Coupling of an Off-Axis Parabolic Mirror, Hyper-Hemispherical High-Resistivity Silicon Lens, and Subwavelength Terahertz Detector for High-Resolution Compact Range Detection

This paper proposes and experimentally validates a hyper-hemispherical high-resistivity silicon lens-coupled high-electron-mobility transistor (HEMT) detector integrated with an off-axis parabolic mirror (OAP) for high-precision terahertz compact range measurements. The design focuses on efficient optical coupling of the silicon lens and minimizing the field of view (FOV) through OAP integration. A prototype detection module is fabricated, demonstrating excellent agreement between the measured FOV and theoretical predictions. Experimental results show a six-fold improvement in spatial resolution at 340 GHz, with the FOV reduced from 9° to $\mathbf{1. 5}^{\circ}$. The proposed design not only suppresses parasitic resonances and spurious signal interference but also maintains broadband responsivity and polarization sensitivity, providing a robust solution for compact range detetion.