Phase-locked semiconductor laser device

A semiconductor laser device comprising:

• a. a laminated structure with a top, bottom and two side faces which are parallel to each other and to the direction of a laser beam to be generated by said device having:
• i. a plurality of first semiconductor layers having substantially the same composition;
• ii. a plurality of second semiconductor layers having a wider band gap and a lower refractive index than said plurality of first semiconductor layers;
• iii. said first and second semiconductor layers stacked such that said first semiconductor layers are sandwiched between said second semiconductor layers;
• b. third semiconductor layers disposed adjacent said side faces, each third semiconductor layer in contact with a respective one of said side faces thereby forming interfaces with said first semiconductor layers, said third semiconductor layers having a band gap which is not narrower than the band gap of said first semiconductor layers and a refractive index which is not higher than the refractive index of said first semiconductor layers, the conductivity type of said third semiconductor layers not being the same as that of said first semiconductor layers;
• c. means to inject current into said interfaces between said first semiconductor layers and said third semiconductor layers;
• and
• d. means acting as an optical resonator for said laser beam.