Optical switches made by nematic liquid crystal switchable mirrors, and apparatus of manufacture

• US 6,999,649 B1
• Filed: 10/28/2002
• Issued: 02/14/2006
• Est. Priority Date: 10/26/2001
• Status: Expired due to Fees

• Current Assignee: Kent Optronics, Inc.
• Original Assignee: Kent Optronics, Inc.
• Inventors: Chen, Zhan, Li, Le
• Primary Examiner(s): Kim, Ellen E.
• Application Number:
  US10/281,538
• Time in Patent Office: 1,205 Days
• Field of Search: 385 16- 18, 349/132, 349/141, 349/168, 349/169, 349/172, 349/177, 349/186
• US Class Current: 385/18
• CPC Class Codes: G02B 6/351 involving stationary waveguides with moving interposed optical elements G02B6/3538 takes precedence; interposed waveguides G02B6/3502
• CPC Class Codes: G02B 6/3546 NxM switch, i.e. a regular array of switches elements of matrix type constellation
• CPC Class Codes: G02F 1/07 based on electro-optical liquids exhibiting Kerr effect
• 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 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/137 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
• CPC Class Codes: G02F 1/213 Fabry-Perot type
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: G02F 1/315 based on the use of controlled internal reflection

Abstract

Technology for constructing a single layer polarization insensitive electrically switchable liquid crystal mirror is disclosed which serves as the basic element for constructing an optical router switch array in free space as well as waveguide format. The optical router switch array includes a plurality of switchable liquid crystal mirror elements having liquid crystal arranged in stack cells and/or in a waveguide configuration. The resulted optical router switches are motionless, polarization insensitive, stable within the operational spectral region, and stable versus temperature. The invention also includes methods for manufacturing a single switchable liquid crystal mirror element and the optical switch arrays. The same technology is further extended to constructing an electrically tunable optical filter that is motionless and polarization insensitive.

Claims

1. An apparatus for switching a beam of light, comprising:

a first liquid crystal material transparent to the beam of light;

a second material transparent to the beam of light, the second material contacting the first liquid crystal material at an interface;

wherein a temperature of the first liquid crystal material is above a clearing temperature and wherein the first liquid crystal material has a first and a second state, the first state being an isotropic state in the absence of an external field, the second state being a forced nematic state in the presence of said external field, and wherein the index of refraction of the liquid crystal material in the first state matches the index of refraction of the second material, and wherein the index of refraction of the first liquid crystal material in the second state does not match the index of refraction of the second material, whereby the beam of light incident on the interface at an angle greater than the critical angle for total internal reflection is not reflected when the first liquid crystal material is in the first state, and whereby the beam of light incident at the angle on the interface is reflected when the first liquid crystal material is in the second state.

2. The apparatus according to claim 1, wherein is a the external field is a electric field.

3. The apparatus according to claim 2 further comprising electrodes in electrical connection with the first liquid crystal.

4. The electrodes in claim 3 are in-plane switching electrodes.

5. The apparatus according to claim 3 further comprising an index matching layer between the electrodes and the first liquid crystal material.

6. The apparatus according to claim 3 further comprising an alignment layer directly contacting the first liquid crystal material.

7. The apparatus according to claim 3, wherein the electrodes are pixilated.

8. The switch matrix element comprising:

a plurality of the apparatuses in claim 7 comprising said liquid crystal in stacked cells;

each one apparatus of the plurality of the apparatuses including pixilated electrodes that are electrically isolated from pixilated electrodes of other apparatuses of the plurality of the apparatuses;

a plurality of substrates transparent to a beam of light, the plurality of the substrates being alternatively arranged between the plurality of the apparatuses so that each one apparatus is separated from the other apparatuses by the arrangement of the plurality of substrates;

wherein the liquid crystal material has a first and a second state, and wherein the index of refraction of the liquid crystal material in the first state matches the index of refraction of the substrates, and wherein the index of refraction of the first liquid crystal material in the second state does not match the index of refraction of the substrates, whereby the beam of light incident on the interface of a pixilated apparatus at an angle greater than the critical angle for total internal reflection is not reflected when the first nematic liquid crystal material is in the first state, and whereby the beam of light incident at the angle on the interface of the pixilated apparatus is reflected when the first liquid crystal material is in the second state.

9. The device according to claim 8, wherein the pixilated electrodes are in-plane switching electrodes.

10. The apparatus according to claim 1, wherein the light is reflected via Fabry-Perot mechanism when the liquid crystal is in the second state.

11. The apparatus according to claim 1, wherein the light is reflected via total internal reflection mechanism when the liquid crystal is in the second state.

12. The apparatus according to claim 1, wherein the external field is a magnetic field.