Sidelobe suppression in a wavelength-tunable optical filter using pair grating structure

Chan-Yong Park; Jeong Soo Kim; Seung-Goo Kang; Dug-Bong Kim

doi:10.1117/12.370175

12 November 1999 Sidelobe suppression in a wavelength-tunable optical filter using pair grating structure

Chan-Yong Park, Jeong Soo Kim, Seung-Goo Kang, Dug-Bong Kim

Proceedings Volume 3795, Terahertz and Gigahertz Photonics; (1999) https://doi.org/10.1117/12.370175
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1999, Denver, CO, United States

Abstract

Grating-assisted codirectional coupler (GACC) filter is considered to be one of the key devices in wavelength division multiplexing (WDM) system because of its superior characteristics of fast and wide range wavelength tuning as well as narrow bandwidth. However, its application has been limited because of a high level sidelobe. In this paper, we propose and demonstrate a novel concept of pair grating in order to suppress the sidelobes in GACC filter. Two different bandgap InGaAsP layers lattice-matched to InP were used as waveguides. A grating layer is inserted between two waveguides. In our structure, a pair grating whose period is 2(Lambda) was composed of two unit gratings and the separation between the unit gratings can be varied. By adjusting the separation, the coupling strength, K(z), can be controlled as Hamming or raised cosine functional form of position variable z. This idea of pair grating is attractive because averaged effective optical index or propagation constant remains unchanged. We fabricated a GACC filter with a weighted coupling strength, and achieved -19 dB sidelobe level, which implies a reduced crosstalk between neighboring channel. This device would be useful for WDM system requiring fast wavelength tuning.

Citation Download Citation

Chan-Yong Park, Jeong Soo Kim, Seung-Goo Kang, and Dug-Bong Kim "Sidelobe suppression in a wavelength-tunable optical filter using pair grating structure", Proc. SPIE 3795, Terahertz and Gigahertz Photonics, (12 November 1999); https://doi.org/10.1117/12.370175

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