Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
1999-07-30
2001-05-29
Healy, Brian (Department: 2874)
Coherent light generators
Particular temperature control
Heat sink
C372S034000, C372S043010, C372S050121
Reexamination Certificate
active
06240113
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an electro-optic apparatus and an associated fabrication method and, more particularly, to an electro-optic apparatus having a microlaser that is capable of efficient heat dissipation as well as associated methods for fabricating the electro-optic apparatus.
BACKGROUND OF THE INVENTION
Modem electro-optic systems are being further miniaturized such that many electro-optic components are commonly mounted upon the same platform. The platform typically includes a submount which may be mounted upon a heat sink, such as a heat pump or the like. As such, the submount is generally formed of a thermally conductive material, such as a metal or semiconductor, in order to provide a path of relatively low thermal impedance from the various electro-optic components mounted upon the submount to the underlying heat sink.
In order to properly function, the various components of the electro-optic system must be precisely aligned. For example, an electro-optic system that includes a pump diode and an associated laser crystal or active gain medium requires that the pump diode be precisely aligned with the laser crystal as well as various other optical components, such as lenses, mirrors and the like. While this alignment has always been somewhat challenging, the alignment of the various components of an electro-optic system has become increasingly critical and increasingly difficult as the various components of the electro-optic systems have become even smaller.
With respect to an electro-optic system that includes a pump diode and an associated laser crystal or active gain medium, the pump diode and the laser crystal also must be precisely spaced from one another in order to produce the desired output, such as signals of the desired frequency. As such, even slight differences in the spacing between a pump diode and a laser crystal, such as submicron differences in the spacing, can cause the laser crystal to emit signals having a slightly different frequency. Since many applications are dependent upon receiving signals of a predetermined frequency, even small shifts or changes in the frequency of the laser crystal output can create problems downstream of the laser crystal.
Once the various electro-optic elements have been appropriately mounted upon the submount, the electro-optic system, including the submount and any underlying heat sink, is commonly mounted in an appropriate package, such as a TO-3 or TO-8 package. As is known to those skilled in the art, electro-optic packages, such as a TO-3 or TO-8 package, includes a number of conductive pins which must be electrically connected to appropriate leads of the electro-optic system in order to provide the necessary electrical energy to the electro-optic system. Even if the various electro-optic components are properly mounted upon the submount, the mounting of the electro-optic system within the package and the establishment of the electrical connections between the conductive pins of the package and respective leads of the electro-optic system can disadvantageously affect the performance of the electro-optic system. In particular, the mounting of the electro-optic system within a package generally requires handling of the electro-optic system which may expose the electro-optic system and, more particularly, the various electro-optic components, to static electricity and other deleterious conditions. In addition, conventional packaging techniques, including the establishment of appropriate electrical connections between the conductive pins of a package and the respective leads of the electro-optic system, may disadvantageously heat the various electro-optic components.
One of the advantages of an electro-optic system that includes a pump diode and an associated laser crystal is the relatively small size of the resulting device. Although small in size, the pump diode and the laser crystal generate significant amounts of heat once in operation. As such, the electro-optic system must provide for sufficient heat dissipation such that the various components, such as the pump diode and laser crystal, can be operated without overheating or otherwise being damaged. In particular, the electro-optic system should be designed such that the pump diode can remain in continuous wave (CW) operation so as to deliver the maximum pump energy to the laser crystal without overheating. Since a significant amount of heat is generated by the CW operation of a pump diode, particularly for the relatively small size of an electro-optic system that includes a pump diode and a laser crystal, conventional electro-optic systems have had difficulty in dissipating the thermal load as quickly and efficiently as required for some applications.
Although a variety of miniaturized electro-optic systems have been developed which include submounts and associated heat sinks for providing at least some heat dissipation for the various electro-optic components, a need still exists for improved techniques for precisely spacing the various electro-optic components of a miniaturized electro-optic system, such as a pump diode and a laser crystal or active gain medium. Moreover, a need still exists for increased heat dissipation for the various components of an electro-optic system so as to permit the electro-optic system to operate continuously without overheating or otherwise damaging the components.
SUMMARY OF THE INVENTION
An electro-optic apparatus and an associated fabrication method are therefore provided that permit an active gain medium to be precisely spaced from the pump source such that signals having the desired characteristics, such as the desired frequency, are emitted. Additionally, the electro-optic apparatus and the associated fabrication method of the present invention provide increased heat dissipation by separating the thermal loads of the pump source and the active gain medium such that the pump source can be operated continuously in order to maximize the pumping of the active gain medium without overheating or otherwise damaging the electro-optic apparatus.
The electro-optic apparatus includes a primary heat sink and at least one submount mounted to the heat sink. Preferably, each submount is formed of a thermally conductive, electrically insulating material in order to transfer heat from the components to the primary heat sink while providing electrical isolation for the components mounted upon the submount. The electro-optic apparatus of the present invention also includes a secondary heat sink mounted to the at least one submount with an active gain medium mounted, in turn, to the secondary heat sink. Typically, the active gain medium is part of a microlaser that also includes a passive Q-switch for regulating the output of the microlaser. According to the present invention, the active gain medium is mounted to the secondary heat sink such that the active gain medium extends in a cantilevered fashion from the secondary heat sink and from the at least one submount to which the secondary heat sink is mounted. The electro-optic apparatus of the present invention also includes a pump source, such as a laser diode, mounted to a sidewall of the at least one submount such that the output of the pump source pumps the active gain medium.
Advantageously, the at least one submount includes first and second submounts, both of which are mounted to the primary heat sink in a spaced apart relationship so as to define a gap therebetween. As such, the secondary heat sink is preferably mounted to the first submount such that the active gain medium extends over at least a portion of the gap defined between the first and second submounts. In addition, the pump source is preferably mounted to the sidewall of the second submount that faces the first submount. As such, the active gain medium preferably overlies the pump source such that the output of the pump source pumps the active gain medium.
In one advantageous embodiment, the first submount is U-shaped and has a pair of upstanding arms. In addition, the secondary hea
Alston & Bird LLP
Healy Brian
Litton Systems Inc.
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