Surface-emitting semiconductor laser device in which an edge-emitting laser is integrated with a diffractive lens, and a method for making the device
a semiconductor laser and diffractive lens technology, applied in semiconductor lasers, instruments, optical elements, etc., can solve the problems of difficult fabrication of devices, difficult single-mode yield control, and sensitive optical characteristics of devices manufactured for very high speed operation
Inactive Publication Date: 2012-11-08
BROADCOM INT PTE LTD
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[0011]The invention is directed to a surface-emitting semiconductor laser device and a method for fabricating the device. The device comprises a substrate having an upper surface and a lower surface, a plurality of semiconductor layers disposed on the substrate, an edge-emitting laser formed in the semiconductor layers for producing laser light of a lasing wavelength, an angled side reflector disposed on an angled side facet formed in one or more of said plurality of semiconductor layers, a lower reflector disposed on or near the lower surface of the semiconductor substrate, and a diffractive lens disposed in at least the uppermost layer of one or more of the semiconductor layers. The edge-emitting laser has an active MQW region having a first end and a second end and a passive MQW region having a first end and a second end. The second end of the active MQW region is joined to the first end of the passive MQW region. The laser has a rear facet corresponding to the first end of the active MQW region and a front facet corresponding to the se
Problems solved by technology
Nevertheless, the device is not straightforward to fabricate due to the inclusion of a waveguide to direct the beam from the laser toward the angled surface.
Also, the geometry of the device may make its optical characteristics sensitive to wafer thickness errors.
VCSELs, however, still have problems with regard to single-mode yield control when manufactured for very high speed operation.
Performing high quality etching presents significant reliability issues, especially when performing dry etching under high operating power due to facet damage that can occur during the dry etching process.
The monolithic integration of a diffractive lens on the same chip in which the edge-emitting laser is integrated requires the performance of multiple Electron Beam Lithography (EBL) exposure and dry etching processes, it would seem that the device fabrication costs would increase.
However, with respect to using a separate lens to correct the beam divergence before the light enters the optical fiber, the overall cost of a monolithic integration of a laser with a diffractive lens is still less than the cost of packaging separate components.
At operating lasing conditions, any remaining oxidized Al-containing material can cause a portion of the injection current to leak through the interface between the InP and the InGaAlAs MQW, which can detrimentally affect device performance and reliability.
Another potential problem is the difficulty associated with using a wet chemical etching process to realize a reverse-mesa ridge structure having a low series resistance.
It can be difficult from a process standpoint to realize a reverse-mesa ridge structure that ends precisely at this interface using photolithographic and wet chemical etching techniques.
In particular, if the reverse-mesa ridge structure extends over the interface, the wet chemical etching of the InP layer can destroy the MQW layers because under the InP layer there is no etch-stop layer.
On the other hand, if the reverse-mesa ridge structure does not reach the interface, this can prevent the injection current from passing through all of the MQW layers, which can result in very large optical losses due to un-injected MQW layers.
These difficulties can reduce manufacturing yield and increase costs.
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[0024]The invention is directed to a surface-emitting semiconductor laser device in which an edge-emitting laser and a diffractive lens are integrated together in the semiconductor laser device. The edge-emitting laser has a first section comprising an active MQW region and a second section comprising a passive MQW region that is transparent to the emission wavelength of the laser. A third section of the surface-emitting semiconductor laser device comprises a semiconductor bulk material. This configuration ensures that the injection current will pass through all of the layers of the active region, thereby preventing optical loss from occurring due to un-injected regions. The configuration also ensures that there is no current passing through the interface between the active MQW region and the bulk semiconductor layer. The latter feature improves performance and device reliability. However, the ridge structure of the laser should extend about 2 to 3 micrometers (microns) over the int...
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A surface-emitting semiconductor laser device is provided that includes an edge-emitting laser integrated in a semiconductor material with various reflectors and a diffractive lens. The edge-emitting laser has a first section comprising an active MQW region, a second section comprising a passive region and a third section comprising a semi-insulating or un-doped semiconductor bulk layer. This configuration ensures that the injection current will pass through all of the layers of the active region, thereby preventing the occurrence of optical losses due to un-injected areas of the MQW active region. In addition, the inclusion of the passive region ensures that there is no current passing through the interface between the active MQW region and the regrown semiconductor bulk layer. The latter feature improves performance and device reliability.
Description
TECHNICAL FIELD OF THE INVENTION[0001]The invention relates generally to semiconductor laser devices and, more particularly, to a surface-emitting semiconductor laser device in which an edge-emitting laser and a diffractive lens are integrated together on the same chip.BACKGROUND OF THE INVENTION[0002]Semiconductor lasers are commonly used in optical transceivers for telecommunications and data communication networks. The lasers used in such optical transceivers are commonly of the edge-emitting type. The edge-emitting laser of an optical transceiver is commonly coupled to the fiber with an aspheric lens or other discrete optical element because the light that the laser emits is not focalized or collimated, i.e., it diverges in a cone shape as it propagates. While the use of lenses to couple edge-emitting lasers to fibers in optical transceivers works reasonably well, it would be desirable to improve transceiver manufacturing economy by minimizing the number of transceiver parts and...
Claims
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Patent Timeline
Login to View More IPC IPC(8): H01S5/18H01S5/34H01L21/30H01S5/185
CPCG02B6/12004H01S5/026H01S5/0267H01S2301/176H01S5/162H01S5/18H01S5/0425H01S5/04253H01S5/185G02B6/4214H01S5/16
InventorFANG, RUI YUROGGERO, GUIDO ALBERTOTALLONE, LUIGI
OwnerBROADCOM INT PTE LTD