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downconversion, n.

Origin: Formed within English, by derivation. Etymons: down- prefix, conversion n.

 a. Electronics. The action or process of converting a signal to one of a lower frequency.

1956   Proc. IRE 44 1183/1   Conversion from a high frequency to a low frequency will be called ‘down-conversion’.
1984   IEEE Trans. Microwave Theory & Techniques 32 1100/2   He discovered that gain could be obtained in down-conversion from a microwave frequency to a much lower frequency.
2018   G. Ghione & M. Pirola Microwave Electronics i. 12   After downconversion, no aliasing arises because the spectral content of the image is the same as that of the desired signal.

1956—2018(Hide quotations)


 b. The action or process of converting a high definition video signal to standard definition.

1980   SMPTE Jrnl. 89 154/3   This information be coded in the release print or tape to guide the down-conversion process automatically.
2006   HWM May 8/1   The new Viera plasma TVs have a full 1080p Digital Processing chipset that processes full-HD video signals in their original condition, without down-conversion.

1980—2006(Hide quotations)


 2. The conversion of a single photon into a pair of photons, each having less energy and momentum than the original.More fully parametric downconversion, spontaneous downconversion, spontaneous parametric downconversion.Downconversion is accomplished by passing a laser beam through a certain type of crystal.In quot. 1965, referring to bosons more generally.

1965   IEEE Jrnl. Quantum Electronics 1 35/1   In the down-conversion process we ‘split’ a pump boson into an idler..and a signal boson.
1986   Physical Rev. Lett. 56 58 (abstract)    In the process of spontaneous parametric down-conversion a signal and an idler photon are created simultaneously.
1995   Appl. Physics B. 60 267/2   Orthogonally polarized signal and idler photons produced by downconversion in a nonlinear crystal are sent in opposite directions through the beam splitter.
2015   A. Furusawa Quantum States of Light ii. 81   A photon pair created by parametric downconversion can be divided into two photons in different paths.

1965—2015(Hide quotations)