Optical DownConverter (ODC) is an example of a non-linear optical process, in which two beams of light of different frequencies
the frequency summing
In a common ODC application, light from a tunable infrared laser is combined with light from a fixed frequency visible laser to produce a microwave created by a wave mixing process.
The ODC use milimeteric microwave cavity that include photonic crystal that provide by two signal frequency light source. The microwave is detected by the cavity antenna.