U.S. patent number RE41,643 [Application Number 10/778,019] was granted by the patent office on 2010-09-07 for high power semiconductor laser diode.
This patent grant is currently assigned to Trumpf Photonics, Inc.. Invention is credited to Joseph Hy Abeles, John Charles Connolly, Dmitri Zalmanovich Garbuzov.
United States Patent |
RE41,643 |
Garbuzov , et al. |
September 7, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
High power semiconductor laser diode
Abstract
A semiconductor laser diode having increased efficiency and
therefore increased power output. The laser diode includes a body
of a semiconductor material having therein a waveguide region which
is not intentionally doped so as to have a doping level of no
greater than about 5.times.10.sup.16/cm.sup.3. Within the waveguide
region is means, such as at least one quantum well region, for
generating an optical mode of photons. Clad regions of opposite
conductivity type are on opposite sides of the waveguide region.
The thickness of the waveguide region, a thickness of at least 500
nanometers, and the composition of the waveguide and the clad
regions are such so as to provide confinement of the optical mode
in the waveguide region to the extent that the optical mode
generating does not overlap into the clad regions from the
waveguide region more than about 5%.
Inventors: |
Garbuzov; Dmitri Zalmanovich
(Princeton, NJ), Abeles; Joseph Hy (East Brunswick, NJ),
Connolly; John Charles (Clarksburg, NJ) |
Assignee: |
Trumpf Photonics, Inc.
(Cranbury, NJ)
|
Family
ID: |
25049618 |
Appl.
No.: |
10/778,019 |
Filed: |
February 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
08757883 |
Nov 27, 1996 |
05818860 |
Oct 6, 1998 |
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Current U.S.
Class: |
372/45.01;
372/43.01 |
Current CPC
Class: |
H01S
5/20 (20130101); B82Y 20/00 (20130101); H01S
5/2031 (20130101); H01S 5/305 (20130101); H01S
5/34306 (20130101) |
Current International
Class: |
H01S
5/00 (20060101) |
Field of
Search: |
;372/43.01,45.01 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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04-234188 |
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Aug 1992 |
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JP |
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07-045909 |
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Feb 1995 |
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JP |
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07-335979 |
|
Dec 1995 |
|
JP |
|
08-064906 |
|
Mar 1996 |
|
JP |
|
08-195529 |
|
Jul 1996 |
|
JP |
|
Other References
Garbuzov et al. (High power seperate confinement heterostructure
AIGaAs/GaAs laser diodes with broadened waveguide) SPIE vol. 2682,
pp. 20-26. cited by examiner .
Ablyazov et al. "Possibility of increasing the maximum radiation
intensity in heterolasers with a wide waveguide, " Sov. J. Quantum
Electron, vol. 20, No. 1, pp. 1320-1323 (1990). cited by other
.
Cockerill et al. "Depressed index cladding graded barrier seperate
confinement single quantum well heterostructure laser, " Appl.
Phys. Lett., vol. 59, No. 21, pp. 2694-2607 (1991). cited by other
.
Emanuel et al., "High-Efficiency AlGaAs-Based Laser Diode at 808 nm
with Large Transverse Spot size, " IEEE Photonics Technology
Letters, vol. 8, No. 10, pp. 1291-1293, (1996). cited by other
.
Garbuzov et al., "High-Power 0.8 .mu.m InGaAsP-GaAs SCH SQW Lasers,
" IEEE Journal of Quantum Electronics, vol. 27, No. 6, pp.
1531-1536 (1991). cited by other .
Garbuzov et al., "High Power seperate confinement heterostructure
AlGaAs/GaAs laser diodes with broadened waveguide, " SPIE, vol.
2692, pp. 20-28, (1996). cited by other .
Mawst et al., "8 W continuous wave front-facet power from
broad-waveguide Al-free 980 nm diode lasers, " Appl. Phys. Lett.,
vol. 69, No. 11, pp. 1532-1534 (1996). cited by other .
Petrescu-Prahova, "High Power low confinement AlGaAs/GaAs single
quantrum well laser diode operating in the fundamental lateral
mode, " Conference Proceedings, Conference on Lasers 7
Electro-Optics (CLEO) Tuesday Afternoon/ Europe, p. 171 (1994).
cited by other .
