Design and optimization of nanooptical couplers based on photonic crystals involving dielectric rods of varying lengths

This study presents design and optimization of compact and efficient nanooptical couplers involving photonic crystals. Nanooptical couplers that have single and double input ports are designed to obtain efficient transmission of electromagnetic waves in desired directions. In addition, these nanooptical couplers are cascaded by adding one after another to realize electromagnetic transmission systems. In the design and optimization of all these nanooptical couplers, the multilevel fast multipole algorithm, which is an efficient full-wave solution method, is used to perform electromagnetic analyses and simulations. A heuristic optimization method based on genetic algorithms is employed to obtain effective designs that provide the highest efficiency values. Two types of optimization strategies are applied using nanorods with a fixed length and using nanorods with varying lengths. This way, photonic crystals consisting of irregular arrays of both identical and nonidentical dielectric elements are designed for the realization of nanooptical couplers. The designs and their numerical results show that it is possible to design and further improve efficient nanooptical couplers with simple and compact geometries based on the principles of photonic crystals. Using relatively simple geometries and a single material, the designed nanooptical couplers are more preferable than the available designs in the literature.


Rigorous designs of nano-optical couplers and absorbers with photonic crystals involving irregular arrays and nonidentical elements
Yazar, Şirin; Ergül, Özgür Salih; Department of Electrical and Electronics Engineering (2021-9)
This thesis presents design and analyses of compact and effective nano-optical couplers and absorbers based on photonic crystals. Single-input and double-input nano-optical couplers that provide electromagnetic wave transmission in desired directions are designed, and important parameters regarding their transmission efficiency are investigated. These designs are further cascaded by adding one after another to create nano-optical transmission systems, whose transmission characteristics are also examined. In...
Computational design of nanoantennas with improved power enhancement capabilities via shape optimization
Işiklar, Göktuǧ; Yazar, Şirin; İbili, Hande; Onay, Gülten; El Ahdab, Zeina; Ergül, Özgür Salih (2023-01-01)
Computational design and analyses of nanoantennas obtained via surface shape optimization are presented. Starting with a kernel geometry, free deformations are applied on selected surfaces to reach optimal designs that can provide improved power enhancement capabilities at desired frequencies. An in-house implementation of genetic algorithms is efficiently combined with the multilevel fast multipole algorithm developed for accurate solutions of plasmonic problems to construct the effective optimization envi...
Computational Design of Optical Couplers for Bended Nanowire Transmission Lines
Tuncyurek, Yunus Emre; Karaosmanoglu, Bariscan; Ergül, Özgür Salih (2017-07-01)
We present computational analysis, optimization, and design of optical couplers that can be useful to improve the transmission along bended nanowires. After demonstrating the deteriorated energy transmission due to sharp bends, which lead to out-of-phase nanowires and diffraction, we use a rigorous simulation environment to design efficient couplers made of spherical particles. For this purpose, an optimization module based on genetic algorithms is combined with the multilevel fast multipole algorithm, lead...
Design and Optimization of Nanoantennas for Nano-Optical Applications
Işıklar, Göktuğ; Ergül, Özgür Salih; Department of Electrical and Electronics Engineering (2020-9)
In this study, design and simulation of plasmonic nanoantenna structures to obtain high power enhancement capabilities at optical frequencies, as well as utilization of nanoantennas for imaging and sensing applications are presented. Plasmonic characteristics of nanoantennas, which depend on many parameters, such as material, frequency, geometry, and size, are investigated in detail via computational analyses of various nanoantenna structures. Numerical solutions of electromagnetic problems are performe...
Accurate solutions of scattering problems involving low-contrast dielectric objects with surface integral equations
Ergül, Özgür Salih (2007-11-16)
We present the stabilization of the surface integral equationsfor accurate solutions of scattering problems involvinglow-contrast dielectric objects. Unlike volume formulations,conventional surface formulations fail to provide accurateresults for the scatteredfields when the contrast of theobject is small. Therefore, surface formulations are requiredto be stabilized by extracting the nonradiating parts of theequivalent currents. In addition to previous strategies forthe stabilization, we introduce a n...
Citation Formats
Ş. Yazar and Ö. S. Ergül, “Design and optimization of nanooptical couplers based on photonic crystals involving dielectric rods of varying lengths,” TURKISH JOURNAL OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCES, vol. 30, no. 6, pp. 2339–2354, 2022, Accessed: 00, 2023. [Online]. Available: