Simultaneous measurement of relative humidity and temperature using EIT-like effect in photonic crystal cavity coupled system integrated with PVA and graphene

Abstract

In this work, we propose a sensor based on a photonic crystal nanobeam cavity (PCNC) coupled system integrated with Polyvinyl alcohol (PVA) and graphene, which uses an electromagnetically induced transparency-like (EIT-like) effect for the simultaneous measurement of relative humidity (RH) and temperature (T). The structure consists of a bus waveguide and two types of one-dimensional PCNC supporting the dielectric and air mode resonance, respectively. The RH-sensitive material PVA is used in the dielectric mode cavity to increase the RH sensitivity and anti-interference ability. We demonstrate that the EIT-like transparency window can be actively and flexibly modulated by adjusting the Fermi level of graphene. In addition, the ability of the system to simultaneously detect RH and T is proved by using the three-dimensional finite-difference time-domain (3D-FDTD) method and the sensor matrix. The RH sensitives for the dielectric and air modes are −542.0 pm/%RH and −258.2 pm/%RH, respectively. The T sensitives for the dielectric and air modes are −14.6 pm/K and 35.4 pm/K, respectively. The sensor achieves a strong anti-interference ability and its footprint is only 12 μm × 2.02 μm. Therefore, our proposed sensor has potential applications in food storage, preservation of museum collections, human health, and biological and chemical experiments.