Waters, et al., "Dark-Line-Resistant Diode Laser at 0.8 .mu.m
Comprising InAlGaAs Strained Quantum Well, " IEEE Pnotonics
Technology Letters, vol. 3, No. 5, pp. 409-411 (1991). cited by
other .
Office Action from corresponding Japanese Application No.
PH09-363805, mailed Feb. 20, 2007, English translation included (15
total pages). cited by other .
Ito, R. and Nakamura, M., Foundation and Application of
Semiconductor Laser, Baifukan Co., Ltd., 1.sup.stEdition,
5.sup.thprinting, pp. 50-53 and 82-84, Mar. 30, 1995 (Japan). cited
by other.
|
Primary Examiner: Nguyen; Dung T
Attorney, Agent or Firm: Fish & Richardson P.C.
Claims
What is claimed is:
1. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type;
.Iadd.wherein:.Iaddend. said photon generating means .[.being.].
.Iadd.is .Iaddend.thinner than the thickness of the waveguide
region and .[.being.]. .Iadd.is .Iaddend.spaced from the clad
.[.layers.]. .Iadd.regions.Iaddend.; the thickness of the waveguide
region and the composition of the waveguide and clad regions
.[.being.]. .Iadd.are .Iaddend.such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 5%.Iadd.; the waveguide region is
of a thickness of at least 500 nanometers; and the waveguide region
has a doping level of no greater than
5.times.10.sup.16/cm.sup.3.Iaddend..
.[.2. The semiconductor laser diode of claim 1 in which the
waveguide region is of a thickness of at least 500
nanometers..].
.[.3. The semiconductor laser diode of claim 2 in which the
waveguide region has a doping level of no greater than
5.times.10.sup.16/cm.sup.3..].
4. The semiconductor laser diode of claim .[.3.]. .Iadd.1
.Iaddend.in which the materials of the waveguide region and the
clad regions have a refractive index which provides confinement of
the optical mode to the waveguide region with an overlap of the
optical mode into the clad regions of no greater than 5%.
5. The semiconductor laser diode of claim 4 in which the means for
generating photons in the waveguide region includes at least one
quantum well region.
6. The semiconductor laser diode of claim 5 in which the means for
generating photons in the waveguide region includes a plurality of
spaced quantum well regions with a barrier region between each pair
of adjacent quantum well regions.
7. The semiconductor laser diode of claim 5 in which the clad
regions are of a semiconductor material having a lower index of
refraction than the materials of the portions of the waveguide
region adjacent the clad regions.
8. The semiconductor laser diode of claim 7 in which the portions
of the waveguide region on each side of the quantum well region is
of a semiconductor material having a bandgap larger than that of
the quantum well region.
9. The semiconductor laser diode of claim 8 in which the portion of
the waveguide region on each side of the quantum well region is of
uniform composition throughout its thickness.
10. The semiconductor laser diode of claim 8 in which each of the
portions of the waveguide region on each side of the quantum well
region has an inner portion adjacent the quantum well region which
has a bandgap greater than the quantum well region and an outer
portion adjacent the clad region which has a bandgap greater than
that of the inner portion.
11. The semiconductor laser diode of claim 8 in which the portion
of the waveguide region on each side of the quantum well region has
a graded composition.
12. A semiconductor laser diode comprising: a body of a
semiconductor material having top and bottom surfaces and opposed
end surface; a waveguide region in the body extending across the
body between the end surfaces, said waveguide region being not
intentionally doped and being of a material which substantially
confines photons therein and allows the flow of photons therealong;
means in the waveguide region for generating an optical mode of
photons; a first clad region of one conductivity type between the
waveguide region and the top surface of the body; and a second clad
region of the opposite conductivity type between the waveguide
region and the bottom surface of the body; .Iadd.wherein:.Iaddend.
said photon generating means .[.being.]. .Iadd.is .Iaddend.thinner
than the thickness of the waveguide region and .[.being.]. .Iadd.is
.Iaddend.spaced from the clad region; the thickness of the
waveguide region and the composition of the waveguide and clad
regions .[.being.]. .Iadd.are .Iaddend.such that the generated
optical mode does not overlap into the clad regions from the
waveguide region more than about 5%.Iadd.; the waveguide region is
of a thickness of at least 500 nanometers; and the waveguide region
has a doping level of not greater than about
5.times.10.sup.16/cm.sup.3.Iaddend..
