Terahertz Single-Photon Measurement System Based on Superconducting MKIDs Array

Terahertz (THz) imaging has emerged as a critical technology for security screening, offering non-invasive detection of concealed objects. However, existing systems face challenges in balancing sensitivity, imaging speed, and scalability. Superconducting Microwave Kinetic Inductance Detectors (MKIDs) present a promising solution due to their low noise, high sensitivity, and compatibility with large-scale arrays. This study focuses on developing a 600 GHz MKID-based imaging system optimized for human security screening, addressing the limitations of current THz imaging technologies. The system employs a hexagonal array of 331 MKID pixels fabricated on a 3-inch high-resistivity silicon wafer. Each pixel consists of a lumped-element resonator with an interdigitated capacitor (IDC) and a thin Al inductor for THz absorption. A Silicon-on-Insulator (SOI) substrate with a suspended optical cavity structure enhances photon absorption efficiency at 600 GHz. The readout system utilizes frequency-domain multiplexing, enabling parallel signal processing across multiple pixels. Cryogenic cooling to 40 mK is achieved using a dilution refrigerator, and THz radiation is generated by a calibrated blackbody source. The system demonstrates a single-pixel noise equivalent power (NEP) of 9.3×10−15W/Hz1/2 and a noise equivalent temperature difference (NETD) of 0.028K/Hz1/2. Compared to existing systems, this design achieves a 62% reduction in noise and 96% lower power consumption per pixel. This work presents a high-performance THz imaging system based on superconducting MKID arrays, achieving unprecedented sensitivity and imaging speed for security screening applications. The innovative use of SOI-based optical cavities and frequency-domain multiplexing enables scalable, low-power operation. Future efforts will focus on expanding pixel counts, optimizing thermal management, and integrating real-time imaging algorithms for practical deployment in security checkpoints.