The project comprises 3 parts. The 1st consists in the study and characterization of Backside Illuminated Silicon Photomultipliers (BISiPM) being developed at FBK. The separation between charge collection and multiplication regions enable several advantages including (a) sensitivity over wide range of wavelength, (b) small pitch cell with 100% Fill Factor, fast response, wide dynamic range and low cross-talk, (c) ultimate intercon density with ultrafast, low-power local electronics The 2nd part consists in developing Wavelength Shifter (WLS) based light-traps that utilize BISiPMs for reading out the light. Large Surface light-trapping Tiles (LSLT) comprise a thin WLS layer sandwiched between low refr. index planes conveying the light at the tile edges, where WLS fibers further convert and the light, which in turn is measured by BISiPMs at the fibers end In the 3rd part, LSLT will be tested at the University of Tokyo as photon detectors for the Intermediate Water Cherenkov Detector IWCD and the Near Detector ND280 of the Hyper-Kamiokande experiment.