We present a new principle and technique that can be used to create light emitting porous silicon submicron patterns of arbitrary shape on silicon wafers. We demonstrate that porous silicon growth can be preferentially initiated at surface defects created by maskless focused ion beam implantation into n-type silicon. During electrochemical polarization, the implanted areas show a significantly lower threshold potential for pore formation than the nonimplanted areas [0.25 V vs 3.8 V standard calomel electrode (SCE)]. For samples electrochemically polarized at potentials below 3.8 V SCE, implanted areas show the typical red-orange photoluminescence of porous silicon while the areas that are not implanted show only the band gap infrared photoluminescence from silicon.