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.