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Expired European patentEurope

Degenerate four-wave mixer using multiple quantum well structures

EP 0137033 B1 · Applicant: AT&T Corp.

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Overview

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Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

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Why it's free to use

  • Filed February 23, 1984 and granted January 8, 1992. A European patent lasts at most 20 years from filing, so its term ended February 23, 2004.
  • A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by August 23, 2009.
  • We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.
FiledFebruary 23, 1984
PublishedApril 17, 1985
GrantedJanuary 8, 1992
Term endedFebruary 23, 2004
Application numberEP 84901164
Classification (CPC)G02F1/3556 +2 more

Timeline

Timeline From EPO dates

1985198719891991199319951997199920012003Application filedFeb 23, 1984PublishedApril 17, 1985Patent grantedJan 8, 1992Term endedFeb 23, 2004

Sources & verification

Official EPO records

Full published documentClaims, description and drawings as a PDF.EPOEuropean Patent RegisterProcedure, status, file inspection and legal events.EPOLinked open EP data recordThe bibliographic record this page is built from.EPO

Cross-check elsewhere

Google PatentsFull text, worldwide family, citing patents and legal events.patents.google.comEspacenetNational family members and their legal status.European Patent Office

Everything on this page comes from the EPO record linked above. EPO data used under CC BY 4.0.