Label-free water sensors using hybrid polymer-dielectric mid-infrared optical waveguides.
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 λ=2.6-2.7 μm 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.
†Materials Processing Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.|§Photonics Devices and Systems Group, Singapore University of Technology and Design, Singapore 487372, Singapore.
Pao Tai
PT
Lin
‡Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, United States.
James
J
Giammarco
‡Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, United States.
Nikolay
N
Borodinov
‡Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, United States.
Mykhailo
M
Savchak
†Materials Processing Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Vivek
V
Singh
†Materials Processing Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Lionel C
LC
Kimerling
§Photonics Devices and Systems Group, Singapore University of Technology and Design, Singapore 487372, Singapore.
Dawn T H
DT
Tan
Kathleen A
KA
Richardson
‡Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634, United States.
Igor
I
Luzinov
†Materials Processing Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Anu
A
Agarwal
drop-cast coating; gradient refractive index; hybrid polymer−dielectric waveguides; label-free detection; mid-infrared absorption; sensor on-a-chip