title: Wide angle near-field optical probes by reverse tube etching.
abstract: We present a simple modification of the tube etching process for the fabrication of fiber probes for near-field optical microscopy. It increases the taper angle of the probe by a factor of two. The novelty is that the fiber is immersed in hydrofluoric acid and chemically etched in an upside-down geometry. The tip formation occurs inside the micrometer tube cavity formed by the polymeric jacket. By applying this approach, called reverse tube etching, to multimode fibers with 200/250 microm core/cladding diameter, we have fabricated tapered regions featuring high surface smoothness and average cone angles of approximately 30 degrees . A simple model based on the crucial role of the gravity in removing the etching products, explains the tip formation process.
authors.affiliation: Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Università di Messina, Salita Sperone 31, 98166 Messina, Italy. patanes@unime.it
authors.forename: S
authors.initials: S
authors.lastname: Patanè
authors.forename: E
authors.initials: E
authors.lastname: Cefalì
authors.forename: A
authors.initials: A
authors.lastname: Arena
authors.forename: P G
authors.initials: PG
authors.lastname: Gucciardi
authors.forename: M
authors.initials: M
authors.lastname: Allegrini