ABSTRACT
An Optical Parametric Oscillator (OPO) is a device in which one or more of the nonlinearly interacting light beams in an optical parametric generation (OPG) process are resonated, usually by placing the nonlinear medium between mirrors with high reflectivity coatings for the resonated wavelength or wavelengths. An OPO is called a Singly Resonant Oscillator, Doubly Resonant Oscillator or a Triply Resonant Oscillator depending on the number of resonated beams at different frequencies. In an OPO, the highest frequency beam, which also has the highest power, is called the ‘pump’, the middle frequency beam is called the ‘signal’ and the lowest frequency beam is called the ‘idler’. To lower the pump power threshold of an OPO, it is necessary to reduce the size of the pump and the signal beams, that is, to focus them tightly.
