The present disclosure relates to a light-emitting device and a method of manufacturing the same.
In a laser light source, realizing high power is a major task. Therefore, semiconductor optical amplifiers (SOA) have been studied as devices that amplify light from a laser light source as well as realizing high power of semiconductor laser devices. Here, an optical amplifier is a device that directly amplifies light without converting an optical signal into an electrical signal. The optical amplifier has a laser structure having no resonator and amplifies incident light with an optical gain of the amplifier.
Since optical amplifiers have been developed mainly for optical communication, semiconductor optical amplifiers of a 405 nm band have rarely been put to a practical use. For example, Japanese Unexamined Patent Application Publication No. 5-067845 discloses a semiconductor optical amplifier of a 1.5 μm band which has a tapered ridge stripe configuration in which a GaInAsP-based compound semiconductor is used. According to the technology disclosed in Japanese Unexamined Patent Application Publication No. 5-067845, in the semiconductor optical amplifier, a mode field is expanded along an optical waveguide width by gradually widening the optical waveguide width in a tapered shape from an optical waveguide serving as a narrow incident side, which satisfies single-mode conditions, to an optical waveguide serving as an output side. Thus, the highest output of the semiconductor optical amplifier is designed to be improved.
In general, semiconductor laser devices or semiconductor optical amplifiers have a layer (In the field of laser diode, the word “layer” is used instead of lamination) structure formed on a base substrate. Here, the layer structure includes n-type compound semiconductor layers (specifically, an n-type clad layer and an n-type light guiding layer) doped with n-type impurities, an active layer, and p-type compound semiconductor layers (specifically, a p-type light guiding layer and a p-type clad layer) doped with p-type impurities generally formed from the side of a base substrate.