2-Bit Terahertz Angle Tunable Chiral Encode for Polarization and Incidence Angle Detection

<jats:p>Polarization and incidence angle detection plays a crucial role in modern photonic and electromagnetic systems. Conventional approaches typically rely on bulky optical components, mechanical scanning, or complex detector arrays, which suffer from high cost, limited integration density, and slow response. Developing compact, passive, and multifunctional devices capable of simultaneously resolving both polarization and angle information remains a significant challenge in the field. Here, we propose and experimentally demonstrate a 2-bit terahertz (THz) angle-tunable-chiral-encoder (ATCE) based on quasi-bound states in the continuum (Q-BIC). The device consists of bilayer asymmetric dual split-ring resonators (ADRR1 and ADRR2) with an intermediate polyimide (PI) layer on a silicon substrate. By tuning the oblique incidence angle θ (±30°), complementary switching of quasi-BICs and complete reversal of chiral response are achieved at 0.757 THz (f1) and 0.806 THz (f2), enabling states of “0” and “1”. Leveraging this distinct angle- and polarization-sensitive response, we further demonstrate its capability for detecting both the incidence angle and polarization state of THz waves. This work provides a simple and efficient platform for THz encoders and intelligent wave sensing, with potential applications in information processing, dynamic modulation, chiral sensing, and polarization detection.</jats:p>