Design of high-Q Cavities in Photosensitive Material-based Photonic Crystal Slab Heterostructures

We propose a novel concept for creating high-Q cavities in photonic crystal slabs (PCS). We show that photonic crystal slab-based double heterostructure cavities, formed by variations in the refractive index, can have large a Q-factor (up to Q = 1× 10), and that such cavities can be implemented in chalcogenide glasses using their photosensitive properties. DOI: 10.2529/PIERS060907042030 In the last few years the study of optical microcavities based on photonic crystal slabs has attracted much attention [1–10]. Almost all of these studies consider a PCS composed of a hexagonal array of cylindrical air holes in a high-index semiconductor slab. There are many possible device applications of compact and efficient PCS nanocavities, such as channel drop filters [1], low-treshold laser [5], and cavity QED experiments [6, 7]. The principal design aim for all these applications is to obtain a high quality factor within a small modal volume. A cavity is usually formed in either of two ways: forming a point cavity or forming a “heterostructure”. Microcavities with the highest Q values achieved to date, have been realised through the use of photonic crystal double-heterostructures [9, 10], where regions of slightly different lattice constant are combined in a single slab to create a cavity. Song et al., constructed double heterostructure PCS, in which a short length of crystal (PC2) with a lattice constant stretched in one direction, interrupts the main crystal (PC1) [9, 10] (see Fig. 1 ).