|Title||Label-Free Water Sensors Using Hybrid Polymer-Dielectric Mid-Infrared Optical Waveguides|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Lin, PTai, Giammarco, J, Borodinov, N, Savchak, M, Singh, V, Kimerling, LC, Tan, DTH, Richardson, KA, Luzinov, I, Agarwal, AM|
|Journal||Acs Applied Materials & Interfaces|
|Pagination||11189 - 11194|
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.