.[.13. The semiconductor laser diode of claim 12 in which the
waveguide region is of a thickness of at least 500
nanometers..].
.[.14. The semiconductor laser diode of claim 13 in which the
waveguide region has a doping level of not greater than about
5.times.10.sup.16/cm.sup.3..].
15. The semiconductor laser diode of claim .[.14.]. .Iadd.12
.Iaddend.in which the materials of the waveguide region and the
clad regions have a refractive index which provides confinement of
the optical mode to the waveguide region with an overlap of the
optical mode into the clad regions of no greater than 5%.
16. The semiconductor laser diode of claim 15 in which the means
for generating photons in the waveguide region includes at least
one quantum well region.
17. The semiconductor laser diode of claim 16 in which the means
for generating photons in the waveguide region includes a plurality
of spaced quantum well regions.
18. The semiconductor laser diode of claim 16 in which the clad
regions are of a semiconductor material having a lower index of
refraction than the materials of the portions of the waveguide
regions adjacent the clad regions.
19. The semiconductor laser diode of claim 18 in which the portions
of the waveguide region on each side of the quantum well region is
of a semiconductor material having a bandgap larger than that of
the quantum well regions.
.Iadd.20. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%; and wherein the means for generating photons in the
waveguide region includes a plurality of spaced quantum well
regions with a barrier region between each pair of adjacent quantum
well regions..Iaddend.
.Iadd.21. The semiconductor laser diode of claim 20, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.22. The semiconductor laser diode of claim 20, wherein the
waveguide region has a doping level of no greater than
5.times.10.sup.16/cm.sup.3..Iaddend.
.Iadd.23. The semiconductor laser diode of claim 20, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.24. The semiconductor laser diode of claim 56, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.25. The semiconductor laser diode of claim 56, wherein the
means for generating photons in the waveguide region includes a
plurality of spaced quantum well regions with a barrier region
between each pair of adjacent quantum well regions..Iaddend.
.Iadd.26. The semiconductor laser diode of claim 20, wherein the
clad regions are of a semiconductor material having a lower index
of refraction than materials of portions of the waveguide region
adjacent the clad regions..Iaddend.
.Iadd.27. The semiconductor laser diode of claim 24, wherein
portions of the waveguide region on each side of the quantum well
region are of a semiconductor material having a bandgap larger than
that of the quantum well region..Iaddend.
.Iadd.28. The semiconductor laser diode of claim 24, wherein
portions of the waveguide region on each side of the quantum well
region each have an inner portion adjacent the quantum well region
with a bandgap greater than the quantum well region and an outer
portion adjacent the clad region with a bandgap greater than that
of the inner portion..Iaddend.
.Iadd.29. The semiconductor laser diode of claim 20, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.30. The semiconductor laser diode of claim 20, wherein the
waveguide region has a length greater than about 2.0
mm..Iaddend.
.Iadd.31. The semiconductor laser diode of claim 20, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.32. The semiconductor laser diode of claim 20, wherein the
waveguide region is of a thickness of about 1.3 .mu.m..Iaddend.
.Iadd.33. The semiconductor laser diode of claim 24, wherein the
quantum well region consists essentially of InGaAs..Iaddend.
.Iadd.34. The semiconductor laser diode of claim 20, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.35. The semiconductor laser diode of claim 24, wherein the
quantum well region consists essentially of InGaAsP..Iaddend.
.Iadd.36. The semiconductor laser diode of claim 20, wherein the
waveguide region consists essentially of InGaAsP..Iaddend.
.Iadd.37. The semiconductor laser diode of claim 20, wherein the
waveguide region comprises In and Ga..Iaddend.
