Freeform wave-guiding and tunable frequency splitting in isotropic disordered photonic band gap materials

Abstract

Using a new class of isotropic disordered photonic bandgap material, we demonstrate freeform photonics waveguides with arbitrary shapes and multi-channel frequency splitters with versatile tuning abilities, useful for signal processing and all-optical circu it applicat ions. ©2012 Optical Society of America OCIS codes: 130.5296, 130.7408, 160.5293, 160.5298 Inside photonic band gap (PBG) materials, light with selected frequencies can be confined and directed along chosen paths of line defects and around sharp corners [1], which is important for a large range of technological developments in telecommunication industry, laser engineering, optical computing, spectroscopy, etc [2]. However, in conventional PBG materials, periodic photonic crystals, only a limited number of rotational symmetries are allowed. The orientations of channels cut in photonic crystals for light guiding are strictly limited by the crystal symmetries, a disadvantage for potential applications.Contradicting the long standing intuition that periodicity or long-range translational order is required in photonic band gap formation, a new class of disordered hyperuniform materials was predicted to possess sizeable and isotropic photonic band gaps [3]. Recently, we have experimentally observed isotropic PBG in these disordered materials [4]. In these isotropic disordered structures there are no preferential symmetry directions; hence it becomes possible to construct freeform channels with arbitrary shapes and bends in them [5]. We also demonstrated that line defects and point defects in these structures can be flexibly decorated to produce sharp resonant structures useful for filtering [5].In terms of signal processing, photonic devices have many advantages over electronics, especially the large bandwidth. Since photons do not interact with each other, light signals of different frequencies can travel independently and simultaneously within the same channel. Hence, very compact frequency splitter becomes essential for large scale all-optical circuit applications. Since this new class of hyperuniform PBG material is isotropic and disordered, it provides the combined advantages of freeform direction choices not restricted by crystalline symmetries and flexible resonant tuning abilities. These advantages will enable the design of complex photonic circuits, for example, compact and tunable frequency splitters.In this paper, we report the first experimental demonstrations of freeform wave-guiding through channels of arbitrary shapes, as well as tunable multi-channel frequency splitting of electromagnetic waves in 2D hyperuniform isotropic disordered PBG materials.The 2D isotropic hyperuniform disordered PBG material constructed for this study consists of a network of Al 2 O 3 cylinders, arranged at a hyperuniform disordered point pattern [3,5]. There is neither Bragg scattering nor long-range translational order in this structure. It was argued that hyperuniformity, combined with uniform local topology and short-range geometric order can exp...