Experimental and numerical study of lithium niobate photonic crystal cavities - Application for gas sensing

When we create a cavity surrounded by a photonic bandgap (PBG) structure with a well defined defect, it leads to the appearance of electromagnetic (EM) mode in the bandgap region called "the defect mode". We report the first study and realization of two types of lithium niobate photonic cavities (LiNbO3 PhCs). The choice of the LiNbO3 substrate is motivated by its capability of combining piezoelectric, electro-optical [1], acousto-optical [2], non-linear optical [3] properties, which offers the perspective of controlling the operating point of photonic devices such as sensors. The two cavities are schematically depicted in figure 1, namely a single hole defect (SHD) cavity in (a) and an H1 cavity in (b). The cavities were fabricated by focused ion beam (FIB) milling [4], on annealed proton exchange (APE) strip waveguide.