As a powerful and compact device for manipulating wavefront of light, metasurface has widely been studied in recent years. However, simultaneous control of full parameters of light (including amplitude, phase, and polarization) over a wide bandwidth is still a great challenge. In our works, we demonstrate that the combination of subwavelength plasmonic structures and detour phase could achieve full parameter control of light. Here, the traditional detour phase is used to manipulate the phase of light, while several different plasmonic structures are designed to control the amplitude and various polarization state distributions. We first introduce a type of detour phase meta-hologram composed of cross-shaped plasmonic nano-silt array which are sensitive to linear polarization with over 1000-nm bandwidth from visible to near-infrared. In a proof-of-concept experiment, we demonstrate 3D object reconstruction and polarization multiplexing images at various prescribed wavelengths from 473 nm to 1550 nm using a specially designed meta-hologram. Then we introduce another design of detour phase meta-hologram which is sensitive to circular polarizations. We choose a pair of oblique plasmonic nano-slits as a unit cell in the hologram, and modulate its polarization response by changing the distance between the two slits in a unit cell. We demonstrate that such design can be used for detecting both topological charge and polarization order of vortex vector beam, or generating holographic patterns with RGB colors. Beneﬁting from high controllability of amplitude, phase, and polarization, our meta-holograms offer great potential in future applications such as 3D displays, optical communications, and beam shaping.
A photo-excited tunable and broad band metamaterial absorber in the terahertz region is proposed. The metamaterial absorber is composed of three layers like the sandwich, the top layer is a ring metal-semiconductor square split ring and the bottom layer is a metallic ground plane, these two layers are separated by a dielectric spacer, which we choose as the polyimide. The conductivity of the silicon can be tuned actively with the incident pump power. We use the full wave simulation and the equivalent circuit parameter to analysis this absorber, and interpreted the phenomena showed when the conductivity of the silicon filled in the gap of ring is changed by the electric field. The proposed equivalent circuit parameter can save more time to design this kind of absorber in need. The proposed photo-excited tunable metamaterial absorber can also be used as terahertz modulators and switches.