Embodiments of the present disclosure generally relate to methods of forming optical devices comprising nanostructures disposed on transparent substrates. A substrate, such as a silicon wafer, is provided as a base for forming an optical device. A transparent layer is disposed on a first surface of the substrate, and a structure layer is disposed on the transparent surface. An etch mask layer is disposed on a second surface of the substrate opposite the first surface, and a window or opening is formed in the etch mask layer to expose a portion of the second surface of the substrate. A plurality of nanostructures is then formed in the structure layer, and a portion of the substrate extending from the window to the transparent layer is removed. A portion of the transparent layer having nanostructures disposed thereon is then detached from the substrate to form an optical device.