Libin Yan

A Flat Lens with Tunable Phase Gradient by Using Random Access Reconfigurable Metamaterial

The first demonstration of an optofluidic metamaterial is reported where resonant properties of every individual metamolecule can be continuously tuned at will using a microfluidic system. This is called a random-access reconfigurable metamaterial, which is used to provide the first demonstration of a tunable flat lens with wavefront-reshaping capabilities.

Adaptable metasurface for dynamic anomalous reflection

In this paper, we demonstrate an adaptable metasurface with a periodic array of liquid-metal ring-shaped resonators. Its optical properties can be dynamically controlled by individually reconfiguring the geometry (shape and orientation) of the resonators. For the proof of concept, by tailoring the phase profile of the scattered electromagnetic wave, a dynamic anomalous reflection is demonstrated, whereby the reflection angle is fixed at −45° for three different normal incident frequencies of 10.5, 12, and 14 GHz. The demonstrated adaptable metasurfaces pave a way for promising applications in multi-frequency tracking radar systems and broadband scanning systems.

Tunable flat lens based on microfluidic reconfigurable metasurface

A tunable flat lens is demonstrated based on reconfigurable metasurface, which is realized via changing the phase gradient of the metasurface in sub-wavelength level. The sub-wavelength metamolecules are formed by enclosing a liquid metal plug within microfluidic cavities, which can be tuned by changing the geometry of the metamolecules. The tunable flat lens is consisted of soft material with controllable functionalities. In simulation, the tuning of the focal length from 5 λ to 7 λ is demonstrated as the proof of concept. This reconfigurable metasurface can be used as a standard guideline to design different electromagnetic wave manipulation systems in realizing the dynamic control of beam steering, anti-reflection and focusing functionalities etc.

0.2 λ0 Thick Adaptive Retroreflector Made of Spin-Locked Metasurface

The metasurface concept is employed to planarize retroflectors by stacking two metasurfaces with separation that is two orders larger than the wavelength. Here, a retroreflective metasurface using subwavelength-thick reconfigurable C-shaped resonators (RCRs) is reported, which reduces the overall thickness from the previous record of 590 λ0 down to only 0.2 λ0 . The geometry of RCRs could be in situ controlled to realize equal amplitude and phase modulation onto transverse magnetic (TM)-polarized and transverse electric (TE)-polarized incidences. With the phase gradient being engineered, an in-plane momentum could be imparted to the incident wave, guaranteeing the spin state of the retro-reflected wave identical to that of the incident light. Such spin-locked metasurface is natively adaptive toward different incident angles to realize retroreflection by mechanically altering the geometry of RCRs. As a proof of concept, an ultrathin retroreflective metasurface is validated at 15 GHz, under various illumination angles at 10°, 12°, 15°, and 20°. Such adaptive spin-locked metasurface could find promising applications in spin-based optical devices, communication systems, remote sensing, RCS enhancement, and so on.

Microfluidic Metasurface for Dispersion-free Anomalous Reflection

Metasurfaces are ultra-thin planar structures designed with extraordinary electromagnetic properties from the interaction between the subwavelength scatterers and the electromagnetic radiation. Nevertheless, the dispersion nature imbedded in the metallic resonator of the metasurfaces leads to the variation of the angle of reflection. The reflection angle changes with the incident frequency of the electromagnetic waves. Here, we demonstrate, for the first time, an active metasurface with dynamically controllable dispersion by individually reconfiguring the geometry (shape and orientation) of the resonators. The latter are liquid metal rings structured and controlled by a microfluidic system. By tailoring the phase profile of the scattered light, we present a dispersion-controllable beam steering function whereby the steering angle is kept at -45˚ for three normal incident frequencies of 10.5, 12 and 14 GHz. Such active metasurfaces have potential applications in 2 directional communication devices, multi-frequency tracking Radar systems, and broadband scanning system.

Dispersion-corrected metasurface for beam deflector and flat lens

In this paper, a reconfigurable metasurface is realized using microfluidic technology, which controls the amplitude and phase of the incident wave at sub-wavelength resolution. A dispersion-corrected beam deflector and a flat lens are demonstrated for proof-of-principle where the flat lens and beam deflector are tuned, in response to the change of the incident wavelength, to maintain their functionalities. This will make various applications such as on-chip spectrometers, high-performance dispersion-controllable devices in the next-generation telecommunication networks, and wavefront-tunable devices.