Semiconductor optical integrated element

A semiconductor optical integrated element comprising:

• a substrate having a surface;
• a laser diode integrated on the surface of the substrate and comprising a laser diode mesa having sides transverse to the surface of the semiconductor substrate, wherein
• the laser diode mesa includes cladding layers and a laser diode core layer having sides exposed at the sides of the laser diode mesa,
• the laser diode core layer is sandwiched between the cladding layers of the laser diode, and
• the cladding layers of the laser diode and the laser diode core layer are stacked on the semiconductor substrate in the laser diode mesa;
• a connection waveguide integrated on the surface of the substrate and comprising a connection waveguide mesa having sides transverse to the surface of the semiconductor substrate, wherein
• the connection waveguide mesa includes cladding layers and a connection waveguide core layer having sides exposed at the sides of the connection waveguide mesa,
• the connection waveguide core layer is sandwiched between the cladding layers of the connection waveguide, and
• the cladding layers of the connection waveguide and the connection waveguide core layer are stacked on the semiconductor substrate in the connection waveguide mesa;
• a modulator integrated on the surface of the substrate and comprising a modulator mesa having sides transverse to the surface of the semiconductor substrate, wherein
• the modulator mesa includes cladding layers and a modulator core layer having sides exposed at the sides of the modulator mesa,
• the modulator core layer is sandwiched between the cladding layers of the modulator, and
• the cladding layers of the modulator and the modulator core layer are stacked on the semiconductor substrate in the modulator mesa,
• the laser diode, the connection waveguide, and the modulator are optically serially connected and integrated so that light generated in the laser diode and output from the laser diode core layer is guided to the modulator core layer of the modulator through the core layer of the connection waveguide;
• at least one semiconductor material, having a larger bandgap energy than bandgap energies of the laser diode core layer and the connection waveguide core layer, covering and embedding the sides of the laser diode core layer and the sides of the connection waveguide core layer at the sides of the laser diode mesa and the connection waveguide mesa;
• and
• a passivation film covering and embedding the sides of the modulator core layer at the sides of the modulator mesa, wherein the laser diode core layer and of the modulator core layer are stripe-shaped.