a. Electronics. The action or process of converting a signal to one of a lower frequency.
b. The action or process of converting a high definition video signal to standard definition.
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.
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