.Iadd.38. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%; and wherein the quantum well region consists essentially
of InGaAs..Iaddend.
.Iadd.39. The semiconductor laser diode of claim 38, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.40. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the quantum well region consists essentially
of InGaAsP..Iaddend.
.Iadd.41. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region consists essentially of
InGaAsP..Iaddend.
.Iadd.42. The semiconductor laser diode of claim 38, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.43. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region has a doping level of no
greater than 5.times.10.sup.16/cm.sup.3..Iaddend.
.Iadd.44. The semiconductor laser diode of claim 38, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.45. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a plurality of spaced quantum well regions within the waveguide
region for generating an optical mode of photons with a barrier
region between each pair of adjacent quantum well regions; and a
clad region on each side of the waveguide region, the clad regions
being at least partially doped to be of opposite conductivity type;
wherein each of said quantum well regions is thinner than the
thickness of the waveguide region and is spaced from the clad
regions; wherein the thickness of the waveguide regions and the
composition of the waveguide and clad regions are such that an
overlapping of the optical mode generated in the waveguide region
into the clad regions is not greater than about 5%..Iaddend.
.Iadd.46. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the clad regions are of a semiconductor
material having a lower index of refraction than the materials of
portions of the waveguide region adjacent the clad
regions..Iaddend.
.Iadd.47. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein portions of the waveguide region on each side
of the quantum well region are of a semiconductor material having a
bandgap larger than that of the quantum well region..Iaddend.
.Iadd.48. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein portions of the waveguide region on each side
of the quantum well region each have an inner portion adjacent the
quantum well region with a bandgap greater than the quantum well
region and an outer portion adjacent the clad region with a bandgap
greater than that of the inner portion..Iaddend.
.Iadd.49. The semiconductor laser diode of claim 38, wherein a
portion of the waveguide region on each side of the quantum well
region has a graded composition..Iaddend.
.Iadd.50. The semiconductor laser diode of claim 38, wherein a
portion of the waveguide region on each side of the quantum well
region has a uniform composition..Iaddend.
.Iadd.51. The semiconductor laser diode of claim 38, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.52. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region has a length greater
than about 2.0 mm..Iaddend.
.Iadd.53. The semiconductor laser diode of claim 38, wherein the
waveguide region has a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.54. A semiconductor laser diode of comprising: a body of a
semiconductor material having therein a waveguide region comprising
In and Ga, which is not intentionally doped and which substantially
confines photons therein and allows the flow of photons therealong;
a quantum well region within the waveguide region for generating an
optical mode of photons; and a clad region on each side of the
waveguide region, the clad regions being at least partially doped
to be of opposite conductivity type; wherein said quantum well
region is thinner than the thickness of the waveguide region and is
spaced from the clad regions; wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region has a thickness of about
1.3 .mu.m..Iaddend.
.Iadd.55. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%; and wherein the waveguide region has a doping level of no
greater than 5.times.10.sup.16/cm.sup.3..Iaddend.
.Iadd.56. The semiconductor laser diode of claim 55, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.57. The semiconductor laser diode of claim 55, wherein the
materials of the waveguide region and the clad regions have a
refractive index that provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.58. The semiconductor laser diode of claim 55, wherein the
clad regions are of a semiconductor material having a lower index
of refraction than materials of portions of the waveguide region
adjacent the clad regions..Iaddend.
.Iadd.59. The semiconductor laser diode of claim 55, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.60. The semiconductor laser diode of claim 55, wherein the
waveguide region has a length greater than about 2.0
mm..Iaddend.
.Iadd.61. The semiconductor laser diode of claim 55, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.62. The semiconductor laser diode of claim 55, wherein the
waveguide region is of a thickness of about 1.3 .mu.m..Iaddend.
.Iadd.63. The semiconductor laser diode of claim 55, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.64. The semiconductor laser diode of claim 55, wherein the
waveguide region consists essentially of InGaAsP..Iaddend.
.Iadd.65. The semiconductor laser diode of claim 55, wherein the
waveguide region comprises In and Ga..Iaddend.
.Iadd.66. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the clad regions are of a semiconductor
material having a lower index of refraction than materials of
portions of the waveguide region adjacent the clad
regions..Iaddend.
