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Phase Sensitive Diffraction Sensor for High Sensitivity Refractive Index Measurement

Kumawat, Nityanand and Varma, Manoj and Kumar, Sunil (2018) Phase Sensitive Diffraction Sensor for High Sensitivity Refractive Index Measurement. In: OPTICAL DIAGNOSTICS AND SENSING XVIII: TOWARD POINT-OF-CARE DIAGNOSTICS, JAN 29-30, 2018, San Francisco, CA.

Full text not available from this repository.
Official URL: https://doi.org/10.1117/12.2289740


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,I-0) as reference and first order I-(0,I-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,I-1) and I-(1,I-1) and performed ratiometric measurements I-(0,I-1)/I-(1,I-1) to eliminate the common mode fluctuations. Since orders I((0,1) )and I-(1,I-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 1.3x10(-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.

Item Type: Conference Paper
Series.: Proceedings of SPIE
Additional Information: Conference on Optical Diagnostics and Sensing XVIII - Toward Point-of-Care Diagnostics, San Francisco, CA, JAN 29-30, 2018
Keywords: Diffraction grating; self-referencing; ratiometric; optical biosensor; refractive index; label-free
Department/Centre: Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited: 28 Jan 2019 08:43
Last Modified: 28 Jan 2019 08:43
URI: http://eprints.iisc.ac.in/id/eprint/61464

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