High‐Efficiency Spatial‐Wave Frequency Multiplication Using Strongly Nonlinear Metasurface

Abstract

In the past decades, metasurfaces have opened up a promising venue for manipulating lights and electromagnetic (EM) waves. In the field of nonlinearity, second-harmonic generation (SHG) is a research focus due to its diverse applications. There have been many researches for realizing SHG in optical regime using nonlinear characteristics of optical materials, but its efficiency is low. In microwave frequencies, SHGs are basically studied in the guided-wave systems. Here, high-efficiency SHGs of spatial waves are presented in the microwave frequency using nonlinear metasurface loaded with active chips at the subwavelength scale. The nonlinear meta-atom is composed of receiving antenna, transmitting antenna, and active circuit of frequency multiplier, which can realize strongly nonlinear response and link the EM signals from the receiving to transmitting antennas. Correspondingly, to achieve the function of spatial-wave frequency multiplication, the working frequency of the transmitting antenna in the meta-atom should be twice as that of the receiving antenna, and hence the active chip is well matched to obtain the signal transforming with high efficiency. Good performance of the spatial-wave frequency multiplication is demonstrated in the proof-of-concept experiments with the best transform efficiency of 85.11% under normal incidence, validating the proposed method.

A Time-Modulated Transparent Nonlinear Active Metasurface for Spatial Frequency Mixing

“…Ref. [17] is singular as it realized a second harmonic generation (SHG) using a lumped frequency multiplier chip, and by virtue of the performance of the active chip, a low harmonic level was realized. To summarize, our transmission-type, continuously modulated metasurfacebased spatial frequency mixer with unwanted harmonics suppression, offers a novel solution to manipulating the spatial wave.…”

“…As a type of surface EM component, a metasurface [9][10][11] with artificially designed structures exhibits novel properties for spatial EM wave manipulation, such as multibeam generation [12], beam steering [13], vortex beam generation [14] and so on. Furthermore, the EM response of the metasurface can be electrically adjusted by loading active devices on every unit cell [15][16][17][18], i.e., the smallest atom of a metasurface.…”

“…Frequency mixing for a spatial EM wave, also referred to as harmonic manipulation, has been researched in [17,23,[27][28][29][30] using the time-modulated metasurface. In those works, a reflection-type metasurface design with discrete EM responses is dominant; however, reflection-type designs inevitably suffer from blockages and are not the best option for system integration.…”

Recent Advances in Reconfigurable Metasurfaces: Principle and Applications

“…Since the amplifiers are digitally controlled, it is very convenient to control the power transmission of this system. Based on the nonlinear feature of the amplifiers, Wang et al have realized the frequency multiplication of microwaves [ 249 ], shown in Figure 12 c. Each unit cell of the proposed metasurface is composed of two patches as receiving and transmitting antenna and frequency multiplication circuits. The incident microwave is received by the receiving antennas and coupled to the frequency multiplication circuits, then, the microwave with doubled frequency is radiated by transmitting antenna.…”

Design of Switchable SHG and THG using Metasurface-based Frequency Mixing System

“…However, this metasurface can only generate harmonics of the modulation frequency, instead of the working frequency of the incident waves. Strongly nonlinear metasurfaces loaded with active circuits of frequency multiplier to achieve spatial-wave SHG is proposed in [24]. This letter presents a switchable SHG and THG using nonlinear metasurface-based system, able to capture, frequency mix and irradiate back an illuminating EM field at frequency f0.…”