- 标题
- 摘要
- 关键词
- 实验方案
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Analysis of core eccentricity on the long period grating in eccentric core fiber
摘要： theoretically. The variation of the transmission spectrum is calculated under different eccentricities on the basis of the coupled-mode theory. The calculation results indicate that the order of the cladding mode that has the largest coupling efficient with the core mode changes with the change of the core eccentricity, which results in the shift of the resonant peaks. In addition, the effective refractive index of the fundamental mode increases with the core eccentricity within a certain range. The model we have proposed can provide a valid reference for designing ECF and writing LPFG in the ECF.
关键词： Coupled-mode theory,Eccentric core fiber,Long period grating
更新于2025-09-16 10:30:52
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[IEEE 2018 International Applied Computational Electromagnetics Society Symposium - China (ACES) - Beijing, China (2018.7.29-2018.8.1)] 2018 International Applied Computational Electromagnetics Society Symposium - China (ACES) - Terahertz metasurface for flexible band-pass filter
摘要： We present a coupled mode theory (CMT) to design terahertz flexible band-pass filter. Based on this theory, we designed three band-pass filters with passband 0.74-0.89, 0.72-0.91 and 0.72-0.95THz. The transmission in the passband is all above 80%. This method can be easily extended to other frequency regime.
关键词： band-pass filter,metasurface,terahertz,coupled-mode theory
更新于2025-09-16 10:30:52
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Parity-Time Symmetry in Laterally Coupled Bragg Waveguides
摘要： We investigate theoretically, in the frame of Coupled-Mode Theory (CMT), a system made of two laterally coupled, index-coupled Bragg waveguides, the modal gain of the amplifying one compensating exactly the modal losses of the other. Reverting to the supermode eigenbasis of the underlying “naked” (non-periodic) Parity-Time Symmetric (PTS) directional coupler, we derive analytically the scattering parameters of the whole structure. We also consider a system made of two purely gain-coupled Bragg waveguides, either in phase or in anti-phase. In each case, we comment upon the gain requirement for achieving a laser oscillation.
关键词： Parity-Time Symmetry (PTS),Coupled-Mode Theory (CMT),Distributed Feedback (DFB),Distributed Bragg Reflector (DBR)
更新于2025-09-12 10:27:22
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A 2?×?1 all-optical multiplexer using Kerr nonlinear nano-plasmonic switch
摘要： In this paper, a novel surface plasmon polariton based 2 × 1 multiplexer, which is based on an adder module and an all-optical controllable nano-plasmonic switching module is presented. It is shown that by applying a pump light, the transmissions of the input signals into the output waveguide can be controlled. The operation of the proposed device is investigated through the use of coupled-mode theory and finite-difference time-domain method. In the proposed adder module, the transmissions of the input signals at the working wavelengths are about 0.7. Based on the simulation results, by applying a pump light intensity of 150 KW/cm2 the transmissions of input signals alter with the extinction ratio of 22.04 dB, which shows a significant switching effect. For a pump light intensity of 150 KW/cm2 the switching times of input signals are measured about 560 fs. It is expected that the proposed 2 × 1 multiplexer can be used in all-optical signal processing, nano-plasmonic circuits, communication, etc.
关键词： Coupled-mode theory (CMT),Kerr nonlinearity,Racetrack-shaped ring resonator,Finite-difference time-domain (FDTD),Nano-plasmonic switch,All-optical multiplexer
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - A Simple Approach, Based on Coupled Mode Theory, to Study PhC Lasers
摘要： PhC lasers have attracted large interest as efficient light-sources in on-chip and chip-to-chip interconnections. They allow for scaling the active volume while maintaining the high cavity Q-factor, thus exhibiting low threshold current and operating energy [1,2]. Methods for studying these laser cavities are typically based on FDTD simulations, which are often time-consuming and do not allow to catch the most relevant physics of these devices. We propose here an alternative and simple approach to analyze active PhC waveguides and lasers. Our approach is based on coupled-mode theory, which has proved to be an effective tool to study lasers with periodic gain and/or refractive index perturbation, as standard DFB lasers. We apply this method to PhC line-defect waveguides and lasers with a small complex refractive index perturbation (to account for gain and refractive index variation) with respect to a reference, unpumped PhC line-defect waveguide [3]. The optical electric field of the TE-like guided mode is expanded as sum of the forward- and backward-propagating Bloch modes of the passive waveguide; the equation governing the evolution (cid:549)+,-(z) of the Bloch modes along the perturbed waveguide are: (cid:2034)(cid:1878)(cid:2032)+ = (cid:1861)(cid:2018)11,(cid:1869)=0((cid:2033)) (cid:2032)++ (cid:1861)(cid:2018)12,(cid:1869)=1((cid:2033)) (cid:1857)+2(cid:1861)(cid:2012)((cid:2033))(cid:1878)(cid:2032)(cid:3398) (cid:3398)(cid:2034)(cid:1878)(cid:2032)(cid:3398) = (cid:1861)(cid:2018)21,(cid:1869)=(cid:3398)1((cid:2033))(cid:1857)(cid:3398)2(cid:1861)(cid:2012)((cid:2033))(cid:1878)(cid:2032)++ (cid:1861)(cid:2018)11,(cid:1869)=0((cid:2033)) (cid:2032)(cid:3398) (1) where k11,q=0 and k12,q=1;21q=-1 are the self- and cross- coupling coefficients calculated as in [3]. An example is in Fig. 1 for refractive