Optical parametric oscillator far below threshold: Experiment versus theory - art. no. 033804

The theory of the optical parametric oscillator is examined and compared to the experiment in the regime of far below threshold. It is found that the output state has no difference from spontaneous parametric down-conversion except that the bandwidth of down-conversion is reduced to that of the reso nator and the conversion rate is enhanced by cavity resonance. The reductio n of the bandwidth of the down-converted fields makes it possible for a dir ect measurement of the time interval distribution between two down-converte d photons. The observed distributions are well explained by the theory. Suc h a narrow-band two-photon source will find wide applications in quantum in formation processing.