Electronically-controllable polarization independent liquid crystal optical medium and devices using same

• US 20070139586A1
• Filed: 12/19/2006
• Published: 06/21/2007
• Est. Priority Date: 12/19/2005
• Status: Active Grant

• Current Assignee: Kent State University
• Original Assignee: Kent State University
• Inventors: Lavrentovich, Oleg, Golovin, Andrii, Gu, Mingxia, Kreminska, Liubov
• Granted Patent: US 8,570,460 B2
• Time in Patent Office: Days
• US Class Current: 349/88
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G02F 2203/06 Polarisation independent
• CPC Class Codes: G02F 2203/12 spatial light modulator

Abstract

A liquid crystalline optical medium includes polymer stabilized liquid crystal material. The polymer stabilized liquid crystal material includes a short pitch cholesteric liquid crystal material stabilized by a polymer material. The effective phase retardation of the polarization independent liquid crystal optical medium can be controlled by external (for example, electric and magnetic) fields.

Claims

1. A liquid crystalline optical medium comprising:

a polymer-stabilized liquid crystal material including a substantially randomly oriented short-pitch cholesteric liquid crystal material stabilized by a polymer material.

2. The liquid crystalline optical medium as set forth in claim 1, wherein (i) a concentration of the polymer material in the polymer-stabilized liquid crystal material and (ii) a highly twisted structure of the short-pitch cholesteric liquid crystal material independently or cooperatively cause the optical medium to interact with light at least at a selected wavelength in a substantially polarization-independent manner.

3. The liquid crystalline optical medium as set forth in claim 2, wherein the polymer material is less than about 25 wt-% of the polymer-stabilized liquid crystal material.

4. The liquid crystalline optical medium as set forth in claim 2, wherein the polymer material is less than about 10 wt-% of the polymer-stabilized liquid crystal material.

5. The liquid crystalline optical medium as set forth in claim 1, wherein the polymer material is between about 5 wt-% and about 25 wt-% of the polymer-stabilized liquid crystal material.

6. The liquid crystalline optical medium as set forth in claim 1, wherein the short-pitch cholesteric liquid crystal material is arranged as domains having an average size of about one micron in the matrix of polymer material.

7. The liquid crystalline optical medium as set forth in any one of claims 1, wherein the short-pitch cholesteric liquid crystal material has a pitch of less than 500 nm.

8. The liquid crystalline optical medium as set forth in any one of claims 1, wherein the short-pitch cholesteric liquid crystal material comprises:

a nematic liquid crystal material; and

a chiral dopant dispersed in the nematic liquid crystal material.

9. The liquid crystalline optical medium as set forth in claim 8, wherein a ratio of the nematic liquid crystal material and the chiral dopant is greater than 8:

1.

10. The liquid crystalline optical medium as set forth in claim 1, further comprising:

an optical cell containing the polymer-stabilized liquid crystal material and including electrodes for selectively applying a voltage across the liquid crystalline optical material.

11. The liquid crystalline optical medium as set forth in claim 1, further comprising:

a laser dye doping said liquid crystalline optical medium such that said liquid crystalline optical medium is a gain medium suitable for use in a lasing device.

12. The liquid crystalline optical medium as set forth in claim 11, wherein:

the laser dye provides gain at a selected wavelength; and

(i) a concentration of the polymer material in the polymer-stabilized liquid crystal material and (ii) a highly twisted structure of the short-pitch cholesteric liquid crystal material independently or cooperatively cause multiple random scattering between domains at the selected wavelength.

13. An optical device comprising:

a polymer-stabilized liquid crystal material including a substantially randomly oriented short-pitch cholesteric liquid crystal material stabilized by a polymer material wherein (i) a concentration of the polymer material in the polymer-stabilized liquid crystal material and (ii) a highly twisted structure of the short-pitch cholesteric liquid crystal material independently or cooperatively cause the polymer-stabilized liquid crystal material to produce a substantially polarization-independent retardation of at least light having a selected wavelength; and

an optical cell containing the polymer-stabilized liquid crystal material and including electrodes for selectively applying a voltage across the polymer-stabilized liquid crystal material.

14. The optical device as set forth in claim 13, wherein the optical device defines a phase modulator providing a change in phase retardation of at least 0.5π

corresponding to a change in applied voltage of less than 10 volts/micron.

15. The optical device as set forth in claim 13, wherein the optical cell is a reflective optical cell, a phase of the light reflected by the optical cell being selectively retarded by the polymer-stabilized liquid crystal material based on the voltage applied via the electrodes.

16. The optical device as set forth in claim 13, wherein the optical cell is a transmission optical cell, a phase of light transmitted through the optical cell being selectively retarded by the polymer-stabilized liquid crystal material based on the voltage applied via the electrodes.

17. The optical device as set forth in claim 13, wherein at least one of the electrodes of the optical cell is an addressable electrode configured to apply voltage across the polymer-stabilized liquid crystal material that is spatially variable over a principal face of the optical cell to effectuate a wavefront correction.

18. The optical device as set forth in claim 17, further comprising:

a voltage source configured to apply spatially varied voltage to the addressable electrode to effectuate the wavefront correction.

19. The optical device as set forth in claim 17, further comprising:

a wavefront analyzer arranged to measure a wavefront of a light beam input to determine a wavefront error and causing the optical cell to correct the determined wavefront error.

20. A method for forming a phase modulator comprising:

disposing a polymer-stabilized liquid crystal material including a short-pitch cholesteric liquid crystal material stabilized by a polymer material in an optical cell that includes electrodes for selectively applying a voltage across the polymer-stabilized liquid crystal material.

21. The method as set forth in claim 20, wherein the disposing comprises:

disposing the liquid crystal material and a pre-polymer material in the optical cell; and

polymerizing the pre-polymer material to form the matrix of polymer material.

22. The method as set forth in claim 21, wherein a photo-initiator is disposed with the liquid crystal material and the pre-polymer material in the optical cell, and the polymerizing comprises:

exposing the liquid crystal material, the pre-polymer material, and the photo-initiator to ultraviolet light.

23. The method as set forth in claim 22, wherein the polymerizing further comprises:

heating the liquid crystal material and a pre-polymer material.

24. The method as set forth in claim 21, wherein the polymerizing comprises:

heating the liquid crystal material and a pre-polymer material.