The invention is directed to a chemical-mechanical polishing pad substrate comprising a porous material having an average pore size of about 0.01 microns to about 1 micron. The polishing pad substrate has a light transmittance of about 10% or more at at least one wavelength of about 200 nm to about 35,000 nm. The invention is further directed to a polishing pad comprising the polishing pad substrate, a method of polishing comprising the use of the polishing pad substrate, and a chemical-mechanical apparatus comprising the polishing pad substrate.