Quasi-phase-matched (QPM) difference frequency generation in a mirrorless counterpropagating configuration

We present a theoretical analysis of second-order nonlinear difference frequency generation (DFG) in a generalized mirrorless quasi-phase-matching (QPM) frame, aimed at a comparison of counterpropagating DFG configuration (CDFG) to other DFG schemes, in view of all-optical processing applications. Field nonlinear coupling equations have been numerically solved under the hypothesis of phase-matched interaction. The evolution of propagating fields within the material and the wavelength conversion efficiency have been calculated in dependence of operating parameters. The increased complexity in the evolution of amplitude and phase for fields interacting in CDFG with respect to forward-propagating DFG (FDFG) is at the basis of a dramatic increase in the wavelength conversion efficiency under particular settings of device parameters.