Fu P.-HChao C.-YDING-WEI HUANG2021-09-022021-09-02202119430655https://www.scopus.com/inward/record.uri?eid=2-s2.0-85097960840&doi=10.1109%2fJPHOT.2020.3043828&partnerID=40&md5=d0f7f51727febe8c45f4d98a7770a04bhttps://scholars.lib.ntu.edu.tw/handle/123456789/580782In this study, the trajectory of a 90° bend is divided into two symmetric halves that are mirror images of each other as referenced to the symmetry axis at 45°, and each half is segmented into small curved sections. The bending radius and waveguide width for every section are parameters to be determined using a particle swarm optimization algorithm. The optimization is performed to maximize the transmission of the waveguide bends, which is calculated by using the three-dimensional finite-difference time-domain technique. The results indicate that the total bending loss of the optimized 90° bends with radii of 2, 3, 4, and 5 μm are 0.0106, 0.0051, 0.0025, and 0.0023 dB, respectively, at the wavelength λ = 1550 nm. In addition, the optimal devices are fabrication tolerant, with fabrication errors in width and height within 10 nm, and less wavelength-dependent compared with circular bends. ? 2009-2012 IEEE.Circular waveguides; Finite difference time domain method; Particle swarm optimization (PSO); Silicon; Bending radius; Fabrication errors; Optimal devices; Silicon waveguide; Symmetry axis; Three dimensional finite difference time domains; Waveguide bend; Waveguide widths; Time domain analysisjournal article10.1109/JPHOT.2020.30438282-s2.0-85097960840