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Radiation-loss-limited fi nesse (F) of the lowest order radial WGMs of a hollow cylindrical dielectric waveguide of index n 2 in a medium of index n 1 = n 3 = 1 plotted
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Metamaterials are artificial media structured on a size scale smaller than the wavelength of external stimuli, that may provide novel tools to significantly enhance the sensitivity and resolution of the sensors. In this paper, we derive the dispersion relation of hollow cylindrical dielectric waveguide, and compute the resonant frequencies and Q fa...
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Context 1
... corresponds to WGM resonances, each characterized by an azimuthal mode number m . From Figure 2, we can observe that the radiation-loss-limited fi nesse increases with normalized radius and mode number. Besides, for a give normalized radius and mode number, the radiation-loss-limited fi nesse increases with the refractive index contrast. These results are beneficial for designing a microring resonator. In the following section, we will simulate the microring resonator and compare its resonant frequencies with the analytical results. Then, the metamaterial sensor constituted by the microring resonator with a layer of metamaterial loaded into its inner side and coupled to a straight waveguide is studied. Simulation models of the microring sensor are illustrated in Figure 3. Figure 3(a) shows the conventional microring sensor with a dielectric core. It is denoted as Model A in the following simulation. The width of the ring and the waveguide is w = 0.3 μ m. The inner and outer radius of the ring is a = 2.2 μ m and b = 2.5 μ m. The distance from outer ring to the waveguide is g = 0.232 μ m. The refractive index of the ring and the waveguide is n = 3.2. Figure 3(b) shows another simulation scenario, of which the dielectric sample is attached to the inner side of the microring. It is denoted as Model B. Figure 3(c) is the simulation model of the proposed metamaterial sensor that is constituted by the microring with a metamaterial layer attached to the inner side. The dielectric core is colored in grey. It is denoted as Model C. In Figure 3(d), the dielectric sample is attached to the inside of the ring adhere to the metamaterial layer. It is denoted as Model D. The permittivity and permeability of the metamaterial layer is ε r = μ = − 1. In what follows, we will simulate the performance of the ...
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... order to estimate the radiation-loss-limited Q factors of WGMs [28,29], complex frequencies of the resonances ω = ω ′ + j ω ′ ′ were introduced into the dispersion equation. The real part ω ′ determines the wavelength of the resonances and the Q factor can be estimated with the expression: Q = ω ′ / 2 ω ′ ′ . This dimensionless parameter generalizes the imaginary part of the solution space. In order to generalize the real part, a normalized radius is defined as X = n 2 2 π b/ λ . To solve for the complex roots of the dispersion equation | M | = 0 , a global optimization scheme can be used to minimize the absolute value of the equation over two variables: Q and X. Figure 2 displays the radiation-loss-limited fi nesse (F = Q/m) vs. normalized radius for a variety of azimuthal mode numbers and index ratios. The family of diagonal lines represents varying refractive index contrast (n = n /n ). The family of nearly ...
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Citations
... However, the operational concept of MM absorbers depends on resonator arrays; therefore, their absorption is frequency-dependent, and they have a narrow absorption bandwidth [26]. For most applications, the absorbers with a wide bandwidth absorption are preferred. ...
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... As a key component of modern photonic integrated circuits, microring resonator (MRR) shows great performance in filtering [1,2], sensing [3][4][5][6], ultra-fast electro-optic modulation (EOM) [7][8][9][10], optical frequency comb generation [11,12] and wavelength division multiplexing [13] due to its unique characteristics such as wavelength selection, compact structure and high quality factor (Q-factor). In the past decades, various material systems of MRR structures have been investigated for opto-electric applications, including graphene [14,15], silicon (Si) [16][17][18], indium phosphide (InP) [19], polymer [20] and lithium niobate [8,10,21]. ...
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