Black optical coating for high-power laser measurements from carbon nanotubes and silicate

We describe a coating based on potassium silicate, commonly known as water glass, and multiwall carbon nanotubes. The coating has a high absorbance (0.96 at 1064 nm in wavelength) and a laser damage threshold that is comparable to that of ceramic coatings presently used for commercial thermopiles for high-power laser measurements. In addition to a potassium silicate-based coating we discuss sodium silicate, lithium silicate, and a commercially available ceramic coating. We document the coating process and experiments that demonstrate that the laser damage threshold at 1064 nm is 15 kW/cm(2).