Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the experimental realization of an isotropic complete photonic band gap (PBG) in a 2D disordered dielectric structure. This structure is designed by a constrained optimization method, which combines advantages of both isotropy due to disorder and controlled scattering properties due to low-density fluctuations (hyperuniformity) and uniform local topology. Our experiments use a modular design composed of Al 2 O 3 walls and cylinders arranged in a hyperuniform disordered network. We observe a complete PBG in the microwave region, in good agreement with theoretical simulations, and show that the intrinsic isotropy of this unique class of PBG materials enables remarkable design freedom, including the realization of waveguides with arbitrary bending angles impossible in photonic crystals. This experimental verification of a complete PBG and realization of functional defects in this unique class of materials demonstrate their potential as building blocks for precise manipulation of photons in planar optical microcircuits and has implications for disordered acoustic and electronic band gap materials. The first examples of synthetic materials with complete photonic band gaps (PBGs) (1, 2) were photonic crystals using Bragg interference to block light over a finite range of frequencies. Because of their crystallinity, the PBGs are highly anisotropic, a potential drawback for many applications. The idea that a complete PBG (blocking all directions and all polarizations) can exist in isotropic disordered systems is striking, because it contradicts the longstanding intuition that periodic translational order is necessary to form PBGs. The paradigm for PBG formation is Bloch's theorem (3): a periodic modulation of the dielectric constant mixes degenerate waves propagating in opposite directions and leads to standing waves with high electric field intensity in the low dielectric region for states just above the gap and in the high dielectric region for states just below the gap. Long-range periodic order, as evidenced by Bragg peaks, is necessary for this picture to hold. The intrinsic anisotropy associated with periodicity may limit the scope of PBG applications greatly and places a major constraint on device design. For example, although 3D photonic crystals with complete PBGs have been fabricated for two decades (4), 3D waveguiding continues to be a challenge. Very recently, Noda and coworkers reported the first successful demonstration of 3D waveguiding (5). However, they found that because of the mismatch of the propagation modes in line defects along various symmetry orientations, vertical-trending waveguides must follow one particular major symmetry direction to effectively guide waves out of the horizontal symmetry plane in a 3D woodpile photonic crystal (5).Recently, disordered photonic media and random textured surfaces have attracted incr...

Abstract:We report the first experimental demonstration of guiding, bending, filtering, and splitting of EM wave in 2D disordered PBG materials, along arbitrarily curved paths, around sharp bends of arbitrary angles, and through Y shape junctions.©2012 Optical Society of America OCIS codes: 130.5296, 130.7408, 160.5293, 160.5298 Line defects in photonic band gap (PBG) materials can confine and guide light through narrow channels and around sharp corners, which is important for large scale all-optical circuit applications [1]. An enormous range of technological developments in telecommunication industry, laser engineering, optical computing, spectroscopy, and radiation, have been suggested, when light with selected frequencies can be directed along chosen paths or be confined within a specific volume in PBG materials [2]. Conventional PBG materials are periodic structures, in which only limited numbers of rotational symmetries are allowed. Angular differences make it difficult to form a complete PBG in periodic structures without a large dielectric contrast. The orientations of channels cut in photonic crystals for light guiding are also restricted by the crystal symmetries, limiting 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 (HPU) 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 wave-guiding and filtering channels with arbitrary bending angles in them.In this paper, we report the first experimental demonstrations of guiding, bending, filtering, and splitting of electromagnetic wave in 2D isotropic disordered PBG materials, along straight or arbitrarily curved paths, around sharp bends of arbitrary angles, and through Y shape junctions. We demonstrate broad band pass through channels of various shapes, as well as versatile and flexible defect tuning abilities for narrow band filtering, in these disordered PBG materials. In our study, nearly 100 percent transmission of electromagnetic waves around sharp corners of arbitrary angles with bending radii smaller than one wavelength is observed experimentally.The 2D isotropic HPU disordered PBG material constructed for this study consists of a network of Al 2 O 3 cylinders and thin sheets.. Each cylinder has three nearest neighbors to which it is connected by sheets. The cylinders are particularly important for forming PBG for the TM polarization, while the connected sheets are important for the TE polarization. There is neither Bragg scattering nor long range order in this structure. It was argued that hyperuniformity, combined with uniform local topology and short-range geometric order can explain the origin of PBGs in these disordered materials [3]. The PBGs are as...

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...

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