Tight focusing of laser beams in a lambda/2-microcavity.
June 27th, 2008 | by admin |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 D, Gutbrod R, Chizhik A, Enderlein J, Schleifenbaum F, Steiner M, Meixner AJ.
Institute of Physical and Theoretical Chemistry, Tuebingen University, Auf der Morgenstelle 8, 72076 Tuebingen, Germany.