Spectroscopy of Bioinspired Organic Microwaveguides and Cavities: Towards Femtomolar Sensing of Analytes

Tiwari, Roshan (2023) Spectroscopy of Bioinspired Organic Microwaveguides and Cavities: Towards Femtomolar Sensing of Analytes. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Roshan Tiwari (14IP045 )) 14IP045.pdf - Submitted Version Restricted to Repository staff only Download (15MB)

Abstract

Optical sensing is both a flourishing and emerging technology sector being employed in various industries such as oil and gas, biomedical technology, construction, etc. With the advent of high-tech gadgets such as smartphones, smartwatches, implants and so on, the demand for miniaturized, portable, and power-saving optical sensors has increased by many folds. In the majority of these sensors, waveguides have been a crucial and efficient sensing platform for ultrasensitive detection. They are usually based on inorganic materials such as silica, silicon nitride, perovskites, etc. But, over the last several years, tremendous efforts have been made in fabricating bioinspired organic optical structures mimicking naturally occurring structures. Moreover, due to their high refractive index contrast and wide optical transparency, they have emerged as an alternative to inorganic waveguides. In our work, we chemically prepared waveguides from organic materials such as a peptide and urea, and enhanced their sensing performance for detecting different analytes by exploiting four different strategies based on optical phenomena including Fano resonance, chromatic aberration, Fabry Perot resonances, and strong evanescent coupling. We observed that the performance of the waveguide sensor in terms of the quality factor increased, from a low value of 20 to hitherto unreported values of more than 1300 - which may facilitate unprecedentedly low sensing thresholds for such devices.

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