Ultra-High Sensitivity Terahertz Dual-Parameter Sensing Based on Eccentric-Core Photonic Crystal Fiber

Abstract

To overcome the temperature cross‑sensitivity common in single‑parameter sensing, as well as the insufficient sensitivity and limited penetration depth of conventional near‑ and mid‑infrared sensors, this paper proposes an ultrahigh‑sensitivity THz dual‑parameter sensor based on an eccentric PCF. The proposed structure features an outer surface coated with a molybdenum disulfide (MoS₂) layer, which creates a surface plasmon resonance (SPR) sensing channel specifically designed for detecting refractive index. Simultaneously, a thermosensitive liquid is filled into the central air holes of the PCF, forming a directional coupling sensing channel dedicated to precise temperature measurement. Numerical simulations show that the two sensing channels exhibit low cross-sensitivity. Within the refractive-index range of 1.33–1.38, the SPR channel achieves an average refractive-index sensitivity of 1080.00 μm/RIU and an FOM of 100.93 RIU⁻¹. For temperatures ranging from − 20 to 40 °C, the directional-coupling channel achieves a temperature sensitivity of − 0.89 μm/°C and an FOM of 2805.50 RIU⁻¹. In addition, benefiting from the characteristics of terahertz-band plasmon‑like resonance, the sensor can theoretically achieve a penetration depth of tens of micrometers. With ultrahigh sensitivity and large penetration depth, the proposed dual‑parameter sensor provides a promising basis for biochemical sensing and trace detection.