Abstract: A method for producing a semiconductor optical device, includes the steps of: forming a semiconductor region including a semiconductor layer on a substrate; preparing a mold including a pattern surface, the pattern surface including an arrangement of patterns each including first to n-th pattern portions; forming a first mask on the semiconductor region with the mold by a nano-imprint technique; forming first to n-th periodic structures in each of the device sections in the semiconductor region by using the first mask, the first to n-th periodic structures respectively corresponding to the first to n-th pattern portions; forming a second mask after the first mask is removed, the second mask including a first pattern on an i-th periodic structure (1?i?n) among the first to n-th periodic structures in a first section of the device sections and including a second pattern on a j-th periodic structure (1?j?n) among the first to n-th periodic structures in a second section of the device sections; and forming first