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Low bend loss femtosecond laser written waveguides exploiting integrated microcrack

Low bend loss femtosecond laser written waveguides exploiting integrated microcrack
Low bend loss femtosecond laser written waveguides exploiting integrated microcrack

We introduce the fabrication and use of microcracks embedded in glass as an optical element for manipulating light propagation, in particular for enhancing waveguide performance in silica integrated optics. By using a femtosecond laser to induce a strong asymmetric stress pattern in silica, uniform cracks with set dimensions can be created within the substrate and propagated along a fixed path. The smoothness of the resulting cleave interface and large index contrast can be exploited to enhance waveguide modal confinement. As a demonstration, we tackle the longstanding high bend-loss issue in femtosecond laser written silica waveguides by using this technique to cleave the outer edge of laser written waveguide bends, to suppress radiative bend loss. The microcrack cross section is estimated to be 15 μm in height and 30 nm in width, for the 10 [Formula: see text] 10 μm waveguides. At 1550 nm wavelength, losses down to 1 dB/cm at 10 mm bend radius were achieved, without introducing additional scattering. Both the cleave stress pattern and waveguide are fabricated with the same multiscan writing procedure, without requiring additional steps, and re-characterisation of the waveguides after 1 year confirm excellent long term performance stability.

femtosecond laser direct writing, Waveguides
2045-2322
Lee, Timothy
beb3b88e-3e5a-4c3f-8636-bb6de8040fcc
Sun, Qi
66e3c3df-5a60-4927-a47a-c4f6020c2fc0
Beresna, Martynas
a6dc062e-93c6-46a5-aeb3-8de332cdec7b
Brambilla, Gilberto
815d9712-62c7-47d1-8860-9451a363a6c8
Lee, Timothy
beb3b88e-3e5a-4c3f-8636-bb6de8040fcc
Sun, Qi
66e3c3df-5a60-4927-a47a-c4f6020c2fc0
Beresna, Martynas
a6dc062e-93c6-46a5-aeb3-8de332cdec7b
Brambilla, Gilberto
815d9712-62c7-47d1-8860-9451a363a6c8

Lee, Timothy, Sun, Qi, Beresna, Martynas and Brambilla, Gilberto (2021) Low bend loss femtosecond laser written waveguides exploiting integrated microcrack. Scientific Reports, 11 (1), [23770]. (doi:10.1038/s41598-021-03116-y).

Record type: Article

Abstract

We introduce the fabrication and use of microcracks embedded in glass as an optical element for manipulating light propagation, in particular for enhancing waveguide performance in silica integrated optics. By using a femtosecond laser to induce a strong asymmetric stress pattern in silica, uniform cracks with set dimensions can be created within the substrate and propagated along a fixed path. The smoothness of the resulting cleave interface and large index contrast can be exploited to enhance waveguide modal confinement. As a demonstration, we tackle the longstanding high bend-loss issue in femtosecond laser written silica waveguides by using this technique to cleave the outer edge of laser written waveguide bends, to suppress radiative bend loss. The microcrack cross section is estimated to be 15 μm in height and 30 nm in width, for the 10 [Formula: see text] 10 μm waveguides. At 1550 nm wavelength, losses down to 1 dB/cm at 10 mm bend radius were achieved, without introducing additional scattering. Both the cleave stress pattern and waveguide are fabricated with the same multiscan writing procedure, without requiring additional steps, and re-characterisation of the waveguides after 1 year confirm excellent long term performance stability.

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Accepted/In Press date: 26 November 2021
Published date: 9 December 2021
Keywords: femtosecond laser direct writing, Waveguides

Identifiers

Local EPrints ID: 452944
URI: http://eprints.soton.ac.uk/id/eprint/452944
ISSN: 2045-2322
PURE UUID: 3c02f31b-1e63-4b0a-b11f-7660a0ff5f80
ORCID for Qi Sun: ORCID iD orcid.org/0000-0002-0850-5463
ORCID for Gilberto Brambilla: ORCID iD orcid.org/0000-0002-5730-0499

Catalogue record

Date deposited: 07 Jan 2022 10:58
Last modified: 28 Apr 2022 02:19

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Contributors

Author: Timothy Lee
Author: Qi Sun ORCID iD

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