DEVICES INCLUDING BIREFRINGENT MEDIUM HAVING CHIRALITY

1 . A device, comprising:

a first birefringent film including a calamitic liquid crystal (“LC”) material configured with a first helical structure; and

a second birefringent film stacked with the first birefringent film and including a discotic LC material configured with a second helical structure.

2 . The device of claim 1 , wherein at least one of the first birefringent film or the second birefringent film is a liquid crystal polymer film.

3 . The device of claim 1 , wherein both of the first helical structure and the second helical structure have a constant helix pitch.

4 . The device of claim 1 , wherein both of the first helical structure and the second helical structure have a varying helix pitch.

5 . The device of claim 1 , wherein one of the first helical structure and the second helical structure has a constant helix pitch, and the other one of first helical structure and the second helical structure has a varying helix pitch.

6 . The device of claim 1 , wherein

for an oblique incident light, the first birefringent film is configured to provide a first phase shift, and the second birefringent film is configured to provide a second phase shift, and

the first phase shift at least partially cancels out the second phase shift.

7 . The device of claim 1 , wherein the first helical structure and the second helical structure have the same handedness.

8 . The device of claim 7 , wherein

the handedness of the first helical structure and the second helical structure is a first handedness, and

a stack of the first birefringent film and the second birefringent film is configured to reflect a first circularly polarized light having the first handedness as a second circularly polarized light having the first handedness, and transmit a third circularly polarized light having a second handedness that is opposite to the first handedness as a fourth circularly polarized light having the second handedness.

9 . A device, comprising:

an optical film including a birefringent medium having a chirality, the birefringent medium including a host material and dyes doped into the host material,

wherein the dyes are configured to absorb a first circularly polarized light having a predetermined handedness more than a second circularly polarized light having a handedness opposite to the predetermined handedness.

10 . The device of claim 9 , wherein molecules of the dyes have molecular helices with an induced axial chirality.

11 . The device of claim 10 , wherein the molecular helices of the molecules of the dyes rotate in a same rotating direction, along a same predetermined direction within a volume of the optical film.

12 . The device of claim 9 , wherein the dyes function as chiral dopants for introducing the chirality.

13 . The device of claim 12 , wherein molecules of the dyes form a plurality of supramolecules within a volume of the optical film, and molecular helices of the supramolecules rotate in a predetermined direction along an axial direction of the optical film.

14 . The device of claim 9 , wherein the optical film is configured to block, via absorption, the first circularly polarized light, and transmit or reflect the second circularly polarized light.

15 . The device of claim 9 , further comprising one or more electrodes coupled to the optical film, and configured to apply a voltage to the optical film to adjust a light transmittance of the optical film for the first circularly polarized light.

16 . A lens assembly, comprising:

a first optical element including a mirror configured to transmit a first portion of a first circularly polarized light having a first handedness; and

a second optical element including a reflective polarizer configured to reflect the first portion of the first circularly polarized light as a second circularly polarized light having the first handedness back toward the mirror,

wherein the reflective polarizer includes a first birefringent film including a calamitic liquid crystal (“LC”) material, and a second birefringent film stacked with the first birefringent film and including a discotic LC material, and

wherein at least one of the first optical element or the second optical element includes a lens.

17 . The lens assembly of claim 16 , wherein

the mirror is further configured to reflect the second circularly polarized light having the first handedness as a third circularly polarized light having a second handedness, and

the reflective polarizer is further configured to transmit the third circularly polarized light having the second handedness as a fourth circularly polarized light having the second handedness.

18 . The lens assembly of claim 16 , wherein at least one of the first birefringent film or the second birefringent film is a liquid crystal polymer film.

19 . The lens assembly of claim 16 , wherein

the calamitic LC material is configured with a first helical structure,

the discotic LC material is configured with a second helical structure, and

at least one of the first helical structure or the second helical structure has a constant helix pitch or a varying helix pitch.

20 . The lens assembly of claim 16 , wherein

for an oblique incident light, the first birefringent film is configured to provide a first phase shift and the second birefringent film is configured to provide a second phase shift, and

the first phase shift at least partially cancels out the second phase shift.