The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 07, 2004
Filed:
Dec. 17, 1999
Qinetiq Limited, London, GB;
Abstract
A light emitting device for generating at least one beam of output radiation from an input current of electrons comprises at least two p-n junction devices for converting the input current of electrons into photons, wherein the p-n junction devices are electrically connected in series such that the input impedance of the light emitting device is substantially equal to the sum of the individual impedance of the p-n junction devices. Hence the quantum efficiency of the light emitting device is substantially equal to the sum of the individual quantum efficiencies of the p-n junction devices. In a preferred embodiment, the light emitting device comprises a plurality of p-n junction devices connected in series such that the input impedance of the light emitting device is equal to 50 &OHgr; without the need for additional circuitry or impedance matching elements. The device may therefore have a 50 &OHgr; impedance over a broad frequency band, limited by the modulation frequency limit of the individual p-n junctions. Typically, the p-n junctions may be AlGaAs, AlGaInP, AlGaInAs or AlGaInAsp laser diode devices. The invention also relates to an optically coupled bipolar transistor device.