Method of manufacturing optical semiconductor apparatus and the apparatus

A method of manufacturing an optical semiconductor apparatus, wherein the apparatus is configured to operate in a single fundamental transverse mode of wavelength range 1400 nm to 1700 nm and the method comprises forming:

• a waveguide layer of a III-V quaternary compound material between an n-doped cladding layer and a p-doped cladding layer;
• the waveguide layer includes a first waveguide part, and a bulk active layer located between the first waveguide part and the p-doped cladding layer, the bulk active layer being asymmetrically within the waveguide layer closer to the p-doped cladding layer than to the n-doped cladding layer;
• a refractive index of the n-doped cladding layer being larger than the p-doped cladding layer, and the waveguide layer being configured to have a constant refractive index throughout excluding the bulk active layer;
• a first end of the first waveguide part is adjacent to the n-doped cladding layer;
• a second end of the first waveguide part is adjacent to a first end of the bulk active layer;
• and
• doping a desired donor density in the first waveguide part equal to or higher than 2*1017 cm−3 for controlling the carrier density dependent internal optical loss in the first waveguide part of the III-V quaternary compound material,
• wherein the apparatus is a broad-area laser.