Versatile Optical Fiber Nanoprobes: From Plasmonic Biosensors to Polarization-Sensitive Devices

We have recently proposed a valuable fabrication route for the integration and patterning of functional materials at nanoscale onto optical fibers, posing the basis for a new technological vision named Lab-on-Fiber. The validation of the proposed process has been carried out through the realization, directly onto the fiber tip, of 2D metallo-dielectric nanocrystals supporting localized surface plasmon resonances. In this work, we demonstrate the effectiveness of the proposed methodology to realize optical nanoprobes for label-free chemical and biological sensing as well as basic components for novel polarization sensitive photonic devices. Specifically, we first demonstrate how it is possible to tailor the field distribution of the plasmonic mode enabling the control on the refractive index sensitivity. With a view toward surface sensitivity, we experimentally observe that the proposed device is able to detect the formation of nanosized overlays over very limited active areas. Moreover, we demonstrate how to control the number and the field distribution of the excited plasmonic resonance posing new basis for the resonance engineering. Finally, we show how to obtain polarization sensitive devices with the same technological platform, by breaking the circular crystal symmetry at both unit cell or entire lattice level.