Room‐temperature operation of an optically integrated double heterostructure (DH) GaAs‐AlxGa1‐xAs injection laser with a distributed Bragg reflector (DBR), with threshold current densities of 5 kA/cm2is reported. The DBR was in the form of a third‐order grating which was ion milled on a passive single heterostructure (SH) waveguide section with the latter taper coupled to the active DH section. The observed half‐power spectral bandwidth was ≲1 A˚. A highly collimated beam output with a half‐power divergence angle of ≲0.3° was also achieved by coupling the scattered light from the oil‐immersed grating at the Bragg angle with a prism.