Coherent light generators – Particular pumping means – Electrical
Patent
1993-12-09
1995-08-08
Scott, Jr., Leon
Coherent light generators
Particular pumping means
Electrical
372 74, H01S 3097
Patent
active
054405793
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a compact electron gun having a cold microdot electron source.
In general terms, the electron gun according to the invention has a cold microdot electron source, a simplified electronic optics compared with known electron guns, as well as a high voltage anode bombarded by the electrons from the cold source. The source-optic-anode assembly is compact and has a volume of a few cubic centimeters.
This electron gun can be used in a semiconductor laser as an electronic pumping means.
A microdot semiconductor laser or MSL is constituted by a semiconductor source as the active medium and a compact microdot electron gun as the pumping means. This structure can be constituted by a solid semiconductor material, thin film semiconductor materials or a heterostructure.
The use of the electron gun according to the invention makes it possible to improve the performance characteristics of the semiconductor laser and in particular makes it possible to obtain an operation with a weak electronic current, an improvement of the laser efficiency, a limitation of thermal problems, an increase in the life of the pumping means, and a better overall reliability of the laser. These improvements are obtained through modifying and optimizing the compact electron gun according to the invention.
A MSL type laser in particular makes it possible to emit a visible laser light from 0.4 to 0.6 .mu.m, which has numerous applications. Thus, such a laser can be used for the optical recording and reading of information, such as on audio and video compact disks (CD-ROM's--compact disks-read only memories ), WORM's (one write-several reads), erasable memories (of the magnetooptical type or phase change type) or in laser printers.
It can also have other applications such as, for example, bar code readers, laboratory instrumentation, spectroscopy, biomedical instrumentation, pointers, spectacles, display by projection, submarine communications, etc.
The compact electron gun according to the invention can also be used in fields other than that of lasers and in general terms in any device where it is necessary to have electrons accelerated with high voltages (typically 0 to 40 kV), which are focussed and in which everything is assembled in a compact manner (typically a few cm.sup.3). For example, it is possible to use the electron gun according to the invention in a X-ray generator.
For the optical recording and reading of information, the compact laser using the electron gun according to the invention makes it possible to increase the recording density and simplify the optical instrumentation. In laser printers, the compact laser using the electron gun according to the invention permits a better definition of the image and an increase in the printing speed compared with known systems.
An electronic pumping-type compact semiconductor laser using an electron gun with a microdot source is described in FR-A-2 661 566 filed in the name of the applicant. This laser has a laser cavity equipped with a semiconductor heterostructure, which is the laser active medium. This heterostructure forms an anode raised to a high voltage and which is bombarded with high-energy electrons supplied by a compact gun.
Electronic pumping-type lasers are used in cases where the semiconductor materials chosen do not make it possible to produce injection laser diodes and when there is no compact optical pumping source.
The advantages of a MSL compared with injection laser diodes is in particular the separation of the functions the pumping elements and laser cavity.
In injection laser diodes (the only commercially available compact lasers), these basic functions (pumping and cavity) are produced on the semiconductor by appropriate P and N-type electrical dopings of the different epitaxied layers and by ohmic contacts.
The different manufacturing operations for obtaining these diodes make it necessary to perfectly control the technology of producing heterostructures and are generally only possible for certain semiconduct
REFERENCES:
patent: 3803510 (1974-04-01), Nicoll
patent: 5125000 (1992-06-01), Labrunie et al.
Accomo Roger
Molva Engin
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