Time-reversed optical parametric oscillation

In recent works, the idea of time-reversed laser oscillation has been proposed and demonstrated to realize a two-channel coherent perfect absorber Y.?D. Chong et al., Phys. Rev. Lett. 105, 053901 (2010); W. Wan et al., Science 331, 889 (2011)]. Here the time reversal of optical parametric oscillation in a nonlinear χ(2) medium is considered and shown to realize a coherent perfect absorber for colored incident signal and idler fields. A detailed analysis is presented for the time-reversed process of mirrorless optical parametric oscillation in the full nonlinear regime.