index perturbation ((cid:507)(cid:81)s(cid:143)(cid:19)) and positive gain g0. This figure proves that, differently from standard DFB lasers, the cross-coupling coefficient is always comparable to the self-coupling coefficient. This is because of the strong z-component of the TE-like electric field of the fundamental guided mode. The coupling coefficients are gain-dependent since gain, not present in the holes, is also a periodic perturbation; k11,q=0 and k12,q=1;21q=-1 are also frequency-dependent because of the slow-light effect and they significantly increase as frequency approaches the band edge. Therefore, Bloch modes at shorter frequency and/or with higher gain of the active waveguide will go through a stronger distributed feedback effect with respect to longer frequency Bloch modes and/or lower active waveguide gain. Based on this model, we have simulated a laser cavity with the geometry as in Fig. 2a, consisting of a pumped active section, a rear passive mirror with material refractive index smaller than the active section and a front passive buffer with material refractive index equal (Type A) , slightly larger (Type B) or smaller (Type C) than the active region. Based on the model of eq. (1), we have calculated the rear and buffer mirror reflection coefficients (S11) (Fig.2a). Threshold condition, found searching for frequency and gain g0 satisfying rL(cid:11)(cid:550)(cid:12)(cid:194) rR(cid:11)(cid:550)(cid:15)(cid:74)0)=1, is in Fig.2b as function of the front buffer number of cells. The different trends of the threshold gain with the number of buffer cells can be explained by the interplay, in determining rR(cid:11)(cid:550)(cid:15)(cid:74)0), between the distributed feedback in both the active region and the front buffer. In Type C, the latter is dominant (nearly doubled with respect to the active region feedback); therefore, threshold gain diminishes as the front buffer reflection increases (similar to a FP laser with increase of the front mirror reflection). On the contrary, in Type A and Type B the role of distributed feedback in the active region plays a major role and the threshold depends on the interference between the active region distributed feedback and the front buffer back reflection. For this reason, Type B shows an optimum number of cells minimizing threshold gain.
关键词： coupled-mode theory,FDTD simulations,PhC lasers,distributed feedback,Bloch modes
更新于2025-09-12 10:27:22
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Resonance || Fano Resonance in High-Permittivity Objects
摘要： In this chapter, Fano resonances in simple structures with high permittivity such as spheres or core-shell particles are analyzed by Mie theory. The Mie scattering coefficients can be decomposed into slow varying backgrounds and narrow resonances, which cause the Fano resonances in scattered field. For structures of arbitrary shapes, temporal coupled-mode theory is applied to explain the Fano resonances found in the scattering cross section. At last, we analyze the periodic structures by using band diagram, and it shows that the Fano resonances can be viewed as the superposition of the Bloch wave and the Mie scattering wave.
关键词： sensor,temporal coupled-mode theory,Mie theory,Fano resonance,photonic crystal
更新于2025-09-09 09:28:46
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Magneto-optical properties of asymmetric one-dimensional magneto-photonic crystals
摘要： We analytically investigate the magneto-optical properties of asymmetric one-dimensional magneto-photonic crystals (MPCs) by using our previously presented coupled mode description. We show that an MPC with one magnetic defect, placed asymmetrically, provides the same number of degrees of freedom as a symmetric double-defect MPC. Consequently, an asymmetric single-defect MPC allows arbitrary transmittance and Faraday rotation at the central frequency, just as a symmetric double-defect MPC, and hence a desired performance can be obtained by the more compact single-defect structure. However, the possible ranges of performance are more restricted than the possible ranges of a double-defect MPC. We present the synthesis relations to design the single-defect MPC. In a similar manner, we show that an asymmetric double-defect MPC provides more degrees of freedom than either a symmetric double-defect or an asymmetric single-defect MPC. The excessive degree allows us to design a more compact MPC than the symmetric double-defect MPCs for a desirable central frequency performance, in the wide possible range that double-defect structures provide.
关键词： Faraday rotation,Synthesis,Magneto-photonic crystals,Coupled mode theory
更新于2025-09-09 09:28:46
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Optical spatial differentiator for a synthetic three-dimensional optical field
摘要： We propose a grating-based spatial differentiator to process a synthetic three-dimensional optical field, where several conventional two-dimensional optical images are stacked at multiple wavelengths. The device simultaneously enables both spatial differentiation and demultiplexing during light diffraction. We show the spatial differentiation resulting from coupling and interference of spatial modes and derive the theoretical condition for spatial differentiation based on spatial coupled-mode theory. We numerically investigate field transformation during diffraction and demonstrate spatial differentiation with image processing of edge detection for a synthetic three-dimensional optical field, where four images are stored at different wavelengths.
关键词： demultiplexing,coupled-mode theory,grating-based,spatial differentiation,optical spatial differentiator,synthetic three-dimensional optical field
更新于2025-09-09 09:28:46