A Flat-top Arrayed Waveguide Grating Using A MMI Based on V-shaped Subwavelength Gratings

We proposed an 8-channel Si₃N₄ arrayed-waveguide grating(AWG) with a flat spectral response by cascading an improved multimode interference coupler (MMI) at the end of the input waveguide. V-shaped subwavelength gratings are added to the MMI. The 1-dB bandwidth of 99.6GHz and 3-dB bandwidth of 137.5GHz are obtained for the fabricated AWG with 200GHz channel spacing. Measured insertion loss and crosstalk can reach -5dB and -20dB, respectively.

I. Introduction

Wavelength Division Multiplexing (WDM) has been widely used with the increasing demand for communication capacity. Arrayed-waveguide grating (AWG) is a typical component in the WDM systems. It consists of input/output waveguides, two free propagation regions (also called star couplers) and array waveguides. Because of the high refractive index difference, the waveguide refractive index of the AWG based on SOI platform is more easily affected by the process error. Then the random phase error is generated in array waveguides, resulting in serious deterioration of the crosstalk. As an alternative platform with a moderate index contrast and lower transmission loss, Si₃N₄ waveguide is of interest [1].