Fishing – trapping – and vermin destroying
Patent
1988-06-30
1990-05-15
Hearn, Brian E.
Fishing, trapping, and vermin destroying
148DIG95, 156662, 372 48, 372 50, 437133, 437987, 437905, H01L 2120, H01L 21205
Patent
active
049258117
DESCRIPTION:
BRIEF SUMMARY
The invention relates to semiconductors, and more particularly to semiconductors which are suitable for optical applications.
It is known that when a P-N junction is electrically excited by a control voltage corresponding to an energy which is greater than its forbidden energy band, it will respond by radiating. The term "semiconductors having light-radiating properties" is used herein to designate those semiconductors in which the radiation is essentially optical in nature, rather than being acoustic.
Such semiconductor are presently obtained using so-called "III-V alloy" materials, i.e. including at least one element from column III of Mendeleev's periodic table and at least one element from column V. More precisely, the elements come from columns IIIA and VA of the current version of said table. Even more precisely, the elements considered are firstly aluminum, gallium, and indium, and secondly phosphorous, arsenic, and antimony.
In known manner, these materials may have or may be given N type conducitivity or P type conducitivity by receiving small quantities of suitable impurities. The initial conductivity of III-V alloys is due to their intrinsic semiconductor properties, and also to residual impurities due to the method by which they are manufactured. For acquired type conducitivity, mention may be made, for example, of zinc, cadmium, magnesium, and beryllium, all of which are suitable for conferring P-type conductivity to gallium arsenide whose initial conductivity is N-type. More generally, since the impurities that should be selected in each case are known, or can be determined, they are not specified each time.
Finally, the person skilled in the art knows that semiconductor structures are generally monocrystalline, unless otherwise specified.
III-V alloys are used, inter alia, for making semiconductor lasers or laser diodes, and these have gained considerable importance since the discovery of the double heterostructure laser diode. Laser diodes are used, in particular, in optical fiber telecommunications, and also for optical disk readers. The term "laser" is used below to designate these semiconductor lasers.
In order to increase the transmission capacity of such systems, wavelength multiplexing can advantageously be used, thus providing a requirement for a "multi-wavelength" laser. However, although "single-wavelength" lasers are the subject of numerous studies, there are very many fewer studies concerning multi-wavelength lasers.
Early proposals were to constitute a double heterostructure stack having different active layers:
W.T. Tsang, "New Multi-wavelength Transverse-Junction Strip Lasers Grown by Molecular Beam Epitaxy Operating Predominantly in Single-longitudinal Modes", Appl. Phys. Lett. 36 (6), 15 Mar. 1980, pp. 441-443;
S. Sakai, T Aoki, M. Tobe, M. Umeno and Y. Amemiya, "Integrated Light Emitters and Photodetectors for Dual-channel Optical Communication", ECOC, Sixth European Conference on Optical Communication, Conference Publication 190, pp. 230, 233;
T. P. Lee, C. A. Burrus, A. G. Dentai, "Dual Wavelength Surface Emitting InGaAsP L.E.D.S.", Electronic Letters, 23 Oct. 1980, Vol. 16, No. 22.
These proposals suffer from the major drawback that all of their wavelengths are excited simultaneously.
Frequency multiplexing is also made possible by laser diodes which include a wavelength-selecting optical grating, also referred to as distributed feedback laser diodes, and described in the following article:
K. Aiki, M. Nakamura and J. Umeda, "Frequency Multiplexing Light Source with Monolithically Integrated Distributed Feedback Diode Lasers", Applied Physics Letters, Vol. 29, No. 8, 15 Oct. 1976.
However, the high technology required for making an integrated grating compromises the use of this method industrially on a large scale.
It has also been suggested that lasers should be made having an active layer with a composition gradient:
ZH. I. Alfrerov, E. N. Arutyunow, S. A. Gurevitch, E. L. Portnoy, N. V. Pronina and V. B. Smirnitsky, "Wavelength Multiplexing DM AlGaAs Injection Laser S
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Electronics Letters, vol. 18, No. 1, 7 Jan. 1982, pp. 18-20, "Dual Wavelength InGaAsP/InP TJS Lasers", S. Sakai et al.
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Dugrand Louis
Menigaux Louis
Bunch William
Hearn Brian E.
L'Etat Francais represente par le Ministre des Postes et
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