Low-Loss Optical Nanofibers with Submicron Waist Diameters and Millimeter-Scale Waist Lengths

TL;DR

This paper presents a heat-and-pull fabrication system for creating low-loss optical nanofibers with submicron diameters and long waist lengths, suitable for advanced optical and atomic physics applications.

Contribution

It introduces a reproducible fabrication method using a multi-hole torch tip and procedures to minimize surface contamination, achieving high transmission efficiency.

Findings

Achieved >99.9% transmission for 200 nm waist diameter fibers

Demonstrated long-term stability with >85% transmission over 1 hour in lab conditions

Provided practical guidelines for nanofiber fabrication and maintenance

Abstract

Optical nanofibers with subwavelength diameters generate strong evanescent fields, enabling efficient light-matter interactions for optical sensing, spectroscopy, and cold-atom experiments. We report a heat-and-pull system for fabricating low-loss optical nanofibers with controllable waist dimensions and investigate the fabrication limits for achieving small waist diameters and long waist lengths. We study factors that influence fabrication performance, including flame geometry, nanofiber dimensions, and surface contamination. Using a multi-hole torch tip that provides a relatively large and uniform heating region, we achieve reproducible fabrication with optical transmission above $99.9\%$ for waist diameters as small as 200 nm for a 1-mm waist length and 250 nm for a 50-mm waist length. We also develop a preparation procedure for fiber splicing and cleaning to minimize transmission loss caused by surface contamination. In addition, we measure long-term transmission degradation due to dust accumulation in a typical laboratory environment and find that nanofibers fabricated in an enclosed setup maintain transmission above $85\%$ for more than 1 hour for nanofibers with a 300-nm waist diameter and waist lengths ranging from 1 to 30 mm. Our work provides practical guidelines for constructing nanofiber fabrication platforms and producing low-loss nanofibers for optics and atomic physics applications.