Search

Dynamic manipulation of terahertz (THz) beams plays an important role in THz application systems. The PB metasurface provides an effective scheme for space separation and deflection of the spin beam. However, mirror symmetry locking of the conjugated spin states severely limits the versatility of the device. In this work, we demonstrate a liquid crystal (LC) cascaded bilayer metasurface that includes an LC layer, anisotropic metasurface, and PB metasurface. By controlling anisotropy and polarization conversion effects, dynamic spin asymmetric transmission is realized. Meanwhile, two different dynamic energy distribution processes are realized between the L and R state with the corresponding deflection side. The results show that the device achieves a large angular spatial dispersion within the frequency-angle scanning range of ±35° to ±75° corresponding to the broadband range of 0.6–1.1 THz. Moreover, it achieves a spin beam spatial separation with a maximum proportion of energy distribution greater than 26 dB, and the active modulation rate in the energy distribution process reaches 98 %. This work provides a dynamic THz spin conversion and efficient large-angle beam scanning, with important potentials in wavelength/polarization division multiplexing and frequency-scanning antenna for large-capacity THz wireless communication, radar, and imaging systems.

Accurate full‐parameter construction of the Jones matrix is of great significance for encoding multiple functions in a single metasurface. Supercells composed of several elements are used for this purpose through coherent superposition. But all the elements in the reported studies should be lossless with near‐unity transmission, which limits the material system and restricts the Jones matrix construction in a unitary manner. Here a non‐unitary matrix decomposition method is proposed to build the supercell using a pair of 0°‐oriented rods and a pair of 45°‐oriented rods for on‐demand design of arbitrary symmetric Jones matrices. This method is applicable for lossy metasurfaces and offers straightforward physical guidance for structure design without optimization. The accuracy of the on‐demand Jones matrix generation is demonstrated by several 3D‐printed alumina metalenses with 3‐, 4‐, and 6‐channel polarization‐multiplexed focusing. The study opens a new pathway for non‐silicon meta‐optics and holds great potential for dynamic or switchable applications. [ABSTRACT FROM AUTHOR]

Dynamic beam scanning with a dynamically tunable beam number, beam direction, and beam polarization remains a challenge in the terahertz gap, which is urgently needed for terahertz radar, next-generation wireless communication, and imaging applications. Different from programmable metasurfaces with element-level phase control, the beam direction is dynamically controlled by two cascaded all-dielectric metasurfaces during in-plane rotation. For a pair of circularly polarized beams with opposite handedness, the scanning field of view (FOV) can be the same or different according to the independent phase modulation in both layers and for both polarization states. Switchable single-beam and dual-beam scanning is achieved by controlling the incident polarization, which covers the ±60° FOV at 0.291 THz with an angular step of 1° and an average gain of 16.2 dBi. The output beam is quasi-circular polarized with an average ellipticity of 0.83. Single beam scanning along a Fibonacci spiral trajectory and dual beam scanning along symmetric and asymmetric trajectories are experimentally validated. Different beam scanning processes are recorded using a terahertz camera, which show good agreement with the theoretical prediction. The wide field-of-view continuous beam scanning with a switchable number of beams and a flexible FOV may have a significant impact on the development of terahertz radar and terahertz intelligent antennas. [ABSTRACT FROM AUTHOR]

Nonreciprocal materials and devices play an irreplaceable role in isolating, routing, and multiplexing. However, in the terahertz (THz) band, their active control mechanisms are still limited. Herein, a THz nonreciprocal photonic spin transmission is demonstrated in the undoped InSb actively manipulated by a light‐magneto‐joint modulation method, in which THz cyclotron resonance of the photoinduced carriers is conjunctively excited by both pump laser and external magnetic field. Moreover, a diffusion model of photoinduced non‐equilibrium carriers and its nonreciprocal dispersion model of magnetized plasma are established to interpret the experimental observation. The results indicate that the light‐magneto‐joint modulation achieves a broadband amplitude‐phase modulation with a higher modulation depth (>2π rad phase shift), as well as an active nonreciprocal spin transmission with magnetic circular dichroism (>20dB) and the Faraday rotation effect (>90°) in InSb, which is more efficient and faster than the traditional thermal excitation. Furthermore, the demonstration in a single‐frequency THz transmission system shows that this light‐magneto‐joint modulation mechanism in InSb can be multifunctionally applied in active control, isolation, and polarization conversion. [ABSTRACT FROM AUTHOR]

Ultra-compact and tunable devices for terahertz (THz) beam manipulation are highly desired in wireless communication and radar scanning. Although the appearance of the Pancharatnam-Berry (PB) metasurface has provided strategies for THz beam scanning, active output power distribution is still difficult to achieve, and the flexibility of beam manipulation is limited by a single metasurface. In this work, we demonstrated an all-dielectric cascaded metasurface consisting of a spin-decoupled metasurface and a PB metasurface. The conjugated characteristic of the PB phase for two photonic spin states is broken with highly efficient high-order diffractions of wave vector superposition through the cascaded metasurfaces, and both spin-symmetric and spin-asymmetric transmissions are obtained by designing the differences in metasurface bandwidth. Moreover, the output power between the deflection beams can be actively tuned by changing the incident polarization state, achieving power modulation ratios of 99.3% and 95.1% for the two conjugated spin beams, respectively. Therefore, this work realizes controllable wave division multiplexing and power distribution and opens new avenues for the design of ultra-compact multifunctional devices. [ABSTRACT FROM AUTHOR]