Tight focusing of laser beams in a lambda/2-microcavity.
We evaluate the field distribution in the focal spot of the fundamental Gaussian beam as well as radially and azimuthally polarized doughnut beams focused inside a planar metallic sub-wavelength microcavity using a high numerical aperture objective lens. We show that focusing in the cavity results in a much tighter focal spot in longitudinal direction compared to free space and in spatial discrimination between longitudinal and in-plane field components. In order to verify the modeling results we experimentally monitor excitation patterns of fluorescence beads inside the lambda/2-cavity and find them in full agreement to the modeling predictions. We discuss the implications of the results for cavity assisted single molecular spectroscopy and intra-cavity single molecular imaging.
Khoptyar
Dmitry
D
Institute of Physical and Theoretical Chemistry, Tuebingen University, Auf der Morgenstelle 8, 72076 Tuebingen, Germany.
Gutbrod
Raphael
R
Chizhik
Anna
A
Enderlein
Jörg
J
Schleifenbaum
Frank
F
Steiner
Mathias
M
Meixner
Alfred J
AJ
D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D007909:Lenses; D008027:Light; D008029:Lighting / Q000295:instrumentation*; D008962:Models, Theoretical; D012542:Scattering, Radiation