.Iadd.67. The semiconductor laser diode of claim 66, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.68. The semiconductor laser diode of claim 66, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.69. The semiconductor laser diode of claim 66, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.70. The semiconductor laser diode of claim 66, wherein the
means for generating photons in the waveguide region includes a
plurality of spaced quantum well regions with a barrier region
between each pair of adjacent quantum well regions..Iaddend.
.Iadd.71. The semiconductor laser diode of claim 66, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.72. The semiconductor laser diode of claim 66, wherein the
waveguide region has a length greater than about 2.0
mm..Iaddend.
.Iadd.73. The semiconductor laser diode of claim 66, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.74. The semiconductor laser diode of claim 66, wherein the
waveguide region is of a thickness of about 1.3 .mu.m..Iaddend.
.Iadd.75. The semiconductor laser diode of claim 66, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.76. The semiconductor laser diode of claim 66, wherein the
waveguide region consists essentially of InGaAsP..Iaddend.
.Iadd.77. The semiconductor laser diode of claim 66, wherein the
waveguide region comprises In and Ga..Iaddend.
.Iadd.78. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region has a length greater
than about 2.0 mm..Iaddend.
.Iadd.79. The semiconductor laser diode of claim 78, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.80. The semiconductor laser diode of claim 78, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.81. The semiconductor laser diode of claim 78, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.82. The semiconductor laser diode of claim 78, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.83. The semiconductor laser diode of claim 78, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.84. The semiconductor laser diode of claim 78, wherein the
waveguide region is of a thickness of about 1.3 .mu.m..Iaddend.
.Iadd.85. The semiconductor laser diode of claim 78, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.86. The semiconductor laser diode of claim 78, wherein the
waveguide region consists essentially of InGaAsP..Iaddend.
.Iadd.87. The semiconductor laser diode of claim 78, wherein the
waveguide region comprises In and Ga..Iaddend.
.Iadd.88. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region is of a thickness of
about 1.3 .mu.m..Iaddend.
.Iadd.89. The semiconductor laser diode of claim 88, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.90. The semiconductor laser diode of claim 88, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.91. The semiconductor laser diode of claim 88, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.92. The semiconductor laser diode of claim 88, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.93. The semiconductor laser diode of claim 88, wherein the
waveguide region consists essentially of AlGaAs..Iaddend.
.Iadd.94. The semiconductor laser diode of claim 88, wherein the
waveguide region consists essentially of InGaAsP..Iaddend.
.Iadd.95. The semiconductor laser diode of claim 89, wherein the
waveguide region comprises In and Ga..Iaddend.
.Iadd.96. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong: means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region consists essentially of
InGaAsP..Iaddend.
.Iadd.97. The semiconductor laser diode of claim 96, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.98. The semiconductor laser diode of claim 96, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.99. The semiconductor laser diode of claim 96, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.100. The semiconductor laser diode of claim 96, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.101. The semiconductor laser diode of claim 96, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
.Iadd.102. The semiconductor laser diode of claim 96, wherein the
quantum well region consists essentially of InGaAsP..Iaddend.
.Iadd.103. A semiconductor laser diode comprising: a body of a
semiconductor material having therein a waveguide region which is
not intentionally doped and which is of a material which
substantially confines photons therein and allows the flow of
photons therealong; means within the waveguide region for
generating an optical mode of photons; and a clad region on each
side of the waveguide region, the clad regions being at least
partially doped to be of opposite conductivity type, wherein said
photon generating means is thinner than the thickness of the
waveguide region and is spaced from the clad regions, wherein at
least a portion of the waveguide region on each side of the means
for generating an optical mode of photons is of a uniform
composition throughout its thickness, wherein the thickness of the
waveguide regions and the composition of the waveguide and clad
regions are such that an overlapping of the optical mode generated
in the waveguide region into the clad regions is not greater than
about 5%, and wherein the waveguide region comprises In and
Ga..Iaddend.
.Iadd.104. The semiconductor laser diode of claim 103, wherein the
waveguide region is of a thickness of at least 500
nanometers..Iaddend.
