TiO2/sapphire Beam Splitter for High-order Harmonics.

TiO₂/sapphire beam splitter (BS) for high-order harmonics was studied and fabricated through taking advantage of the self-limiting nature of atomic layer epitaxy (ALE). Theoretical calculation indicated that the highest reflectivity of the TiO₂/sapphire BS was 44.8 % at 21.24 nm, which corresponds to the 37^th-order harmonics of the 800-nm pump pulse and then the optimal thickness of the TiO₂ layer was 67.4 nm. Incident angle was set at 70.5° for TiO₂, which corresponds to the Brewster's angle of the 800-nm pump pulse. Moreover, experimental results indicated that refractive indices (λ = 632.8nm) of the TiO₂ films were almost constant at a value of 2.59 and growth rate of TiO₂ films was 0.077nm/cycle, which corresponds to 885 cycles in order to deposit the TiO₂ layer with the optimal film thickness as an anti-reflection layer. [ABSTRACT FROM AUTHOR]