Optical nanofibers and spectroscopy

TL;DR

This paper reviews advancements in tapered optical nanofibers with sub-wavelength diameters, highlighting their fabrication, characterization, and applications in sensitive evanescent wave spectroscopy for various media and quantum systems.

Contribution

It introduces a precise flame pulling fabrication method, an in situ optical measurement technique, and demonstrates diverse spectroscopic applications including organic molecules, quantum dots, and vapor detection.

Findings

Successful fabrication of tapered fibers with controlled profiles

Demonstration of linear and nonlinear spectroscopy on surface-adsorbed molecules

First implementation of a single-fiber bi-modal interferometer

Abstract

We review our recent progress in the production and characterization of tapered optical fibers with a sub-wavelength diameter waist. Such fibers exhibit a pronounced evanescent field and are therefore a useful tool for highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist or of the medium surrounding. We use a carefully designed flame pulling process that allows us to realize preset fiber diameter profiles. In order to determine the waist diameter and to verify the fiber profile, we employ scanning electron microscope measurements and a novel accurate in situ optical method based on harmonic generation. We use our fibers for linear and non-linear absorption and fluorescence spectroscopy of surface-adsorbed organic molecules and investigate their agglomeration dynamics. Furthermore, we apply our spectroscopic method to quantum dots on the surface of the fiber waist and to caesium vapor surrounding the fiber. Finally, towards dispersive measurements, we present our first results on building and testing a single-fiber bi-modal interferometer.