Design and demonstration of an optical cavity-based biosensor using three wavelengths to improve fabrication tolerance.

As diseases and cancers progress, the chances of survival depreciate; early detection is vital for improving success rates. Despite dedicated research, diagnosis has remained static—initial consultation, scanning, and then biopsies and complex immunoassay techniques are needed to receive a diagnosis. Biosensors produce a multi-faceted benefit. Early diagnosis reduces costs, saves time, and most importantly, improves quality of life. It is imperative to further develop these biosensing solutions and make diagnosis more accessible. Current diagnostic procedures require multi-million-dollar facilities, and tests are performed by highly skilled personnel. This work is dedicated to alleviating initial costs by designing and fabricating a low-cost optical cavity-based biosensor for quantitative detection at the point of care, and to provide tools to better understand bodily processes in efforts to find cures. In recent years, the optical cavity-based biosensor discussed henceforth has demonstrated high sensitivity in biosensing experiments, however the fabrication tolerance of the device itself drastically hinders the success rate of measurements. Before, the resonant changes of two wavelengths were used in conjunction with a differential detection method for biodetection experiments. The sensitive region was limited, however, and it often involved waiting overnight for the channel to be suitable for testing. To increase usability and reduce the required time to prepare the cavity for biodetection, a third laser wavelength is integrated into the optical system to expand fabrication tolerance and reduce the channel priming time. In simulation, the third wavelength expanded the fabrication tolerance from 30 nm to 70 nm. The addition of a third wavelength was demonstrated to improve the success rate of measurements by 7% despite a larger variation in cavity width and reduce the channel priming time from 0 –23 hours to 0 –20 minutes.