Plasmonic Crystal Cavity on Single-Mode Optical Fiber End Facet for Label-Free Biosensing

TL;DR

This paper introduces a novel plasmonic crystal cavity on a single-mode fiber end facet that significantly enhances label-free biosensing performance, overcoming previous broad resonance limitations and achieving high sensitivity and low detection limits.

Contribution

The authors design, fabricate, and characterize a plasmonic crystal cavity on a fiber end facet, demonstrating a twentyfold improvement in figure-of-merit for biosensing compared to prior devices.

Findings

Figure-of-merit of 68 RIU^-1 achieved

Refractive index detection limit of 3.5×10^-6 RIU

Novel glue-and-strip process for gold nanostructure transfer

Abstract

All surface plasmon resonance (SPR) devices on single-mode optical fibers' (SMF) end facets, as reported up to date, are limited by severely broad and shallow resonance spectra. The consequent poor performance when they are used as refractive index sensors, together with the challenge of nanofabrication on fiber end facets, has prohibited the development of such devices for label-free biosensing. Meanwhile, the planewave coupled, multimode fiber and fiber sidewall SPR counterparts are extensively employed for label-free biosensing. In this paper, we report the design, fabrication and characterization of a plasmonic crystal cavity on a SMF end facet, which shows high performance label-free sensing capability that comes from a steep cavity resonance near the plasmonic bandedge. The experimental figure-of-merit is 68 RIU^-1, which is over twenty times improvement to previous reports. The refractive index detection limit is 3.5*10^-6 RIU at 1 s integration time. We also describe a novel glue-and-strip process to transfer gold nano structures onto fiber end facets.