SERS-active Photonic Crystal Fiber

The waveguide characteristics and the accessibility of air or liquid inside the axially arrayed cladding air channels along the fiber length make photonic crystal fiber (PCF) a potentially powerful sensing platform. PCF has been explored for sensing measurements utilizing laser absorption, fluorescence and Raman scattering (including surface-enhanced Raman scattering (SERS)). SERS active PCF can be fabricated by immobilization of nanoparticles in the cladding air channels of the PCF. We first time reported that the measured SERS intensity using hyperspectral Raman imaging spectroscopy system arises exclusively from the forward-propagating core mode as a result of evanescent field interaction with R6G in the inner most ring of the cladding air channels.

To engineer 2-dimensional (2D) microstructure designs of PCF for optimal harvesting of optical properties is important for both fundamental and applied research standpoints. The accessibility to the axially aligned cladding air channels by a gas or liquid medium makes index-guiding, solid-core PCFs, a particularly attractive platform for evanescent-field sensing. Both theoretical and experimental studies have consistently indicated that the PCF microstructure plays a critical role in the evanescent-field based sensing and measurements. SERS-active PCFs can be used as a robust optofluidic platform for fundamental studies of chemical, biological, and catalytic interactions with label-free, sensitive, and molecular finger-printing capabilities, chemical sensing and detection, in-situ process monitoring, and other yet-to-be-foreseen applications.