This paper presents an optimized design for racetrack resonators based on Multimode Interference (MMI) couplers on the silicon on insulator (SOI) platform. The design approach takes into account the effects of bend and transition losses within the racetrack waveguide. For the first time, new positions and geometries of access waveguides are suggested and optimized to improve device performance. | TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 12, SOÁ 13 - 2009 OPTIMIZED DESIGN OF MMI COUPLERS BASED MICRORESONATORS Le Trung Thanh La Trobe University, Melbourne, Bundoora Campus, Vic 3086, Australia ABSTRACT: This paper presents an optimized design for racetrack resonators based on Multimode Interference (MMI) couplers on the silicon on insulator (SOI) platform. The design approach takes into account the effects of bend and transition losses within the racetrack waveguide. For the first time, new positions and geometries of access waveguides are suggested and optimized to improve device performance. Key words: Optical waveguides, multimode interference (MMI) coupler, single mode, silicon on insulator (SOI). Racetrack resonators (also called microresonators in this paper) are basic building blocks for applications in the field of optical communications. Using this structure, basic signal processing functions such as wavelength filtering, routing, switching, modulation, and multiplexing can be achieved [1]. Most racetrack resonators have been designed and fabricated using directional couplers as a coupling element between the ring and the bus waveguides [2]. However, with the advantages of the relaxed fabrication tolerances and the ease of integration of these devices into more complex photonic integrated circuits, small size, and low excess loss, MMI couplers have been used instead of using directional couplers [3]. Operation of the MMI devices is based on the self-imaging principle in which an input field profile is reproduced in single or multiple images at periodic intervals along the propagation direction of the waveguide [4]. In a bent waveguide, the modal field shifts outwards as the radius of curvature is decreased. Therefore, one of the most challenging problems for using MMI couplers in the racetrack resonators is effects of the bent waveguides on the performance of the device [5]. This paper considers the effects of the bent waveguides on the .
