Localized surface plasmonic resonance study of silver nanocubes for photonic crystal fiber sensor

Photonic crystal fiber (PCF) refractive index sensor was analyzed utilizing silver nanocubes, which were embedded in the large air hole of the PCF. According to quasi-state theoretical functions, we have simulated the dependence of extinction ratio for the silver nanocube, one is on the refractive index of the surrounding medium, another is on the operational wavelength at a given length of the nanocube. It is founded that the resonance wavelength (i.e. optimal wavelength) evidently exists for a given refractive index n and linearly increases when the refractive index of the medium surrounding the silver nanocube linearly increases. The sensitivity of the sensor versus the refractive index of the medium surrounding the nanocube and via the edge length of the nanocube is discussed in detail. The sensitivity R is 103 larger and linearly increases when the medium refractive index surrounding the nanocube increases for a given edge length L (e.g. L=30 nm). The sensitivity R and the spectrum width exponentially decrease when the edge length L of the nanocube increases, for a given refractive index of the medium, n (e.g. n=2.0). Based on the results, the silver nanocube with 30 nm edge length at the refractive index 2.0 is chosen as our objective. The sensitivity of the sensor is 3774.2 nm/RIU. The confinement of light in the PCF also is shown at resonance wavelength 551 nm. This study provides a basis for investigating the PCF refractive index sensor based on the LSPR of the metal nanoparticles.

► For given L, the R is 103 larger and increases linearly with medium refractive index. ► For given n, the R and spectrum width exponentially decrease with L increasing. ► Wavelength of the resonance peak increases with the increase of the index number. ► Sensitivity of the sensor is 3774.2 nm/RIU.