title: Diffractive Optical Analysis for Refractive Index Sensing using Transparent Phase Gratings.
abstract: We report the implementation of a micro-patterned, glass-based photonic sensing element that is capable of label-free biosensing. The diffractive optical analyzer is based on the differential response of diffracted orders to bulk as well as surface refractive index changes. The differential read-out suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6 × 10(-7) was achieved with this technique with scope for further improvement.
authors.affiliation: Center for Nano Science and Engineering, Indian Institute of Science, Bangalore.
authors.forename: Nityanand
authors.initials: N
authors.lastname: Kumawat
authors.affiliation: Robert Bosch Center for Cyber Physical Systems, Indian Institute of Science, Bangalore.
authors.forename: Parama
authors.initials: P
authors.lastname: Pal
authors.affiliation: Center for Nano Science and Engineering, Indian Institute of Science, Bangalore.|Dept of Electrical Communication Engineering, Indian Institute of Science, Bangalore.
authors.forename: Manoj
authors.initials: M
authors.lastname: Varma
mesh_terms: D015374:Biosensing Techniques; D008962:Models, Theoretical; D055095:Optics and Photonics