Liquid Crystal Purity Detection Using Surface Plasmon Resonance Phenomena

Abstract

The development of Liquid crystals (LCs) based technology is happening at a quick pace to design various switchable optical devices due to the exceptional electro-optical properties of LCs. The purity of an LC is the primary concern for these applications. Here, we propose a straightforward and effective optical method to detect the purity of an LC using surface plasmon resonance phenomena. The Kretschmann configuration is used in the proposed technique, and an LC cavity is formed over the metal layer using a glass substrate. Various impurities are added in the pure LC, which disturbs the molecular arrangement of the LC molecules, and hence, the refractive index of LC changes. We have numerically calculated and experimentally observed the shift in the resonance angle for the impure LC as compared to the pure one. The impurity in the LC is evident from the significant shift in the resonance angle. The experimentally measured sensitivity of the proposed technique is around 150⁰/RIU, which is comparable to the other Kretschmann configuration-based sensors. This sensitivity is suitable for LC material, especially for their uses in optics and photonics applications. In comparison to the existing LC purity detection method, the key advantages of the proposed method are its lightweight, compact design, label-free detection, and real-time monitoring capabilities.