Two-photon polymerization-based 3D laser fabrication of interfacing micro-structures for optical interconnects and lab-on-chip applications

Research output: ThesisPhD Thesis

Abstract

In this PhD research, two-photon polymerization (2PP)-based 3D laser fabrication is used to fabricate interfacing micro-structures with sub-micrometer precision. In this technology, a femtosecond pulsed laser together with a highnumerical aperture microscope objective is used to initiate the nonlinear process of two-photon absorption inside a droplet of photoresist material. As such, a highly localized polymerization of the photoresist is obtained, which gives rise to high-resolution micro-structures. The main goal of this research is to develop micro-structures that address some major challenges associated with different interfacing components for optical telecommunication applications, and to explore their fabrication using the 3D nanoprinting technology. As data transport is booming in private, social and economic applications, fiber-to-thehome (FTTH) is found to be a future-proof solution for providing broadband internet connections. With this work, we therefore aim at facilitating and speeding up the deployment of FTTH networks and related interconnection components.
The first objective is the development of mode-field adapting taper structures on optical fiber tips to be used in expanded beam connectors and fiber-to-chip interfaces. Expanded beam components strongly relax the alignment tolerances and lower the sensitivity to contamination of physical contact fiber connections, whereas down-tapered structures facilitate the coupling of optical fibers towards so-called photonic integrated circuits. Our approach consists of designing
adiabatic taper structures and fabricating them directly on the tip of cleaved optical fibers through 2PP. We make use of mode solving and finite-difference time-domain simulation software to optimize the taper structures towards compact and highly efficient designs. The 3D-printed tapers on optical fiber tips are characterized towards their geometry and surface roughness with dedicated cleanroom metrology equipment and a proof-of-concept demonstrator is built to measure the optical performance of the fabricated components in their target applications.
A second objective in this PhD aims at increasing the optical connection capacity through space-division multiplexing by making use of multi-core fibers instead of single-core fibers. The major challenge in aligning multi-core fibers is that more than one core has to be aligned with the same alignment accuracy as for a single-core fiber. For this purpose, we investigate the design and 2PP fabrication of a mechanical keying feature on the cladding side surface of these fibers to
control their rotational position with respect to each other. In addition, we explore the development of diffractive beam splitting elements that could facilitate the highly compact multiplexing from a single-core fiber to a multi-core fiber.
Apart from the above-mentioned optical telecom related objectives, we also investigated the use of the 2PP technology for the fabrication of interfacing micro-structures for lab-on-chip applications. Biomimetic scaffolds are fabricated with the aim of creating an artificial liver-on-chip for in-vitro screening of drugs, and substrates with 2PP nano-pillars are explored for their use in surface-enhanced Raman spectroscopy detection measurements.
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
Supervisors/Advisors
  • Van Erps, Jürgen, Supervisor
  • Thienpont, Hugo, Co-Supervisor
Award date19 Jan 2021
Publication statusPublished - 2021

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