Coherent light generators – Particular beam control device – Tuning
Reexamination Certificate
1999-06-04
2001-08-14
Scott, Jr., Leon (Department: 2881)
Coherent light generators
Particular beam control device
Tuning
C372S043010, C372S036000, C372S081000, C372S066000, C372S107000
Reexamination Certificate
active
06275513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to semiconductor laser assemblies, and more particularly to semiconductor lasers that hermetically sealed with a seal cap.
2. Description of Related Art
A variety of devices are formed on wafers including but not limited to lasers, photodetectors, filters electronic circuits and MEMs. These devices are formed on the wafers utilizing a variety of standard multi-processing steps and procedures. The wafer is typically moved from one process station to another until the final device is completed on the wafer. The devices are then tested. Following testing, the wafer is diced and individual devices are then mounted, electrical connections are made and then there is a final sealing.
This type of wafer scale manufacturing exposes the individual devices to contaminants and corrosive elements found in the atmosphere because of the lengthy time it takes to complete the manufacturing process. Corrosive elements, such as moisture and oxygen, can cause a degradation in the device that is made.
Laser diodes typically include an n-type substrate, an active layer, a p-type clad layer and a p-type cap layer that is laminated over the n-type substrate. In one such semiconductor laser, the n-type substrate is formed of AlGaAs and the active layer is formed of GaAs. An electrode is selectively formed on the obverse surface of the laser diode in an opening of the p-type cap layer. A rear electrode is formed on the reverse surface of the substrate. The resulting structure is a laser diode chip more commonly known as a double heterostructure (DH structure). This laser diode chip can be mounted on a radiation plate. The assembly is then encapsulated to hermetically seal the device. Different methods of encapsulation include the use of metal packages or caps with a light transmitting window, lenses or optical fibers. Wafer scale encapsulation is used on low power light emitting devices where the devices are typically encapsulated with an encapsulating resin layer typically formed of a transparent epoxy resin or the like.
Because the epoxy resin abuts directly against a light-emitting end face of the laser diode from which an output beam is emitted, the resin can become decomposed due to the heat from the output beam. As the degradation increases, the light emission efficiency of the laser diode declines. In some cases, the promoted decomposition results in the formation of a cavity in the encapsulating resin layer in the vicinity of the light-emitting end face.
In one diode laser chip, the output beam has a power 5 mW and an oscillation wavelength of 780 nm is continuously oscillated in a state close to its maximum rating. A conical broken area with a bottom diameter is formed in the encapsulating resin layer in the vicinity of the light-emitting end face after about 1000 hours of operation. Additionally, the encapsulating resins layer often melts and breaks.
There is a need for improvement in wafer scale manufacturing processes and procedures along with the resultant devices that are created. There is a further need to seal the individual devices on the wafer before corrosive environment elements create a degradation.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide sealed micro-optomechanical, micro-electromechanical and micro-optoelectrical devices.
Another object of the present invention is to provide micro-optomechanical, micro-electromechanical and micro-optoelectrical devices that are sealed at the wafer level.
A further object of the invention is to provide a wafer assembly of a plurality of micro-optomechanical, micro-electromechanical or micro-optoelectrical devices formed and individually sealed on the wafer.
Yet another object of the present invention is to provide a wafer sealed tunable semiconductor laser assembly.
These and other objects of the present invention are achieved in a wafer assembly that includes a wafer substrate. A plurality of micro-optomechanical, micro-electromechanical or micro-optoelectrical devices are positioned on a surface of the wafer substrate. Each micro-optomechanical, micro-electromechanical or micro-optoelectrical device has a seal surface. A plurality of seal caps are coupled to the micro-optomechanical, micro-electromechanical or micro-optoelectrical devices. Each seal cap has a seal ring. The seal cap seal ring is coupled to a seal surface of the micro-optomechanical, micro-electromechanical or micro-optoelectrical device to form a hermetic seal.
In another embodiment, a tunable semiconductor laser assembly includes a laser with a seal surface. A semiconductor active region is positioned between upper and lower confining regions of an opposite type semiconductor material. First and second reflective members are positioned at opposing edges of the active and confining regions. A seal cap is provided which includes a seal ring. The seal cap seal ring is coupled to the seal surface to form a hermetic seal.
In another embodiment, a tunable semiconductor laser assembly includes a heatsink. A laser is coupled to the heatsink. The laser includes a semiconductor active region positioned between upper and lower confining regions of opposite type semiconductor material. First and second reflective members are positioned at opposing edges of the active and confining regions. A seal cap includes a seal ring. The seal cap seal ring is coupled to the seal surface to form a hermetic seal.
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patent: 5
Chang-Hasnain Constance
Dato Renato
Worland Philip
Yu Rang-Chen
Bandwidth 9
Jr. Leon Scott
Wilson Sonsini Goodrich & Rosati
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