Backflow-assisted time-resolved phase modulation in nematic liquid crystal Pi-Cells

By monitoring the time-dependent phase modulation behavior, we demonstrate the benefits of backflow on the phase modulation depth of nematic liquid crystal (LC) pi-cells in comparison to the phase modulation observed for other nematic LC device configurations. Specifically, results are presented for the time-resolved phase modulation of three different nematic LC device configurations under a range of electric field conditions: pi-cell (parallel-rubbed alignment layers), Fre & PRIME;edericksz cell (anti-parallel rubbed alignment layers), and a hybrid aligned nematic (HAN) device. The time-dependent behavior is obtained experimentally with a Michelson interferometer with a piezoelectric scanning mirror in the reference arm, which provides a continuous phase ramp in the reference signal. By recording the interference signal intensity, it is then possible to extract the change in optical phase as a function of time. It is shown that both the pi-cell and Fre & PRIME;edericksz cell exhibit a modulation that is greater than pi radians for a double-pass configuration (2 pi radians for a four-pass configu-ration), with the lowest voltage amplitude corresponding to pi phase modulation being observed for the pi-cell. Through the time-resolved response, it is shown that the presence of backflow hinders the dynamic phase response of the Fre & PRIME;edericksz device but does not negatively impact the behavior of the pi-cell. These results are found to be in good agreement with simulations of the phase modulation for the three nematic devices when backflow is taken into consideration.

Automated summary

The study investigates the time-dependent phase modulation behavior of liquid crystal devices under different electric field conditions. It shows that backflow benefits the phase modulation of the pi-cell, but hinders the dynamic phase response of the Freedericksz cell, in agreement with simulations.