There is provided a semiconductor laser comprising a gain section and an
adjacent Bragg section, wherein output laser light is emitted via a facet
at an interface between air and the gain section, the Bragg section
comprising a distributed reflecting structure having a length
substantially greater than required to ensure single longitudinal mode
operation of the laser in which the side-mode suppression ratio (SMSR) is
35 dB or more, thereby in use substantially suppressing optical feedback
from a facet at an interface between the Bragg section and air, and
wherein an interface between the Bragg section and the gain section is
quantum well intermixed, thereby rendering the interface substantially
anti-reflecting at the wavelength of the laser.
