@article{83a35423cac349009616d76de888f930,
title = "Graded wavelength one-dimensional photonic crystal reveals spectral characteristics of enhanced fluorescence",
abstract = "One-dimensional photonic crystal (PC) slabs are capable of enhancing the excitation of fluorescent material adsorbed on their surface. In this report, we demonstrate and verify by electromagnetic computer simulations that resonant leaky modes spectrally overlapping the laser wavelength used for fluorescent excitation are responsible for the enhanced excitation, and that the Q -factor of the PC resonance is proportional to the resonant electric field intensity and thus proportional to the fluorescent enhancement factor. As a demonstration, we have fabricated a single PC slab surface with an intentional spatial gradient in the resonant wavelength and demonstrate enhanced fluorescence only from locations on the PC surface with a leaky mode corresponding to a 633 nm HeNe laser used to excite Cyanine 5 dye deposited uniformly across the PC. The results show that enhanced fluorescence signals for one-dimensional PC slabs originate from increased excitation of the fluorescent dye.",
author = "Mathias, {Patrick C.} and Nikhil Ganesh and Wei Zhang and Cunningham, {Brian T.}",
note = "Funding Information: This work was supported by SRU Biosystems and the National Science Foundation (Grant No. BES 0427657). The authors thank the staff of the Micro and Nano Technology Laboratory and colleagues from the Nano Sensors Group for their suggestions and input. Any opinions, findings, and conclusions or recommendations in this work are those of the authors and do not necessarily reflect the views of the National Science Foundation. FIG. 1. (a) Atomic force microscopy image of a portion of the photonic crystal surface. (b) Side view of the model used in Rigorous Coupled-Wave Analysis computations of the structure response. Dimensions are based on data from AFMs of the structure at various steps in fabrication. The structure period was 360 nm. The grating height was 60 nm, the SiO 2 height was 145 nm, and the TiO 2 thickness was varied from 70 to 220 nm. (c) Simulated transmission response as a function of wavelength under TE illumination for a region of the structure resonant at 633 nm. (d) Simulated electric field intensity for the structure in (b) when illuminated with 633 nm TE-polarized light at normal incidence. FIG. 2. (a) Sample transmission spectra from four locations on the graded wavelength photonic crystal at near-normal incidence. (b) Resonant wavelength as a function of position for the actual graded wavelength photonic crystal and for a simulated structure. FIG. 3. (a) Fluorescence image of the entire graded wavelength photonic crystal device after application of a Cyanine-5 conjugated streptavidin monolayer. (b) Line profile from one horizontal line spanning the photonic crystal on the fluorescent image. (c) Simulated average electric field intensity on the top surface of the photonic crystal under normally incident 633 nm TE-polarized illumination, for the range of TiO 2 thicknesses deposited on the actual structure. (d) Simulated average electric field intensity as in (c), with an angle of incidence of 0.25 ° . FIG. 4. (a) Line profile from one horizontal line spanning the region of the device without a photonic crystal on the fluorescent image. (b) Simulated average electric field intensity on the top surface of the off-device region under normally incident 633 nm TE-polarized illumination, for the range of TiO 2 thicknesses deposited on the actual structure. FIG. 5. Simulated transmission at an incidence angle of 0.25 ° for two TiO 2 thicknesses (87 and 92 nm) at which distinct peaks exhibit minimum transmission at a wavelength of 633 nm. ",
year = "2008",
doi = "10.1063/1.2917184",
language = "English (US)",
volume = "103",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics",
number = "9",
}