Beam-adjustment-free crosstalk reduction in 10GHz-spaced arrayed-waveguide grating via photosensitivity under UV laser irradiation through metal mask

The crosstalk of a 10 GHz-spaced 32 channel arrayed-waveguide grating has been reduced from –17 to –30 dB and from –16 to –27 dB for the TE and TM modes, respectively, via the photosensitivity under 193 nm ArF excimer laser irradiation. A metal mask with a window was placed on the arrayed waveguides and the unmasked arrayed waveguides were irradiated until the crosstalk was reduced to the desired value. This technique means that fine adjustment of the laser beam on individual arrayed waveguides is no longer necessary.