Photonic crystal single transverse mode defect structure for vertical cavity surface emitting laser
View Patent ↗The invention is directed to a photonic crystal defect structure for a vertical cavity surface emitting laser (VCSEL). In accordance with the invention, a set of holes is formed in a pattern with one or more missing holes forming a defect in the pattern of the photonic crystal, according to a proscribed depth, hole diameter, and pattern pitch which will insure operation in a single transverse mode.
1. A vertical cavity surface emitting laser including a vertical cavity, the laser comprising:
a substrate;
a bottom distributed Bragg reflector;
a top distributed Bragg reflector;
an electrical current aperture;
top and bottom electrodes; and
the vertical cavity between said bottom and said top distributed Bragg reflectors containing an active region; wherein said vertical cavity includes:
a plurality of holes arranged in a plurality of patterns; and
at least one missing hole defect in each of said patterns, a ratio of the hole diameter divided by the hole pitch being dependent upon the hole depth and set to produce single transverse mode operation; wherein some of said patterns are different and some are matched to provide transverse optical coupling.
2. The structure of claim 1 , wherein patterns are matched by having matched dimensions of said holes, pitch between holes, hole depth and defect radius.
3. A vertical cavity surface emitting laser including a vertical cavity, the laser comprising:
the substrate;
a bottom distributed Bragg reflector;
a top distributed Bragg reflector;
an electrical current aperture;
top and bottom electrodes; and
a vertical cavity between said bottom and said top distributed Bragg reflectors containing an active region; wherein said vertical cavity includes:
a plurality of holes arranged in a pattern; and
at least one missing hole defect in the pattern, a ratio of the hole diameter divided by the hole pitch being dependent upon the hole depth and set to produce single transverse mode operation;
wherein a radius of said missing hole defect is set to achieve single mode operation; and
wherein dimensions are set such that the V-parameter of the laser is set such that V eff is less than ˜2.405, wherein V eff is defined by:
V
eff
=
2
π
r
λ
n
eff
2
-
(
n
eff
-
γ
Δ
n
)
2
where λ is an operating wavelength, r is an equivalent defect radius, n eff is the effective refractive index of the said vertical cavity without a photonic crystal hole pattern and defect structure present, Δn is the refractive index reduction introduced by the said pattern and said one or more defects, and y is the depth dependence single transverse mode factor.
4. The laser of claim 3 , wherein said plurality of holes and said defect are finite depth holes formed in said top distributed Bragg reflector.
5. The laser of claim 3 , wherein said plurality of holes are finite depth holes that extend through said vertical cavity and extend through at least a part of each of said top and bottom distributed Bragg reflectors.
6. The laser of claim 3 , wherein said plurality of holes are infinite depth holes.
7. The laser of claim 3 , comprising a plurality of defects arranged in said pattern.
8. The structure of claim 7 , wherein said pattern comprises a seven point defect pattern.
9. The structure of claim 8 , further comprises additional seven point defect patterns.
10. The laser of claim 3 , wherein said electrical current aperture comprises an oxidized region in said vertical cavity.
11. The laser of claim 3 , wherein said electrical current aperture comprises an ion implanted region in said vertical cavity.
12. The laser of claim 3 , wherein Δn is set through optimization to an increased amount that maintains V eff is less than ˜2.405.
13. The laser of claim 12 , wherein Δn is set to be greater than 10 −3 .
14. A photonic crystal defect structure in a vertical cavity surface emitting laser including a vertical cavity, the laser comprising:
a substrate;
a bottom electrode electrically contacting said substrate;
a bottom distributed Bragg reflector formed on an opposite side of said substrate from said bottom electrode;
a top distributed Bragg reflector;
a plurality of finite depth holes arranged in a pattern and a missing hole defect in the pattern, the pattern being formed in at least a portion of said top distributed Bragg reflector, the diameter, pitch and depth of the holes being defined by a depth dependence single transverse mode factor;
the vertical cavity including claddings that clad an active region, said vertical cavity being between said top and bottom distributed Bragg reflectors; and
a top electrode including an aperture larger than the pattern;
comprising a plurality of said patterns, wherein some of said patterns are different and some are matched to provide transverse optical coupling.
15. A photonic crystal defect structure in a vertical cavity surface emitting laser, comprising:
a plurality of holes arranged in a pattern; and
at least one missing hole defect in the pattern, a ratio of the hole diameter divided by the hole pitch being dependent upon the hole depth and set to produce single transverse mode operation;
wherein a radius of said missing hole defect is set to achieve single mode operation; and
wherein dimensions are set such that the V-parameter of the laser is set such that V eff is less than ˜2.405, wherein Vis defined by:
V
eff
=
2
π
r
λ
n
eff
2
-
(
n
eff
-
γ
Δ
n
)
2
where γ is an operating wavelength, r is an equivalent defect radius, n eff is the effective refractive index of the said vertical cavity without a photonic crystal hole pattern and defect structure present, Δn is the refractive index reduction introduced by the said pattern and said one or more defects, and γ is the depth dependence single transverse mode factor.