Window in thin polishing pad

A polishing pad includes a polishing layer stack that has a polishing surface, a bottom surface, and an aperture from the polishing surface to the bottom surface. The polishing layer stack includes a polishing layer that has the polishing surface. A fluid-impermeable layer spans the aperture and the polishing pad. A first adhesive layer of a first adhesive material is in contact with and secures the bottom surface of the polishing layer to the fluid-impermeable layer. The first adhesive layer spans the aperture and the polishing pad. The light-transmitting body is positioned in the aperture and has a lower surface in contact with, is secured to the first adhesive layer, and is spaced apart from a side-wall of the aperture by a gap. An adhesive sealant of a different second material is disposed in and laterally fills the gap.