PhD :"High curvature micro-lenses for advanced optical fiber applications"

PhD defence : Tony Hajj

Team: IPP

Date & time : Friday, September 22nd at 10:00 AM at ICube, Illkirch (Room C429)

Title : "High curvature micro-lenses for advanced optical fiber applications"

Abstract : This PhD introduces a novel fabrication technique for creating molded polymer-based fiber micro-lenses. The technique allows micro-lenses of high optical quality and durability, along with offering advanced design flexibility to be produced. Furthermore, we have demonstrate that the technique is compatible with non-traditional optical fibers, including mid-infrared non-silica-based fibers, hollow core fibers, and multi-core fibers. Successful implementation of the technique resulted in the integration of high-curvature micro-lens arrays into both 4-core and 37-core fibers. This integration enabled the generation of highly focused multi-beams with diffraction-limited beam diameters.

This PhD research has encompassed two distinct applications. The first involves the enhancement of light coupling efficiency for interband cascade lasers using mid-infrared fibers. Notably, this endeavor resulted in a successful doubling of efficiency in both single and multi-mode fibers. The second application centers around facilitating high-resolution silicon etching. To address this, an extensive investigation into the power tolerance of the micro-lenses has been conducted, revealing a remarkable tolerance threshold of ≥ 2 W (57 µJ) in nanosecond pulse regime. This threshold substantially surpasses the requirement for silicon etching with highly focused beams, featuring a laser spot with a full width at half maximum of approximately 1 µm.

The jury will be composed of:

• GROSJEAN Thierry: Reporter (DR CNRS, Femto-ST)
• BOUWMANS Géraud: Reporter (Professor, University of Lille)
• THUAL Monique: Examiner (Professor, University of Rennes)
• Assia Guessoum: Examiner (Lecturer, HDR, University of Sétif 1)
• Nacer-E. Demagh: Invited member (Professor, University of Sétif 1)
• CHABROL Gregoire: Thesis co-supervisor (Lecturer, HDR, Icam Strasbourg, ICube)
• LECLER Sylvain: Supervisor (Professor, INSA Strasbourg)