Over the past years, DNA-chip technology has exploded. Yet scientists using such devices have to face many problems. One of them, due to the very low concentration of biological species to be detected, is the weakness of fluorescence signal collected through the reading system (microscope or scanner). To solve this problem, we proposed to use optical thin films technology. We studied the potentialities of this method step by step. The first step was to be able to understand, explain and forecast the fluorescence emitted by a DNA-chip in terms of fluorescence angular patterns. A theoretical and experimental study enabled us to master this issue even in the case of multi-layers substrates. Using this knowledge we were then able to explain, through simulations, the potentialities of this new type of substrates in terms of fluorescence enhancement. Thus we showed that a theoretical enhancement of twenty-fold (compare to a glass substrate) was achievable.