Rigorous space-time coupled-wave analysis for patterned surfaces with temporal permittivity modulation [Invited]

Inampudi, Sandeep; Salary, Mohammad Mahdi; Jafar‐Zanjani, Samad; Mosallaei, Hossein

doi:10.1364/ome.9.000162

Cited by 41 publications

(32 citation statements)

References 59 publications

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“…This approach yields accurate results in the adiabatic regime of modulation ( f m ≪ f 0 ) which is the case here and in practical electro‐optical platforms. The validity of this approach is verified by comparing the results against the numerically exact rigorous space‐time wave analysis (RSTWA) method capable of accurate characterization of scattering from periodic time‐modulated grating structures with drastic difference in the timescale of modulation and optical frequencies in Section S5 (Supporting Information). The adiabatic approach not only provides an intuitive insight into harmonic generation mechanism of time‐modulated metasurfaces through spatiotemporal phase of transmitted/reflected fields but also leads to a significant reduction in the waveform optimization time.…”

Section: Time‐modulated Metasurfacementioning

confidence: 99%

“…Dynamic modulation of a metasurface provides the required momentum for the transition of fundamental frequency to higher‐order frequency harmonics defined as f n = f 0 + nf m with the integer

n \in ℤ

denoting the order of generated frequency harmonics . As such, unlike static and quasi‐static metasurfaces which can only change the spatial features of scattered light, dynamically modulated metasurfaces provide control over the spectral content of the scattered light as well.…”

Section: Time‐modulated Metasurfacementioning

confidence: 99%

“…As the most prominent example, we consider implementation of a frequency diverse transmitarray. The concept of frequency diverse arrays was proposed for the first time in the RF array antennas and it has been recently extended to the passive and active optical metasurfaces . Unlike the conventional phased transmitarrays which use a progressive phase delay to transmit the light toward a specific direction by imparting a spatial phase gradient to the wavefront, a frequency diverse transmitarray implements a progressive frequency shift between the elements to impart a “spatiotemporal” phase gradient to the wavefront of light.…”

Section: Applicationsmentioning

confidence: 99%

“…A high‐speed continuous tuning mechanism for all‐dielectric metasurfaces not only allows for real‐time control over the optical response but also enables realization of time‐modulated metasurfaces by applying time‐varying external stimuli. Despite their linearity, time‐modulated metasurfaces exhibit frequency‐mixing property and lead to generation of higher‐order frequency harmonics which are consisted of fundamental frequency up‐ and down‐modulated by the frequency of biasing . Unlike frequency conversion in nonlinear metasurfaces which requires high optical intensities and operates for one excitation at a time, frequency conversion in time‐modulated metasurfaces can be achieved for simultaneous excitations with arbitrary intensities.…”

Section: Introductionmentioning

confidence: 99%

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A Dynamically Modulated All‐Dielectric Metasurface Doublet for Directional Harmonic Generation and Manipulation in Transmission

Salary

Farazi

Mosallaei

2019

Advanced Optical Materials

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metasurface to achieve a certain functionality in reflection or transmission mode. Recent years have witnessed the development of phase-gradient metasurfaces with different configurations for a wide range of applications such as beam-steering, focusing, and holography. [1,2] These structures allow for integration of various functionalities into a flat surface thus leading to a dramatic reduction in the footprint of optical systems by replacing conventional bulky optical components.Spatiotemporal control over the phase of transmitted and reflected lights across the 2π span is the key to achieve the desired functionalities. The phase tuning mechanisms of metasurfaces have been mostly based on varying the size of nanoantennas within the resonant scattering regime or rotating half-wave plate elements to imprint a geometric phase shift on the circularly polarized light scattered with the opposite handedness. [3,4] For a nanoantenna supporting a single isolated electric or magnetic resonance, the maximal resonant phase agility is π which hinders full control over the light wavefront without employing a back mirror. Metasurfaces with both electric and magnetic responses can be used to overcome this limitation via spectrally overlapping [5] and interleaving [6] electric and magnetic resonances for operation in transmission and reflection modes, respectively. The spectral overlap of electric and magnetic dipole resonances in a Huygens' metasurface satisfies the first Kerker condition leading to suppressed backward scattering from the elements thus eliminating the reflection and giving rise to maximal transmission with 2π phase agility. Although Huygens' metasurfaces have been constructed using metallic elements in microwave regime, bringing plasmonic Huygens' metasurfaces into optical frequencies is challenging due to their complex geometries and arrangements, and is further hindered by the significant increase in the ohmic loss of plasmonic materials at higher frequencies. [7] All-dielectric metasurfaces consisted of high-index subwavelength elements embedded in a low-index environment can eliminate these limitations in that they can support both electric and magnetic resonances with simple geometries and do not suffer from significant dissipative losses. [8][9][10] Moreover, they are fully compatible with standard In this paper, an electrically tunable all-dielectric metasurface doublet is proposed operating at mid-infrared frequency regime with dynamic 2π phase span in transmission mode. Each layer of the metasurface consists of a periodic array of silicon nanobars configured into p-i-n junctions in which the double carrier injection into the intrinsic region under forward bias allows for tuning of the silicon refractive index. The physical mechanism is based on the spectral overlap of high quality factor guided mode resonances supported by each constituent layer establishing an extreme Huygens' operation regime of nearly reflectionless transmission with steep phase spectrum. The short response time of field-driven car...

