Enhancing the sensitivity of silicon photonic ultrasound sensors by optimizing the stiffness of polymer cladding

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

Abstract

Ultrasound is widely used in medical imaging, and photo-acoustics is an upcoming imaging modality for the diagnosis of diseases. Future applications require a large matrix of small, sensitive, and broadband ultrasound sensors. However, current high-end systems still use piezo-electric material to detect ultrasound, with limited sensitivity and bandwidth. Silicon photonic circuits can meet the requirements of size, bandwidth, and scalability when designed as ultrasound sensors. Namely, a silicon photonic waveguide deforms when the ultrasound pressure waves impinge on it, leading to a change in effective refractive index, ne, due to geometrical and photo-elastic effects [1]. However, these effects are weak, which limits the intrinsic sensitivity of silicon photonic ultrasound sensors [2]. To significantly enhance sensitivity, silicon waveguides have been combined with acousto-mechanical structures, which achieved acoustomechanical-noise-limited sensing [3], but this is not compatible with standard photonic platforms. Besides that, recent demonstrations of waveguides coated with polymers also improved sensitivity of the silicon photonic ultrasound sensors significantly, but not sufficient to reach acoustomechnical-noise-limited sensing [4]. Here, we study the effect of mechanical and opto-mechanical properties of polymer claddings on the sensitivity of silicon photonic ultrasound sensors. Our aim is to enhance the sensitivity of these devices by implementing tailored polymer coatings. First, we model the refractive index sensitivity of these type of waveguides, i.e. the change in effective refractive index ne due to the incident ultrasound plane-wave with a pressure P, and we (Equation presented) where nc, p12, E, and v are refractive index, elasto-optic coefficient, Young's modulus (stiffness), and Poisson's ratio of the cladding material, respectively. We assume the change in cladding index dominates sensitivity.

Original languageEnglish
Title of host publicationProceedings of the Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023
PublisherIEEE
Number of pages1
ISBN (Electronic)979-8-3503-4599-5
DOIs
Publication statusPublished - 2023
Event2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023 - Munich, Germany
Duration: 26 Jun 202330 Jun 2023

Conference

Conference2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023
Country/TerritoryGermany
CityMunich
Period26/06/2330/06/23

Bibliographical note

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care
Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

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