Hydrofluoric acid flow etching of low-loss subwavelength-diameter biconical fiber tapers

Citation

Zhang, E. J., Sacher, W. D., & Poon, J. K. S. (2010). Hydrofluoric acid flow etching of low-loss subwavelength-diameter biconical fiber tapers. Optics Express, 18(21), 22593.
The citation follows the format: Author 1 Last, Author 1 First Initial., Author 2 Last, Author 2 First Initial, & Author 3 Last, Author 3 First Initial. (Year). Title of article. Title of Journal, Volume Number(Issue Number), Page range. DOI: Digital Object Identifier. 

Keywords

• Subwavelength-diameter biconical fiber tapers (SBFTs)
• Hydrofluoric acid etching
• Low-loss
• Surface tension driven flows
• Marangoni effect
• Optical transmission
• Taper fabrication
• Microdroplets
• Adiabatic taper transitions
• Erbium doped silica microsphere laser

 Brief

A new acid-etch method is presented for fabricating low-loss subwavelength-diameter biconical fiber tapers that utilizes surface tension driven flows of hydrofluoric acid microdroplets to achieve losses less than 0.1 dB/mm, an order of magnitude improvement over previous techniques. 

Summary

This article presents a new method for fabricating low-loss subwavelength-diameter biconical fiber tapers (SBFTs) using hydrofluoric acid (HF) etching. The key innovation is the use of surface tension driven flows of HF microdroplets, which allows for the creation of adiabatic taper transitions with minimal surface corrugations. This method results in SBFTs with losses less than 0.1 dB/mm for waist diameters between 500 nm to 1 µm, and losses below 0.05 dB/mm for waist diameters above 1 µm. This is a significant improvement over previous acid-etch techniques, which have exhibited insertion losses in excess of 10 dB even at micron-scale waist diameters. The article also demonstrates an application of the fabricated SBFTs: a fiber taper coupled erbium microsphere laser.

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