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Section: Time‐modulated Metasurfacementioning

confidence: 99%

“…Dynamic modulation of a metasurface provides the required momentum for the transition of fundamental frequency to higher‐order frequency harmonics defined as f n = f 0 + nf m with the integer

n \in ℤ

Section: Time‐modulated Metasurfacementioning

confidence: 99%

Section: Applicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Dynamically Modulated All‐Dielectric Metasurface Doublet for Directional Harmonic Generation and Manipulation in Transmission

Salary

Farazi

Mosallaei

2019

Advanced Optical Materials

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“…To perform calculations of thermal emission and absorption, we extend the formalism of radiative heat transfer [25,26] to include time-varying dielectric functions. This formalism combines rigorous coupled wave analysis [27,28] with the fluctuation-dissipation theorem [29] to compute thermal emission for spatio-temporally modulated layered structures. In our system, the modulated layer does not have loss and hence by itself does not generate thermal radiation.…”

mentioning

confidence: 99%

Photonic Refrigeration from Time-Modulated Thermal Emission

Buddhiraju

Fan

2020

Phys. Rev. Lett.

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Active photonic cooling is of significant importance to realize robust, compact, vibration-free, allsolid-state refrigeration. Currently proposed photonic cooling approaches are based on luminescence and impose stringent requirements on luminescence efficiency. We propose a new photonic cooling mechanism arising from temporal modulation of thermal emission. We show that this mechanism has a high thermodynamic performance that can approach the Carnot limit and yet does not rely on luminescence. Further, our work opens exciting new avenues in active, time-modulated control of thermal emission for cooling and energy harvesting applications.

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Topological Space‐Time Photonic Transitions in Angular‐Momentum‐Biased Metasurfaces

Sedeh

Salary

Mosallaei

2020

Advanced Optical Materials

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In this paper, topological space‐time photonic transition of light in angular‐momentum‐biased metasurfaces is established, which yields a superposition of orbital‐angular‐momentum (OAM)‐carrying beams at distinct frequency harmonics upon scattering whose topological charges and frequency shifts are correlated. A reflective dielectric metasurface is considered that consists of silicon nanodisk heterostructures integrated with indium‐tin‐oxide and gate dielectric layers placed on a back mirror forming a dual‐gated field effect modulator. The metasurface is divided into several azimuthal sections wherein the nanodisk heterostructures are interconnected via biasing lines. Addressing each azimuthal section with radio‐frequency biasing signals separately allows for flexible implementation of different spatiotemporal modulation profiles. Active tuning of OAM states with high mode‐purity is demonstrated, which yields minimal cross‐talk between OAM channels in a mode‐multiplexed communication system. Moreover, the role of spatiotemporal modulation profile on the spectral and spatial diversity of OAM states is explored. It is shown that angular‐momentum‐biased metasurfaces allow opportunities for hybridized mode‐division and wavelength‐division multiple access through multiplexing and multicasting across distinct OAM states and wavelengths. The nonreciprocity of topological space‐time photonic transitions across the temporal frequency domain and Hilbert space of OAM states is also investigated giving rise to distinct twisted light channels in up‐ and down‐links.

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Rigorous space-time coupled-wave analysis for patterned surfaces with temporal permittivity modulation [Invited]

Cited by 41 publications

References 59 publications

A Dynamically Modulated All‐Dielectric Metasurface Doublet for Directional Harmonic Generation and Manipulation in Transmission

A Dynamically Modulated All‐Dielectric Metasurface Doublet for Directional Harmonic Generation and Manipulation in Transmission

Photonic Refrigeration from Time-Modulated Thermal Emission

Topological Space‐Time Photonic Transitions in Angular‐Momentum‐Biased Metasurfaces

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