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.

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 λ down to only 0.2 λ . 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.

In this paper, we demonstrate an adaptable metasurface with a periodic array of liquid-metal ringshaped 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 À45 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.

A single metasurface is demonstrated with powerful manipulating capability to arbitrarily and independently tune the phase profiles of orthogonal polarization states using subwavelength tunable cross‐shaped element (TCE) arrays. Here, the arbitrary control of the phase profiles must be distinguished from the semiarbitrary phase control using multiple predesigned metasurfaces with one‐to‐one functionality. The decoupled tuning of phase profiles for orthogonal polarization states bestows the metasurface with additional degree of freedom to manipulate the electromagnetic wave for multifunctionality. As a proof of concept, a tunable polarization beam splitter, a dynamic beam steering component, and a quarter waveplate are demonstrated using one single metasurface. This metasurface has promising applications on versatile and function‐switchable photonic components, such as polarization optical devices, compact functional devices, communication systems, and wave controlling devices, to name just a few.

Here we demonstrate the two-tier manipulation of holographic information using frequency-selective metasurfaces. Our results show that these devices can diffract light efficiently at designed frequency and environmental conditions. By changing the frequency and refractive index of the surrounding environment, the metasurfaces produce two different holographic images. We anticipate that these environmental dependent, frequency-selective metasurfaces will have practical applications in holographic encryption and sensing.

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