There is a growing trend towards the development of high resolution and multiplexing metasurface holograms. In this paper, we propose the reconstruction of polarization multiplexing terahertz (THz) holographic images based on transmissive metasurface. The metasurface composed of all-dielectric meta-atoms is designed as a multi-foci metalens and the focal points of the metalens are utilized as the pixels of a reconstructed image. We analyze the effects of focal length and phase pixel number of the metalens on focal point to achieve high-resolution holographic images. In addition, by switching the polarization of incident lights, holographic images with different patterns are reconstructed on its focal plane. Such high-resolution and polarization multiplexing metasurface holograms is promising for applications in THz communications, information engineering, and encryption.

In this work, we introduce quantum-mechanical adiabatic passage into the design of spatial acoustic four-waveguide (WG) couplers. Thanks to the agreement in form between the Schrödinger equation in quantum mechanics and the coupled-mode equation of classical wave, the behavior of propagating wave in coupled WGs is capable of mapping to quantum states driven by external fields. By coupling the input and output WGs with a mediator WG in space, an apparent beam splitting is realized and the ratio of intensity can be customized arbitrarily by altering the space-dependent coupling strengths. Moreover, a one-way propagation feature is exhibited in the spatial coupler when an appropriate loss is introduced in the mediator WG owing to the existence of dark state. This work builds a bridge between quantum adiabatic technology and acoustic beam splitter, which may have potential applications in acoustic communication, filtering and detection.

We demonstrate multi-channel metasurface holograms, where the pixels of holographic images are represented by the focal points of metalens, leading to the nanoscale resolution. The required phase profiles are implemented by elaborately arranging the hybrid all-dielectric meta-atoms with specific orientation angles. For verification, two-channel single-color images are reconstructed on the focal plane of the metalens by polarization control. Alternatively, three-channel color holograms are exhibited by manipulating the incident wavelengths. More uniquely, the metalens can be further engineered to generate polarization-wavelength multiplexing color holograms in six channels. Our work provides an effective approach to reconstructing holographic images and enables potential applications including color display, information engineering, and optical encryption.

An asymmetric metasurface capable of a dynamically controlled electromagnetically induced transparency (EIT) analogue is proposed by changing the polarization direction of the incident light. The metasurface composed of Z-L shape meta-atoms exhibits a narrowband transparency window at 1.858 THz for y-polarization incidence. This EIT window originates from the destructive interference between magnetic dipole (MD), toroidal dipole (TD) and electric quadrupole (EQ) resonances, where the coupling of MD and TD serves as bright mode and EQ acts as dark mode. By varying the polarization angle (φ) of the incident light, the transmission of the dip at 1.856/1.861 THz can be tuned from 0.90/0.95 to 0.08/0.03. Meanwhile, the Q-factor of 640.55 and the group delay of 117.21 ps are achieved at φ = 120°. This work will promote the development of novel multipolar supported EIT metasurfaces.

We report a high-efficiency geometric-phase metasurface composed of hybrid all-dielectric nanofins, of which the conversion efficiency 93% is obtained in visible frequency. Such high efficiency originates from the stimulation of the anti-ferromagnetic resonance modes of polarization-dependent parity, i.e. even and odd number of anti-parallel magnetic dipoles would introduce π phase delay among two orthogonal components of the transmitted field. We further demonstrate the generation of the focused optical vortex (OV), Bessel OV and autofocusing Airy OV with the hybrid all-dielectric metasurfaces, which shows promising applications in flexible optical trapping and optical communications.

Metasurfaces, with superiority in integration and flexibility compared to conventional bulky optical elements, open a perspective in generating perfect optical vortex (POV). However, the generation of POV beams with simultaneous high-efficiency, multi-functionality, and broadband is still challenging. Here, we design POV generators based on highly efficient all-dielectric metasurfaces and produce POV beams in simulation in the visible region with maximum generation efficiency of 74%. Such high efficiency originates from the stimulation of the resonance modes of polarization-dependent parity in the well-designed unit cell. By superposing two sets of phase profiles, polarization-controlled POV generators are obtained. Furthermore, the POV generator exhibits broadband property due to the geometric phase independent of the incident wavelengths. Our work provides an effective approach for generating controllable POV beams, promoting the construction of integrated and multi-functional optical systems.