Waveform-Dependent Absorbing Metasurfaces

Abstract

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high power pulses but not for high power continuous waves (CWs), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e. CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.Conventional absorbers [1,2] are independent of incoming power levels and therefore absorb not only destructive high power signals but also small signals necessary for antenna communications. These two effects can be decoupled by introducing nonlinearity into a periodic structure or metasurface [3] such that the artificially engineered surface possesses a low power surface impedance that is different from its high power absorbing response. Furthermore, we can take advantage of the fact that high power microwave signals generally come from pulsed sources, and design a structure in which the high power microwave energy is rectified and stored as a static field in the surface, and then dissipated between pulses. This provides freedom in the choice of lossy components, allowing us to further decouple the high power absorption properties from the small signal behavior and also design the surface to respond specifically to short pulses.Many nonlinear metamaterials and metasurfaces derive their nonlinear properties from altering the resonant paths of induced electric currents with nonlinear media (e.g. through semiconductive substrates [4][5][6][7] or geometrical modifications induced by heating [8] or magnetic force [9,10]). These differ from our nonlinear metasurfaces based on diodes or nonlinear circuits. Diodes switch between nonconducting and conducting states depending on the applied voltage and therefore are capable of handling incoming signals differently depending on the magnitude. Because diodes rectify high power signals and convert much of the energy to a static field, our nonlinear metasurfaces perform differently from others that convert incoming signals into high order modes [11,12] or exploit wave mixing techniques [13].To understand how such a structure absorbs high power pulse energy consider Figs. 1 (a) and (b). Our metasurface is composed of circuit components (i.e. diodes, capacitors and resistors) as well as a conductive ground plane and periodic metal patches, separated by a dielectric substrate, Rogers 3003. During a pulse (i.e. * hirokiwaka@gmail.com † dsievenpiper@eng.ucsd.edu Fig. 1 (a)) high power surface currents propagate on the patches. Once the voltage difference across a diode reaches the turn-on voltage, electric charges flow into a capacitor and the energy is stored. Between pulses ( Fig. 1 (b)) the stored ele...

Broadband Switchable 3d Structure Used for Protecting Information Equipment From Electromagnetic With Strong Field

“…The metasurface transmits low power signals but absorbs high intensity ones. Similar works were done by Wakatsuchi et al [8,9]. Wall et al proposed a broadband switching nonlinear metamaterial, which reflected the low power signals and propagated the high power ones [10].…”

“…Katko et al using PIN diodes designed RF limiter metamaterial [4]. In 2016, Kim et al presented a nonlinear metasurface based on the nonlinear circuits [5][6][7][8][9]. The metasurface transmits low power signals but absorbs high intensity ones.…”

Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

“…Nanoimprint lithography is a more promising technique for combining many advantages of the former, such as high-resolution, large-scaled production and low processing cost [73]. The unique properties and the development of fabrication techniques have allowed metasurfaces to be applied in various fields, such as flat optics [33][34][35], nonlinear effects [101][102][103][104][105][106][107], photonic Hall effects [108][109][110], electromagnetically-induced transparency [111], cloaking [112][113][114][115][116][117], etc., as shown in Figure 2. For instance, the applications of metasurfaces in the field of flat optics mainly include anomalous reflection/refraction [34,81,82], wave plates [79,80], flats lens/axicons [83][84][85], mirrors [88], hologram [90][91][92][93][94][95], filters [96], optical vortex generation [34,85,98,99], polarization beam splitter [100], etc.…”

Switchable nonlinear metasurfaces for absorbing high power surface waves

“…[12][13][14] Compared to prior works, this structure provides high power absorption regardless of the incoming waveform using a much simpler circuit, requiring only a single diode per cell, and no reactive components. Furthermore, we demonstrate nonlinear attenuation of surface waves over a large area and suppressed leakage of high power signals thorough a narrow gap by surrounding it with a nonlinear coating.…”

“…Note that although a TEM waveguide was used in simulation, and a TE waveguide was used in the measurement, both have similar electric and magnetic field profiles and can be expected to identify similar performance trends. 12,13 The TEM waveguide allows a much simpler simulation, but the required boundary conditions are not available for experiments.…”