Impact of the parasitic photothermal effect on the performance of an optomechanical nanoantenna for NIR radiation detection

This paper investigates the impact of the opto-thermomechanical (OTM) parasitic response of an optomechanical nanoantenna on the main opto-electromechanical (OEM) transduction mechanism involved in the near-infrared (NIR) radiation detection. Through comprehensive experimental and computational analyses, we have modelled how this parasitic effect overlaps with the desired opto-electromechanical response. Utilizing COMSOL Multiphysics, we have simulated thermal, optical, and mechanical interactions within the optomechanical structure. Our findings indicate that the parasitic OTM effect significantly influences the device's mechanical deflection, driven primarily by localized heating at the microcantilever's free end. Experimental data validates simulation results, demonstrating the parasitic response's dominance over the intended functionality. A figure of merit (FoM), defined as the ratio between the transducing OEM signal over the parasitic OTM response has been defined to quantify the performance of the optomechanical nanoantenna detector, as well as to propose geometry design improvements to optimize this performance.