PURPOSE: To raise the coupling efficiency, and to eliminate a variation of a characteristic caused by an operation of an optical device, by constituting an optical an optical filter by providing plural pieces of grooves whose depth is a roughly equal to or deeper than thickness of a passive waveguide layer, and whose width is a desired width, at a desired interval, on the passive waveguide in the vicinity of a semiconductor optical element, and providing an optical function device.

CONSTITUTION: A semiconductor laser 9 constitutes a resonator between a cleavage plane 12 and an end face 8 and oscillates a laser, therefore, it comes not to be influenced by an operation of a function device 11 which has been provided behind it. As for an examples of an optical filter 10, grooves 20-1W20-7 are formed on a waveguide layer 5, and this groove is scraped deeply to the extent that it reaches the bottom part of the waveguide layer 5 or a buffer layer 2. As for a position of the optical filter 10, it can be positioned in any part on the way of the waveguide layer 5 between the semiconductor laser 9 and the function device 11, therefore, L can be determined by aiming at an oscillation wavelength. When such a super-narrow band optical filter is used, an oscillation of the semiconductor laser becomes extremely effective for simplifying a mode.