Opt Quant Electron (2007) 39:571–575 DOI 10.1007/s11082-007-9108-2 Design and simulation of apodized wavelength filters using Gaussian-distributed sidewall grating Tzong-Yow Tsai · Yen-Cheng Fang · Zhi-Cheng Lee · Jong-Rong Chen Received: 18 February 2005 / Accepted: 11 July 2007 / Published online: 4 August 2007 © Springer Science+Business Media, LLC 2007 Abstract An accurate design for an apodized integrated optical wavelength filter using Gaussian-distributed sidewall Bragg grating is proposed, 2-dimensionally simulated and analyzed using the finite-difference time-domain method. It is verified that for various grating periods, the central wavelengths of the reflection bands are all fixed at designed 1.55 μm with the side lobes well suppressed. Keywords Apodized Bragg grating · Finite difference time domain (FDTD) · Photonic band gap (PBG) 1 Introduction Bragg grating is an essential component used for directional coupling and wavelength filtering in modern optical communication. It has been widely studied and fabricated in single-mode optical fibers, as well-known fiber bragg grating (FBG) (Hill and Meltz 1997), and surface- corrugated waveguides (Spuehler and Erni 2000; Giorgio et al. 2002; Wiesmann et al. 2003) in photonic integrated circuits (PIC). The reflection bandwidth and the band position of Bragg grating are determined by the effective refractive indices of guided modes and the grating period. Manufacture of grating-on-top ridge waveguides is challenging because effective refractive indices are generally sensitive to the etched depths which are delicate to stably control. Similar grating effects can be obtained by grating etched on the waveguide sidewalls. The advantage of using sidewall grating is that the device can be fabricated in one single etching process instead of multiple delicate etching processes required for a grating-on-top waveguide. Besides, the alternating effective indices of sidewall grating are determined by the lateral guiding widths that are defined in the procedure of photolithography and less dependent of the etching process. In addition, for most of ridge waveguides, the lateral T.-Y. Tsai (B ) · Y.-C. Fang · Z.-C. Lee · J.-R. Chen Lasers and Photonics Laboratory 92A71, The Institute of Microelectronics & The Department of Electrical Engineering, National Cheng Kung University, #1 University Road, 701, Tainan, Taiwan ROC e-mail: tzongyow@mail.ncku.edu.tw 123