Dynamic Control of the Extraordinary Optical Scattering in Semicontinuous 2D Metamaterials

Abstract

COMMUNICATIONmetallic metasurface operating in transmission mode is typically in the order of a few percents. [ 3,4,[7][8][9] Recently, it was demonstrated that the effi ciency can reach 24.7% in the microwave region with a thickness of 1/1000 λ . [ 19 ] However, the theoretically predicted upper limit 25% is the intrinsic obstacle for its further improving. [ 20 ] In the last several years, it was demonstrated that coherent control could be used to dynamically change the light-matter interaction on the metasurface. [21][22][23] Electromagnetic wave could be completely absorbed by an ultrathin metasurface in an unexpected broad frequency range with coherent illumination, [ 23 ] which broke the classic bandwidth-thickness limit. [ 5 ] Besides, the polarization states could also be coherently controlled as demonstrated in previous work, and the effi ciency could reach near 100% with frequency-independent property. [ 24,25 ] Very recently, spatial mode multiplexing by coherent control method is also reported. [ 26 ] Furthermore, the coherent control method provides a viable alternative for the signal processing based on nonlinear materials. Since nonlinear process is not needed anymore, the signal intensity as well as the thermal problems can be dramatically reduced. [ 21,27 ] Here we show that nanoslit arrays with semicontinuous shape perforated in metallic screen could generate continuous phase distribution, thus altering the Snell's law in a more smooth way. A coherent control method is utilized to surpass the intrinsic effi ciency limit of the metasurface in transmission mode and realize dynamic control over the generalized Snell's law. Our proof-of-concept experiment validates this method, providing a promising route to the practicality of a variety of devices based on metasurface structures.In this paper, an ultrathin metallic metasurface with semicontinuous space-variant slit is used to generate perfect linear phase distribution, which has been demonstrated to have broader working bandwidth and higher effi ciency compared to metasurfaces based on discrete metallic structures. [ 28 ] By defi ning ξ as the angle between the slit and the x -axis as shown in Figure S1 (Supporting Information) and recalling that Φ = 2 σζ is the PB phase (see Supporting Information), the tangent dy / dx = σ tan( k a x /2) can be directly integrated over the x -axis to obtain the analytic curve as followswhere k a is the additional horizontal wavevector of the generated beam, σ = ±1 denotes the left and right handed circular polarization (LCP and RCP). Since different circular polarization only introduce a reverse of the sign, we chose σ = 1 in the following discussion. As one of the basis of traditional optics, Snell's law allows one to calculate the refl ection and refraction angles for light passing from one medium to another. [ 1 ] For hundreds of years, it was thought that this law is a fundamental aspect of optics. After the pioneering work of Maxwell in 1865, the essence of Snell's law is now attributed to the continuity of e...

Multicolor 3D meta-holography by broadband plasmonic modulation

“…The slit is designed to be angled with respect to the x axis and to provide different phase shifts. According to the local phase shift associated with the spin-orbit interaction and propagating bounded wave exchange ( 22 ), the phase of the cross-polarized light (Φ) depends on the orientation angle (φ) of the nanoslit by the relation Φ = 2φ for circular polarization incident light, which is used to determine the angle of the nanoslit ( 34 , 35 ). It is worth mentioning that such a nanoslit is efficient for a broadband wavelength covering the visible range (380 to 780 nm).…”

Subwavelength Optical Engineering with Metasurface Waves

“…However, previous nanoantennas used to obtain geometric phase generally have a wavelength‐dependent scattering amplitude, which deteriorates the broadband response. In order to overcome this problem, semicontinuous nanoantennas or their complementary structures such as catenary‐shaped nanoantennas and nanoapertures are proposed recently to achieve a broadband response in both amplitude and phase modulations . By further combining dispersion engineering to mimic the ideal dispersion required for frequency‐independent applications, various broadband and high‐efficient reflective metadevices, i.e., metamirrors, have been demonstrated experimentally recently …”

“…The concept of CPA can also be employed in solar STPV system to realize frequency‐selective broadband absorbers, or be extended into other areas such as all‐optical logical operations, coherent polarization conversion, coherent abnormal deflection and spin‐Hall effect, subwavelength focusing, and lasing and antilasing in a single cavity . Figure f illustrates a novel image processing method based on CPA effect, where images A and B projected by coherent light onto an absorbing metasurface result in deletion (shown) or addition of image features, depending on the phase difference between the interacting beams.…”

High‐Efficiency Ultrathin Dual‐Wavelength Pancharatnam–Berry Metasurfaces with Complete Independent Phase Control

“…[16][17][18][19] In addition, the concept of meta surface has also been adopted in many other research areas, such as the elastic meta surfaces [20,21] and acoustic metasurfaces. [24][25][26][27][28][29][30][31][32][33] For instance, several multiwavelength devices are realized by grouping different sized resonators into a building block. The wavelengthdependent behavior of the metasurfaces is one of the critical limitations in existing metasurface devices.…”

“…[22,23] Although metasurfaces have been widely studied since their emergence, most metasurface devices are designed to operate at a single wavelength, and their function alters or the performance deteriorates as the wavelength is varied due to the dispersion nature. [24][25][26][27][28][29][30][31][32][33] For instance, several multiwavelength devices are realized by grouping different sized resonators into a building block. Therefore, a number of investigations have been conducted to circumvent this limitation at two or more distinct wavelengths recently.…”