A radiation detector is provided including a photosensor, a scintillator, and a light guide arranged between the scintillator and the photosensor and configured to guide light from the scintillator to the photosensor, the light guide including a nano-composite that includes nanoparticles that determine a refractive index of the nano-composite. The nano-composite includes a polymer material and the nano-particles, wherein the nano-particles are uniformly distributed throughout the polymer material so that the refractive index of the nano-composite is uniform throughout the nano-composite. Alternatively, the nano-particles are distributed throughout the polymer material so that the refractive index of the nano-composite is equal to the refractive index of the photosensor at a first boundary of the nano-composite that contacts the photosensor, is equal to the refractive index of the scintillator at a second boundary of the nano-composite that contacts the scintillator, and varies uniformly throughout the nano-composite between the first and second boundaries.