Phonon polariton resonances in the mid-infrared spectral range demonstrate properties superior to noble metal-based plasmonics,owing to smaller dissipative loss and better field confinement.However,a conventional way ...Phonon polariton resonances in the mid-infrared spectral range demonstrate properties superior to noble metal-based plasmonics,owing to smaller dissipative loss and better field confinement.However,a conventional way to excite the localized phonon resonance involves ion etching,which reduces the attainable quality factors(Q-factors)of the resonators.We show that by introducing a deep subwavelength layer of dielectric gratings on a phononic substrate,localized dipolar resonance and higher order modes with high Q-factors 96 and 195,respectively,can be excited.We further demonstrate,via experiments and simulations,that the resonant wavelength and field confinement can be controlled by coupling the localized hybrid mode with propagating surface phonon-polaritons.We also observed for the first time the coupling between a localized dipolar mode and a propagating higher-order surface phonon-polariton mode.The results will be useful in designing on-chip,low-loss,and highly integrated phononic devices in the infrared spectral domain.展开更多
We demonstrate terahertz(THz) frequency laser emission around 3.2 THz from localized modes in one-dimensional disordered grating systems. The disordered structures are patterned on top of the double-metal waveguide of...We demonstrate terahertz(THz) frequency laser emission around 3.2 THz from localized modes in one-dimensional disordered grating systems. The disordered structures are patterned on top of the double-metal waveguide of a THz quantum cascade laser. Multiple emission peaks are observed within a frequency range corresponding to the bandgap of a periodic counterpart with no disorder, indicating the presence of mode localization aided by Bragg scattering. Simulations and experimental measurements provide strong evidence for the spatial localization of the THz laser modes.展开更多
With the advent and rapid development of the transformation optics and metamaterials,invisibility cloaks have captivated much attention in recent years.While most cloaking schemes suffer from limited bandwidth,the car...With the advent and rapid development of the transformation optics and metamaterials,invisibility cloaks have captivated much attention in recent years.While most cloaking schemes suffer from limited bandwidth,the carpet cloak,which can hide an object on a reflecting plane,can operate over a broadband frequency range.However,the carpet cloaks experimentally realized thus far still have several limitations.For example,the quasi-conformal mapping carpet cloak leads to a lateral shift of the reflected light ray,while the birefringent carpet cloak only works for a specific polarization.In this work,we propose a conformal transformation scheme to tackle these two problems simultaneously.As an example,we design a mid-infrared carpet cloak in a silicon platform and demonstrate its polarization-insensitive property as well as the minimized lateral shift over a broad frequency band from 24 to 28.3 THz.展开更多
基金This work was supported by funding from the Ministry of Education,Singapore(Grant Nos.MOE2016-T2-2-159,MOE2016-T2-1-128,MOE2015-T2-2-007,and MOE Tier 1 RG164/15)the National Research Foundation,Competitive Research Program(No.NRF-CRP18-2017-02)+1 种基金NSFC(No.61704082)A.D.acknowledges funding support from the Singapore Ministry of Education Academic Research Funds Tier 3 under Grant No.MOE2016-T3-1-006(S).
文摘Phonon polariton resonances in the mid-infrared spectral range demonstrate properties superior to noble metal-based plasmonics,owing to smaller dissipative loss and better field confinement.However,a conventional way to excite the localized phonon resonance involves ion etching,which reduces the attainable quality factors(Q-factors)of the resonators.We show that by introducing a deep subwavelength layer of dielectric gratings on a phononic substrate,localized dipolar resonance and higher order modes with high Q-factors 96 and 195,respectively,can be excited.We further demonstrate,via experiments and simulations,that the resonant wavelength and field confinement can be controlled by coupling the localized hybrid mode with propagating surface phonon-polaritons.We also observed for the first time the coupling between a localized dipolar mode and a propagating higher-order surface phonon-polariton mode.The results will be useful in designing on-chip,low-loss,and highly integrated phononic devices in the infrared spectral domain.
基金Ministry of Education-Singapore(MOE)(MOE 2016-T2-1-128)Agency for Science,Technology and Research(A*STAR)(1426500050)+2 种基金National Research Foundation Singapore(NRF)(NRF-CRP18-2017-02)Engineering and Physical Sciences Research Council(EPSRC)(EP/P021859/1)Royal Society and Wolfson Foundation
文摘We demonstrate terahertz(THz) frequency laser emission around 3.2 THz from localized modes in one-dimensional disordered grating systems. The disordered structures are patterned on top of the double-metal waveguide of a THz quantum cascade laser. Multiple emission peaks are observed within a frequency range corresponding to the bandgap of a periodic counterpart with no disorder, indicating the presence of mode localization aided by Bragg scattering. Simulations and experimental measurements provide strong evidence for the spatial localization of the THz laser modes.
基金Ministry of Education-Singapore(MOE 2018-T2-2-189(S),MOE2018-T2-1-176)National Research Foundation Singapore(NRF-CRP18-2017-02,NRFCRP22-2019-0006)+1 种基金Agency for Science,Technology and Research(A18A7b0058,A20E5c0095)National Natural Science Foundation of China(61871127).
文摘With the advent and rapid development of the transformation optics and metamaterials,invisibility cloaks have captivated much attention in recent years.While most cloaking schemes suffer from limited bandwidth,the carpet cloak,which can hide an object on a reflecting plane,can operate over a broadband frequency range.However,the carpet cloaks experimentally realized thus far still have several limitations.For example,the quasi-conformal mapping carpet cloak leads to a lateral shift of the reflected light ray,while the birefringent carpet cloak only works for a specific polarization.In this work,we propose a conformal transformation scheme to tackle these two problems simultaneously.As an example,we design a mid-infrared carpet cloak in a silicon platform and demonstrate its polarization-insensitive property as well as the minimized lateral shift over a broad frequency band from 24 to 28.3 THz.
