Gold-coated optical fiber supermode interferometer for insulin bio-sensing

In this work, we present a supermode interferometer for biosensing application. The interferometer was fabricated with a segment of a seven-core fiber fusion-spliced to a standard single-mode fiber. We have found that when a thin gold layer was deposited on the multicore fiber (MCF) end facet, the response of the interferometer to refractive index (RI) changes was polarization dependent. The highest sensitivity to RI was achieved for a similar to 10 nm-thick gold coated sample when P-polarized light was used. The gold-coated sample was later biofunctionalized and then used for insulin detection. The sensor was able to detect insulin with a concentration level of 10(-8) g/ml.