HIGH-EFFICIENCY AND HIGH-RESOLUTION FIBEROPTIC PROBES FOR NEAR-FIELD IMAGING AND SPECTROSCOPY

We demonstrate that fiber-optic probes with an intermediate section fo llowed by a rapidly tapering tip lend to transmission efficiency enhan cement of better than four orders-of-magnitude at 60 nm tip diameter a nd more than five orders-of-magnitude at smaller than 40 nm tip diamet er over typical taffy-pulled fiber probes, Our highest resolution prob es have a tip diameter of 30 nm with a transmission efficiency of 0.02 %. and as an example we image tobacco mosaic virus with a resolution b etter than 35 nm. The probes are made in a two-step process involving pulling and then etching that permits both high efficiency and control of the mechanical resonance properties. The efficiency is enhanced by reducing the distance that the electromagnetic mode travels in the cu t-off mode of the fiber probe. The higher resolution is achieved becau se sharper tips can be made through the etching process. (C) 1997 Amer ican Institute of Physics.