Integrated table-top facility for the study of Whispering Gallery Modes in dynamic liquid micro-cavities coupled to sub-micron tapered fibers

TL;DR

This paper presents an integrated table-top setup for studying high-Q Whispering Gallery Modes in liquid micro-cavities, emphasizing in situ fabrication of sub-micron tapered fibers for efficient light coupling and mode excitation.

Contribution

It introduces a reliable method for fabricating high-quality tapered fibers and demonstrates their use in exciting high-Q WGMs in liquid and solid micro-cavities.

Findings

Achieved over 85% transmission in tapered fibers.

Successfully excited WGMs with Q up to 7×10^7.

Developed a real-time monitoring technique for fiber tapering.

Abstract

A complete integrated table-top facility for the study of high-$Q$ Whispering Gallery Modes in solid and liquid micro-cavities is described, with emphasis on the in situ fabrication of reliable tapered fibers of sub-micron waist sizes for coupling light into time-dependent liquid micro-cavities. The experimental parameters have been chosen to get nearly adiabatic tapers, with their waist size consistent with the theoretical model. The oscillations in the transmitted power during fiber tapering are monitored to check the coupling of higher order modes and identify the point when the fiber is suitable for pure single mode coupling. The fabricated tapered fibers have greater than 85% transmission on the average and very good polarization fidelity. The tapered fibers have been used for efficiently exciting and detecting WGMs of $Q\sim10^7$ in silica microspheres and of $Q$ up to $7\times10^7$ in microdrops of silicone oils.