Optical semiconductor device and optical control apparatus

An optical semiconductor device comprising:

• a substrate;
• an optical modulator provided on the substrate;
• an optical waveguide provided on the substrate, one end of the optical waveguide being connected to a light emission side of the optical modulator and another end of the optical waveguide being present at an end portion of the substrate;
• a phase adjusting unit provided on a path of the optical waveguide and configured to adjust a phase of light guided in the optical waveguide;
• and
• an optical amplification unit provided on the path of the optical waveguide and configured to amplify power of the light guided in the optical waveguide, wherein
• a minimum value or a maximum value of a transmittance spectrum having a ripple that periodically fluctuates with respect to a frequency because of multiple reflection of the light that occurs between the one end and the other end of the optical waveguide is matched with a wavelength of the light input to the optical modulator by phase adjustment of the phase adjusting unit, and an error vector amplitude is minimized.