PURPOSE: To take out a high output of light from the front side of a substrate, by integrating a plurality of current injection regions on the same semiconductor substrate, the using a non-linear optical medium for a light-taking-out region.

CONSTITUTION: A part of the light (phase ) generated in one current injection region 21a is propageted to a current injection region 21b via a light-taking-out region 22 of non-linear optical medium. In a similar manner, a part of the light (phase ) generated in the other current injection region 21 b is propagated to a current injection region 21a via the light-taking-out region 22 of non-linear optical medium. As the result, the phase of the light generated in the respective current injection regions 21a and 21b is matched. That is, the respective current injection regions 21a and 21b generated the light in phase, which can be taken out from the surface side of a semiconductor substrate by a second order diffraction grating on the non-linear optical medium formed in the light-taking-out region 22. The coherent light output can be doubled thereby.