.Iadd.105. The semiconductor laser diode of claim 103, wherein the
materials of the waveguide region and the clad regions have a
refractive index which provides confinement of the optical mode to
the waveguide region with an overlap of the optical mode into the
clad regions of no greater than 5%..Iaddend.
.Iadd.106. The semiconductor laser diode of claim 103, wherein the
means for generating photons in the waveguide region includes at
least one quantum well region..Iaddend.
.Iadd.107. The semiconductor laser diode of claim 103, wherein the
thickness of the waveguide region and the composition of the
waveguide and clad regions are such that an overlapping of the
optical mode generated in the waveguide region into the clad
regions is not greater than about 2%..Iaddend.
.Iadd.108. The semiconductor laser diode of claim 103, wherein the
waveguide region is of a thickness of about 0.7 .mu.m..Iaddend.
Description
The present invention is directed to a semiconductor laser diode
having increased output power, and, more particularly, to a high
power semiconductor laser diode having an enlarged waveguide.
BACKGROUND OF THE INVENTION
A semiconductor laser diode basically comprises a body of a
semiconductor material or materials having a waveguide region and a
clad region on each side of the waveguide region. Within the
waveguide region is a region, such as a quantum well region, in
which photons are generated when the diode is properly biased by
and electrical current. The clad regions are doped to be of
opposite conductivity type and are of a material having a lower
refractive index than the material of the waveguide region so as to
attempt to confine the photons to the waveguide region.
In the design of laser diodes heretofore made and known to those
skilled in the art as being of optimum design, the thickness of the
waveguide region was limited in extent, usually to be in the order
of 0.2 to 0.3 micrometers (.mu.m), so as to achieve a minimization
of the threshold current. To achieve the minimization of the
threshold current, a substantial overlapping of the optical mode
generated in the waveguide region into the adjacent doped regions,
such as the dad regions, occurred. Although a major portion of the
optical mode generated in the waveguide region remains and travels
along the waveguide region, a portion of the optical mode at each
end thereof extends into, i.e., overlaps into, the regions of the
diode adjacent the waveguide region. This typically results in
undesirable optical propagation losses. The propagation loss in a
clad region contributes to the propagation loss of the lasing mode
to the extent of the propagation loss of said clad region
multiplied by the overlap factor of the clad region by the lasing
mode. The overlap factor of a clad region is the proportion of
photons which are carried in the clad region. Throughout this
specification the term "propagation loss" means the propagation
loss of the lasing mode. Thus, the overall efficiency of the device
is reduced, thereby limiting directly and indirectly the output
power capability of the device. Another constant on typical
semiconductor laser diodes heretofore made has been the length of
the diode, i.e., the distance between its ends. The longer the
laser diode, the lower the thermal and electrical resistance of the
diode and therefore, in general, the larger the output power.
However, because of the lower efficiency resulting from the
propagation losses, the length of the laser diode has been
limited.
High efficiency, high power lasers have long been pursued for such
applications as optical pumping of solid state and fiber laser,
direct material processing, printing, communications, sensing, etc.
Therefore, it would be desirable to improve the efficiency and
reduce the losses of such laser diodes so as to increase the output
power of the devices.
SUMMARY OF THE INVENTION
A semiconductor laser diode formed of a body of a semiconductor
material. The body includes a waveguide region which is not
intentionally doped and having therein means for generating
photons. A separate clad region is on each side of the waveguide
region and the clad regions are at least partially doped to be of
opposite conductivity types. The thickness of the waveguide region
and the composition of the waveguide and clad regions are such that
an overlapping of the optical mode generating in the waveguide
region into the clad regions is no greater than about 5%.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a basic semiconductor laser diode
which incorporates the present invention;
FIG. 2 is a representation of a separate confinement
heterostructure (SCH) laser diode which can incorporate the present
invention;
FIG. 3 is a representation of a stepped SCH laser diode which can
incorporate the present invention: and
FIG. 4 is a representation of a GRIN-SCH form of laser diode which
can incorporate the present invention.
DETAILED DESCRIPTION
Referring initially to FIG. 1, a semiconductor laser diode which
incorporates the present invention is generally designated as 10.
