Broad area laser including anti-guiding regions for higher-order lateral mode suppression
A broad area laser diode is configured to include an anti-guiding layer located outside of the active region of the device. The anti-guiding layer is formed of a high refractive index material that serves to de-couple unwanted, higher-order lateral modes (attributed to thermal lensing problems) from the lower-order mode output beam of output signal from the laser diode. The anti-guiding layer is formed using a single epitaxial growth step either prior to or subsequent to the steps used to grow the epitaxial layers forming the laser diode itself, thus creating a structure that provides suppression of unwanted higher-order modes without requiring a modification of specific process steps used to fabricate the laser diode itself.
1. A laser diode formed on a substrate and comprising
a quantum well emitter region disposed between an n-type waveguiding layer and a p-type waveguiding layer;
an n-type cladding layer disposed over the n-type waveguiding layer and a p-type cladding layer disposed over the p-type waveguiding layer;
a first electrical contact region disposed over a portion of the p-type cladding layer and a second electrical contact region disposed beneath a portion of the substrate, an overlapping combination of the first and second electrical contact regions with the quantum well emitter region defining an active area of the laser diode; and
an anti-guiding layer formed in a location above or below the active area of the laser diode, the anti-guiding layer formed of a material with a refractive index sufficient to de-couple unwanted, higher-order lateral modes and direct the unwanted, higher-order lateral modes out of the active area of the laser diode and into the anti-guiding layer.
2. The laser diode as defined in claim 1 wherein
the anti-guiding layer is disposed above the first electrical contact region and configured to include a trench opening exposing a portion of the first electrical contact region, a defined width of the trench opening defining a width of the active area of the laser diode, the laser diode comprising an inverted ridge configuration.
3. The laser diode as defined in claim 2 wherein the first electrical contact region comprises a layer of highly-doped semiconductor material and the anti-guiding layer comprises an epitaxial layer grown on an exposed surface of the layer of highly-doped semiconductor material of the first electrical contact region, the epitaxially grown layer thereafter patterned and etched to form the trench opening.
4. The laser diode as defined in claim 1 wherein
the laser diode comprises a ridge structure laser diode and the anti-guiding layer is disposed below the active area of the laser diode, between the substrate and the n-type cladding layer.
5. The laser diode as defined in claim 4 wherein the anti-guiding layer comprises an epitaxial layer grown on an exposed surface of the substrate, with remaining layers of the laser diode formed over the epitaxially-grown anti-guiding layer.
6. The laser diode as defined in claim 1 wherein the anti-guiding layer exhibits an index of refraction greater than the quantum well emitter region, and the cladding layers.
7. The laser diode as defined in claim 6 wherein the anti-guiding layer comprises a material selected from the group consisting of: GaAs, AlGaAs, InGaAs, and GaInP.
8. The laser diode as defined in claim 1 wherein the first electrical contact region comprises a layer of highly-doped semiconductor material.
9. The laser diode as defined in claim 1 wherein the second electrical contact region comprises at least one metal layer formed to coat a portion of the substrate bottom surface.
10. A broad area laser diode formed on a substrate and comprising
a quantum well emitter region disposed between an n-type waveguiding layer and a p-type waveguiding layer;
an n-type cladding layer disposed over the n-type waveguiding layer and a p-type cladding layer disposed over the p-type waveguiding layer,
a first electrical contact region disposed over the p-type cladding layer and having a width W associated with a width of an emission region of the laser diode;
a second electrical contact region disposed beneath an exposed substrate surface, an overlapping combination of the first and second electrical contact regions with the quantum well emitter region defining an active region of the broad area laser diode, with a width of the active region associated with the created width W of the first electrical contact region; and
an anti-guiding layer formed in a location above or below the active region of the laser diode, the anti-guiding layer formed of a material with a refractive index sufficient to de-couple unwanted, higher-order lateral modes and direct the unwanted, higher-order lateral modes away from the active region of the laser diode so as to minimize the lateral divergence of a beam emitted by the broad area laser diode.
11. The broad area laser diode as defined in claim 10 wherein
the anti-guiding layer is disposed over the first electrical contact region and configured to include a trench opening exposing a portion of the first electrical contact defining the emission region of the laser diode, the laser diode comprising an inverted ridge configuration.
12. The broad area laser diode as defined in claim 11 wherein the first electrical contact region comprises a layer of highly-doped semiconductor material and the anti-guiding layer comprises an epitaxial layer grown on an exposed surface of the layer of highly-doped semiconductor material, the epitaxially grown layer thereafter patterned and etched to form the trench opening.
13. The broad area laser diode as defined in claim 10 wherein
the laser diode comprises a ridge structure laser diode, with the width of the ridge associated with the width of a beam emitted by the laser diode, and the anti-guiding layer is disposed between the substrate and the n-type cladding layer.
14. The broad area laser diode as defined in claim 13 wherein the anti-guiding layer comprises an epitaxial layer grown on an exposed surface of the substrate, with remaining layers of the laser diode grown epitaxially in a single step together with the anti-guiding layer.