Refractive Index Sensor Using Photonic Serial Loop Structures

Introduction: This work presents a theoretical and numerical approach to the design of a highly sensitive refractive index sensor operating in the visible spectrum. The proposed sensor features a simple configuration utilizing serial loop structures that can support defect modes within the photonic bandgap. Methods: These defect modes arise from the introduction of geometric and material imperfections at the loop level of the structure. By employing continuous medium interface response theory, we calculate the Green function for composite systems, enabling the determination of dispersion relations and transmission rates. Results: Numerical simulations indicate that the sensor achieves a remarkable sensitivity of S =1090 nm/RIU and a detection limit DL = 7.10-3 RIU. The quality factor Q of the sensor demonstrates distinct characteristics, exhibiting a high sensitivity to minute variations in refractive index. Conclusion: These results show that the structure we have designed is suitable for applications such as biosensors, gas detectors and medical diagnostic devices.