Single-mode SU-8 waveguide fabricated using ultrafast direct laser writing

Ng, K. B. and Chong, Wu Yi and Lim, C. S. and Ahmad, Harith (2022) Single-mode SU-8 waveguide fabricated using ultrafast direct laser writing. Optik, 270. ISSN 0030-4026, DOI

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In this work, we demonstrated the application of femtosecond laser direct writing using the two -photon polymerization (TPP) technique in the fabrication of single-mode optical waveguide in SU-8 photoresist. It was found that the polymerization of SU-8 using 780 nm femtosecond laser requires a fluence of 1.8-10 kJ/cm2, where 2.5 kJ/cm2 is sufficient to create a flat-top surface waveguide for a 1.8 mu m thick SU-8 film. To reduce the coupling loss of the waveguide, the waveguide width was enlarged with double scan of the femtosecond laser by shifting the sample laterally with a center-to-center spacing of 0.5 mu m between scans. The optimized waveguide has an insertion loss of 11 dB, with an approximated propagation loss of 1.27 dB/cm. Based on the information obtained, a directional coupler was fabricated. The resulting coupling ratio of the directional coupler is 47 % and 53 % at each port. To further demonstrate the viability of the proposed technique to fabricate complex waveguide structures, a vertically suspended waveguide has been designed and fabricated.

Item Type: Article
Funders: Malaysia Ministry of Higher Education Fundamental Research Grant Scheme (FRGS/1/2020/STG07/UM/01/2)
Uncontrolled Keywords: Two-photon polymerization; SU-8; Optical waveguide; Direct laser writing
Subjects: Q Science > QD Chemistry
Divisions: Deputy Vice Chancellor (Research & Innovation) Office > Photonics Research Centre
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 20 Jul 2023 01:02
Last Modified: 20 Jul 2023 01:02

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