OPO

Optical parametric oscillator (OPO)

is a nonlinear process where one photon (called pump) is converted into two photons with shorter frequencies (The higher frequency is called signal and the lower idler). The OPO consists of a resonator and a nonlinear medium. The optical resonator is designed to resonate the signal and/or idler waves and leads to amplitude gain of the signal and the idler (parametric amplification).