Wide angle near-field optical probes by reverse tube etching.
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.
Patanè
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Dipartimento di Fisica della Materia e Tecnologie Fisiche Avanzate, Università di Messina, Salita Sperone 31, 98166 Messina, Italy. patanes@unime.it
Cefalì
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Arena
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Gucciardi
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Allegrini
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