title: Compact waveguide crossings with a cascaded multimode tapered structure.
abstract: A compact waveguide crossing constructed by a cascaded multimode tapered structure is numerically presented. By using an eigenmode expansion method, we observe that the phase difference between the two lowest guided modes can be changed after a multimode waveguide junction because of the coupling between these two guided modes. Accordingly, we propose a fourfold symmetric waveguide crossing composed of three cascaded tapered structures with Gaussian profiles on each branch. Analyzed by the finite difference time domain method, this waveguide crossing has the size of 4160  nm×4160  nm, insertion loss of 0.13 dB, cross talk of -43.5  dB, and backreflection of -33.6  dB at the wavelength of 1550 nm and broad transmission spectrum at the wavelength range of 1500-1600 nm.
authors.forename: Chyong-Hua
authors.initials: CH
authors.lastname: Chen
mesh_terms: D000465:Algorithms; D015374:Biosensing Techniques; D003198:Computer Simulation; D004574:Electromagnetic Fields; D004867:Equipment Design; D020342:Finite Element Analysis; D008027:Light; D016011:Normal Distribution; D055620:Optical Phenomena; D055095:Optics and Photonics; D012031:Refractometry / Q000295:instrumentation*; D012542:Scattering, Radiation; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry
chemical_list: D012825:Silicon