Optical fiber surface-enhanced Raman scattering (SERS) sensors offer a potential solution to monitoring low chemical
concentrations in-situ or in remote sensing scenarios. We demonstrate the use of nanoimprint lithography to fabricate
SERS-compatible nanoarrays on the end faces of standard silica optical fibers. The antireflective nanostructure found on
cicada wings was used as a convenient template for the nanoarray, as high sensitivity SERS substrates have previously
been demonstrated on these surfaces. Coating the high fidelity replicas with silver creates a dense array of regular
nanoscale plasmonic resonators. A monolayer of thiophenol was used as a low concentration analyte, from which strong
Raman spectra were collected using both direct endface illumination and through-fiber interrogation. This unique
combination of nanoscale replication with optical fibers demonstrates a high-resolution, low-cost approach to fabricating
high-performance optical fiber chemical sensors.
The spin-on photoresist SU8 from MicroChem has a relatively high refractive index (n=1.57 at 1550nm) compared with other polymers. It is stable and has high optical transmission at optical communication wavelengths. In this paper we study rib waveguides fabricated using SU8 as the core layer and thermoset polymers UV15 (n=1.50 at 1550nm) from Master Bond and NOA61 (n=1.54 at 1550nm) from Gentec as the cladding layers. The rib height is varied from 0.3 to 1.7μm high. This is part of the SU8 layer sandwiched between the cladding layers. The waveguides are tested to determine the effects of varying this geometry for single mode optical transmission. The lengths of the waveguides were 1.5 cm to 5 cm.