Type of Document	Dissertation
Author	D'Alberto, Tiffanie Gabrielle
Author's Email Address	hafne13@vt.edu
URN	etd-345617310975300
Title	Long-Period Gratings as Immuno-Diagnostic biosensors
Degree	Master of Science
Department	Electrical and Computer Engineering
Advisory Committee	Advisor Name Title Besieris, Ioannis M. Claus, Richard O. Murphy, Kent A. Committee Chair
Keywords	BIOSENSOR FIBER OPTICS EVANESCENT FIELD DIFFRACTION GRATINGS IMMUNOASSAY
Date of Defense	1997-01-27
Availability	unrestricted
Abstract ABSTRACT This research presents a novel biosensor which utilizes the refractive index sensitivity of a fiber optic long-period grating. The long period grating couples light from the forward propagating guided core mode of a single-mode fiber into discrete circularly symmetric cladding modes. Due to imperfections in the cladding surface, loss bands are seen in the transmission spectrum corresponding to the coupled wavelengths. Based on the phase-matching condition between the coupling and coupled modes, the loss bands shift with changes in the refractive index of the surrounding medium. The grating surface is chemically treated to covalently bond antibody to the cladding of the sensor. Treatment with the proper antigen increases the effective index seen by the cladding modes and affects the placement of the loss bands. This sensor demonstrates specific antigen binding capacity with loss band shifts of 10 nm or more. The device offers several advantages over the widely used Enzyme-Linked Immuno-Sorbent Assays. Diagnostic applications can be expanded beyond the tests presented here.
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