Au nanorod-coupled microfiber optical humidity sensors

We demonstrate a high-sensitivity relative humidity (RH) sensor taking advantage of single-band narrow plasmon resonance of a single Au nanorod coupled to a whispering gallery cavity mode of a polyacrylamide microfiber. From the resonance peak shift, the sensor could achieve a sensitivity up to 0.51 nm/% RH with a cavity size of about 2 mu m. By coupling multiple Au nanorods along the microfiber axis, we demonstrate a position dependent microfiber optical humidity sensor with a 1 5-mm spatial resolution, which can be potentially reduced to micrometer level, paving a way toward high-resolution distributed microfiber optical sensors. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement