Dynamic modulation yields one-way beam splitting

Abstract

This article demonstrates the realization of an extraordinary beam splitter, exhibiting one-way beam splitting-amplification. Such a dynamic beam splitter operates based on nonreciprocal and synchronized photonic transitions in obliquely illuminated space-time-modulated (STM) slabs which impart the coherent temporal frequency and spatial frequency shifts. As a consequence of such unusual photonic transitions, a is exhibited by the STM slab. Beam splitting is a vital operation for various communication systems, including circuit quantum electrodynamics, and signal-multiplexing and demultiplexhg. Despite the beam splitting is conceptually a simple operation, the performance characteristics of beam splitters significantly influence the repeatability and accuracy of the entire system. As of today, there has been no approach exhibiting a nonreciprocal beam splitting accompanied with transmission gain and an arbitrary splitting angle. Here, we show that oblique illumination of a periodic and semi-coherent dynamically-modulated slab results in coherent photonic transitions between the incident light beam and its counterpart space-time harmonic (STH). Such transitions introduce a unidirectional synchronization and momentum exchange between two STHs with same temporal frequencies, but opposite spatial frequencies. Such a beam splitting technique offers high isolation, transmission gain and zero beam tilting, and is expected to drastically decrease the resource and isolation requirements in communication systems. In addition to the analytical solution, we provide a closed-form solution for the electromagnetic fields in STM structures, and accordingly, investigate the properties of the wave isolation and amplification in subluminal, superluminal and luminal ST modulations.

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

“…This creates a new paradigm for designing dynamic metasurfaces with 2π phase span and uniform amplitude. Furthermore, time‐modulated metasurfaces give rise to several exotic space‐time scattering phenomena and can be envisioned for a variety of novel applications such as magnetless nonreciprocal components, Doppler cloaking and illusion, pulse shaping, extreme energy accumulation, and localization of light . Development of all‐dielectric time‐modulated metasurfaces is of particular interest as they can enable directional harmonic generation and manipulation in transmission mode by establishing a Huygens' operation regime, eliminating the bidirectionality of harmonics generated by time‐modulated metasurfaces with single isolated resonances.…”

Space-Time Modulation: Principles and Applications

“…It eliminates issues of conventional nonreciprocity techniques, such as bulkiness, heaviness and incompatibility with integrated circuit technology associated with magnetbased nonreciprocity, power restrictions of nonlinear-based nonreciprocity, and frequency limitations and low power handling of transistor-based nonreciprocity. It provides asymmetric interband photonic transitions [7]- [14], subluminal and superluminal phase velocities, and asymmetric dispersion diagrams [4], [11], [13], [14], and holds potential for energy accumulation [15]. Various enhanced-efficiency magnet-free microwave and optical components have been recently realized by taking advantage of the unique properties of ST modulation, including isolators [9], [11], [16]- [19], circulators [20]- [23], Manuscript pure frequency mixer [24] metasurfaces [25]- [28], one-way beam splitters [12], [14], nonreciprocal antennas [29]- [31], and advanced wave engineering [32].…”

Programmable Nonreciprocal Meta-Prism

“…The proposed polychromatic metasurface takes advantage of magnet-free nonreciprocity induced by unilateral transistors. Magnet-free nonreciprocal metasurfaces provide huge degrees of freedom for arbitrary alteration of the wavevector and temporal frequency of electromagnetic waves 21,22,[30][31][32][33][34][35][36][36][37][38][39] . Furthermore, the metasurface prism is constituted of frequency-dependent spatially variant phase shifters for spatial decomposition of wave components.…”