GaN Photonic Crystal-Based, Enhanced Fluorescence Biomolecule Detection System
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1040-Q09-29
GaN Photonic Crystal-Based, Enhanced Fluorescence Biomolecule Detection System J. M. Dawson1, J. R. Nightingale1, R. P. Tompkins2, X. Cao1, T. H. Myers2, L. A. Hornak1, and D. Korakakis1 1 Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV, 26506 2 Department of Physics, West Virginia University, Morgantown, WV, 26506 ABSTRACT The need for small form factor, portable biosensing platforms is prevalent across a wide range of medical, environmental, and defense applications. This paper presents the design of a novel, integrated optofluidic photonic crystal biosensor architecture that shows potential for meeting the single molecule detection requirements of these application areas. GaN is being targeted as the photonic crystal slab material due to its transparency in the visible spectral range and also the potential for creating high aspect ratio photonic crystal lattices via polarity inverted MBE growth. Results of optical modeling efforts indicating 10-15x resonant enhancement of fluorescent emission and polarity inversion GaN growth techniques will be discussed. INTRODUCTION
Figure 1: (a) Photonic crystal biosensor architecture (inset: top view of air holes that make up the PC lattice and defect (image center)). (b) Labeled biomolecules passing through the defect flow channel get excited by a pump beam within higher frequency photonic crystal air bands (inset: simulation indicating pump frequency mode propagation in PC slab). (c) The emission intensity of the fluorescing label is enhanced due to the resonant nature of the defect cavity (inset: simulation indicating optical confinement and enhancement of fluorescent emission frequency in PC defect cavity).
The detection of biomolecules through the use of fluorescence emission has become commonplace in performing environmental and biomedical diagnostics for counter-bioterrorism, DNA/protein identification and classification, agricultural sciences, and many other applications [1]. Fluorescence emission methods offer excellent sensitivity and low detection limits for a wide range of fluorescent label/molecule combinations [2]. However, the ‘bench-top’ nature of diagnostic systems that employ these methods does not lend well to sample analysis outside of a dedicated laboratory. The combination of optics and microfluidics into optofluidic systems has provided a means of creating portable integrated platforms for performing fluorescence emission analyses in fieldable systems [3]. Photonic crystal (PC) materials enable the application of optical bandgap engineering in optofluidic systems, further enhancing their utility and range of function [4]. A photonic bandgap can be formed in a photonic crystal material by periodically varying the refractive index in 1, 2, or 3 dimensions, creating a nanoscale lattice structure that is analogous to the atomic structure found in
homogenous crystalline materials. The design and fabrication of this engineered lattice, as well as the controlled introduction of lattice d
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