Abstract: A distributed feedback ridge waveguide semiconductor laser diode having a waveguide region with a typical thickness of at least 500 nanometers and an effective refractive index difference between the ridge structure and exposed portions of the waveguide region which surround the ridge structure of less than 0.001. This permits the width of the ridge to be expanded beyond 3.5 microns thus translating directly to higher power outputs at 1.55 &mgr;m wavelengths, where carrier diffusion and carrier heating limit current density injected into the active region.

Abstract: A semiconductor laser diode and method are described, wherein the path of the current through the device between the positive and negative conductors is controlled. Lateral spread of the gain current in the active region is prevented by implanting protons in areas of the active layer flanking a desired gain region. The implanted regions become less conductive, and prevent lateral spread of the gain current. The position of the implanted regions can be selected so that the gain current only crosses a portion of the active layer that supports desired lateral modes of the laser light.

Abstract: A mode matching gain element for an optical system is described, that supports a single mode of the optical signal, and that matches the incoming wavefront to a required outgoing wavefront. The incoming wavefront is passed through a phase conjugating structure, and the mode of the gain element is matched to the mode of the input and output optic fibers. The phase conjugating structure includes lenses or mirrors which time-reverse the incoming signal.