AbstractPhotosensitive devices represent a key solution for several current and future categories of experiments in which photon detection is the crucial point for the observation of physical phenomena. Astro particle experiments for instance, one of the most promising observation channels for High Energy Physics, typically study energetic phenomena in which charged particles originating from the interactions or decays of primary particles radiate Cherenkov or fluorescence light, which is then detected by photosensitive devices. In these fields of applications, the Silicon Photomultipliers (SiPM) devices based on the limited Geiger-mode avalanche (generally G-APD, Geiger Avalanche Photons Detectors), are extensively under study. Unfortunately, applications of SiPMs are very limited by their small sensitive surfaces. In order to overcome the limits of the small dimensions of the sensitive area of SiPM devices, different solutions are reported. In particular it is discussed the use of Optical Concentrators with the correct refraction index, characteristic and geometry for the improvement of the sensitive surface dimensions of a SiPM device.