Switchable polymer-dispersed liquid crystal optical elements

• US 7,068,405 B2
• Filed: 12/03/2004
• Issued: 06/27/2006
• Est. Priority Date: 07/12/1996
• Status: Expired due to Fees

• Current Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Science Applications International Corporation
• Inventors: Sutherland, Richard L., Hagan, Bill, Epling, Bob, Kelly, William
• Primary Examiner(s): Nguyen, Thong
• Assistant Examiner(s): Lavarias, Arnel C.
• Application Number:
  US11/002,116
• Publication Number:
  US 20050099662A1
• Time in Patent Office: 571 Days
• Field of Search: 359/15, 359/34, 359/1, 359/3, 359/7, 359/8, 359/35, 359/566, 359/569, 359/573, 430/1, 430/2, 349/201, 349/202, 349/193, 349/183, 385/37, 385/16
• US Class Current: 359/34
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02F 1/1326 Liquid crystal optical waveguides or liquid crystal cells specially adapted for gating or modulating between optical waveguides
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 1/13712 the liquid crystal having negative dielectric anisotropy
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G02F 2201/346 distributed (Bragg) reflector
• CPC Class Codes: G02F 2203/05 wavelength dependent
• CPC Class Codes: G02F 2203/055 wavelength filtering
• CPC Class Codes: G02F 2203/585 Add/drop devices
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 2001/026 Recording materials or recording processes G03H2226/11 takes precedence; corresponding details, see subgroups of G03H2260/00
• CPC Class Codes: G03H 2001/0264 Organic recording material
• CPC Class Codes: G03H 2001/2231 Reflection reconstruction
• CPC Class Codes: G03H 2001/2234 Transmission reconstruction
• CPC Class Codes: G03H 2260/12 Photopolymer
• CPC Class Codes: G03H 2260/33 Having dispersed compound

Abstract

Transmission and reflection type holograms may be formed utilizing a novel polymer-dispersed liquid crystal (PDLC) material and its unique switching characteristics to form optical elements. Applications for these switchable holograms include communications switches and switchable transmission, and reflection red, green, and blue lenses. The PDLC material of the present invention offers all of the features of holographic photopolymers with the added advantage that the hologram can be switched on and off with the application of an electric field. The material is a mixture of a polymerizable monomer and liquid crystal, along with other ingredients, including a photoinitiator dye. Upon irradiation, the liquid crystal separates as a distinct phase of nanometer-size droplets aligned in periodic channels forming the hologram. The material is called a holographic polymer-dispersed liquid crystal (H-PDLC).

Claims

1. A method for forming a switchable holographic filter comprising:

inserting a first end of a first optical fiber into a first end of a capillary tube and inserting a first end of a second optical fiber into a second end of a capillary tube, leaving a space within the capillary tube between the first end of the first optical fiber and the first end of the second optical fiber;

filling the space within the capillary tube with a polymerizable material;

exposing the polymerizable material to light radiation, thereby forming a switchable holographic filter within the capillary tube; and

removing the capillary tube.

2. The method according to claim 1, further comprising:

attaching a first GRIN lens to the first end of the first optical fiber and a second GRIN lens to the first end of the second optical fiber, prior to inserting the first end of the first optical fiber and the first end of the second optical fiber into the capillary tube.

3. The method according to claim 1, wherein filling the space within the capillary tube includes injecting the polymerizable material into the capillary tube via a syringe.

4. The method according to claim 3, further comprising:

positioning the filled capillary tube between at least two optical flats;

clamping the at least two optical flats together with the filled capillary tube therebetween; and

injecting an index matching solution in all spaces between the filled capillary tube and the at least two optical flats.

5. The method according to claim 4, wherein exposing the polymerizable material to radiation includes irradiating the filled capillary tube with two beams of radiation.

6. The method according to claim 5, wherein the two beams of radiation are incident upon the filled capillary tube from the same side.

7. The method according to claim 6, further comprising:

positioning the exposed capillary within a groove etched into a substrate; and

depositing a set of finger electrodes on the surface of the substrate on either side of the groove containing the exposed capillary.

8. The method according to claim 6, further comprising wrapping a coil of wire around the exposed capillary.

9. The method according to claim 6, further comprising positioning the exposed capillary between at least two heating elements.

10. The method according to claim 1, wherein the polymerizable material comprises:

(a) a polymerizable monomer comprising at least one acrylate;

(b) at least one type of liquid crystal material;

(c) a chain-extending monomer;

(d) a coinitiator; and

(e) a photoinitiator.

11. A magnetically switchable holographic filter formed in accordance with the method of claim 1 further comprising:

a coil of wire wrapped around a polymerized portion of the switchable holographic filter.

12. The magnetically switchable holographic filter according to claim 11, wherein the switchable grating is made of a polymer-dispersed liquid crystal material.