PhD defence of Mohsen Rezaei - Chalcogenide and ZBLAN Optical Fiber Components

Monday, July 18, 2022 12:00to14:00
McConnell Engineering Building Room 603, 3480 rue University, Montreal, QC, H3A 0E9, CA


The mid-infrared (MIR) wavelength range of the electromagnetic spectrum (2-20 µm) coincides with the fundamental vibrational frequencies of a vast majority of molecules, hence is crucially important for chemical sensing and molecular spectroscopy. The development of efficient MIR technologies requires optical fiber components. Currently, commercially available optical fiber components are mostly made of silica with a functionality limited to the transmission window of silica fiber (up to 2 µm), and thus, not suitable for the MIR applications. Chalcogenide and fluoride fibers, on the other hand, possess much wider transmission windows, up to 6 μm for ZBLAN and 20 µm for chalcogenide fiber, and have provided the possibility of MIR optical fiber components realization.

This dissertation presents several optical fiber components designed and fabricated using chalcogenide and ZBLAN fibers. The first single-mode broadband and wavelength division multiplexing (WDM) chalcogenide optical fiber couplers (OFCs), as well as polarization beam-splitters, are demonstrated. The OFCs functionality is engineered with a careful design of their geometry resulting in any arbitrary coupling ratio from 99:1 to 50:50. Also, the first all-chalcogenide ring fiber laser is presented. The compact device is made from the combination of an As2Se3 OFC for the insertion of pump light and extraction of laser light, as well as an As2S3 nonlinear gain fiber to ensure laser oscillation. In addition, nonlinear chalcogenide OFCs with a power-dependent coupling coefficient are designed and demonstrated. These nonlinear OFCs enable all-optical switching and will be useful for passive mode-locking. Finally, single-mode ZBLAN OFCs are demonstrated. The OFCs are fabricated using a multiple-sweep tapering technique that allows precise and repeatable control of the OFCs’ geometry, which results in OFCs’ single-modedness and reproducibility while limiting crystallization. This is an important step towards the extension of optical fiber technologies in the MIR.

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