Graded wavelength filter based wavelength detection for a distributed feedback laser biosensor

Altaf, Kashif

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https://hdl.handle.net/2142/14767 Copy

Description

Title

Graded wavelength filter based wavelength detection for a distributed feedback laser biosensor

Author(s)

Altaf, Kashif

Issue Date

2010-01-06T17:50:15Z

Director of Research (if dissertation) or Advisor (if thesis)

Cunningham, Brian T.

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Graded wavelength filter
• wavelength detection.

Abstract

A compact and low-cost wavelength detection system has been designed that works for the readout of the distributed feedback (DFB) laser biosensor. The detection system is based on a charge-coupled device (CCD) array, and on a guided mode resonance filter (GMRF) that is composed of a linear dielectric grating and a linearly graded high-refractive-index titanium dioxide (TiO2) thin film, whose thickness varies as a function of position on the surface. The size of the setup is almost the same as the size of the CCD chip. The GMRF exhibits linearly varying wavelength reflectance characteristics, i.e., resonant wavelength values that are a function of the thickness of the TiO2 film. The filter is designed to perform real-time biosensing of a DFB laser biosensor that is also composed of a linear dielectric grating, an active dye-doped polymer layer and a uniform-thickness TiO2 thin film deposited on its surface. When excited with a high energy pulsed Nd:YAG laser, the DFB laser emits narrowband stimulated emission whose wavelength changes as a function of the effective refractive index of the DFB structure being excited. Alternating oppositely charged polyelectrolyte monolayers have been deposited on the DFB surface that generate wavelength shifts in small steps due to increasing thickness of the polyelectrolyte stack, thereby changing the effective refractive index with each adsorbed monolayer. The gratings for both the graded wavelength filter (GWF) and the DFB laser structures are fabricated by a low-cost and high-throughput process of nanoreplica molding. The wavelength sensing mechanism is found to be robust and measures wavelength shifts with a spectral resolution of 308 pm.

Graduation Semester

2009-12

Permalink

http://hdl.handle.net/2142/14767

Copyright and License Information

Copyright 2009 Kashif Altaf

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