The invention provides a simple metallic film manufacturing method for manufacturing an arrayed waveguide grating able to set each light transmitting central wavelength to a set wavelength at optionally predetermined temperature. The variable sampling rate enables extended operational time before replacement of the battery. An initial search procedure determines one or more signal metric maps for one or more selected offset adjustment corrections from the one or more offset adjustment corrections. The at least one layer difference adjustment film includes a layer difference adjustment film formed on a region excluding a region corresponding to the second through electrode.