INTEGRATED-TYPE SEMICONDUCTOR LASER ELEMENT, SEMICONDUCTOR LASER MODULE, AND OPTICAL TRANSMISSION SYSTEM

摘要

An integrated semiconductor laser element includes: an optical coupler that can couple output light from a plurality of semiconductor lasers that oscillate at different oscillation wavelengths from one another, each of the semiconductor laser oscillating in a single mode; and a semiconductor optical amplifier that amplifies output light from the optical coupler. At least one of 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 and an expanded width portion formed on a light output side with a width wider than a width of the equal width portion. In order to substantially match the gain peak wavelength in the operating state and the gain peak wavelength of the semiconductor laser obtained by setting the composition, the width of the expanded width portion is set according to a total thickness of well layers of the active layer such that a total volume of the well layers of the active layer is increased to a level that suppresses a band filling phenomenon.