Browsing by Subject "Photonic structure"

Now showing 1 - 7 of 7

Open Access
Asymmetric light propagation in chirped photonic crystal waveguides
(Optical Society of American (OSA), 2012) Kurt H.; Yilmaz, D.; Akosman, A.E.; Özbay, Ekmel
We report numerical and experimental investigations of asymmetric light propagation in a newly designed photonic structure that is formed by creating a chirped photonic crystal (PC) waveguide. The use of a non-symmetric distribution of unit cells of PC ensures the obtaining of asymmetric light propagation. Properly designing the spatial modulation of a PC waveguide inherently modifies the band structure. That in turn induces asymmetry for the light's followed path. The investigation of the transmission characteristics of this structure reveals optical diode like transmission behavior. The amount of power collected at the output of the waveguide centerline is different for the forward and backward propagation directions in the designed configuration. The advantageous properties of the proposed approach are the linear optic concept, compact configuration and compatibility with the integrated photonics. These features are expected to hold great potential for implementing practical optical rectifier-type devices. © 2012 Optical Society of America.
Open Access
Diffraction inspired unidirectional and bidirectional beam splitting in defect-containing photonic structures without interface corrugations
(American Institute of Physics Inc., 2016) Colak, E.; Serebryannikov, A. E.; Usik, P. V.; Özbay, Ekmel
It is shown that strong diffractions and related dual-beam splitting can be obtained at transmission through the nonsymmetric structures that represent two slabs of photonic crystal (PhC) separated by a single coupled-cavity type defect layer, while there are no grating-like corrugations at the interfaces. The basic operation regimes include unidirectional and bidirectional splitting that occur due to the dominant contribution of the first positive and first negative diffraction orders to the transmission, which is typically connected with different manifestations of the asymmetric transmission phenomenon. Being the main component of the resulting transmission mechanism, diffractions appear owing to the effect exerted by the defect layer that works like an embedded diffractive element. Two mechanisms can co-exist in one structure, which differ, among others, in that whether dispersion allows coupling of zero order to a wave propagating in the regular, i.e., defect-free PhC segments or not. The possibility of strong diffractions and efficient splitting related to it strongly depend on the dispersion properties of the Floquet-Bloch modes of the PhC. Existence of one of the studied transmission scenarios is not affected by location of the defect layer.
Open Access
Large bandwidth mode order converter by differential waveguides
(Optical Society of American (OSA), 2015) Oner, B.B.; Üstün, K.; Kurt H.; Okyay, Ali Kemal; Turhan-Sayan G.
In this article, we propose a large bandwidth mode-order converter design by dielectric waveguides with equal lengths but different cross-sectional areas. The efficient conversion between even and odd modes is verified by inducing required phase difference between the equal length waveguides of different widths. Y-junctions are composed of both tapered mode splitter and combiner to connect mono-mode waveguide to multi-mode waveguide. The converted mode profiles at the output port show that the device operates successfully at designed wavelengths with wide bandwidth. This study provides a novel technique to implement compact mode order converters and direction selective/sensitive photonic structures. © 2015 Optical Society of America.
Open Access
Physics and applications of defect structures in photonic crystals
(Springer, 2003) Özbay, Ekmel; Bayındır, Mehmet; Shumovsky, Alexander S.; Rupasov, V. I.
We propose and demonstrate a new type of propagation mechanism for electromagnetic waves in photonic band gap materials. Photons propagate through coupled cavities due to interaction between the highly localized neighboring cavity modes. We report a novel waveguide, which we called coupled-cavity waveguide (CCW), in three-dimensional photonic structures. By using CCWs, we demonstrate lossless and reflectionless waveguide bends, efficient power splitters, and photonic switches. We also experimentally observe the splitting of eigenmodes in coupled-cavities and formation of defect band due to interaction between the cavity modes. The tight-binding (TB) approach, which is originally develop for the electronic structures, is applied to the photonic structures, and compared to the experimental results. Our achievements open a new research area, namely physics and applications of coupled-cavities, in photonic structures. We think that our results are very important for constructing future all-optical components on a single chip.
Open Access
Two types of single-beam deflection and asymmetric transmission in photonic structures without interface corrugations
(Optical Society of America, 2016) Serebryannikov, A. E.; Colak, E.; Magath, T.; Özbay, Ekmel
We study single-beam deflection and asymmetry in transmission, two aspects of the same phenomenon that appear in the topologically simple, nonsymmetric, photonic crystal (PhC)-based structures without corrugations at the interfaces. Strong diffractions enabling efficient blazing, i.e., redistribution of the incident wave energy in favor of the desired higher diffraction order(s), can be achieved owing to the defect-like layer(s) embedded in a regular slab of PhC. The main features, together with the peculiarities of the two basic transmission types and relevant coupling and deflection scenarios, are discussed, for one of which a part of the PhC works in the evanescent-wave regime. Performances are suggested, in which efficient single-beam deflection and asymmetry in transmission can be obtained even when the irregular layer is deeply embedded. More than 97% of the incident wave energy can be converted into a single deflected beam that is associated with the first negative diffraction order, even though the entire structure is nonsymmetric and the diffractive element is located at some distance from the incidence interface.
Open Access
Two-dimensional complex parity-time-symmetric photonic structures
(American Physical Society, 2015-02) Turduev, M.; Botey, M.; Giden, I.; Herrero, R.; Kurt, H.; Özbay, Ekmel; Staliunas, K.
We propose a simple realistic two-dimensional complex parity-time-symmetric photonic structure that is described by a non-Hermitian potential but possesses real-valued eigenvalues. The concept is developed from basic physical considerations to provide asymmetric coupling between harmonic wave components of the electromagnetic field. The structure results in a nonreciprocal chirality and asymmetric transmission between in- and out-coupling channels into the structure. The analytical results are supported by a numerical study of the Bloch-like mode formations and calculations of a realistic planar semiconductor structure. © 2015 American Physical Society.
Open Access
Two-dimensional ferroelectric photonic crystals: Optics and band structure
(Taylor & Francis Inc., 2013-09-20) Simsek S.; Mamedov, A. M.; Özbay, Ekmel
In this report we present an investigation of the optical properties and band structure calculations for the photonic structures based on the functional materials- ferroelectrics. A theoretical approach to the optical properties of the 2D and 3D photonic crystals which yields further insight in the phenomenon of the reflection from different families of lattice planes in relation to the presence of photonic gaps or photonic bands. We calculate the photonic bands and optical properties of LiNbO3 based photonic crystals. Calculations of reflection and transmission spectra show the features correspond to the onset of diffraction, as well as to additional reflectance structures at large values of the angle of incidence. © 2013 Copyright Taylor and Francis Group, LLC.