Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 4Citation - Scopus: 4Photonic Crystal Textiles for Heat Insulation(American Institute of Physics, 2023) Çetin, Zebih; Tunçtürk, Yiğit; Sözüer, Hüseyin SamiIn this work, we have studied transmission properties of a photonic crystal-like structure that can be woven into fabrics. An interesting possibility emerges when considering the potential energy savings through suppression of radiation. It is a well-established fact that every object at a finite temperature inherently emits electromagnetic waves. Within the specific context of the human body, radiation takes on a crucial role as a fundamental mechanism governing heat dissipation. Thus, exploring ways to manage or mitigate this radiation could offer innovative approaches to optimize energy consumption and enhance heat regulation. It is well known that a photonic crystal can block electromagnetic energy with a specific frequency that is falling into a photonic bandgap. By using the numerical method called a finite-difference time domain, we have shown that this property of a periodic structure can be used to make textiles to save energy that is used to heat a human body environment. Numerical calculations have shown that by using the proposed photonic crystal structure, 53 % of electromagnetic energy is reflected. Although we mainly focused on textiles, it is worth highlighting that the same fundamental principle can be extended to diverse fields; for example, this structure can be integrated with construction materials and effectively function as a radiation heat insulator. © 2023 Author(s).Article Citation - WoS: 1Citation - Scopus: 1Fully Three-Dimensional Analysis of a Photonic Crystal Assisted Silicon on Insulator Waveguide Bend(World Scientific Publishing, 2018) Eti, Neslihan; Çetin, Zebih; Sözüer, Hüseyin SamiA detailed numerical study of low-loss silicon on insulator (SOI) waveguide bend is presented using the fully three-dimensional (3D) finite-difference time-domain (FDTD) method. The geometrical parameters are optimized to minimize the bending loss over a range of frequencies. Transmission results for the conventional single bend and photonic crystal assisted SOI waveguide bend are compared. Calculations are performed for the transmission values of TE-like modes where the electric field is strongly transverse to the direction of propagation. The best obtained transmission is over 95% for TE-like modes.Article Citation - WoS: 12Citation - Scopus: 12High Transmission Through a 90° Bend in a Polarization-Independent Single-Mode Photonic Crystal Waveguide(The Optical Society, 2015) Erol, Adem Enes; Sözüer, Hüseyin SamiWe propose a polarization-independent single-mode waveguide, using a two-dimensional square photonic crystal with a complete band gap. The waveguide is tuned such that both TE and TM modes have the same group velocity and zero group velocity dispersion at the centergap frequency. We also present results for a 90° bend with transmission values of 98% for both modes.Article Citation - WoS: 3Citation - Scopus: 4Photonic Crystal Assisted 90° Waveguide Bend(World Scientific Publishing Co. Pte Ltd, 2011) Sözüer, Hüseyin Sami; Şengün, Hediye DuyguThe 90° waveguide bend is an important component of optical circuit applications. We propose several models for such a bend, some of them assisted by a two-dimensional photonic crystal with a bandgap in the desired range of operating frequencies. We show that a photonic crystal assisted bend reduces bending loss by several orders of magnitude for transverse electric modes. © 2011 World Scientific Publishing Company.Article Citation - WoS: 14Citation - Scopus: 18Robustness of One-Dimensional Photonic Band Gaps Under Random Variations of Geometrical Parameters(American Physical Society, 2005) Sözüer, Hüseyin Sami; Sevim, KorayThe supercell method is used to study the variation of the photonic bandgaps in one-dimensional photonic crystals under random perturbations to thicknesses of the layers. The results of both plane wave and analytical band structure and density of states calculations are presented along with the transmission coefficient as the level of randomness and the supercell size is increased. It is found that with the supercell size fixed at 1024 unit cells, higher bandgaps disappear first as the randomness is gradually increased. The lowest bandgap is found to persist up to a randomness level of 55%. However, as the supercell size is increased all bandgaps are observed to approach pseudogaps but with very low density of states. It is shown that harmonics of a relatively small cluster of closely spaced defects largely account for the bulk of the modes that populate the photonic bandgaps.