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Proceedings Paper

Phase sensitive diffraction sensor for high sensitivity refractive index measurement
Author(s): Nityanand Kumawat; Manoj Varma; Sunil Kumar
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Paper Abstract

In this study a diffraction based sensor has been developed for bio molecular sensing applications and performing assays in real time. A diffraction grating fabricated on a glass substrate produced diffraction patterns both in transmission and reflection when illuminated by a laser diode. We used zeroth order I(0,0) as reference and first order I(0,1) as signal channel and conducted ratiometric measurements that reduced noise by more than 50 times. The ratiometric approach resulted in a very simple instrumentation with very high sensitivity. In the past, we have shown refractive index measurements both for bulk and surface adsorption using the diffractive self-referencing approach. In the current work we extend the same concept to higher diffraction orders. We have considered order I(0,1) and I(1,1) and performed ratiometric measurements I(0,1)/I(1,1) to eliminate the common mode fluctuations. Since orders I(0,1) and I(1,1) behaved opposite to each other, the resulting ratio signal amplitude increased more than twice compared to our previous results. As a proof of concept we used different salt concentrations in DI water. Increased signal amplitude and improved fluid injection system resulted in more than 4 times improvement in detection limit, giving limit of detection 1.3×10-7 refractive index unit (RIU) compared to our previous results. The improved refractive index sensitivity will help significantly for high sensitivity label free bio sensing application in a very cost-effective and simple experimental set-up.

Paper Details

Date Published: 20 February 2018
PDF: 6 pages
Proc. SPIE 10501, Optical Diagnostics and Sensing XVIII: Toward Point-of-Care Diagnostics, 105010C (20 February 2018); doi: 10.1117/12.2289740
Show Author Affiliations
Nityanand Kumawat, New York Univ. Abu Dhabi (United Arab Emirates)
Manoj Varma, Indian Institute of Science (India)
Sunil Kumar, New York Univ. Abu Dhabi (United Arab Emirates)
New York Univ. (United States)


Published in SPIE Proceedings Vol. 10501:
Optical Diagnostics and Sensing XVIII: Toward Point-of-Care Diagnostics
Gerard L. Coté, Editor(s)

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