A method for providing a vertical optical via for a semiconductor substrate is described. The semiconductor substrate has a front surface and a back side. A hard mask having an aperture therein is formed on the front surface. Part of the semiconductor substrate exposed by the aperture is removed to form a via hole. The via hole has a width not exceeding one hundred micrometers and a bottom. Cladding layer(s) and core layer(s) are provided in the via hole. The core layer(s) have at least a second index of refraction greater than that of the core layer(s). A portion of the semiconductor substrate including the back side is removed to expose a bottom portion of the core layer(s) and a bottom surface of the semiconductor substrate. The vertical optical via includes the cladding and core layers. The vertical optical via extends from the front surface to the bottom surface.