Absorptance enhancement in fs-laser-treated CVD diamond

Surface texturing by fs-laser pulses has been performed in order to enhance optical absorptance of chemical vapour deposited diamond. The induced surface structures have been studied as a function of treatment dose D. Periodic structure with ripples of 170 nm has been observed for a D = 5.0 kJ cm−2, although not well defined texturing and damaged structures have been obtained for both lower and higher doses. Raman investigations point out negligible changes in crystal bulk for all investigated samples, thus suggesting that physical properties of the crystal were not changed by the treatment. Optical absorptance is strongly enhanced by fs-laser texturing and it is an increasing function of the treatment dose. The absorptance of solar spectrum saturates up to values larger than 90%. The obtained outstanding enhancement of photon absorption represents a preliminary and promising step for the exploitation of synthetic diamond in future high-efficient conversion devices for solar concentration based on photon-enhanced thermionic emission effect.