A method provides security to a computer network by selectively blocking network transmissions from selected IP addresses. A first arrangement includes a positioning mechanism for translating the nonlinear optical medium so OPO resonant modes propagate through one of multiple longitudinal regions arranged for differing odd orders of quasi-phase-matching. The region of contact between the optic and the haptic extends into the edge of the optic, similar to the interface between a bicycle tire and the rim that holds it in place.