effect and geometry [@RodriguesPRL2006]. As the experiments are performed at short distances, it cannot be described with the assumption of perfect reflection, where analytical results are available [@EmigPRA03; @EmigPRL05]. Again, the general scattering formula (\[formule\]) shows the ability to give an estimation for the lateral force for arbitrary relative values of the length scales $\lambda_{\rm C}$, $\lambda_{\rm P}$ and $L$, provided the corrugation amplitudes $a_{i=1,2}$ remain the smallest length scales of the problem.

We consider two metallic mirrors, both sinusoidally corrugated along one dimension, with the same corrugation wavelength $\lambda_{C}$, separated by a distance $L$ and facing each other with a relative spatial mismatch $b$ between the corrugation crests -see Fig.(\[fig:4\]).

The profiles $h_{i=1,2}({\bf r})$, ${\bf r}=(x,y)$, of the two uniaxial (along $y$) corrugated mirrors are defined by the two functions $h_{1} = a_{1}\cos\left(k_{\rm C}x\right)$ and $h_{2}=a_{2}\cos\left(k_{\rm C}\left(x-b\right)\right)$ with $k_{\rm C}= 2\pi / \lambda_{\rm C}$ the wavevector associated to the corrugation wavelength $\lambda_{\rm C}$. We take both profiles with zero spatial averages. At the second order in the corrugations, cross-terms of the form $a_{1}a_{2}$ appear which contribute to the lateral force because the energy depends on the transverse mismatch $b$.

This fact, a consequence of the correlation between the two 