Optical parametric oscillator

An optical parametric oscillator (OPO) is a parametric oscillator that oscillates at optical frequencies. It converts an input laser wave (called "pump") with frequency ω p {\displaystyle \omega _{p}} into two output waves of lower frequency ( ω s , ω i {\displaystyle \omega _{s},\omega _{i}} ) by means of second-order nonlinear optical interaction.