Applications in silicon photonics: arrayed waveguide chemical sensor and photon sieve fiber probe for improved light coupling

  • Ricardo J. Janeiro

Student thesis: Doctoral Thesis

Abstract

The introduction of the microchip in 1950's revolutionized electronics, with the integration of multiple functions in a compact, monolithic platform, that was easily scalable. A similar promise holds for the optical microchip, with the integration of optical building blocks with electronics, supporting the increasing performance pressure of current and future technological applications, from optical communications to the future of computing, artificial intelligence and sensing. Indeed, driven by developments in the fabrication technology primarily developed towards the microelectronic industry, the last decades have seen a strong expansion and progress of integrated optics. Sharing this growth in interest with the rest of the integrated optics field are integrated optical sensors, remarkable for their low cost, lowpower consumption, compactness, electromagnetic interference immunity, size, scalability and integration. However such sensors usually suffer from limited chemical selectivity and reusability. The work developed towards this thesis aimed at the fabrication and characterization of a sensor architecture capable of tackling those drawbacks, while being flexible enough to allow for alternative and cheaper interrogation schemes. The proposed refractive index sensor, built on a silicon-on-insulator (SOI) platform, is based on arrayed waveguide interference. It supports a top polydimethylsiloxane (PDMS) polymer cladding, used to encapsulate the waveguides providing an expandable and permeable low index material. This cladding material acts as the chemical transducer element, changing its optical properties when in contact with a chemical of interest, therefore allowing for high sensitivity and chemical selectivity. In specific, PDMS exhibits large swelling when in contact with different volatile organic compounds (VOCs), whose presence, in the context of environmental and public health protection, is important to properly monitor. In order to improve of the sensor characterization, an optical fiber probe was developed, incorporating a phase photon sieve (PS) on the tip of a standard single mode telecom fiber by focused ion beam (FIB) milling. The PS is constituted by an array of pillars arranged over the zones of an underlying Fresnel zone plate, and allows improved light coupling between the nanopatterned fiber and the photonic chip with high optical efficiency and alignment tolerance.
Date of AwardJul 2018
Original languageAmerican English
SupervisorJaime Viegas (Supervisor)

Keywords

  • Integrated Optics; Silicon Photonics; Optical Sensor; Chemical Selectivity; Light Coupling; Diffraction.

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