Laser diode 10 comprises a body 12 of a semiconductor material or
materials having a bottom surface 14, top surface 16, end surfaces
18 and side surfaces 20. The body 12 includes a waveguide region 22
extending there-across. Within the waveguide region 22 is an active
region 24 in which photons are generated when an appropriate
electrical bias is placed across the diode 10. The active region 24
may be of any structure well known in the laser diode art which is
capable of generating photons. Preferably, the active region 24
comprises one or more quantum wells. The waveguide region 22
includes layers 26 on each side of the active region 24 which are
of undoped semiconductor material having a doping level of no
greater than about 5.times.10.sup.16 atoms/cm.sup.3.
On each side of the waveguide region 22 is a separate clad region
28 and 30. The clad regions 28 and 30 are layers of a semiconductor
material of a composition which has a lower refractive index than
the materials of the layers 26 of the waveguide region 22. Also,
the clad regions 28 and 30 are at least partially doped to be of
opposite conductivity type. The doping level in the clad regions 28
and 30 are typically between about 5.times.10.sup.17/cm.sup.3 and
2.times.10.sup.19/cm.sup.3. For example, the clad region 28 between
the waveguide region 22 and the top surface 16 of the body 12 may
be of P-type conductivity and the clad region 30 between the
waveguide region 22 and the bottom surface 14 of the body 12 may be
of N-type conductivity.
A contact layer 32 of a conductive material, such as a metal, is on
and in ohmic contact with the P-type conductivity clad region 28.
The contact layer 32 is in the form of a strip which extends
between the end surfaces 18 of the body 12 and is narrower than the
width of the body 12, i.e., the distance between the side surfaces
20 of the body 12. A contact layer 34 of a conductive material,
such as a metal, is on and in ohmic contact with the N-type
conductivity clad region 30. The contact layer 34 extends across
the entire area of the bottom surface 14 of the body 12.
In the laser diode 10 to achieve the higher efficiency and thus the
higher output power, the thickness of the waveguide region 22 and
the composition of the waveguide region 22 and the clad regions 28
and 30 must be such that the optical mode generated by the active
region 24 does not overlap from the waveguide region 22 into the
clad regions 28 and 30 by more than 5%, and preferably by not more
than 2%. However, the amount of overlap of the photons into the
clad regions 28 and 30 need not be less than 1%. This means that
the amount of the optical mode, which is mainly in the waveguide
region 22, that extends into (overlaps) the clad regions 28 and 30
is no greater than about 5% of the total optical mode. To achieve
this, the thickness of the waveguide region should be at least 500
nanometers (nm) and the composition of the waveguide region 22 and
the clad regions 28 and 30 should be such that the refractive index
of the regions provides the confinement of the optical mode in the
waveguide region 22 to the extent that the overlap of the optical
mode into the clad regions 28 and 30 is not greater than 5%. The
various regions of the body 12 may be made of any of the well known
semiconductor materials used for making laser diode, such as but
not limited to gallium arsenide, aluminum gallium arsenide, indium
phosphide, indium gallium arsenide and such quaternary materials as
indium, gallium arsenide phosphide. However, the materials used for
the various regions must have refractive indices which provide the
desired confinement of the optical mode. The clad regions 28 and 30
may be doped uniformly throughout their thickness or may be graded
with little or no doping at their junction with the waveguide
region 22 and the heaviest doping at the respective surface of the
body 12.
Referring to FIG. 2, there is schematically shown one form 36 of a
laser diode in accordance with the present invention. Laser diode
36 is similar in structure to the laser diode 10 shown in FIG. 1
and includes a waveguide region 38 having therein a single quantum
well region 40 of undoped In.sub.20Ga.sub.80As and a separate
confinement layer 42 of undoped Al.sub.30Ga.sub.70As on each side
of the quantum well region 40. A P-type conductivity clad region 44
is on one side of the waveguide region 38 and an N-type
conductivity clad region 46 is on the other side of the waveguide
region 38. Each of the clad regions 44 and 46 are of
Al.sub.60Ga.sub.30As. Although the laser diode 36 is shown as
having only a single quantum well region 40, it may have a
plurality of quantum well regions which are spaced apart by barrier
regions as is well known in the laser diode art.
