| Phoxonic crystals(PXCs)are periodic structure that can generate both photon and phonon bandgaps simultaneously.Due to its excellent ability to simultaneously control both electromagnetic and elastic waves,it has attracted much attention in recent years.The common realization method focuses on the double band gap effect of photon and phonon.Compared with the band gap effect,the application of the self-collimation effect of the anomalous dispersion of the passband requires neither bandgap nor the introduction of defects,and it can still be produced even in the case of a low refractive index ratio and a low filling ratio.Further research on the application of enhanced acousto-optic coupling in this type of self-collimation waveguide has shown great advantages.On the other hand,Exploring the topological transport of waves in phoxonic crystals is of great significance to promote the practical application of optomechanical topological devices.In this paper,based on finite element method,several problem such as the control of the passband of the phoxonic crystals,the self-collimation effect,the acousto-optic(AO)coupling effect and the topological effect of the boundary state are discussed.The main research work includes:Firstly,we studied the simultaneous self-collimation transmission of electromagnetic waves and elastic waves and the way of controlling the beam path in the two-dimensional defect-free air hole phoxonic crystals.The current self-collimation beam splitting method is single.Different acoustic and optical simultaneous self-collimation beam splitters can be constructed by designing reasonable phoxonic crystals structures.The self-collimating beam has a more flexible beam splitting way,which can meet the application of different situations.Secondly,we verify the acousto-optic coupling effect of the phoxonic self-collimation waveguide in two-dimensional defect-free air hole phoxonic crystals.The results show that the strength of the AO interaction can be comparable to that based on defect-based phoxonic waveguide using the bandgap effect.Furthermore,compared with the bandgap waveguides(BGWs),this new platform realizing enhanced AO interaction has a relatively simple technological process in actual fabrication because no defects are needed and there is no limitation for some nonlinear materials with low refractive index.Thirdly,we study the valley topological transport characteristics of two-dimensional air-hole phoxonic crystals.In the absence of circulating fluid flow or external magnetic flux,the topological states of light and sound are displayed simultaneously.The topological valley spin state of light and sound is achieved by simply rotating the angle of the scatterer to break the mirror symmetry.It further shows that the boundary state appears in the band gap,and the electromagnetic wave and elastic wave can simultaneously carry out topological valley transport along the interface.In addition,these edge states are robust to defects such as disturbances,and exhibit low-loss backscatter suppression characteristics.The phoxonic crystals studied in this paper can simultaneous manipulate sound and light by controlling the dispersion surface of light and sound,and realize the function of simultaneously controlling electromagnetic waves and elastic waves.The coupling characteristics between electromagnetic wave and elastic wave are obtained,which provides a new platform for acousto-optic integrated regulation and the enhancement of acousto-optic coupling.In addition,the phoxonic crystals studied in this paper can obtain the topological valley spin states of light and sound simultaneously by simply rotating the scatterer,thus realizing the topological valley transport of electromagnetic and elastic waves simultaneously.This research provides an application for the sound and light topological model and is of great value in the design of topological devices... |
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