Hybrid silicon-tellurium-dioxide DBR resonators coated in PMMA for biological sensing

Dawson B Bonneville; Mitchell Albert; Ramis Arbi; Muhammad Munir; Bruno L Segat Frare; Khadijeh Miarabbas Kiani; Henry C Frankis; Andrew P Knights; Ayse Turak; Kyla N Sask; Jonathan D B Bradley

doi:10.1364/BOE.485824

Hybrid silicon-tellurium-dioxide DBR resonators coated in PMMA for biological sensing

Biomed Opt Express. 2023 Mar 17;14(4):1545-1561. doi: 10.1364/BOE.485824. eCollection 2023 Apr 1.

Authors

Affiliations

¹ Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada.
² Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L7, Canada.
³ School of Biomedical Engineering, McMaster University, Hamilton, Canada.

Abstract

We report on silicon waveguide distributed Bragg reflector (DBR) cavities hybridized with a tellurium dioxide (TeO₂) cladding and coated in plasma functionalized poly (methyl methacrylate) (PMMA) for label free biological sensors. We describe the device structure and fabrication steps, including reactive sputtering of TeO₂ and spin coating and plasma functionalization of PMMA on foundry processed Si chips, as well as the characterization of two DBR designs via thermal, water, and bovine serum albumin (BSA) protein sensing. Plasma treatment on the PMMA films was shown to decrease the water droplet contact angle from ∼70 to ∼35°, increasing hydrophilicity for liquid sensing, while adding functional groups on the surface of the sensors intended to assist with immobilization of BSA molecules. Thermal, water and protein sensing were demonstrated on two DBR designs, including waveguide-connected sidewall (SW) and waveguide-adjacent multi-piece (MP) gratings. Limits of detection of 60 and 300 × 10^-4 RIU were measured via water sensing, and thermal sensitivities of 0.11 and 0.13 nm/°C were measured from 25-50 °C for SW and MP DBR cavities, respectively. Plasma treatment was shown to enable protein immobilization and sensing of BSA molecules at a concentration of 2 µg/mL diluted in phosphate buffered saline, demonstrating a ∼1.6 nm resonance shift and subsequent full recovery to baseline after stripping the proteins with sodium dodecyl sulfate for a MP DBR device. These results are a promising step towards active and laser-based sensors using rare-earth-doped TeO₂ in silicon photonic circuits, which can be subsequently coated in PMMA and functionalized via plasma treatment for label free biological sensing.