Optical Circulation and Isolation Based on Indirect Photonic Transitions of Guided Resonance Modes

Shi, Yu; Han, Seung-Hoon; Fan, Shanhui

doi:10.1021/acsphotonics.7b00420

Cited by 83 publications

(78 citation statements)

References 43 publications

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“…In this section, we look at one of the highly applauded features of space-time gradient metasurfaces which is the magnetless nonreciprocal response [34,[36][37][38][39][40][41][42][43][44][45] and explore the utility of modulation-induced phase shift in obtaining a strong nonreciprocal response and isolation via spatial decomposition of frequency harmonics. The origin of nonreciprocity in space-time gradient metasurfaces is the difference in the imparted momentum by the metasurface to the forward and backward propagating waves.…”

Section: Nonreciprocal Response and Isolationmentioning

confidence: 99%

“…The origin of nonreciprocity in space-time gradient metasurfaces is the difference in the imparted momentum by the metasurface to the forward and backward propagating waves. This comes to the picture when the light is carrying a momentum along the direction of spatiotemporal modulation which is the case in oblique incidence [34,38,45]. In fact, the nonreciprocal response of the time-modulated metasurface under oblique incidence can be understood through figure 12, where by flipping the sign of incident angle, the received fields at the opposite observation angles will be of opposite frequency harmonic order.…”

Section: Nonreciprocal Response and Isolationmentioning

confidence: 99%

“…Moreover, timemodulated metasurfaces hold a great potential to extend the degree of light manipulation. It has been demonstrated that space-time photonic transitions of guided modes into leaky-modes in spatiotemporallymodulated metasurfaces can enable dynamic nonreciprocal beam-scanning [38,42,45]. Such a paradigm has a narrow operational bandwidth and is ill-suited for more advanced functionalities.…”

Section: Introductionmentioning

confidence: 99%

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Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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Modulation of metasurfaces in time gives rise to several exotic space-time scattering phenomena by breaking the reciprocity constraint and generation of higher-order frequency harmonics. We introduce a new design paradigm for time-modulated metasurfaces, enabling tunable engineering of the generated frequency harmonics and their emerging wavefronts by electrically controlling the phase delay in modulation. It is demonstrated that the light acquires a dispersionless phase shift regardless of incident angle and polarization, upon undergoing frequency conversion in a timemodulated metasurface which is linearly proportional to the modulation phase delay and the order of generated frequency harmonic. The conversion efficiency to the frequency harmonics is independent of modulation phase delay and only depends on the modulation depth and resonant characteristics of the metasurface, with the highest efficiency occurring in the vicinity of resonance, and decreasing away from the resonant regime. The modulation-induced phase shift allows for creating tunable spatially varying phase discontinuities with 2π span in the wavefronts of generated frequency harmonics for a wide range of frequencies and incident angles. Specifically, we apply this approach to a time-modulated metasurface in the Teraherz regime consisted of graphene-wrapped silicon microwires. For this purpose, we use an accurate and efficient semi-analytical framework based on multipole scattering. We demonstrate the utility of the design rule for tunable beam steering and focusing of generated frequency harmonics giving rise to several intriguing effects such as spatial decomposition of harmonics, anomalous bending with full coverage of angles and dual-polarity lensing. Furthermore, we investigate the angular and spectral performance of the time-modulated metasurface in manipulation of generated frequency harmonics to verify its constant phase response versus incident wavelength and angle. The nonreciprocal response of the metasurface in wavefront engineering is also studied by establishing nonreciprocal links with large isolations via modulationinduced phase shift. The proposed design approach enables a new class of high-efficiency tunable metasurfaces with wide angular and frequency bandwidth, wavefront engineering capabilities, nonreciprocal response and multi-functionality.

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Section: Nonreciprocal Response and Isolationmentioning

confidence: 99%

Section: Nonreciprocal Response and Isolationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

2018

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“…It is important to notice that, according to this definition, there is no frequency conversion between ports. Wave isolation realized with space-time modulated media has been demonstrated in a few papers [29,31,35,47], where the classical scattering matrix [see Eq. (20)] is not suitable to describe those systems.…”

Section: A Metasurface Isolatorsmentioning

confidence: 99%

Theory and Design of Multifunctional Space-Time Metasurfaces

et al. 2020

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Integrating multiple functionalities into a single metasurface is becoming of great interest for future intelligent communication systems. While such devices have been extensively explored for reciprocal functionalities, in this work, we integrate a wide variety of nonreciprocal applications into a single platform. The proposed structure is based on spatiotemporally modulated impedance sheets supported by a grounded dielectric substrate. We show that, by engineering the excitation of evanescent modes, nonreciprocal interactions with impinging waves can be configured at will. We demonstrate a plethora of nonreciprocal components such as wave isolators, phase shifters, and circulators, on the same metasurface. This platform allows switching between different functionalities only by modifying the pumping signals (harmonic or non-harmonic), without changing the main body of the metasurface structure. This solution opens the door for future real-time reconfigurable and environment-adaptive nonreciprocal wave controllers.

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“…Over the past few years, there has been a surge of interest in the nonreciprocal [19,20,33,[43][44][45][77][78][79] and asymmetric [80][81][82][83][84] wave transmission, reflection and absorption. Here, we investigate the realization of nonreciprocal, asymmetric and angle-asymmetric wave diffraction by STP gratings.…”

Section: Asymmetric and Nonreciprocal Response Of Diffraction Ordementioning

confidence: 99%

Generalized Space-Time-Periodic Diffraction Gratings: Theory and Applications

2019

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This paper studies the theory and applications of the diffraction of electromagnetic waves by space-time periodic (STP) diffraction gratings. We show that, in contrast with conventional spatially periodic grating, a STP diffraction grating produces spatial diffraction orders, each of which is formed by an infinite set of temporal diffraction orders. Such spatiotemporally periodic gratings are endowed with enhanced functionalities and exotic characteristics, such as asymmetric diffraction pattern, nonreciprocal and asymmetric transmission and reflection, and an enhanced diffraction efficiency. The theory of the wave diffraction by STP gratings is formulated through satisfying the conservation of both momentum and energy, and rigorous Floquet mode analysis. Furthermore, the theoretical analysis of the structure is supported by time and frequency domain FDTD numerical simulations for both transmissive and reflective STP diffraction gratings. Additionally, we provide the conditions for Bragg and Raman-Nath diffraction regimes for STP gratings. Finally, as a particular example of a practical application of the STP diffraction gratings to communication systems, we propose an original multiple access communication system featuring full-duplex operation. STP diffraction gratings are expected to find exotic practical applications in communication systems, especially for the realization of enhanced-efficiency or full-duplex beam coders, nonreciprocal beam splitters, nonreciprocal and enhanced-resolution holograms, and illusion cloaks.• It is shown that each single spatial-temporal diffraction order is diffracted at a distinct angle of

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Optical Circulation and Isolation Based on Indirect Photonic Transitions of Guided Resonance Modes

Cited by 83 publications

References 43 publications

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Electrically tunable harmonics in time-modulated metasurfaces for wavefront engineering

Theory and Design of Multifunctional Space-Time Metasurfaces

Generalized Space-Time-Periodic Diffraction Gratings: Theory and Applications

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