Improving unrestricted imaging quality of a triangular lattice photonic crystal slab by modifying surface configuration

► We propose a photonic crystal (PC) structure based on Si material only by replacing square lattice, proposed by Luo, with triangular lattice to obtain an unrestricted imaging. ► Imaging quality of this triangular lattice PC slab is studied using the finite-difference time-domain simulations. ► In order to achieve a high-quality image, an appropriate surface termination is chosen. In addition, by adjusting the surface air-hole radius of the PC slab, the imaging quality can be further improved. ► Coupled-mode theory analysis shows that these methods can excite two kinds of surface modes, which can improve the quality of the image by coupling with the Bloch wave in the PC.