Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
1998-01-09
2001-04-17
Arroyo, Teresa M. (Department: 2881)
Coherent light generators
Particular temperature control
Heat sink
C372S034000
Reexamination Certificate
active
06219364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser module with a cooler system using a Peltier element, and more particularly, to the improvement of a metal substrate secured on the Peltier element.
2. Description of the Related Art
Semiconductor laser modules are currently used for optical fiber telecommunications particularly as signal light sources of cable televison (cATV) systems and excitation light sources of fiber amplifiers. Such semiconductor laser modules typically contain a Peltier element that operates as an electronic cooler in order to realize a high output power and stable operation of the module and a metal substrate is mounted onto the top of the Peltier element such that optical components such as a laser diode chip, a photodiode chip and/or a lens and electric components such as a thermistor, inductors and/or resistors are arranged on the metal substrate.
Such semiconductor laser modules are so configured as to cool the entire metal substrate and maintain the temperature of the laser diode chip to a constant level by detecting the temperature by means of the thermistor bonded near the laser diode chip and feeding back the detected temperature to the Peltier element to drive the latter.
Semiconductor laser modules using a Peltier element as a cooler are disclosed, inter alia, in JP-A62-117382 and JP-A-62-276892.
In a prior art semiconductor laser module, the metal substrate is made of a single metal having a large thermal conductivity. On the other hand, the ceramic panel is made of a ceramic having a small thermal expansion coefficient. In this case, in order to enhance the power output capability of the semiconductor laser module, the metal substrate is preferably made of a metal having a much larger thermal conductivity, to enhance the heat radiating effect. This will be explained later in detail.
In the above-described prior art semiconductor laser module, however, there is a large difference in thermal expansion coefficient between the metal substrate and the ceramic panel. Therefore, the metal substrate and the ceramic panel are subjected to large thermal stress. As a result, the Peltier element can become destroyed in a thermal environment test involving rapid temperature changes.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor laser module including a Peltier element that has an enhanced cooling potential when operating for a high power output level and is made less vulnerable to damage in a thermally harsh environment by making the panel of the Peltier element and the metal substrate arranged on top of it show a small difference in expansion coefficient.
According to the present invention, in a semiconductor laser module including a laser diode chip, a metal substrate for mounting the laser diode chip thereon, and a Peltier element having a panel coupled by metal solder to the metal substrate, the metal substrate is formed by a first metal member having a larger thermal conductivity than about 290 W/m·deg and a second metal member having a thermal expansion coefficient close to that of the panel.
REFERENCES:
patent: 4661959 (1987-04-01), Kaneko
patent: 4998256 (1991-03-01), Ohshima et al.
patent: 5436920 (1995-07-01), Minemoto et al.
patent: 0 477 841 A2 (1992-04-01), None
patent: 0 590 232 A1 (1994-04-01), None
patent: 62-117382 (1987-05-01), None
patent: 62-276892 (1987-12-01), None
patent: 1-243488 (1989-09-01), None
patent: 2-102756 (1990-08-01), None
patent: 4-240607 (1992-08-01), None
patent: 5-96810 (1993-12-01), None
patent: 7-131112 (1995-05-01), None
Office Action issued by Japanese Patent Office, Jul. 13, 1999 (including partial English translation).
Patent Abstracts of Japan, vol. 012, No. 167.
Arroyo Teresa M.
Monbleau Davienne
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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