Broadband, Lensless and Optomechanically Stabilised Coupling into Microfluidic Hollow-Core Photonic Crystal Fiber Using Glass Nanospike

TL;DR

This paper introduces a novel, self-aligning, and stabilizing method for broadband light coupling into liquid-filled hollow-core photonic fibers using a glass nanospike with optomechanical trapping, enhancing robustness and reducing reflections.

Contribution

It presents a new technique employing a nanospike with optomechanical trapping for stable, broadband, and efficient coupling into liquid-core fibers, improving upon traditional methods.

Findings

Achieved stable nanospike alignment using ~300 mW trapping laser at 1064 nm.

Successfully launched broadband supercontinuum light (575-1064 nm) into HC-PCF.

System remains robust against liquid flow and minimizes back-reflections.

Abstract

We report a novel technique for launching broadband laser light into liquid-filled hollow-core photonic crystal fiber (HC-PCF). It uniquely offers self-alignment and self-stabilization via optomechanical trapping of a fused silica nanospike, fabricated by thermally tapering and chemically etching a single mode fiber into a tip diameter of 350 nm. We show that a trapping laser, delivering ~300 mW at 1064 nm, can be used to optically align and stably maintain the nanospike at the core center. Once this is done, a broadband supercontinuum beam (~575 to 1064 nm) can be efficiently and close to achromatically launched in the HC-PCF. The system is robust against liquid-flow in either direction inside the HC-PCF and the Fresnel back-reflections are reduced to negligible levels compared to free-space launching or butt-coupling. The results are of potential relevance for any application where the efficient delivery of broadband light into liquid-core waveguides is desired.