Selective field localization in random structured media

We have introduced a method to find optimized structured media exhibiting large internal electric field amplitudes. The method is based on a genetic algorithm in which a spatial fitness function according to the computed field distribution in the interior of media is defined and maximized. The main feature of our method is that it enables localization of light at a desired layer (or more) within the structure. The enhancements are demonstrated to be up to about 70-fold in |E|(2) by use of only seven layers. The results are interesting for nonlinear and sensor applications, which due to compact size and few number of structure layers, are also desirable for fabrication purposes.