A v-shaped microstructured optical fiber (MOF)-based surface plasmon resonance (SPR) sensor is proposed for simultaneous measurement of temperature and refractive index (RI). Such a v-shaped structure could be coated with the gold layer conveniently, simplifying the sensor fabrication. We theoretically investigate the coupling property between the core mode and the plasmon mode, the polarized characteristics of the core modes, the behavior features of the resonance peaks and the sensing performance of the sensor at different temperatures and RIs. The simulation results demonstrate that the v-shaped structure can support two polarized resonance peaks (x- and y-polarized peaks) that have different response characteristics for the changes of temperature and RI, the temperature coefficients of x- and y-polarized peaks are 11.8 and 6.2 pm / ° C, the RI coefficients of x- and y-polarized peaks are 1408 and 1505 nm / RIU, respectively.
We demonstrate a temperature sensor based on surface plasmon resonances supported by a six-hole microstructured optical fiber (MOF). The air holes of the MOF are coated with a silver layer and filled with a large thermo-optic coefficient liquid mixture (ethanol and chloroform). The use of all six fiber holes and their relatively large size should facilitate the coating of the silver and the filling of the liquid mixture. Temperature variations will induce changes of coupling efficiencies between the core-guided mode and the plasmonic mode, thus leading to different loss spectra that will be recorded. The refractive index of the liquid mixture is close to that of the MOF material, which will enhance the coupling efficiency and the sensitivity. Our numerical results indicate that temperature sensitivity as high as 5.6 nm/K can be achieved and that the most sensitive range of the sensor can be tuned by changing the volume ratios of ethanol and chloroform.
A subwavelength core microstructured optical fiber (MOF) temperature sensor based on infiltration with chloroform is
proposed. Fiber core is surrounded by three large holes which can facilitate the infiltration of the chloroform. The
refractive index of chloroform is sensitive to the temperature of the environment. Mode loss of the guided mode caused
by index change of chloroform is obtained by solving Maxwell’s equation with finite element method (FEM), and is
used as a criterion for sensitivity estimation. The relationship between the sensitivity of temperature sensor and the core
diameter of MOF is investigated. Our simulation results show that the subwavelength core MOF is very promising for
developing a linear response to temperature sensor of significantly reduced core size.
Two kinds of optical modulation processes are designed based on nested split-ring resonators in the terahertz regime. By photo-conductivity induced mode switching effect, the resonant structure and resonant mode will be changed, and the two contrary tunable resonant properties are obtained. Without illumination, the two designs both have three resonant peaks. As the intensity of illumination increases, for the first design, the first and the third resonant peaks disappear and a broadband resonant peak at the second resonant frequency is formed eventually; however, the second design realizes an exactly opposite modulation process. Moreover, in order to identify the modulation mechanism, we discuss and analyze the distributions of the electric fields and surface currents in detail. Our designs can be implemented in tunable terahertz functional devices and provide important reference value for the design of terahertz metamaterial.
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