Cylindrical diffraction grating couplers and distributed feedback resonators for guided wave devices

In a cylindrical waveguide configured to confine and guide the energy of propagating waves and including at least one wave-transmitting medium having a substantially cylindrical boundary and having disposed on said boundary a first diffraction grating, which comprises a plurality of substantially closed loop grating lines extending along said cylindrical boundary in planes parallel to the phase fronts of said guided waves and being spaced and shaped to scatter energy between said guided waves and waves which are not guided by said waveguide;

• the improvement wherein said cylindrical waveguide further includes means for reflecting said guided waves back and forth in an axial direction within said waveguide, thereby producing counter-propagating guided waves forming a standing wave pattern within said waveguide, for enhancing the scattering of energy by said first diffraction grating.

In an apparatus for the generation of a laser beam including a semiconductor laser resonator having a substrate and an active region deposited thereon, said laser beam being emitted out of said resonator essentially perpendicular to the surface of said substrate;

• the improvement wherein said semiconductor laser resonator includes means for selecting the energy distribution in the standing wave pattern of a lasing mode in a plane parallel to said surface, thereby controlling the characteristic of said laser beam.