High-performance all-optical pressure sensor utilizing optimized photonic crystal nanocavity

This paper presents the design and development of an optical pressure sensor based on a two-dimensional photonic crystal nanocavity, operating within the wavelength range of 1950.2-2091.4 nm. The sensing mechanism is based on the linear relationship between the shift in resonance wavelength and the refractive index variation of the cavity induced by the external applied pressure. The refractive index variation is modeled using COMSOL Multiphysics, and the cavity design is thoroughly optimized by adjusting the size and number of air holes in and around the cavity to achieve a high-quality factor and enhanced sensitivity. The photonic band structure and sensing parameters are evaluated and analyzed using plane wave expansion and finite-difference time-domain techniques, respectively. The results indicate a red shift in the resonant wavelength with increasing pressure, achieving an extraordinary high-quality factor of 1.0443×10⁶, and a pressure sensitivity of 20.17 nm/GPa. Furthermore, the sensor exhibits a maximum refractive index sensitivity of 506.184 nm/RIU, a high figure of merit of 2.4155×10⁵RIU^-1, and a low detection limit of 4.14×10^-7RIU, collectively indicating excellent sensing performance. In addition, the sensor demonstrates stable operation in a wide temperature range (0°C-540°C), and a detailed investigation is conducted to evaluate the impact of fabrication-induced roughness on overall performance.