Silicon-Based Arrayed waveguide gratings for WDM and spectroscopic analysis applications

We compare the performance of silicon-based arrayed waveguide gratings (AWGs) with star couplers of Rowland and Confocal configurations, respectively, for both TE and TM polarizations. The star coupler with Rowland configuration and constant projection period for phased array waveguides on the tangent line at the grating pole shows sufficiently small aberration for all output channels of AWGs, achieving a better spectral performance compared to the Confocal configuration. The spectral performance of AWGs is also highly dependent on phase errors resulting from fabrication imperfections which are unavoidable in current fabrication technology, hence it is of significant importance to make the phase region of AWGs as small as possible. Using the optimized star coupler configuration, ultracompact large channel spacing AWGs employing a single bend with a different radius for each waveguide in the phase array and a S-shaped waveguide array, respectively, are fabricated and compared, together with high resolution (de)multiplexers utilizing the cascade of (N + 1) x (N + 1) AWGs and polarization combiner-rotator/rotator-splitter. High resolution ultracompact spectrometers using bidirectional (N + 1) x (N + 1) AWGs operating at TE and TM polarizations are also designed and fabricated. All the experimental results indicate that a smaller footprint for the phase region of AWGs contributes to an improved performance in their spectral responses. We also discuss the ways to reduce the size of phase region and suggest that decreasing the pitch of adjacent output waveguides on the imaging plane is an effective way. This paper provides design considerations for silicon-based AWGs towards various applications such as wavelength division multiplexing (WDM) and spectroscopic analysis.

Automated summary

This study compares the performance of silicon-based arrayed waveguide gratings (AWGs) with star couplers of Rowland and Confocal configurations for TE and TM polarizations. It is found that the star coupler with Rowland configuration and constant projection period on the tangent line at the grating pole achieves better spectral performance. The spectral performance of AWGs is highly dependent on phase errors, and reducing the size of the phase region can improve spectral responses.