Tomographic refractive index profiling of direct laser written waveguides

Barré N, Shivaraman R, Ackermann L, Moser S, Schmidt M, Salter P, Booth MJ, Jesacher A (2021)

Publication Language: English

Publication Type: Journal article

Publication year: 2021

Journal

Optics Express Optical Society of America

Book Volume: 29

Pages Range: 35414-35425

Journal Issue: 22

URI: https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-22-35414&id=460543

DOI: 10.1364/OE.434846

Open Access Link: https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-22-35414&id=460543

Abstract

The fabrication of complex integrated photonic devices via direct laser writing is a powerful and rapidly developing technology. However, the approach is still facing several challenges. One of them is the reliable quantitative characterization of refractive index (RI) changes induced upon laser exposure. To this end, we develop a tomographic reconstruction algorithm following a modern optimization approach, relying on accelerated proximal gradient descent, based on intensity images only. Very recently, such algorithms have become the state of the art in the community of bioimaging, but have never been applied to direct laser written structures such as waveguides. We adapt the algorithm to our concern of characterizing these translation-invariant structures and extend it in order to jointly estimate the aberrations introduced by the imaging system. We show that a correct estimation of these aberrations is necessary to make use of data recorded at larger angles and that it can increase the fidelity of the reconstructed RI profiles. Moreover, we present a method allowing to cross-validate the RI reconstructions by comparing en-face widefield images of thin waveguide sections with matching simulations based on the retrieved RI profile.

Authors with CRIS profile

Lisa Ackermann Lehrstuhl für Photonische Technologien Michael Schmidt Lehrstuhl für Photonische Technologien

Additional Organisation(s)

Erlangen Graduate School in Advanced Optical Technologies

Involved external institutions

University of Oxford GB United Kingdom (GB) Medizinische Universität Innsbruck AT Austria (AT)

How to cite

APA:

Barré, N., Shivaraman, R., Ackermann, L., Moser, S., Schmidt, M., Salter, P.,... Jesacher, A. (2021). Tomographic refractive index profiling of direct laser written waveguides. Optics Express, 29(22), 35414-35425. https://dx.doi.org/10.1364/OE.434846

MLA:

Barré, Nicolas, et al. "Tomographic refractive index profiling of direct laser written waveguides." Optics Express 29.22 (2021): 35414-35425.

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