UNCORRECTED PROOF ARTICLE INFO Article history: Received 23 April 2016 Accepted 17 June 2016 Available online xxx Keywords: Power combiner Coupled resonator optical wave- guide Photonic crystal THz ABSTRACT A new 2 × 1 power combiner scheme based on two-dimensional photonic crystal has been designed us- ing hexangular waveguides. These waveguides are created by reducing the radius of inner rods in alternate manner which subsequently leads to coupled resonator optical waveguide structure. In this design, the outer hexagon has two input ports and the output port is embedded in the inner hexagonal. Due to geometrical and metallurgical engineering, the photonic bandgap locates in the THz region. Three different radii of coupled resonator optical waveguide rods have been studied. It has been shown that the structure with largest inner rods provides better power output. © 2016 Published by Elsevier Ltd. Optik - International Journal for Light and Electron Optics xxx (2016) xxx-xxx Contents lists available at ScienceDirect Optik - International Journal for Light and Electron Optics journal homepage: www.elsevier.com Photonic crystal power combiner based on hexagonal waveguides Mona Zahednamazi, a Alireza Alikhani, a, ⁎ Seyedeh Mehri Hamidi b a Aerospace Research Institute, Ministry of Science, Research and Technology, Shahrake Gharb, Tehran, 14665-834, Iran b Shahid Beheshti University, Laser and Plasma Research Institute, Magneto-Plasmonic Lab, Daneshju Boulevard, Tehran 1983969411, Iran, 1. Introduction A power combiner is a passive device which accepts multiple incoming signals, combines them and transfers an output signal. When it is used in reverse, it may function as a power splitter [1]. There are many designs for power combiners with operating frequency ranges in radio frequency (RF) or microwave [2–6]. Electronic RF power combiners are divided into two main cate- gories: Resistive [7] and hybrid [8] power combiners that use resistors and transformers, respectively. Resistive approach is simple and has low cost although its loss rate is high. On the other hand, the hybrid approach has low loss but suffers from complexity and high cost. In microwave frequency range, the common power combiner is Wilkinson combiner [9]. Another type of power combiner that has recently attracted much attention is photonic crystal (PhC) based power combiner. This type commonly encompasses two configurations of T- and Y- junctions [10–14]. Photonic Crystal is a material with periodicity in refractive index and it is a unique medium for wave optical engineering due to its photonic bandgap [15]. By designing the waveguides propagating light with a frequency within the photonic bandgap, var- ious optoelectronic devices can be designed [16–20]. Employing PhCs in optoelectronic devices results in size reduction and low cost because PhC circuit has a small number of commercial components. The most important characteristic which makes photonic crystals unique medium for optoelectronic devices and in this case for power combiners is the possibility of designing lossless bends. This facility is provided by coupled resonator optical waveguide (CROW) which is an array of cavity defects that traps electromagnetic wave for the frequency within the photonic bandgap an provides the outstanding feature of making lossless bend [21]. In this paper, we design a new structure for power combining which has two hexagonal waveguides that guide the light with THz frequency. We study three CROW structures with different radii of microcavity rods. We have simulated the propagation of light wave using FullWAVE module in RSoft CAD which is based on finite difference time domain (FDTD) method. Also, the perfectly matched layers have been considered as boundary condition. ⁎ Corresponding author. Email address: aalikhani@ari.ac.ir, roboali@gmail.com (A. Alikhani) http://dx.doi.org/10.1016/j.ijleo.2016.06.068 0030-4026/© 2016 Published by Elsevier Ltd.