WIDE FIELD-OF-VIEW POLARIZATION SWITCHES AND METHODS OF FABRICATING LIQUID CRYSTAL OPTICAL ELEMENTS WITH PRETILT
A switchable optical assembly comprises a switchable waveplate configured to be electrically activated and deactivated to selectively alter the polarization state of light incident thereon. The switchable waveplate comprises first and second surfaces and a first liquid crystal layer disposed between the first and second surfaces. The first liquid crystal layer comprises a plurality of liquid crystal molecules that are rotated about respective axes parallel to a central axis, where the rotation varies with an azimuthal angle about the central axis. The switchable waveplate additionally comprises a plurality of electrodes to apply an electrical signal across the first liquid crystal layer.
1 . A switchable optical assembly, comprising:
a switchable waveplate configured to be electrically activated and deactivated to selectively alter the polarization state of light incident thereon, said switchable waveplate having a central axis and comprising:
first and second surfaces, wherein the central axis is normal to said first and second surfaces;
a first liquid crystal layer disposed between said first and second surfaces, said first liquid crystal layer comprising a plurality of liquid crystal molecules that are longer than wide along respective longitudinal directions, wherein the respective longitudinal directions of the liquid crystal molecules vary with respective azimuthal angles about said central axis corresponding to respective locations of the liquid crystal molecules with respect to the central axis; and
a plurality of electrodes to apply an electrical signal across said first liquid crystal layer, wherein said liquid crystal molecules form one or more concentric rings about said central axis.
2 . The switchable optical assembly of claim 1 , wherein the first and second surfaces comprise planar surfaces.
3 . The switchable optical assembly of claim 1 , wherein the first and second surfaces comprise planar surfaces on planar substrates.
4 . The switchable optical assembly of claim 1 , wherein said respective longitudinal directions are orthogonal to respective radial directions from said central axis to said liquid crystal molecules.
5 . The switchable optical assembly of claim 1 , wherein said plurality of liquid crystal molecules have orientations such that said plurality of liquid crystal molecules are arranged in a rotationally symmetric arrangement about said central axis.
6 . The switchable optical assembly of claim 1 , wherein said first liquid crystal layer comprises a stack of sublayers and said liquid crystal molecules are included in a first sublayer of the stack of sublayers.
7 . The switchable optical assembly of claim 6 , wherein said stack of sublayers includes additional sublayers having liquid crystal molecules that have the same azimuth angles about the central axis and the same radial distances from the central axis as the liquid crystal molecules included in the first sublayer and oriented the same as the liquid crystal molecules included in the first sublayer.
8 . The switchable optical assembly of claim 6 , wherein said stack of sublayers includes additional sublayers having liquid crystal molecules that have the same azimuth angles about the central axis and the same radial distances from the central axis as the liquid crystal molecules included in the first sublayer and progressively twisted, the amount of twist increasing with increasing distance from said first sublayer.
9 . The switchable optical assembly of claim 1 , further comprising a second liquid crystal layer.
10 . The switchable optical assembly of claim 9 , wherein said second liquid crystal layer comprises a stack of sublayers, said stack of sublayers having liquid crystal molecules that have the same azimuth angles about the central axis and the same radial distances from the central axis as the liquid crystal molecules included in the first sublayer of the first liquid crystal layer, said liquid crystal molecules in said stack of sublayers in said second liquid crystal layer progressively twisted, the amount of twist increasing with distance from said first liquid crystal layer.
11 . The switchable optical assembly of claim 9 , wherein said second liquid crystal layer has liquid crystal molecules that are twisted with distance from the first liquid crystal layer so as to mirror the twist of the liquid crystal molecules in the first liquid crystal layer.
12 . The switchable optical assembly of claim 9 , wherein said first liquid crystal layer comprises a stack of sublayers, and wherein said second liquid crystal layer comprises a stack of sublayers, wherein a sublayer of said second liquid crystal layer closest to the first liquid crystal layer comprises liquid crystal molecules having substantially the same orientation as the liquid crystal molecules in a sublayer of the first liquid crystal layer that is closest to said second liquid crystal layer.
13 . The switchable optical assembly of claim 9 , wherein said first liquid crystal layer comprises a stack of sublayers, and wherein said second liquid crystal layer comprises a stack of sublayers, wherein a sublayer of said second liquid crystal layer farthest from to the first liquid crystal layer comprises liquid crystal molecules having substantially the same orientation as the liquid crystal molecules in a sublayer of the first liquid crystal layer that is farthest from the second liquid crystal layer.
14 . The switchable optical assembly of claim 9 , wherein said switchable waveplate is configured to diffract light at a diffraction efficiency greater than 95% within a wavelength range including at least 450 nm to 630 nm.
15 . The switchable optical assembly of claim 9 , wherein the liquid crystal molecules in said first and second liquid crystal layers have opposite twist sense.
16 . The switchable optical assembly of claim 11 , wherein each of the liquid crystal molecules of the first and second liquid crystal layers are twisted by a net angle that is between 60 degrees and 80 degrees.
17 . The switchable optical assembly of claim 9 , further comprising at least one electrode configured to apply a signal across said second liquid crystal layer.
18 . The switchable optical assembly of claim 1 , wherein the switchable optical assembly further comprises a first waveplate lens comprising a liquid crystal layer, said first waveplate lens having different optical power for different polarizations of light incident thereon, and
wherein the switchable optical assembly is configured to be selectively switched between at least two lens states including:
a first lens state configured to have a first optical power, and
a second lens state configured to have a second optical power different than the first optical power.
19 . The switchable optical assembly of claim 18 , wherein the second optical power is zero optical power.
20 . The switchable optical assembly of claim 1 , wherein said plurality of liquid crystal molecules have orientations such that said plurality of liquid crystal molecules have at least 4-fold rotational symmetry about said central axis.