Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Reexamination Certificate
2002-02-11
2004-01-13
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
C385S088000, C385S093000, C372S034000, C372S036000
Reexamination Certificate
active
06676306
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a high power light source. More specifically, the present invention is directed to a light source comprising a plurality of laser diode modules having high optical power and arranged in high density.
DESCRIPTION OF THE RELATED ART
Normally, laser diode modules are employed as signal light sources of optical fiber communications, especially, signal light sources of main trunk systems/CATV systems, and light-excitation light sources of fiber amplifiers. In such a laser diode module, a Peltier-effect element is built therein, and various optical components and various electronic components are arranged on a metal substrate mounted on the Peltier-effect element in order to realize high optical power and stable operations of the laser diode module. The optical components are a laser diode chip, a photodiode chip, a lens, and the like whereas, the electronic components are a thermistor element, an inductor, a resistor, and the like.
It should be noted that the above-explained Peltier-effect element is a thermocouple semiconductor. In the case that the Peltier-effect element is made from a p-type semiconductor, when a DC current is supplied to the Peltier-effect element, heat is moved along the current flowing direction. In the case that the Peltier-effect element is made from an n-type semiconductor, when a DC current is supplied thereto, heat is moved along a direction opposite to the current flowing direction, so that a temperature difference is produced between both ends of the thermocouple semiconductor. In a cooling system using such a Peltier-effect element, a low-temperature side thereof is used for cooling, and a high-temperature side thereof is used for heat dissipation, while utilizing the above-explained temperature difference.
In the laser diode module, a temperature of the above-explained laser diode chip is detected by the thermistor element positioned in the vicinity of the laser diode chip. The laser diode module includes the following structure which is capable of keeping the temperature of the laser diode chip constant. That is, the thus detected value of the temperature is fed back so as to drive the Peltier-effect element, so that the entire metal substrate where the laser diode chip is arranged is cooled.
FIG. 5
depicts a conventional laser diode module.
FIG. 5
is a sectional view for schematically showing the conventional laser diode module. As shown in
FIG. 5
, the laser diode module includes a mount
113
for mounting thereon both a laser diode chip
111
and a heat sink
112
, a chip carrier
115
for mounting thereon a monitoring photodiode chip
114
, a lens holder
116
, a metal substrate
110
a
for mounting thereon a resistor, an inductor, and a circuit board (not shown); and a Peltier-effect element
117
. The Peltier-effect element
117
is fixed on a heat dissipating plate
118
of a package by metal solder. It should also be noted that ceramics plates
119
A and
119
B are arranged on upper and lower portions of a Peltier-effect element
117
.
FIG. 6
is a sectional view for showing the laser diode module, taken along a line A to A′ in FIG.
5
. As shown in
FIG. 6
, as an essential portion of the laser diode module, a thermistor
121
and the laser diode chip
111
are mounted on the heat sink
112
. As a metal solder used to adhere the Peltier-effect element
117
to the metal substrate
110
a
, soft solder
122
is employed in order to relax a thermal expansion difference between the two members.
The above-explained metal substrate is in general made of a single material such as copper tungsten (CuW: weight distribution ratio of copper is 10% to 30%). When the metal substrate is adhered to the Peltier-effect element, low-temperature soft solder such as indium tin (InSn) is employed so as to relax the thermal expansion difference between the two materials.
However, recently, more severe requests are made with respect to both the cooling capability of the laser diode module, and the temperature environmental reliability (namely, capability of maintaining normal functions under the condition even when temperature varies).
At first, in order to improve the cooling capability, the size of the Peltier-effect element should be made large, and also the metal substrate mounted on the upper portion thereof must be made from the high heat transfer material. Since the temperature adjusting time (namely, time duration until target temperature is reached) is reduced due to improvements in the cooling capability of the Peltier-effect element, the temperature stress given to the metal substrate mounted on the Peltier-effect element is also increased. As a result, the adverse influence given by the difference of the heat expansion coefficients between the Peltier-effect element and the metal substrate is increased. As a result, there is such a problem that cracks and exfoliation will occur, because the soft solder used to adhere the both members is slid. Moreover, since the soldering creep phenomenon which is specific to the soft solder becomes apparent, such a low-temperature hard solder as bismuth tin (BiSn) must be employed as the solder for adhering the Peltier-effect element to the metal substrate.
To solve the above-explained problem, Japanese Patent Provisional Publication No. Hei 10-200208 discloses a semiconductor laser module including a metal substrate made of two different kinds of metal materials. FIG.
7
schematically shows a conceptional structure of the semiconductor laser module. As shown in
FIG. 7A
, the semiconductor laser module is manufactured as follows: a metal substrate
210
is adhered to a Peltier-effect element
207
with ceramics boards
209
A and
209
B mounted on upper and lower surfaces thereof by using hard solder
212
. An LD chip
201
and a thermistor
211
are mounted on the metal substrate
210
through a heat sink
202
and a sub-mount
203
together with a lens of an optical system. The thermistor
211
is employed so as to keep the temperature of the LD chip
201
constant.
The metal substrate
210
is adhered onto the upper surface of the Peltier-effect element
207
in such manner that a heat flow derived from the LD chip
201
directed to the Peltier-effect element
207
is in perpendicular thereto. In particular, the metal substrate
210
is formed in such a manner that a first metal member
213
is arranged at a center portion of the substrate including a portion located directly below the LD
201
, and a second metal member
214
is arranged so as to surround the first metal member. Furthermore, as depicted in
FIG. 7B
, the metal substrate
210
is manufactured in such a manner that the first metal member
213
is formed by such a metal member having a large heat conductivity, whereas the second metal member
214
is made of such a metal member having a heat expansion coefficient smaller than that of the first metal member
213
.
In other words, it is expected that since the above-explained metal substrate
210
is employed, the heat expansion of the entire metal substrate can be reduced, the heat condution thereof can be improved so as to increase the cooling performance. At the same time, it is expected that reliability of the Peltier-effect element is improved.
It should also be noted that in general, a plurality of laser diode modules functioning as a light output source are mounted on either the light-excitation light source or the optical-signal light source. A laser diode module is combined with other optical components so as to be used in an optical amplifier.
In accordance with the above-explained prior art, it is so expected that the cooling performance of the Peltier-effect element may be improved and also the reliability of the Peltier-effect element may be increased in each of the laser diode modules. However, in the case that the respective laser diode modules output higher optical power, and also a large number of such high-power laser diode modules are arranged in high density to be driven, the resulting heat generated from
Ikeda Masami
Nagamatsu Shinya
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Palmer Phan T. H.
The Furukawa Electric Co. Ltd.
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