title: Coupled external cavity photonic crystal enhanced fluorescence.
abstract: We report a fundamentally new approach to enhance fluorescence in which surface adsorbed fluorophore-tagged biomolecules are excited on a photonic crystal surface that functions as a narrow bandwidth and tunable mirror of an external cavity laser. This scheme leads to ∼10× increase in the electromagnetic enhancement factor compared to ordinary photonic crystal enhanced fluorescence. In our experiments, the cavity automatically tunes its lasing wavelength to the resonance wavelength of the photonic crystal, ensuring optimal on-resonance coupling even in the presence of variable device parameters and variations in the density of surface-adsorbed capture molecules. We achieve ∼10(5) × improvement in the limit of detection of a fluorophore-tagged protein compared to its detection on an unpatterned glass substrate. The enhanced fluorescence signal and easy optical alignment make cavity-coupled photonic crystals a viable approach for further reducing detection limits of optically-excited light emitters that are used in biological assays.
authors.affiliation: Department of Physics, University of Illinois, Urbana-Champaign, USA.
authors.forename: Anusha
authors.initials: A
authors.lastname: Pokhriyal
authors.forename: Meng
authors.initials: M
authors.lastname: Lu
authors.forename: Chun
authors.initials: C
authors.lastname: Ge
authors.forename: Brian T
authors.initials: BT
authors.lastname: Cunningham
mesh_terms: D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D017785:Photons; D045663:Quantum Dots / Q000737:chemistry; D019809:Streptavidin / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D019809:Streptavidin
keywords: external-cavity laser; fluorescence enhancement; nanostructured surface; photonic crystal