A Novel Square-Core Photonic Crystal Fiber Sensor with Enhanced Sensitivity for Trace-Level Detection of Agricultural Pesticides

Abstract

This study proposes and numerically evaluates a terahertz (THz) photonic crystal fiber (PCF) sensor with a hexagonal cladding structure and a square-shaped core for ultra-sensitive pesticide detection. The numerical results demonstrate exceptionally high relative sensitivities for ten commonly used pesticide chemicals, namely methyl parathion, dimethoate, methomyl, empenthrin, terallethrin, cyphenothrin, prallethrin, fenvalerate, cypermethrin, and allethrin. Among them, cypermethrin exhibits the lowest confinement loss of 7.84 × 10^–14 dB/m with the relative sensitivity of 99.93177% at the optimum frequency of 1.7 THz, indicating excellent sensing performance. It is proven that the proposed square-core configuration significantly enhances the light–analyte interaction, leading to improved sensing performance for the detection of different pesticide analytes based on their individual optical responses. The proposed PCF structure shows strong potential for high-precision pesticide detection by distinguishing different analytes based on their refractive index-dependent optical responses and promising applications in industrial terahertz waveguide technologies, as well as in real-time agricultural monitoring and food production systems, to detect pesticide residues, ensuring improved crop safety, food quality, and environmental protection.

Received: 25 March 2026 | Revised: 10 July 2026 | Accepted: 20 September 2026

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Author Contribution Statement

B. Swaathy: Methodology, Formal analysis, Data curation, Writing – original draft. R. Niranjana: Methodology, Validation, Formal analysis, Data curation, Writing – review & editing. Ancemma Joseph: Conceptualization, Validation, Visualization, Supervision, Project administration, Funding acquisition. P. Mohanraj: Validation, Writing – review & editing.