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The states that form within untwisted nematic devices with symmetric surface pretilts. The symmetric state forms during sudden application of a voltage above the Fréedericksz tilt threshold, , but decays into the states over time.
Experimental (left) and simulated (right) device responses to sudden application of different applied voltages (, and the material is ZLI-1132). At each voltage, the state forms initially, and then decays to the states. By using higher applied voltages, the state lifetime is increased significantly. The transition from the state to the states occurs more suddenly in simulation than in the real device. This is because the model assumes that the transition occurs uniformly across the whole pixel area, whereas this is not the case in reality (see Fig. 5).
Simulated state lifetime dependence on when applying suddenly to a thickness device. Left: the transmission through the device after voltage application. Right: the time taken for the transmission to reach its equilibrium state level. The value of was fixed at , while was varied. Decreasing produces a director profile with higher tilt for a given voltage. This higher tilt decouples the surfaces and the center of the device, increasing the state lifetime significantly.
Experimental and simulated comparisons between devices filled with ZLI-1132 and MDA-01-2012. The two materials have very similar properties, except that the ratio of MDA-01-2012 is much lower than that of ZLI-1132 (see Fig. 3). The state lifetime is significantly increased with increased applied voltage and by using a material with low .
(Color online) Photomicrographs of the MDA-01-2012 device after sudden application of . The state to state transition is seen to occur through a two-dimensional process, with isolated domains of the states forming and subsequently growing to engulf the whole pixel area. Domain walls between the two states are clearly visible after .
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