Guided-mode resonance in planar photonic crystals: Application to sensing

This dissertation addresses the design, fabrication and characterization of planar photonic crystals that employ the guided-mode resonance effect for sensing and detection applications. A theoretical basis for these applications is first developed, followed by the demonstration of a near-ultraviolet reflectance filter that provides high reflection efficiency in the 400-450 nm spectral range. The response of photonic crystal label-free biosensors is shown to be greatly improved by the use of a near-ultraviolet device, and this improvement in performance is shown to stem from the enhanced surface sensitivity and lowered bulk sensitivity for devices operating in this wavelength range. The application of PCs for wavelength detection is demonstrated by developing a system employing a continuously variable reflectance filter. The system is composed of only two components and allows detection of wavelength changes as small as 0.011 nm. Visible wavelength PCs are also studied for application as fluorescence enhancement biosensors. For the first time, a PC capable of a dual enhancement modality (enhanced excitation and enhanced extraction of fluorescence) is demonstrated for boosting quantum dot fluorescence by over two orders of magnitude. The distance dependence of the enhanced excitation effect is studied and provides clarification for its mechanism and suggests that the PC can be modified to accommodate a wide range of analyte sizes. Finally the enhanced extraction effect is studied in detail using a model system involving quantum dots and waveguide gratings. The results suggest that enhanced extraction can greatly improve the output of fluorophores that are spectrally and spatially matched to the device. A practical demonstration of this effect is carried out in the detection of the cytokine TNF-alpha.