Deep UV lithography process in generic InP integration for arrayed waveguide gratings

Low-excess-loss arrayed waveguide gratings are enabled by unique application of deep UV lithography in InP integrated photonics through reduced feature sizes and more specifically, well-resolved inter-waveguide gap dimensions. Submicrometer wafer-flatness is shown to be required to achieve critical dimension uniformity better than 10 nm on 3-inch substrates. Arrayed waveguide grating devices were fabricated and the effect of inter-waveguide gap scaling on the excess losses, was measured and compared to simulations. Excess losses down to 0.15 dB were demonstrated to be lower than predicted with 2D simulations. The tapering of the etch depth inside the gaps due to the lag effect of the etch process may explain the improvements.