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Utilizing the randomness of light propagation through scattering media for sensing application (Conference Presentation)
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Paper Abstract

As widely known, random diffraction effect due to refractive index inhomogeneity is considered as an annoying factor for propagating light through scattering media. Here, instead of overcoming the random diffraction, we utilize the natural randomness of strongly scattering media and their sensitivity to inhomogeneity of refractive index to develop a novel optical sensor. Unlike various sensing technologies with trade-off among complexity, sensitivity and stability, here we demonstrate a very simple sensing technique which uses scattering media to achieve super sensitivity, speedy response time and possibly high stability. In our sensing principle, a lasing beam passing through a turbid medium creates a speckle pattern on a camera due to interference of random refracted light off the scattering media. Light is scattered multiple times at multiple interfaces between ground glass and the surrounding environment creating a speckle pattern which is sensitive to the environment’s refractive index. The correlation of speckle patterns indicates the change of refractive index around the scattering medium. Simply placing the rough surface of ground glass in contact with sensing solutions, we are able to measure glucose, or sodium chloride concentration with sensitivity in the order of micro grams per liter. More interestingly, the sensitivity of the proposed approach could be improved simply by adding more scattering surfaces in contact with the target medium. Therefore, our simple technique could be very useful for prominent applications in refractive index sensing such as measuring solution concentration, distinguishing different gases, detecting pressure change and so on.

Paper Details

Date Published: 4 March 2019
Proc. SPIE 10890, Label-free Biomedical Imaging and Sensing (LBIS) 2019, 108900M (4 March 2019); doi: 10.1117/12.2509829
Show Author Affiliations
Vinh Tran, Nanyang Technological Univ. (Singapore)
Sujit Sahoo, Nanyang Technological Univ. (Singapore)
Indian Institute of Technology Goa (India)
Dong Wang, Nanyang Technological Univ. (Singapore)
Cuong Dang, Nanyang Technological Univ. (Singapore)

Published in SPIE Proceedings Vol. 10890:
Label-free Biomedical Imaging and Sensing (LBIS) 2019
Natan T. Shaked; Oliver Hayden, Editor(s)

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