Active terahertz beam deflection based on a phase gradient metasurface with liquid crystal-enhanced cavity mode conversion

Abstract

Active manipulation of terahertz (THz) beam deflection and intensity is highly desired for possible applications in wireless communication, radar, and remote sensing. Here, by integrating the phase-gradient metasurfaces and tunable liquid crystal materials, we demonstrate an active THz beam deflection device based on polarization mode conversion. The resonant modes in the photonic cavity formed by the double-layer metasurface and the tunable anisotropic liquid crystal material in the cavity not only improve the polarization conversion efficiency of the device, but also actively regulate the resonance matching conditions. As a consequence, a beam deflection of 47.5° with 50% diffraction intensity at 0.69 THz is achieved in the x-to-y polarization conversion mode, and this beam can be actively modulated with an ultrahigh modulation depth of 99.6% by rotating the anisotropic optical axis of liquid crystals. Moreover, the proposed device can also work as the deflection of 32.5° in the y-to-x polarization conversion mode at 0.94 THz with a maximum diffraction intensity of 38% and an intensity modulation depth of 97.8%. This work provides a new approach based on liquid crystal photonic devices for wavefront manipulation and active modulation for THz waves.

Zn2+-Enhanced Lithium Magnesium Molybdate Ultralow Temperature Cofired Ceramics for Terahertz Wavefront Modulation Applications

“…The three structures are grouped to form a unit, and the arrangement pattern is determined as “010101...”, which is shown schematically in Figure f. The calculation details of the wavefront deflection angle are given in eq S6 in the Supporting Information. , The electric field intensity and phase of the wavefront of the whole array at 0.5 THz are simulated to verify our design. Figure presents the wavefront condition in the x – o – z plane under the incident of co-polarized and cross-polarized waves.…”

“…Wavefront modulation refers to the modulation of the inherent properties (amplitude, phase, and polarization state) of electromagnetic waves, which usually include vortex beams, airy beams, holographic imaging, and wavefront deflection. − 5G/6G communication systems need to use the above functions to cope with various application scenarios, which means that the development of functional devices for microwave and terahertz wavefront modulation has to be accelerated. − High efficiency, high frequency, low error, and low latency become the challenges that need to be addressed simultaneously. − In this context, ceramic materials with excellent dielectric properties in the microwave and terahertz regions have emerged. − This provides a new degree of freedom for the design of microwave and terahertz wavefront modulation devices, namely, the modulation of the performance parameters (dielectric constant, loss, temperature stability coefficient, amplitude, and phase) of the ceramic material. As long as the process-driven material parameters are adapted to the device structure, the challenge presented above can be accomplished perfectly.…”

Metalens in Improving Imaging Quality: Advancements, Challenges, and Prospects for Future Display

“…[200] Liquid crystal is the most frequently used phase change material in electrical tuning. [201][202][203] The representative work as, Kim et al achieved the dynamic switching of the holographic display in 2020, as Turning modes of liquid-crystal-integrated metasurface, ii. electrical tuning, iii.…”

“…[ 200 ] Liquid crystal is the most frequently used phase change material in electrical tuning. [ 201–203 ] The representative work as, Kim et al. achieved the dynamic switching of the holographic display in 2020, as shown in Figure (a) implementing three tuning methods: electrical tuning, thermal tuning, and pressure tuning, respectively, for the same device.…”

Diffractive optical computing in free space

“… TiO 2 38 , GaN 40 , Si 36 , etc. Power Efficiency GHz-THz Single wavelength 26% (classification) 66 31-72% (lens) 199 50% (beam steering) 200 68% (lens) 197 Broadband 76–91% (unidirectional imager) 201 N/A N/A 30–68% (lens) 202 Visible-NIR Single wavelength 99% 203 75% (lens) 204 80% (reflection, holography) 98 86% (lens) 38 Broadband 95% (lens) 205 N/A 8.4–11% 206 40% 40 Reconfigurability GHz-THz Layer swapping 18 N/A Electrically-tuned 121 , 207 (single-unit-level 0–2π phase programmability) Optical pumping tuned by DMD 208 Visible-NIR Spatial light modulator 27 N/A Substrate stretching 103 1D liquid crystal supercells 100 Spectral Bandwidth GHz-THz Lens 0.3–1.5 THz 209 0.4–0.6 THz 210 4.2–4.5 THz 211 0.3–0.8 THz 202 Imaging, Beam steering, Linear transformations 0.37–0.4...…”