Unidirectional reflectionless phenomenon in periodic ternary layered material

Yang, Erchan; Lü, Yonghua; Wang, Yong; Dai, Yanmeng; Wang, Pei

doi:10.1364/oe.24.014311

Cited by 41 publications

(24 citation statements)

References 19 publications

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“…A particularly interesting case of unidirectional reflectionless transmission is unidirectional invisibility, for which the transmitted wave is identical to that without the local structure [5]. Unidirectional reflectionless transmission has been studied on various PT -symmetric optical structures, including one-dimensional (1D) structures [5,6], planar layered structures [8][9][10][11][12], planar inhomoge- * Corresponding author: ljyuan@ctbu.edu.cn neous structure [13], two-dimensional (2D) closed waveguides [14], and 2D coupled waveguide resonator systems [15]. Experimental demonstrations have been reported for PT -symmetric photonic lattices [16] and microscale SOI waveguides [17].…”

Section: Introductionmentioning

confidence: 99%

Unidirectional reflectionless transmission for two-dimensional PT -symmetric periodic structures

Yuan

2019

Phys. Rev. A

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Unidirectional reflectionless propagation (or transmission) is an interesting wave phenomenon observed in many PT -symmetric optical structures. Theoretical studies on unidirectional reflectionless transmission often use simple coupled-mode models. The coupled mode theory can reveal the most important physical mechanism for this wave phenomenon, but it is only an approximate theory, and it does not provide accurate quantitative predictions with respect to geometric and material parameters of the structure. In this paper, we rigorously study unidirectional reflectionless transmission for two-dimensional (2D) PT -symmetric periodic structures sandwiched between two homogeneous media. Using a scattering matrix formalism and a perturbation method, we show that real zeroreflection frequencies are robust under PT -symmetric perturbations, and unidirectional reflectionless transmission is guaranteed to occur if the perturbation (of the dielectric function) satisfies a simple condition. Numerical examples are presented to validate the analytical results, and to demonstrate unidirectional invisibility by tuning the amplitude of balanced gain and loss. arXiv:1909.01517v1 [physics.optics]

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Section: Introductionmentioning

confidence: 99%

Unidirectional reflectionless transmission for two-dimensional PT -symmetric periodic structures

Yuan

2019

Phys. Rev. A

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“…This is especially true for nonperiodic non-PT-symmetric systems, which are relatively easy to fabricate and more compact. Although Yang et al demonstrated broadband unidirectional reflectionless light transport at an EP in a periodic ternary-layered structure consisting of lossy and lossless dielectrics [126], large-sized periodic structures are not easy to implement in densely integrated optical chips.…”

Section: ) Smentioning

confidence: 99%

Unidirectional reflectionless light propagation at exceptional points

et al. 2017

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Abstract:In this paper, we provide a comprehensive review of unidirectional reflectionless light propagation in photonic devices at exceptional points (EPs). EPs, which are branch point singularities of the spectrum, associated with the coalescence of both eigenvalues and corresponding eigenstates, lead to interesting phenomena, such as level repulsion and crossing, bifurcation, chaos, and phase transitions in open quantum systems described by non-Hermitian Hamiltonians. Recently, it was shown that judiciously designed photonic synthetic matters could mimic the complex non-Hermitian Hamiltonians in quantum mechanics and realize unidirectional reflection at optical EPs. Unidirectional reflectionlessness is of great interest for optical invisibility. Achieving unidirectional reflectionless light propagation could also be potentially important for developing optical devices, such as optical network analyzers. Here, we discuss unidirectional reflectionlessness at EPs in both parity-time (PT)-symmetric and non-PT-symmetric optical systems. We also provide an outlook on possible future directions in this field.

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“…In such structures the reflection is zero when measured from one end of the structure at optical exceptional points, and nonzero when measured from the other end. Unidirectional light reflectionlessness can also be attained in non-PT-symmetric structures with unbalanced gain and loss [18][19][20][21][22][23][24][25][26][27][28][29][30]. This is due to the fact that exceptional points exist in a larger family of non-Hermitian Hamiltonians [18].…”

Section: Introductionmentioning

confidence: 99%

Using phase-change materials to switch the direction of reflectionless light propagation in non-PT-symmetric structures

Veronis

Huang

Shen

et al. 2018

Active Photonic Platforms X

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Using phase-change materials to switch the direction of reflectionless light propagation in non-PT-symmetric structures," Proc. SPIE 10721, Active ABSTRACTWe introduce a non-parity-time-symmetric three-layer structure, consisting of a gain medium layer sandwiched between two phase-change medium layers for switching of the direction of reflectionless light propagation. We show that for this structure unidirectional reflectionlessness in the forward direction can be switched to unidirectional reflectionlessness in the backward direction at the optical communication wavelength by switching the phase-change material Ge 2 Sb 2 Te 5 (GST) from its amorphous to its crystalline phase. We also show that it is the existence of exceptional points for this structure with GST in both its amorphous and crystalline phases which leads to unidirectional reflectionless propagation in the forward direction for GST in its amorphous phase, and in the backward direction for GST in its crystalline phase. Our results could be potentially important for developing a new generation of compact active free-space optical devices. We also show that phase-change materials can be used to switch photonic nanostructures between cloaking and superscattering regimes at mid-infrared wavelengths. More specifically, we investigate the scattering properties of subwavelength three-layer cylindrical structures in which the material in the outer shell is the phase-change material GST. We first show that, when GST is switched between its amorphous and crystalline phases, properly designed electrically small structures can switch between resonant scattering and cloaking invisibility regimes. The contrast ratio between the scattering cross sections of the cloaking invisibility and resonant scattering regimes reaches almost unity. We then also show that larger, moderately small cylindrical structures can be designed to switch between superscattering and cloaking invisibility regimes, when GST is switched between its crystalline and amorphous phases. The contrast ratio between the scattering cross sections of cloaking invisibility and superscattering regimes can be as high as ~ 93%. Our results could be potentially important for developing a new generation of compact reconfigurable optical devices.

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Unidirectional reflectionless phenomenon in periodic ternary layered material

Cited by 41 publications

References 19 publications

Unidirectional reflectionless transmission for two-dimensional PT -symmetric periodic structures

Unidirectional reflectionless transmission for two-dimensional PT -symmetric periodic structures

Unidirectional reflectionless light propagation at exceptional points

Using phase-change materials to switch the direction of reflectionless light propagation in non-PT-symmetric structures

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