LC modulator devices based on non-uniform electrode structures
Liquid crystal modulator optical devices and more specifically shutters and smart windows are presented. The liquid crystal modulator devices are characterized by a reduced polymer content which is eliminated from the material composition of the liquid crystal layer and characterized by non-uniform electrode structures in the liquid crystal structure configured to generate spatially non-uniform electric fields and therefore non-uniform molecular reorientation of liquid crystal molecules. This arrangement advantageously makes light scattering electrically controllable.
1. A liquid crystal modulator for modulating incident light, the modulator comprising:
two substrates;
a cholesteric Liquid Crystal (CLC) material contained by said substrates and having a helically ordered LC molecular orientation in a ground state;
at least one non-uniform electrode arranged on at least one of said substrates;
an outer uniform electrode arranged on one of said substrates; and
an opposed uniform electrode arranged on another of said substrates;
wherein said outer uniform electrode is separated from said non-uniform electrode by an insulator, and
wherein said CLC material has at least three states:
the helically ordered ground state for reflection;
a non-uniform ordered state for light dispersion when a voltage is applied between the non-uniform electrode and the opposed uniform electrode; and
a uniform ordered state for a uniform transparent state when a voltage is applied between the outer uniform electrode and the opposed uniform electrode.
2. The modulator of claim 1 , further comprising a drive circuit connected to said at least one electrode layer and configured to provide at least one drive signal for controlling said LC material to be in one of said states.
3. The modulator of claim 1 , wherein said electrode layer is rubbed to provide alignment for said CLC, said CLC being aligned in a ground state to be in said reflection state.
4. The modulator of claim 1 , wherein said electrode layer is covered by an alignment layer mechanically rubbed to provide alignment for said CLC, said CLC being aligned in a ground state to be in said reflection state.
5. The modulator of claim 4 , comprising first and second alignment layers that are mechanically rubbed to provide alignment along in the same line.
6. The modulator of claim 1 , wherein said modulator comprises two layers of said CLC material contained by at least three substrates, wherein said modulator is polarization independent.
7. The modulator of claim 1 , wherein said electrode layer comprises chaotically distributed holes therein.
8. The modulator of claim 1 , wherein said electrode layer comprises a directional hole pattern therein.
9. The modulator of claim 1 , wherein said electrode layer comprises a transparent electrode having a stripe pattern.
10. The modulator of claim 1 , wherein said CLC material comprises a cholesteric LC material of a first helicity, further comprising polymeric matrix set in the presence of said cholesteric LC material of a second opposite helicity.
11. The modulator of claim 10 , comprising a temperature gradient structure providing a chirp in the pitch of the helical structure of said cholesteric LC material.
12. The modulator of claim 1 , wherein said CLC includes a dichroic dopant that is aligned with a director of said CLC for absorption in a specific spectral range that is variable with an orientation of said CLC.
13. The modulator of claim 12 , wherein said dopants are selected to absorbing light to generate a variation of temperature and thus shift the resonant wavelength of reflection, thus providing thus a self-adjustable modulator.
14. The modulator of claim 1 , wherein said CLC is a dual frequency CLC material, and a different scattering, broadening or steering of light is achieved using a frequency below a critical frequency and using a frequency above a critical frequency.
15. A liquid crystal modulator comprising:
at least one liquid crystal cell having substrates containing a cholesteric liquid crystal material;
an outer uniform transparent electrode on a first one of said substrates;
an insulation layer on said outer electrode;
a non-uniform, patterned, electrode on said insulation layer;
an opposed uniform transparent electrode on a second one of said substrates;
wherein a voltage applied between said outer uniform electrode and said opposed uniform electrode with said non-uniform electrode floating provides a uniform electric field to create a uniform alignment of said liquid crystal material, and a voltage of less than ten volts applied between said non-uniform electrode and said opposed uniform electrode creates a pattern of non-uniform electric fields to create a pattern of variable liquid crystal material alignment and consequently dispersion of light.
16. A modulator as claimed in claim 15 , wherein said opposed electrode is segmented and controlled by more than one voltage to provide additional control with the help of the outer uniform electrode and said non uniform electrode over the electric field providing light broadening and steering functions and fast transitions back to the uniform alignment without broadening or steering.