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

We present a theoretical analysis of second-order nonlinear difference freq uency generation (DFG) in a generalized mirrorless quasi-phase-matching (QP M) frame, aimed at a comparison of counterpropagating DFG configuration (CD FG) to other DFG schemes, in view of all-optical processing applications. F ield nonlinear coupling equations have been numerically solved under the hy pothesis of phase-matched interaction. The evolution of propagating fields within the material and the wavelength conversion efficiency have been calc ulated in dependence of operating parameters. The increased complexity in t he evolution of amplitude and phase for fields interacting in CDFG with res pect to forward-propagating DFG (FDFG) is at the basis of a dramatic increa se in the wavelength conversion efficiency under particular settings of dev ice parameters.