Title page for ETD etd-345617310975300

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
Date of Defense 1997-01-27
Availability unrestricted
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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