Coherent light generators – Particular resonant cavity – Distributed feedback
Reexamination Certificate
1998-10-29
2001-02-06
Davie, James W. (Department: 2881)
Coherent light generators
Particular resonant cavity
Distributed feedback
C372S046012
Reexamination Certificate
active
06185241
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a vertical cavity surface emitting laser (“VCSEL”) and, more particularly, to a metal spatial filter layer to enhance modal reflectivity for the fundamental mode in a VCSEL.
Vertical cavity surface emitting lasers are very desirable light sources for high speed laser printing, optical fiber communications and other applications. VCSELs have several advantages over edge emitting lasers including an emitted beam with a small angular divergence, a circular, anastigmatic beam and ease of fabrication into one or two dimensional arrays.
For many of these applications, a single mode output is required from the VCSEL. However, VCSELs tend to have poor spatial mode discrimination and nonuniform current injection. One of the challenges in the current state of VCSEL technology is the achievement of higher levels of output power with single mode behavior.
One means to achieve a single mode VCSEL is to enhance the reflectivity for the fundamental mode within the laser aperture.
It is an object of the present invention to provide a vertical cavity surface emitting laser operating in a single mode.
SUMMARY OF THE INVENTION
The present invention provides an annular metal layer between a conductive oxide layer and a dielectric mirror in a vertical cavity surface emitting laser. The annular metal layer defines the output window for the laser cavity which matches the TEM
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fundamental mode of the light beam emitted by the active region of the VCSEL. The metal layer outside the output window provides modal reflectivity discrimination against high order transverse modes of the light beam emitted by the active region of the VCSEL.
Other objects and attainments together with a filler understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5493577 (1996-02-01), Choquette et al.
patent: 5887013 (1999-03-01), Lee et al.
patent: 5892786 (1999-04-01), Lott
patent: 6075804 (2000-06-01), Deppe et al.
Morgan et al., “Transverse Mode Control of Vertical-Cavity Top-Surface-Emitting Lasers”,IEEE Photonics Technology Letters, vol. 4, No. 4, Apr. 1993, pp. 374-377.
Davie James W.
Propp William
Xerox Corporation
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