The effects of optical and material properties on designing of a photonic crystal mechanical sensor

Photonic crystal nanocavities, which can be used to localize electromagnetic fields in a low refractive index region, hold great promise in fabricating micromechanical sensors for their potential applications in physical, chemical and biological engineering. In this paper, effects of optical and material properties on the performance of three different types of photonic crystal based mechanical sensors, i.e., force, displacement, and strain sensors, are investigated. The microcantilevers of sensors are made in Si and Si/SiO₂ and exhibited in air and water atmosphere. As we found, both the resonant wavelength and the resonant wavelength shift for microcantilever mechanical sensors exhibit a linear relationship to the signal detection parameters (i.e., force, displacement, and strain) both in air and water. The sensitivity of force and strain sensors operated in water is higher than that in air. Si/SiO₂ bilayer microcantilever sensor shows a higher sensitivity in force detection, whereas the Si cantilever sensor shows a higher sensitivity in strain and vertical displacement detection. The optical, material and mechanical properties of sensor material have great effect on the sensitivity of the new photonic crystal based microcantilever mechanical sensor.