Dielectric microspheres illuminated by a tightly focused Gaussian beam can focus light on a tiny spot with subwavelength dimensions along the three directions of space. We report here a detailed experimental and theoretical study of the interaction between a single fluorescent molecule and this peculiar electromagnetic distribution. The microsphere increases the excitation intensity sensed by the molecule up to a factor of 2.2, while at the same time it allows for a collection efficiency of up to 60% by redirecting the light emitted at large incidences toward the optical axis. By combining these two effects, the number of collected fluorescence photons can be increased up to a factor of 5. We quantify the evolution of the excitation and collection contributions with the microsphere dimensions and compare our experimental findings with numerical simulations.
© 2009 Optical Society of AmericaFull Article | PDF Article
Steven C. Hill, Hasan I. Saleheen, Michael D. Barnes, William B. Whitten, and J. Michael Ramsey
Appl. Opt. 35(31) 6278-6288 (1996)
Jérôme Wenger, Davy Gérard, José Dintinger, Oussama Mahboub, Nicolas Bonod, Evgeny Popov, Thomas W. Ebbesen, and Hervé Rigneault
Opt. Express 16(5) 3008-3020 (2008)
Davy Gérard, Jérôme Wenger, Alexis Devilez, David Gachet, Brian Stout, Nicolas Bonod, Evgeny Popov, and Hervé Rigneault
Opt. Express 16(19) 15297-15303 (2008)