Polishing pads with a polishing surface layer having an aperture or opening above a transparent foundation layer are described. In an example, a polishing pad for polishing a substrate includes a foundation layer having a global top surface and a transparent region. A polishing surface layer is attached to the global top surface of the foundation layer. The polishing surface layer has a polishing surface and a back surface. An aperture is disposed in the polishing pad from the back surface through to the polishing surface of the polishing surface layer, and aligned with the transparent region of the foundation layer. The foundation layer provides an impermeable seal for the aperture at the back surface of the polishing surface layer. Methods of fabricating such polishing pads are also described.