Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – Plural light emitting devices
Reexamination Certificate
1998-12-04
2002-07-09
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
Plural light emitting devices
C257S092000, C257S095000, C257S099000, C438S026000, C438S046000, C438S047000, C372S046012, C372S049010
Reexamination Certificate
active
06417524
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to light emitting diodes, and more particularly, to high-power superluminescent diodes.
BACKGROUND
High-power superluminescent diodes (SLDS) are useful as low-coherent light sources for optical sensing, fiber-optic gyroscopes, and medical instrumentation, and also as gain media for mode-locked lasers and broad-band tunable lasers. An example of a conventional SLD is shown in FIG.
1
. The device
10
includes a body
11
including an active layer
12
, an electrode
13
, and a narrow stripe
14
of a conductive material. When current is passed between the electrode
13
and the stripe
14
, the active layer
12
is activated such that it generates light in the region beneath the stripe
14
. The stripe
14
is placed at an angle &thgr; with respect to the sides
15
,
16
of the body
11
to minimize feedback within the stripe
14
, which causes spectral modulation. Examples of conventional SLDs are provided in U.S. Pat. Nos. 4,821,277, 4,958,355, 4,821,276, 4,793,679, and 4,789,881, each of which is incorporated herein by reference.
The requirements of high-power and single-waveguide-mode operation impose conflicting constraints on the SLD stripe design. For example, output power is increased by increasing the width of the stripe
14
. Such an increase in width, however, often results in the conversion to, and support of, multiple transverse modes, thus making the SLD unsuitable for many applications such as coupling to a single-mode optical fiber.
In efforts to increase SLD power while minimizing multiple transverse modes, tapered stripes have been developed as shown in FIG.
2
. The tapered stripe design is described, for example, in J. N. Walpole et al., “High-Power Strained-Layer InGaAs/AlGaAs Tapered Traveling Wave Amplifier,” 61 (7)
Appl. Phys. Lett
. 740-42 (1992), which is incorporated herein by reference. In the example
20
shown in
FIG. 2
, the stripe
24
is “tapered” such that the distance between its sides
25
,
26
increases as one moves from the side
16
to the side
15
of the body
11
. The taper of the stripe
24
collimates light out of the side
15
without causing significant conversion to higher order transverse modes or significant radiation from the sides of the underlying active layer. One potential problem associated with the structure shown in
FIG. 2
, however, is that the width of the stripe
24
at the body side
15
is relatively large such that it is difficult to couple the device
20
to a single-mode fiber. Furthermore, this wide structure often results in dark-line defects, thus reducing the useful lifetime of the device
20
.
SUMMARY OF THE INVENTION
The present invention provides light emitting diodes each comprising a body of semiconductor material having a first side surface, a second side surface, and a top surface; and a stripe of conductive material over the top surface of the body. The stripe has a first segment and a second segment, each extending from the first side surface to the second side surface of the body. The width of the stripe is therefore defined by the distance between these two segments. The first and second segments of the stripe are configured such that they are substantially non-parallel, and the width of the stripe at its ends is less than the width of the stripe intermediate its ends.
One advantage of the present invention is that, when configured at an angle with respect to the end faces, it provides superluminescent diodes of high output power.
Another advantage of the present invention is that it provides superluminescent diodes characterized by broad output spectra without significant spectral modulation.
Another advantage of the present invention is that it provides superluminescent diodes that minimize higher order transverse modes.
Another advantage of the present invention is that it provides a high power optical amplifier.
Another advantage of the present invention is that it can be configured as a high power laser by providing external feedback.
Yet another advantage of the present invention is that it provides superluminescent diodes of high output power that are amenable to coupling to single-mode fibers.
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patent: 3636397 (1972-01-01), Addamiano et al.
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patent: 4793679 (1988-12-01), Toda et al.
patent: 4821276 (1989-04-01), Alphonse et al.
patent: 4821277 (1989-04-01), Alphonse et al.
patent: 4856014 (1989-08-01), Fiqueroa et al.
patent: 4958355 (1990-09-01), Alphonse et al.
patent: 4990971 (1991-02-01), Le Creff
patent: 5309001 (1994-05-01), Watanabe et al.
patent: 5321714 (1994-06-01), Paoli
patent: 5818857 (1998-10-01), Palmer
Alphonse G A Et Al.: “New high-power single-mode superluminescent diode with low spectral modulation” CLEO '96. Summaries of Papers Presented at the Conference on Lasers and Electro-Optics, Anaheim, Ca, Jun. 2-7 1996, Technical Digest Series, Conference Edition (IEEE CAT. No. 96CH35899), vol. 9, 1996, pp. 107-108 (Tuesday Jun. 4) XP002125434 Washington, DC, US, Opt. Soc. America, US *the whole document*.
Patent Abstracts of Japan vol. 013, No. 507 (E-725), Mar. 10, 1989 )—& JP 63 276287 A (Fujitsu Ltd), Nov. 14, 1988 * abstract; figure 2*.
Patent Abstracts of Japan vol. 013, No. 507 (E-845), Nov. 14, 1989 —& JP 01 205479 A (NEC Corp), Aug. 17, 1989 * abstract; figures 1,3*.
Supplementary European Search Report corresponding to application No. 97928710.9-2203-US9709199.
Duane Morris LLP
Kang Donghee
Plevy Arthur L.
Princeton Lightwave Inc.
Thomas Tom
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