Wide angle near-field optical probes by reverse tube etching

Area of Science:

• Materials Science
• Optical Engineering
• Microscopy

Background:

• Fabricating fiber probes for near-field optical microscopy (SNOM) requires precise control over tip geometry.
• Existing tube etching methods have limitations in achieving desired taper angles and surface smoothness.

Purpose of the Study:

• To present a novel modification of the tube etching process for enhanced fiber probe fabrication.
• To improve the taper angle and surface quality of fiber probes for SNOM.

Main Methods:

• A new technique, reverse tube etching, was developed.
• Fiber probes were fabricated by immersing optical fibers in hydrofluoric acid in an upside-down geometry.
• Tip formation occurred within the micrometer tube cavity of the polymeric jacket.

Main Results:

• The reverse tube etching method successfully increased the taper angle by a factor of two.
• Fabricated tapered regions exhibited high surface smoothness.
• Average cone angles of approximately 30 degrees were achieved for multimode fibers (200/250 microm core/cladding diameter).

Conclusions:

• Reverse tube etching is an effective method for producing high-quality fiber probes for SNOM.
• The process allows for precise control over taper angle and surface morphology.
• Gravity plays a crucial role in the etching product removal, influencing tip formation.