The optical response of the silver nano-sphere with two spindle-shaped cavities in a sub-wavelength quartz fiber

We propose and experimentally study a fiber-optic filter in hourglass configurations, where a silver nano-sphere is trapped in the quartz fiber and two air spindle-shaped cavities are formed on both sides of it. By using two fiber tapers as the input source and the probe, we measured the transmission and reflection spectra of the configuration. The results show that it is transparent for resonance wavelength and absorptive for other wavelengths, respectively. The 1544 nm and 1557 nm resonance peaks were observed in the single and double hourglass configuration. Such a device can be useful in optical filters and biochemical sensors.