Single-mode SU-8 waveguide fabricated using ultrafast direct laser writing
Document Type
Article
Publication Date
11-1-2022
Abstract
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.
Keywords
Two-photon polymerization, SU-8, Optical waveguide, Direct laser writing
Divisions
photonics
Funders
Malaysia Ministry of Higher Education Fundamental Research Grant Scheme (FRGS/1/2020/STG07/UM/01/2)
Publication Title
Optik
Volume
270
Publisher
Elsevier
Publisher Location
HACKERBRUCKE 6, 80335 MUNICH, GERMANY