguiding propagation of the Gaussian beams using 3D calculation tools. Several initial configurations will be studied (mode sizes, axial distance and lateral misalignments). The studied devices will be prepared and characterized in the LAAS clean room. Finally, the new potentialities offered by additive manufacturing by 3D printing will also be exploited in our Multifab platform to integrate the flexible self-written link in a compact module foldable at 90°.
This research work may have implications for communications, but also in the field of miniaturized spectroscopy and sensors.
It will be conducted within the MICA team and the technological and characterization platforms of the LAAS-CNRS, a unit of the Centre National de la Recherche Scientifique (CNRS), in close collaboration with the IS2M-CNRS for the materials aspects.
Constraints and risks
Laser safety training and work in clean room planned.
Required skills: the candidate should have a strong background in optics optoelectronics / photonics, as well as a strong interest for experimental work and optical characterization.
Applications that do not match the required skills and/or whose cover letter is not related to the subject will not be considered.
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