PROBLEM TO BE SOLVED: To integrate on a semiconductor substrate by the use of semiconductor manufacturing technique by setting the attenuation quantity generated at propagating a first light wave in a waveguide passage smaller than the attenuation quantity generated at propagating a second light wave in a waveguide passage.
SOLUTION: When a TM mode wave propagating in the z-direction as signal light is supposed, the magnetic vector of TM mode wave is oscillated in the y-direction. Accordingly, a magnetic material layer 8a is formed so as to extend along the y-direction. and magnetized in the +y-direction, namely so as to direct from the depth side of a space to this side. By magnetizing in such direction, the attenuation quantity against signal light propagated in the z-direction becomes minimum, and the attenuation quantity against reflection wave or scattered light propagated in the opposite direction (-z-direction) can be made maximum. In this way, this device is constituted so that by change of equivalent refraction factor of non-reciprocity, the attenuation quantity generated at propagating in the first direction in the light waveguide passage is smaller than the attenuation quantity generated at propagating a second light wave propagated in a second direction in a wave guide passage.