Both theory and experiment have proven that the above-mentioned uniformly twisted and arranged structure has the properties of an optical waveguide, that is, when polarized light propagates from the upper electrode surface through the twisted and arranged liquid crystal to the lower electrode surface, the polarization direction will rotate 90 degrees.

      Take two polarizing plates and stick them on both sides of the glass. The transmission axis of P1 is the same as the orientation direction of the upper electrode. The transmission axis of P2 is the same as the orientation direction of the lower electrode. Therefore, the transmission axes of P1 and P2 are orthogonal to each other.

       When no driving voltage is applied, the natural light from the light source passes through the polarizer P1, leaving only linearly polarized light parallel to the transmission axis.  When this linearly polarized light reaches the output surface, its polarization plane is rotated 90°. At this time, the polarization plane of light is parallel to the transmission axis of P2, so light passes through.

       When sufficient voltage is applied (usually 1 to 2 volts), under the attraction of the electrostatic field, except for the liquid crystal molecules near the substrate that are “anchored” by the substrate, other liquid crystal molecules tend to align parallel to the direction of the electric field. As a result, the original twisted structure is destroyed and becomes a uniform structure, as shown on the right side of Figure 1. The polarization direction of the polarized light transmitted from P1 no longer rotates when propagating in the liquid crystal, and maintains the original polarization direction until it reaches the lower electrode. At this time, the polarization direction of the light is orthogonal to P2, so the light is turned off.