| CPC H01S 5/2205 (2013.01) [H01S 5/22 (2013.01); H01S 5/223 (2013.01); H01S 5/2231 (2013.01); H01S 5/227 (2013.01)] | 21 Claims |
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1. An optical device comprising:
(a) a substrate;
(b) a bottom doped semiconductor layer on the substrate;
(c) a top doped semiconductor layer on the bottom doped layer so that the bottom doped layer is between the substrate and the top doped layer, the top and bottom doped layers being of opposite n- or p-doping types;
(d) a semiconductor active layer between the top and bottom doped layers, the active layer being arranged so as to emit light and exhibit optical gain at a nominal optical wavelength λ0 through radiative recombination of charge carriers at the active layer resulting from forward-biased drive current flowing between the top and bottom doped layers through the active layer;
(e) an optical waveguide structure including an optical gain section, the optical waveguide structure (i) defining lateral and longitudinal directions parallel to the top and bottom doped layers, (ii) supporting one or more optical modes that spatially overlap portions of the bottom doped, top doped, and active layers in the optical gain section, and (iii) being arranged as a buried-heterostructure waveguide (BHWG) structure that includes in the optical gain section a longitudinal strip of the active layer between lateral current-blocking layers that comprise doped semiconductor material of opposite n- or p-doping type as the bottom doped layer and extend laterally between the top and bottom doped layers and medially at least partly across the strip of the active layer between the active layer and the top doped layer;
(f) a pair of longitudinal, laterally spaced-apart strips of higher-index semiconductor material positioned along the BHWG structure, the higher-index semiconductor material having a refractive index higher than refractive indices of the top and bottom doped layers, arrangement of the spaced-apart strips resulting in a corresponding optical intensity lateral profile across the active layer of a selected one of the one or more of the optical modes, the optical intensity lateral profile having a higher fraction of optical intensity within its full width at half maximum intensity (FWHM) compared to a corresponding mode of an otherwise identical reference BHWG structure that lacks the spaced-apart strips; and
(g) one or more drive current structures that define a drive current path along which the drive current flows through the active layer in the optical gain section, the one or more drive current structures including (i) the lateral current-blocking layers and (ii) one or more current restrictors that comprise doped semiconductor material of opposite n- or p-type doping as the top doped layer, extend laterally between the lateral current-blocking layers and the top doped layer, extend medially only to lateral edges of the strip of the active layer between the active layer and top doped layer, and are arranged to form and be laterally spaced apart by a longitudinal gap therebetween or therethrough that is positioned along the strip of the active layer, filled with material of the top doped layer, and arranged so as to constrain the drive current to flow through the gap, wherein width of the gap is no less than width of the strip of the active layer,
(h) wherein the optical waveguide structure, the one or more drive current structures, or both, are positioned and arranged to result in a selected degree of spatial overlap between (i) a drive current lateral profile across the active layer in the optical gain section and (ii) the corresponding optical intensity lateral profile across the active layer in the optical gain section of the selected one of the one or more optical modes.
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