Frequency Conversion of Laser Light

In the wave picture of electromagnetic radiation, the intensity I of the light transmitted by any material depends on the value of the electric field , according to the equation 

1 Up-conversion. It is also possible to add the laser light of frequency vL to some other light, for instance luminescence light of frequency vF to obtain a whole spectrum of frequencies vL + vF. The two beams of light are mixed 

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