Ultra-sensitive surface absorption spectroscopy using sub-wavelength diameter optical fibers
arXiv:cond-mat/0701264 · doi:10.1364/OE.15.011952
Abstract
The guided modes of sub-wavelength diameter air-clad optical fibers exhibit a pronounced evanescent field. The absorption of particles on the fiber surface is therefore readily detected via the fiber transmission. We show that the resulting absorption for a given surface coverage can be orders of magnitude higher than for conventional surface spectroscopy. As a demonstration, we present measurements on sub-monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules at ambient conditions, revealing the agglomeration dynamics on a second to minutes timescale.
4 pages, Fig.1a corrected y-axis, p.2 minor text changes to facilitate the understanding of eq. 4 and 6