Thesis
Broadband planar waveguide to vertical mode couplers
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T17603
- Person Identifier (Local)
- 202153458
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The research presented in this thesis focuses on the development of a broadband and low loss vertical coupling regime for photonic integrated circuits, using a combination of laser lithography and grayscale lithography. Existing coupling regimes in photonic integration often struggle to meet four key requirements: low optical loss, broad spectral bandwidth, rapid fabrication turnaround, and wafer scale testability. To address this, a low cost platform based on SU8 on glass was fabricated, employing a multistage process with grayscale lithography to realise 2.5D turning mirrors at 45°, coated with a highly reflective thin film comprising 50 nm titanium and 200 nm gold. Planar SU8 waveguides were fabricated to embed the turning mirrors, enabling a broadband edge coupled waveguide to vertical mirror architecture. Optical characterisation of these devices was carried out across a wavelength range of 516 to 1630 nm, with measurements of facet coupling losses, propagation losses, and additional mirror related coupling losses. The optical losses introduced by the mirror across the measured spectral band were below 1 dB when collected in free space. For wafer scale testability, direct coupling to single mode fibre at 1550 nm was demonstrated with losses of 0.8 dB. Finally, hybrid integration of the waveguide vertical couplers was achieved through additional microfabrication and transfer printing of µLEDs and VCSEL arrays. Successful probing of these active photonic devices was achieved, and end facet imaging was recorded.
- Advisor / supervisor
- Strain, Michael
- Resource Type
- DOI
Relations
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PDF of thesis T17603 | 2026-02-23 | Public | Download |