Limited-diffraction light propagation with axicon-shape photonic crystals

Abstract

Electromagnetic beams are subject to spatial spreading as they propagate. I have investigated the light propagation passing through a finite-aperture, which is obtained by two-dimensional square-lattice photonic crystals (PCs). It is found that the beam that is coupled to the free-space by exiting the axicon-shape PC resists considerably against the diffraction. The inspection of the beam profile in the transverse to the propagation direction reveals the appearance of the side-lobes, and I have attributed the limited-diffraction beam propagation to these artificially created lobes. I optimize the length of the aperture while keeping the width constant and show that an order of magnitude improvement for beating the diffraction length is achievable. The advantages of the presented PC-based axicon over the bulk refractive axicons are the compactness and integrated nature of the former one, in addition to the flexibility of engineering individual unit cells of PC structure. (C) 2009 Optical Society of America