Biophotonics: Biophotonic Sensors Based on Polymer Microspheres Evanescently Coupled to Optical Fiber

Polytechnic University Of New York, Brooklyn NY

Investigators

Abstract

0119273 Arnold The applicant proposes to investigate photonic sensors based on dielectric microspheres evanescently coupled to optical fibers, and to develop microsphere sensors for biochemical and biological sensing. The unprecedentedly narrow optical resonances in such microspheres open an avenue for a novel class of all-optical sensors which can measure local properties by detecting optical frequency shifts of the resonances. Many photonic resonance modes occur in a microsphere in an extremely narrow linewidth. The resonance spectrum is obtained by scanning the wavelength of the laser transmitted through the fiber into the microsphere and observing the intensity through a read-out fiber coupled to the microsphere. Resonance wavelength shifts are extremely sensitive to changes in the diameter and the refractive index of the sphere as well as the refractive index of the medium surrounding the sphere. The latter quantities are determined by the temperature, adsorption of a second substance onto the sphere surface, the isotropic and anisotropic stress, and the concentration of a chemical in the solution surrounding the sphere. Efforts will be especially targeted at developing microscopic sensing heads for biofluids. For this purpose fibers and microspheres, all made of polymers that can be rendered biocompatible will be used. The high specificity in biomolecular interactions will enable detection of a specific RNA, protein, enzyme, substrate, and antigen. The goal is to allow one to prepare as many kinds of sensors as the number of biomolecules. Availability of miniature, high-sensitivity biophotonic sensors will facilitate the development of 'device on a chip' and other parallel chemical and biological analysis systems in combinatorial chemistry.