1. A method for fabricating a waveguide construction, comprising steps of:providing a layered structure by:
forming a first-type InGaAsP layer on a substrate;
forming a first-type InP layer on the first-type InGaAsP layer;
forming an active layer containing gallium on the first-type InP layer;
forming a second-type InP layer on the active layer; and
forming a second-type InGaAsP layer on the second-type InP layer;
forming an SiO2 patterned layer on the second-type InGaAsP layer, wherein the SiO2 patterned layer comprises a plurality of SiO2 regions, and at least one channel facing toward a desired direction is formed between the SiO2 regions; and
performing a rapid thermal annealing treatment on the layered structure having the SiO2 patterned layer, wherein the rapid thermal annealing treatment has a treating temperature ranged from 720° C. to 760° C. and a treating time ranged from 60 seconds to 240 seconds.