Micro-lensed single-mode optical fiber with high numerical aperture
Abstract
We show that the output mode of a single-mode optical fiber can be directly focused to a sub-wavelength waist with a finite working distance by tapering the fiber to a diameter of the order of the wavelength and terminating it with a spherically/hemispherically shaped tip. Numerical simulations show that a beam waist with a width of as small as 0.62\lambda can be formed. We fabricate micro-lensed fibers and construct a probe-scanning confocal reflection microscope. Measurements on gold nano-particles show a spatial profile with a width of 0.29\lambda for \lambda = 850 nm, which is in good agreement with the numerical simulations. Due to their monolithic structures, these micro-lensed fibers will be flexible substitutes for conventional compound lenses in various experimental conditions such as cryogenic temperature and ultra-high vacuum.
Cite
@article{arxiv.1305.5937,
title = {Micro-lensed single-mode optical fiber with high numerical aperture},
author = {Shinya Kato and Sho Chonan and Takao Aoki},
journal= {arXiv preprint arXiv:1305.5937},
year = {2013}
}