Referring to FIG. 3, another form of the laser diode in accordance
with the present invention is schematically shown and generally
designated 48. Laser diode 48 comprises a waveguide region 50
having therein three quantum well regions 52 of InGaAsP and spaced
apart by barrier regions 54 of InGaAsP having a bandgap of 1.0 eV.
At each side of the quantum well regions 52 are inner confinement
layers 56 also of InGaAsP having a bandgap of 1.0 eV. Adjacent each
of the inner confinement layers 56 is an outer confinement layer 58
of InGaAsP having a bandgap of 1.13 eV. Adjacent the outer
confinement layers 58 are clad regions 60 and 62 of InP which are
doped N-type and P-type respectively. The clad regions 60 and 62
are doped to a level of between 5.times.10.sup.17/cm.sup.3 and
2.times.10.sup.19/cm.sup.3. The N-type clad region 60 is doped
uniformly throughout its thickness, but the P-type clad region 62
may have a graded doping from a lowest level at the interface with
the outer confinement layer 58 to a highest level at its
surface.
Laser diodes 48 were made with the quantum well regions 52 being of
a thickness of 4.5 nm, and the barrier regions being of a thickness
of 16 nm. The inner confinement layers 56 were of a thickness of 30
nm. In one laser diode 48 the outer confinement layers were of a
thickness of 300 nm. and in another laser diode 48 the outer
confinement layers were of a thickness of 600 nm. This provided
laser diodes 48 in which the total thickness of the waveguide
regions 50 were 0.7 and 1.3 .mu.m respectively. When tested the
laser diodes were found to have an increasing efficiency with
increased thickness. The laser diode 48 having the 1.3 .mu.m thick
waveguide region 50 had an efficiency 1.3 time higher and threshold
currents 10-20% lower than the laser diode 48 having the 0.7 thick
waveguide region 50. Output powers of 4.6 W, CW and 6.8 W, quasi-CW
at wavelengths of 1.42 to 1.5 .mu.m were obtained from these laser
diodes 48.
Referring to FIG. 4, still another form of a laser diode
incorporating the present invention is schematically shown and is
generally designated as 62. Laser diode 62 has a waveguide region
64 in which is a quantum well region 66. On each side of the
quantum well region 66 is a confinement region 68. Clad regions 70
and 72 of N-type and P-type conductivity are at opposite sides of
the waveguide region 64. In the laser diode 62 the confinement
regions 68 are of a material whose composition is graded to
provided a graded band gap. Although the laser diode 62 is shown
with a single quantum well region 66 it can have a multiple number
of quantum well regions spaced by barrier regions, such as shown in
the laser diode 48 shown in FIG. 3.
Thus there is provided by the present invention a laser diode
having a thicker waveguide region, at least 500 nm in thickness,
and which has a small overlap of the optical mode into the clad
regions, no greater than bout 5%. Since the waveguide region is not
intentionally doped, it has a small thermal and electrical
resistance, so that the optical mode can travel through the
waveguide region with little optical loss. Since only a small
portion of the optical mode overlaps into the more highly doped
clad regions, which have a greater thermal and electrical
resistance, there is only a small optical loss in the clad regions.
Since the optical losses are lower, the device has a greater
efficiency and a greater optical power output. In addition, the
laser diode of the present invention provides a larger area spot
size of the emitted beam. The larger spot size reduces the damage
to the emitting surface of the laser diode so as to increase the
operating lifetime of the laser diode. In addition, the laser diode
of the present invention can be made longer, i.e., lengths of 2
millimeters or longer. Since there is lower losses in the laser
diode it can be made longer to provide greater power output.
Furthermore, although the laser diode shown and described is of a
separate confinement quantum well structure, it should be
understood that the present invention can be used in laser diodes
of any of the well known structure, such as lateral waveguiding
ridge structures, buried structures, gain-guided structures,
distributed feedback structures, distributed Bragg reflector
structures, etc.
* * * * *