Reflection and transmission of obliquely incident light by chiral sculptured thin films fabricated using asymmetric serial-bideposition (ASBD) technique

Chiral sculptured thin films (STFs) were grown using the asymmetric serial-bideposition (ASBD) technique, whereby (i) two sub-deposits of unequal heights are made separated by a substrate rotation of 180° about the central normal axis, and (ii) consecutive subdeposit pairs are separated by a small substrate rotation δ on the order of a few degrees. Eight samples were prepared with sub-deposit heights in ratios of 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 5:1, 7:1, and 9:1. A finely ambichiral STF was also grown. All nine samples were grown with the same vapor flux direction and to have 10 periods with the same thickness. The spectrums of all eight circular remittances of every sample were measured over a wide range of incidence angle θ^inc. Red-shifting and narrowing of the circular Bragg regime was observed with increasing sub-deposit-height ratio for all values of θ^inc, arriving at a limit with the 9:1 sample. The finely ambichiral sample has a circular Bragg regime similar to that of the 9:1 sample, but the latter exhibits much better discrimination between incident left circularly polarized light and right circularly polarized light than the former.