Preliminary Experimental Results of Dual Grating-Assisted Directional Coupler on SOI

Mashanovich, Goran Z., Reed, Graham T., Passaro, Vittorio M.N., Headley, William R., Timotijevic, Branislav, Atta, Raghied M.H., Josey, Mike, Ensell, Graham and Evans, Alan G.R. (2005) Preliminary Experimental Results of Dual Grating-Assisted Directional Coupler on SOI. SPIE Photonics West, San Jose, California, United States. 22 - 27 Jan 2005.

Abstract

The recent interest in silicon based photonics, and the trend to reduced device dimensions in photonic circuits generally, has led to the need for more converters to couple from optical fibres to such small devices. A range of structures have been proposed and in some cases demonstrated, including three dimensional tapers, inverted tapers and micromachined prisms. We have previously reported theoretical analyses of a Dual Grating Assisted Directional Coupler (DGADC), which promises high efficiency coupling over modest spectral linewidths. In this paper we report preliminay experimental results on the fabrication of such devices, together with an evaluation of the coupling efficiency. The approach has been to fabricate a demonstrator device for a particular arrangement of waveguide couping parameters, i.e. we have fabricated a device that couples easily from fibre, because the input waveguide is approximately 5micro m in cross sectional dimensions. The mode converter then couples to a 0.25 micro m silicon waveguide, primarily because comparison exist in the literature. These results are compared with the predicted efficiency, and the results are discussed both in terms of the constituent parts of the DGADC, as well as the fabrication limitations. Whilst our device is not optimised we demonstrate that it has promise for very high efficiency coupling.

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Contributors

Author: Goran Z. Mashanovich

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