Porous silicon one-dimensional photonic crystals (PSi-1DPCs) are capable of sensing solutions and liquids based on the smallest variation of the refractive indices. In the present work, we present a novel metal/PSi-1DPC as a liquid sensor based on Tamm/Fano resonances. The operating wavelength range is from 6.35 to 9.85 μm in the mid-infrared (MIR) spectral region. Different metals (Al, Ag, Au, and Pt) are attached to the top surface of the PSi-1DPCs structure to show Tamm/Fano resonances more clearly. To the best of our knowledge, it is the first time that Tamm/Fano resonances exhibit simultaneously in PSi-1DPCs within the same structure. The reflection spectra were calculated for the metal/PSi-1DPC structure by using the transfer matrix method (TMM) and the Bruggeman’s effective medium approximation (BEMA). The simulations show that the Tamm/Fano resonances are red-shifted towards the higher wavelengths with increasing the refractive index of the pores. The Ag/PSi-1DPC sensor showed the highest performance. Its sensitivity can be reached to the value 5018 nm/RIU with a high-quality factor of about 2149.27. We predict the proposed sensors can be easily fabricated and we expect them to show higher performance than other reported sensors of this type. Therefore, it will be of interest in the field of optical sensing in different fields.

In this research, the sensing NaI (sodium iodide)–water concentration is achieved by using a local resonant two-dimensional solid–liquid phononic crystal (PnC) design. The sensor design consists of a square arrangement from stainless steel as a host matrix and a periodic array of water-filled circular scatterers. The sensing mechanism is based on the resonance frequencies confined around the NaI waveguide embedded in the middle of the sensor structure. Numerical simulations are carried out based on the finite element method (FEM). Our results showed that the resonant peak frequency varies significantly with the different NaI–water concentrations in the waveguide. Also, the sensor can differentiate between concentrations from 6%–45% with a 1% step, which is very acceptable for accurate detection and can solve many challenges in medical applications. Further, the sensor provided high performance for all NaI–water concentrations. For example, for a concentration range of 6% − 7%, the sensor has a sensitivity of 1714 Hz, a resolution of 59.5 Hz, a quality factor of 1401, a figure of merit (FOM) of 28, and a signal-to-noise ratio of 2.

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