PURPOSE: To provide an optical part where phase adjustment is executed by mode distribution and a frequency is highly efficiently increased.

CONSTITUTION: The optical part 7 increases the frequency of electromagnetic radiation and it is provided with a non-linear optical waveguide 11 provided on a supporting substrate 9. The satellite layer 15 of a high refraction factor is provided on at least one side of the non-linear optical waveguide 11 so as to overlap the field distribution of a basic wave and a frequency increasing wave. Thus, frequency increasing efficiency can be improved.