In situ observation of slow and tunnelling light at the cutoff wavelength of an optical fiber

TL;DR

This paper experimentally demonstrates slow and tunneling light phenomena at the cutoff wavelength in a standard optical fiber, enabling detailed study of light behavior with minimal losses and high uniformity.

Contribution

It provides the first in situ observation of slow and tunneling light in a standard optical fiber, overcoming fabrication challenges and highlighting potential applications.

Findings

Demonstrated slow axial propagation in optical fiber

Measured nanosecond tunneling times across micron-scale barriers

Utilized standard fiber with record uniformity and low losses

Abstract

Slow waves and tunneling waves can meet at the cutoff wavelengths and/or transmission band edges of optical and quantum mechanical waveguides. The experimental investigation of this phenomenon, previously performed using various optical microstructures, is challenged by fabrication imperfections and material losses. Here, we demonstrate this phenomenon in situ for whispering gallery modes slowly propagating along a standard optical fiber, which possesses the record uniformity and exceptionally small transmission losses. Slow axial propagation dramatically increases the longitudinal wavelength of light and allows us to measure nanosecond-long tunneling times along tunable potential barriers having the width of hundreds of microns. This demonstration paves a simple and versatile way to investigate and employ the interplaying slow and tunneling light.