Oxidation-free nanoscale optomechanical sensor incorporating a triangular truss resonator for crosstalk-free bimodal pressure and temperature sensing

Recently, we have witnessed significant advancements made by researchers in using silver-based Metal-Insulator-Metal (MIM) plasmonic devices for their improved performance. However, the practical applicability of these sensors is still under scrutiny. Very few studies have been conducted looking for alternative approaches to improve the viability of deploying these sensors for use in challenging operational conditions. This paper articulates a novel MIM-based dual-function optomechanical sensor utilizing oxidation-free gold as the plasmonic material, capable of sensing pressure and temperature in parallel. To the best of the authors' knowledge, this marks the first instance of investigating an optical MIM pressure sensor using oxidation-resistant gold as the plasmonic material. The proposed sensor consists of a Triangular Truss Resonator (TTR) and a pair of Rectangular Cavities (RCs) coupled to a straight waveguide. The TTR is utilized for sensing pressure, while the RCs are responsible for detecting temperature variations. Employing the Finite Element Method (FEM), we numerically investigated the device's transmission spectrum, which comprised two independent resonant wavelengths, namely mode 1 and mode 2, enabling dual-function sensing capabilities with distinct and independent responses. The sensor demonstrates a notable pressure sensitivity of 77.1 nm MPa^-1, along with a temperature sensitivity of 0.488 nm °C^-1. Its impressive performance metrics, coupled with the use of oxidation-resistant gold, not only ensure enhanced performance and stability of the sensor but also offer a significantly extended operational lifespan. These traits highlight the sensor's potential for real-world applications in diverse scenarios, positioning it as a compelling candidate for substituting oxidation-prone silver and finding its use in real-world innovative optomechanical sensing platforms.