Photonic crystal fiber as an optofluidic platform for surface-enhanced Raman scattering

Abstract

As both a waveguide and a gas/liquid transmission cell, photonic crystal fiber (PCF) allows synergistic integration of optics and microfluidics to form an unconventional optofluidic platform with long interaction path. In this paper, we report our strategy to achieve surface-enhanced Raman scattering (SERS) PCF optofluidics by polyelectrolyte-mediated immobilization of Ag nanoparticles (NPs) inside the fiber air channels. Through forward propagating Raman measurements and hyperspectral Raman imaging, we demonstrate the realization of SERS-active PCF optofluidics with accumulative Raman signal gain along the entire fiber length using both solid-core PCF (SC PCF) and hollow-core PCF (HC PCF). By numerical simulation and Raman measurements, we show that suspended-core PCF (SP PCF) consisting of a silica core surrounded by three large air channels conjoined by a thin silica web is the most robust platform of the three SC PCF microstructures investigated for evanescent-field SERS spectroscopy.