A method for producing an optical semiconductor device 1, wherein the substrate has a surface index of A, and the ridge and the grooves are formed such that exposed slanting surfaces of the ridge and the grooves have inclination angles from about 25 degrees from a surface to {HEAD ~ about 54 degrees} from {TAIL ~ a surface} 
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A method for producing an optical semiconductor device 1 , wherein the substrate has a surface index of A , and the ridge and the grooves are formed such that exposed slanting surfaces of the ridge and the grooves have inclination angles from about 25 degrees from a surface to { HEAD ~ about 54 degrees } from { TAIL ~ a surface }
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