Label-Free Water Sensors Using Hybrid Polymer-Dielectric Mid-Infrared Optical Waveguides

TitleLabel-Free Water Sensors Using Hybrid Polymer-Dielectric Mid-Infrared Optical Waveguides
Publication TypeJournal Article
Year of Publication2015
AuthorsLin, PTai, Giammarco, J, Borodinov, N, Savchak, M, Singh, V, Kimerling, LC, Tan, DTH, Richardson, KA, Luzinov, I, Agarwal, AM
JournalAcs Applied Materials & Interfaces
Pagination11189 - 11194
Date Published2015/06/03/

A chip-scale mid-IR water sensor was developed using silicon nitride (SiN) waveguides coated with poly(glycidyl methacrylate) (PGMA). The label-free detection was conducted at lambda = 2.6-2.7 mu m because this spectral region overlaps with the characteristic O-H stretch absorption while being transparent to PGMA and SiN. Through the design of a hybrid waveguide structure, we were able to tailor the mid-IR evanescent wave into the PGMA layer and the surrounding water and, consequently, to enhance the light-analyte interaction. A 7.6 times enhancement of sensitivity is experimentally demonstrated and explained by material integration engineering as well as waveguide mode analysis. Our sensor platform made by polymer-dielectric hybrids can be applied to other regions of the mid-IR spectrum to probe other analytes and can ultimately achieve a multispectral sensor on-a-chip.