Tailoring diamond's optical properties via direct femtosecond laser nanostructuring

We demonstrate a rapid, accurate, and convenient method for tailoring the optical properties of diamond surfaces by employing laser induced periodic surface structuring (LIPSSs). The characteristics of the fabricated photonic surfaces were adjusted by tuning the laser wavelength, number of impinging pulses, angle of incidence and polarization state. Using Finite Difference Time Domain (FDTD) modeling, the optical transmissivity and bandwidth was calculated for each fabricated LIPSSs morphology. The highest transmission of ~99.5% was obtained in the near-IR for LIPSSs structures with aspect ratios of the order of ~0.65. The present technique enabled us to identify the main laser parameters involved in the machining process, and to control it with a high degree of accuracy in terms of structure periodicity, morphology and aspect ratio. We also demonstrate and study the conditions for fabricating spatially coherent nanostructures over large areas maintaining a high degree of nanostructure repeatability and optical performance. While our experimental demonstrations have been mainly focused on diamond anti-reflection coatings and gratings, the technique can be easily extended to other materials and applications, such as integrated photonic devices, high power diamond optics, or the construction of photonic surfaces with tailored characteristics in general.