Programmable Nonreciprocal Meta-Prism

Abstract

Optical prisms are made of glass and map temporal frequencies into spatial frequencies by decomposing incident white light into its constituent colors and refract them into different directions. Conventional prisms suffer from their volumetric bulky and heavy structure and their material parameters are dictated by the Lorentz reciprocity theorem.. Considering various applications of prisms in wave engineering and their growing applications in the invisible spectrum and antenna applications, there is a demand for compact apparatuses that are capable of providing prism functionality in a reconfigurable manner, with a nonreciprocal/reciprocal response. Here, we propose a nonreciprocal metasurface-based prism constituted of an array of phase-and amplitude-gradient frequency-dependent spatially variant radiating super-cells. In conventional optical prisms, nonreciprocal devices and metamaterials, the spatial decomposition and nonreciprocity functions are fixed and noneditable. Here, we present a programmable metasurface integrated with amplifiers to realize controllable nonreciprocal spatial decomposition, where each frequency component of the incident polychromatic wave can be transmitted under an arbitrary and programmable angle of transmission with a desired transmission gain. Such a polychromatic metasurface prism is constituted of frequency-dependent spatially variant transistor-based phase shifters and amplifiers for the spatial decomposition of the wave components. Interesting features include three-dimensional prism functionality with programmable angles of refraction, power amplification, and directive and diverse radiation beams. Furthermore, the metasurface prism can be digitally controlled via a field-programmable gate array (FPGA), making the metasurface a suitable solution for radars, holography applications, and wireless telecommunication systems.

Lightweight Low-Noise Linear Isolator Integrating Phase-Engineered Temporal Loops

“…Isolators can be realized by the simultaneous breaking of time-reversal symmetry and spatial inversion [1][2][3]. Conventional techniques and structures for the realization of isolators include magnetically biased two-dimensional electron gas systems [4], gyroelectric waveguides [5], transistor-loaded transmission lines [6][7][8][9][10][11][12], magnetic ferrites [1,[13][14][15][16][17][18][19], nonlinearity [20], and space-time-modulation [21][22][23][24]. Although these approaches have their own unique advantages and applications, they suffer from distinct limitations and disadvantages that restrict their applications.…”

“…For instance, magnetically biased isolators require bulky magnets and are incompatible with integrated circuit technology [25]. An alternative approach is transistor-based isolators [8,10,12] which eliminate the bulky magnet and are compatible with integrated-circuit technology but suffer from limited power handling and noise performance, and are of limited availability at high frequencies. Nonlinear isolators may be a good choice for some applications but they only provide isolation to high power signals, while they pass low-level signals quasi-reciprocally [26].…”

Lightweight Low-Noise Linear Isolator Integrating Phase-Engineered Temporal Loops

“…Isolators can be realized by the simultaneous breaking of time-reversal symmetry and spatial inversion [1][2][3]. Conventional techniques and structures for the realization of isolators include magnetically biased two-dimensional electron gas systems [4], gyroelectric waveguides [5], transistor-loaded transmission lines [6][7][8][9][10][11][12], magnetic ferrites [1,[13][14][15][16][17][18][19], nonlinearity [20], and space-time-modulation [21][22][23][24]. Although these approaches have their own unique advantages and applications, they suffer from distinct limitations and disadvantages that restrict their applications.…”

“…For instance, magnetically biased isolators require bulky magnets and are incompatible with integrated circuit technology [25]. An alternative approach is transistor-based isolators [8,10,12] which eliminate the bulky magnet and are compatible with integrated-circuit technology but suffer from limited power handling and noise performance, and are of limited availability at high frequencies. Nonlinear isolators may be a good choice for some applications but they only provide isolation to high power signals, while they pass low-level signals quasi-reciprocally [26].…”

Magnet-Free Circulator Formed By A Time-Varying Nonreciprocal Phase Shifter

“…Nonmagnetic nonreciprocity is conventionally achieved through nonreciprocal properties of transistors at microwave frequencies, [7][8][9][10][11][12][13] and electro-optical modulators at optical frequencies. 14 However, these techniques substitute the absence of cumbersome magnetic bias for other tangible drawbacks, such as poor noise performance and strong nonlinearities of transistors, or the complexity and large size of the electro-optical modulators.…”