Slab-waveguide irradiation of UV laser light for photosensitive phase error compensation of arrayed-waveguide gratings

The photosensitive refractive index change in a slab waveguide was utilized to compensate for the phase error of an arrayed-waveguide grating. The UV laser irradiation of a slab waveguide has certain advantages. The irradiation of several different parts of the waveguide can compensate for a large phase error of the order of ten radians. Phase error compensation can be achieved even when there is no space on the arrayed-waveguide part to place a mask for irradiation.