Liquid crystal polarization hologram device comprising an optic axis with a spatially varying orientation and compensated wavy structures

1. A device, comprising:

a polarization hologram polymer layer having a wavy surface, an optic axis of the polarization hologram polymer layer being configured with a spatially varying orientation in a first predetermined in-plane direction; and

a compensation layer disposed at the wavy surface of the polarization hologram polymer layer and configured to compensate for the wavy surface in shape.

2. The device of claim 1 , wherein

the polarization hologram polymer layer includes optically anisotropic molecules, orientation of the optically anisotropic molecules varying in the first predetermined in-plane direction, and

the wavy surface includes peaks and valleys alternately spaced in the first predetermined in-plane direction.

3. The device of claim 2 , wherein

the peaks of the wavy surface correspond to first regions of the polarization hologram polymer layer in which the optically anisotropic molecules are substantially aligned in the first predetermined in-plane direction, and

the valleys of the wavy surface correspond to second regions of the polarization hologram polymer layer in which the optically anisotropic molecules are substantially aligned in a second predetermined in-plane direction that is perpendicular to the first predetermined in-plane direction.

4. The device of claim 1 , wherein the compensation layer includes an optically clear adhesive.

5. The device of claim 1 , wherein the polarization hologram polymer layer includes a liquid crystal polymer.

6. The device of claim 1 , wherein the polarization hologram polymer layer includes a photo-sensitive polymer.

7. The device of claim 1 , wherein the polarization hologram polymer layer includes an amorphous polymer.

8. The device of claim 1 , wherein

an average refractive index of the polarization hologram polymer layer is n p-average =(n e +n o )/2, n o and n e being an ordinary refractive index and an extraordinary refractive index of the polarization hologram polymer layer, respectively,

the compensation layer is an optically isotropic layer with refractive index of n c , and

a difference between the refractive index n c and a refractive index n a of an outside environment of the device is less than a difference between the average refractive index n p-average and the refractive index n a .

9. The device of claim 8 , wherein the refractive index n c of the compensation layer is substantially the same as the average refractive index n p-average of the polarization hologram polymer layer.

10. The device of claim 1 , wherein

an average refractive index of the polarization hologram polymer layer is n p-average (n e +n o )/2, n o and n e being an ordinary refractive index and an extraordinary refractive index of the polarization hologram polymer layer, respectively,

the compensation layer is an optically anisotropic layer, an average refractive index Ile-average of the compensation layer being (n x +n y )/2, n x and n y being principal refractive indices in orthogonal directions at a film plane of the compensation layer, and

a difference between the average refractive index n c-average and a refractive index n a of an outside environment of the device is less than a difference between the average refractive index n p-average and the refractive index n a .

11. The device of claim 10 , wherein the average refractive index n c-average of the compensation layer is substantially the same as the average refractive index n p-average of the polarization hologram polymer layer.

12. The device of claim 1 , wherein the device is a Pancharatnam-Berry phase (“PBP”) device or a polarization volume hologram (“PVH”) device.

13. A method, comprising:

providing a polarization hologram polymer layer having a wavy surface and an optic axis configured with a spatially varying orientation in a first predetermined in-plane direction; and

forming a compensation layer over the wavy surface of the polarization hologram polymer layer to compensate for the wavy surface in shape.

14. The method of claim 13 , wherein:

the polarization hologram polymer layer includes optically anisotropic molecules, orientations of the optically anisotropic molecules varying in the first predetermined in-plane direction,

the wavy surface includes peaks and valleys alternately spaced in the first predetermined in-plane direction,

the peaks correspond to first regions of the polarization hologram polymer layer in which the optically anisotropic molecules are substantially aligned in the first predetermined in-plane direction, and

the valleys correspond to second regions of the polarization hologram polymer layer in which the optically anisotropic molecules are substantially aligned in a second predetermined in-plane direction that is perpendicular to the first predetermined in-plane direction.

15. The method of claim 14 , wherein forming the compensation layer over the wavy surface of the polarization hologram polymer layer further comprises:

applying a liquid optically clear adhesive layer to the wavy surface of the polarization hologram polymer layer to fill the valleys to flatten the wavy surface; and

curing the liquid optically clear adhesive layer to form the compensation layer.

16. The method of claim 13 , wherein

an average refractive index of the polarization hologram polymer layer is n p-average (n e +n o )/2, n o and n e being an ordinary refractive index and an extraordinary refractive index of the polarization hologram polymer layer, respectively,

the compensation layer is an optically isotropic layer with a refractive index of n c , and

a difference between the refractive index n c and a refractive index n a of an outside environment of the device is less than a difference between the average refractive index n p-average and the refractive index n a .

17. The method of claim 13 , wherein the refractive index n c of the compensation layer is substantially the same as the average refractive index n p-average of the polarization hologram polymer layer.

18. A method, comprising:

determining one or more relationships between an average height of a wavy surface of a testing polarization hologram polymer layer and one or more polymerization parameters, the testing polarization hologram polymer layer having an optic axis configured with a spatially varying orientation in a first predetermined in-plane direction;

determining one or more values of the one or more polymerization parameters that render the average height of the wavy surface of the testing polarization hologram polymer layer to be a predetermined average height; and

fabricating a final polarization hologram polymer layer using a polymerization process based on the determined one or more values of the one or more polymerization parameters, the fabricated final polarization hologram polymer layer having a wavy surface with the predetermined average height.

19. The method of claim 18 , wherein in each of the testing polarization hologram polymer layer and the final polarization hologram polymer layer,

optically anisotropic molecules are arranged with orientations varying in the first predetermined in-plane direction,

the wavy surface includes peaks and valleys alternately spaced in the first predetermined in-plane direction,

the peaks correspond to first regions in which the optically anisotropic molecules are substantially aligned in the first predetermined in-plane direction, and

the valleys correspond to second regions in which the optically anisotropic molecules are substantially aligned in a second predetermined in-plane direction that is perpendicular to the first predetermined in-plane direction.

20. The method of claim 18 , wherein the one or more polymerization parameters include a concentration of initiators in a birefringent medium, an exposure intensity, an exposure polarization, and an exposure temperature used in the polymerization process of the birefringent medium.