Patent ID: 8404133

Claim:
A method for manufacturing a planar optical waveguide device of which a core includes a plurality of alternatively arranged fin portions and valley portions along a longitudinal direction of the core to form a grating structure, in which the core widths of the fin portions are wide and the core widths of the valley portions are narrow, and the core widths of the fin portions and the core widths of the valley portions vary along the longitudinal direction, the method comprising: a high refractive index material layer forming step of forming a high refractive index material layer made of a high refractive index material which constitutes at least a part of said core portion which includes the fin portions and the valley portions; a photoresist layer forming step of forming a photoresist layer on said high refractive index material layer; a first exposure step of forming shaded portions on said photoresist layer using a first photomask, said first photomask being a phase-shifting photomask and the lateral widths of said shaded portions at positions corresponding to the valley portions are substantially equal to the respective core widths of the valley portions and the lateral widths of said shaded potions at positions corresponding to the fin portions are wider than the respective core widths of the fin portions and exposing said photoresist layer at the outside of said shaded portions; a second exposure step of forming shaded portions on said photoresist layer using a second photomask, said second photomask being a binary photomask and the lateral widths of said shaded portions at positions corresponding to the valley portions are wider than the respective core widths of the valley portions and the lateral widths of said shaded portions at positions corresponding to the fin portions are substantially equal to the respective core widths of the fin portions; a development step of developing the photoresist layer; and an etching step of etching the high refractive index material layer using the photoresist pattern resulted from said development step to form the fin portions and the valley portions, wherein pitches, which are each defined as a sum of a longitudinal length of one of the fin portions and a longitudinal length of one of the valley portions adjacent to said one of the fin portions along a longitudinal direction of the core, vary and are non-chirped.