Edge-emitting semiconductor laser with photonic-bandgap structure formed by intermixing
View Patent ↗A separate-confinement heterostructure, edge-emitting semiconductor laser having a wide emitter width has elongated spaced apart intermixed and disordered zones extending through and alongside the emitter parallel to the emission direction of the emitter. The intermixed zones inhibit lasing of high order modes. This limits the slow axis divergence of a beam emitted by the laser.
1. An edge-emitting semiconductor laser, comprising:
a separate confinement heterostructure, the heterostructure having an active region, the active region including an active layer located between upper and lower waveguide layers, the active region being located between upper and lower cladding layers, and the active, waveguide and cladding layers being ordered crystalline epitaxially-grown layers;
a cap layer located above a region of the upper cladding layer and defining a resonator region in the active region, the resonator region having a slow-axis parallel to the plane of the layers therein, a fast-axis perpendicular to the slow-axis, a longitudinal axis perpendicular to the fast- and slow-axes and first and second opposite sides parallel to the longitudinal axis; and
a plurality of elongated disordered regions formed in at least one ordered crystalline waveguide layer of the active region, spaced apart from each other and extending parallel to the longitudinal axis of the resonator region, and located at least outside of the resonator region on both opposite sides thereof.
2. The edge-emitting semiconductor laser of claim 1 , wherein the disordered regions have a refractive index lower that of the waveguide layer in which the disordered regions are located.
3. The edge-emitting semiconductor laser of claim 1 , wherein the disordered regions are also located within the resonator region.
4. The edge-emitting semiconductor laser of claim 3 , wherein the disordered regions are symmetrically distributed about the longitudinal axis of the resonator region with a first spacing between an innermost two of the disordered regions being greater than a second spacing between all other adjacent regions, thereby providing two periodically spaced groups of the disordered regions symmetrically disposed about the longitudinal axis of the resonator region.
5. The edge-emitting semiconductor laser of claim 1 , wherein the disordered regions extend through the active region from the upper waveguide layer thereof into the lower waveguide layer thereof.
6. The edge-emitting semiconductor laser of claim 1 , wherein the disordered regions outside the resonator region extend through the upper cladding layer into the upper waveguide layer.
7. The edge-emitting semiconductor laser of claim 1 , wherein there are 10 of the disordered regions on each side of the resonator region.
8. The edge-emitting semiconductor laser of claim 1 , wherein the layers of the heterostructure have an arrangement and composition for delivering radiation in a wavelength range between about 700 nm and 1100 nm, the disordered regions have a width between about 10 and 50 micrometers and are spaced-apart by a distance between about 70 and 100 micrometers.
9. The edge-emitting semiconductor laser of claim 8 , wherein, the active layer has a composition Al z Ga (l-z) As; the upper and lower waveguide layers have a composition Al y Ga (l-y) As; and the upper and lower cladding layers have composition Al x Ga (l-x) As, where x>y>z.
10. The edge-emitting semiconductor layer of claim 9 , wherein the cap layer is a layer of p-type gallium arsenide.