Analysis of a photonic crystal cavity based on absorbent layer for sensing applications

We present a photonic crystal (PhC) cavity based on a single hole defect filled with a sensitive absorbent layer for sensing applications. A preliminary study performed with the plane wave expansion method shows that the resonance peak of the cavity mode is 0.5 nm shifted for a 1 nm thickness variation of the sensitive layer. A Lorentz dispersion model implemented in a two-dimensional-finite difference time domain homemade code shows that the absorption of the layer can be exploited for enhancing the sensitivity of the sensor. With the proposed geometry, we find that a variation in the refractive index of 10−7 leads to a variation in the transmittivity of 23% at the resonance peak. This study is proposed for the development of a compact benzene sensor on a MgO doped lithium niobate PhC.