Abstract
The present invention provides an optical device, and the optical device comprises a luminous element and a gradient-index optical thin film composed by nanoparticles stacks. The luminous element has a light emitting surface. The nanoparticles based gradient-index optical thin film comprises a plurality of dielectric layers with different refractive, and the dielectric nanoparticle layers are stacked upward from the light emitting surface to let the gradient-index nanoparticle thin film cover the light emitting surface. It is noted that the refractive indexes of the dielectric nanoparticle layers decrease bottom up. In the meantime, a method for manufacturing the abovementioned optical device is also disclosed in the present invention.