Active solid-state devices (e.g. – transistors – solid-state diode – Encapsulated – With heat sink embedded in encapsulant
Reexamination Certificate
2002-05-14
2004-04-27
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Encapsulated
With heat sink embedded in encapsulant
C257S720000, C372S034000, C372S102000, C219S210000, C385S020000, C385S027000, C385S050000
Reexamination Certificate
active
06727598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an improved thermally tunable system.
2. Background of the Related Art
A conventional thermally tunable semiconductor laser system is shown in FIG.
1
. With a thermally tunable semiconductor laser, the output wavelength of the semiconductor laser can be tuned thermally since the refractive index changes with temperature. The conventional thermally tunable laser system
10
of
FIG. 1
includes a semiconductor laser designated by the reference numeral
20
. The semiconductor laser
20
includes an active region and a tuning region. In this case, the active region includes a gain section
45
. The tuning region includes a phase section
40
and a grating section
35
.
The semiconductor laser
20
is positioned on a heat sink
30
. A heater
90
is provided, as shown in FIG.
1
. The heater
90
provides thermal power for tuning of the phase and grating sections
35
and
40
to a desired wavelength or wavelengths. A layer of oxide
23
separates the heater
90
from electrical contact
21
. A contact layer
22
and a cladding layer
24
are provided between the electrical contacts
21
and the various sections
35
,
40
, and
45
of the device.
In the prior art devices, all sections of the semiconductor laser
20
are tuned by changing the temperature of the heat sink
30
. However, at least the following problems arise with the prior art devices.
First, the material used for the gain section is usually highly temperature sensitive. That is, increasing the temperature can reduce the gain dramatically. As a result, the temperature can not be increased too much, and thus the tuning range is very limited.
Second, since the laser chip is very thin, generally only about 100 &mgr;m thick, thermal power injected into the chip is very rapidly transferred to the heat sink. As a result, power utilization is very inefficient. Accordingly, often times the heaters are burned out the heaters are burned out before a reasonably high temperature can be reached.
SUMMARY OF THE INVENTION
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
The invention provides an improved thermally tunable apparatus that solves at least the above mentioned problems of the prior art.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
REFERENCES:
patent: 4286232 (1981-08-01), Puech et al.
patent: 5022730 (1991-06-01), Cimini et al.
patent: 5325392 (1994-06-01), Tohmori et al.
patent: 5642371 (1997-06-01), Tohyama et al.
patent: 5717712 (1998-02-01), Swaminathan et al.
patent: 6332322 (2001-12-01), Tanaka
S. L. Woodward et al. “A DBR Laser Tunable by Resistive Heating”, IEEE Photonics Technology Letters, vol. 4, No. 12, Dec. 1992, pp. 1330-1332.
Shinji Sakano et al. “Tunable DFB Laser with a Striped Thin-Film Heater”, IEEE Photonics Technology Letters, vol. 4, No. 4, Apr. 1992, pp. 321-323.
Hiroyuki Ishii et al., “Narrow Spectral Linewidth Under Wavelength Tuning in Thermally Tunable Super-Structure-Grating (SSG) DBR Lasers”, IEEE Journal of Selected Topics In Quantum Electronics, vol. 1, No. 2, Jun. 1995, pp. 401-407.
Fleshner & Kim LLP
Nelms David
Tran Long
University of Maryland Baltimore County
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