Fabrication and characterization of optical nanofiber tips

TL;DR

This paper presents a simple, cost-effective chemical etching method to fabricate optical nanofiber tips with sub-500 nm diameters, suitable for advanced optical applications.

Contribution

A novel two-step HF acid etching process for fabricating optical nanofiber tips with controlled dimensions and high optical transmission.

Findings

Optical transmission exceeds 30%

Tip diameters are less than 500 nm

Technique is easy and cost-effective

Abstract

We demonstrate the fabrication of an optical nanofiber tip (ONFT) using a two-step chemical etching technique. This technique employs 30% and 24% hydrofluoric (HF) acid for the first and second steps, respectively. In the first step, a silica single-mode fiber with clad diameter of 125 um and core diameter of 10 um is immersed in the HF acid for 90 minutes. The resultant fiber diameter is reduced to 45 um. In the second step, such a fiber is again immersed in the HF acid for 60-80 minutes. The etching time is controlled to achieve the desired tip diameter of the ONFT. We characterize fabricated ONFTs by measuring optical transmission and surface morphology. The observed optical transmissions are more than 30% and tip diameters are less than 500 nm. The measured results readily reveal the merit of the employed technique as it is easy and cost-effective. Due to the strong confinement of the electromagnetic field at the tip of ONFTs, these structures lay versatile platforms with potential applications in sensing, photonics, and quantum optics.