A light emitting device has a fiber stub component, a grating chip, a semiconductor optical amplifier, a photodiode, and a mount member. The fiber stub component is comprised of a ferrule and an optical fiber. The fiber stub component, grating chip, and semiconductor optical amplifier are mounted on the mount member and are optically coupled to each other. An optical cavity is comprised of a light reflecting surface of the semiconductor optical amplifier and a diffraction grating of the grating chip. In this configuration, the light emitting device can provide laser light of a desired wavelength, without use of a pigtail fiber. The light emitting device can be constructed in smaller size than those using the pigtail fiber.