We studied the impact of the lithography mask
discretization on silicon arrayed waveguide grating performance. When we decreased the mask grid from 5nm to 1nm, we observed an experimental improvement in crosstalk of 2.7-6.0dB and cumulative crosstalk improvement of 1.2- 5.0dB, depending on the wavelength channel spacing and the number of output channels. We demonstrate the effect for AWGs with 200GHz and 400GHz channel spacing, with 4, 8 and 16 output wavelength channels. With 1nm mask grid the average crosstalk is -26dB and -23dB for 400GHz and 200GHz devices, respectively. This is the lowest crosstalk for silicon AWGs reported to our knowledge. A simulation study is performed by looking specifically at phase errors due to mask grid snapping (ignoring other phase error
sources), which shows an expected improvement in crosstalk of 12dB.
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