Patent ID: 8457169

Claim:
An integrated semiconductor laser element comprising: a plurality of semiconductor lasers that oscillate at different oscillation wavelengths from one another, each of the semiconductor lasers oscillating in a single mode; an optical coupler that couples output light from the semiconductor lasers; and a semiconductor optical amplifier that amplifies output light from the optical coupler, wherein active layers of the semiconductor lasers and an active layer of the semiconductor optical amplifier have a same thickness and a same composition that is set to have a gain peak wavelength near a center of a wavelength band formed by the oscillation wavelengths of the semiconductor lasers, the semiconductor optical amplifier includes an equal width portion formed on a side of the optical coupler to guide the output light in a single mode, an expanded width portion which is formed on a light output side and has a width wider than a width of the equal width portion, and a tapered portion between the equal width portion and the expanded width portion, the total volume of well layers of the active layer of the semiconductor optical amplifier is equal to or greater than 100 μm 3 , an electric current injected into the semiconductor optical amplifier is equal to or greater than 200 mA, and the width of the expanded width portion is set based on a total thickness of well layers of the active layer of the semiconductor optical amplifier such that a gain peak wavelength of the semiconductor optical amplifier in an operating state substantially matches the gain peak wavelength of the semiconductor lasers.