LIQUID CRYSTAL WAVEGUIDE FOR DYNAMICALLY CONTROLLING POLARIZED LIGHT

• US 20120269478A1
• Filed: 01/30/2012
• Published: 10/25/2012
• Est. Priority Date: 01/22/2004
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Vescent Photonics Incorporated
• Inventors: Anderson, Michael H., Rommel, Scott D., Davis, Scott R.
• Granted Patent: US 8,989,523 B2
• Time in Patent Office: Days
• US Class Current: 385/3
• CPC Class Codes: G02F 1/133757 with different alignment orientations
• CPC Class Codes: G02F 1/295 Analog deflection from or in an optical waveguide structure]

Abstract

Waveguide and associated methods for controlling an optical phase delay (OPD) of TE polarized light traveling along a propagation direction through a waveguide are disclosed. In one example, the method includes providing the waveguide with a core, at least one cladding; initially aligning at least a portion of the liquid crystal molecules in an initial orientation with their longitudinal axes oriented at an out-of-plane tilt angle, and their longitudinal axis oriented at an in-plane angle; providing the waveguide with a pair of electrodes for receiving a control signal; and applying the control signal to the pair of electrodes to rotate the liquid crystal molecules from the initial orientation, thereby controlling the optical phase delay of the TE polarized light traveling through the waveguide.

Claims

1. A method for controlling an optical phase delay of TE polarized light traveling along a propagation direction through a waveguide, comprising:

providing the waveguide with a core, at least one cladding, wherein the at least one cladding has liquid crystal molecules disposed therein, the liquid crystal molecules having longitudinal axes;

initially aligning at least a portion of the liquid crystal molecules in an initial orientation with their longitudinal axes oriented at an out-of-plane tilt angle of 0 to 90 degrees, and their longitudinal axis oriented at an in-plane angle in the range of approximately 1 to 90 degrees measured relative to the propagation direction;

providing the waveguide with a pair of electrodes for receiving a control signal; and

applying the control signal to the pair of electrodes to rotate the liquid crystal molecules from the initial orientation, thereby controlling the optical phase delay of the TE polarized light traveling through the waveguide.

2. The method of claim 1, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein the operation of applying the control signal controls the optical phase delay of the TM polarized light.

3. The method of claim 2, wherein the optical phase delay for the TE polarized light is greater than the optical phase delay for the TM polarized light.

4. The method of claim 1, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein the operation of applying the control signal increases the optical phase delay of the TM polarized light and simultaneously decreases the optical phase delay of the TE polarized light traveling through the waveguide.

5. The method of claim 1, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein the operation of applying the control signal decreases the optical phase delay of the TM polarized light and simultaneously increases the optical phase delay of the TE polarized light traveling through the waveguide.

6. The method of claim 1, wherein initially aligning at least a portion of the liquid crystal molecules is in an initial orientation with their longitudinal axes substantially perpendicular to the propagation direction of the TE polarized light and substantially within a plane of the waveguide.

7. The method of claim 1, wherein the liquid crystal molecules are nematic liquid crystal molecules.

8. The method of claim 1, wherein the operation of providing the waveguide with the pair of electrodes further comprises:

providing a first electrode adjacent to the cladding; and

providing a ground plane;

wherein the operation of applying the control signal to the pair of electrodes includes applying a voltage between the first electrode and the ground plane.

9. The method of claim 1, wherein the initially aligning operation further comprises:

providing an alignment layer orientating the liquid crystal molecules in the initial orientation.

10. A waveguide for controllably altering the optical path length of TE light traveling through the waveguide along a propagation direction, comprising:

a core for guiding the TE light through the waveguide;

at least one cladding having liquid crystal molecules disposed therein, the liquid crystal molecules having longitudinal axes, the at least one cladding adjacent the core;

an alignment layer adjacent to the at least one cladding, the alignment layer initially aligning at least a portion of the liquid crystal molecules in an initial orientation with their longitudinal axes oriented at an out-of-plane tilt angle of 0 to 90 degrees, and their longitudinal axes oriented at an in-plane angle in the range of approximately 1 to 90 degrees measured relative to the propagation direction; and

a pair of electrodes for receiving a voltage, for creating an electric field between the electrodes and through the at least on cladding, the electric field being oriented substantially perpendicular to the propagation direction of the TE light traveling through the waveguide;

wherein as the voltage is applied to the pair of electrodes, alignment of the liquid crystals changes so the optical phase delay changes for the TE light traveling through the waveguide.

11. The waveguide of claim 10, wherein the core has an index of refraction greater than approximately 1.55.

12. The waveguide of claim 10, wherein the core includes tantalum pentoxide material.

13. The waveguide of claim 10, wherein the at least one cladding includes an upper cladding and a lower cladding, the upper and lower claddings positioned about the core.

14. The waveguide of claim 10, wherein the pair of electrodes includes a first electrode adjacent to the cladding and a ground plane, and wherein the voltage is applied across the first electrode and the ground plane.

15. A waveguide for controllably altering the optical path length of TE light traveling through the waveguide along a propagation direction, comprising:

a core for guiding the TE light through the waveguide;

at least one cladding having liquid crystals molecules disposed therein, the liquid crystal molecules having longitudinal axes;

an alignment layer adjacent to the at least one cladding, the alignment layer initially aligning at least a portion of the liquid crystal molecules in an initial orientation; and

a pair of electrodes positioned about the core, the pair of electrodes for receiving a control signal for creating an electric field between the electrodes, the electric field being oriented substantially perpendicular to the propagation direction of the TE light traveling through the waveguide;

wherein as the control signal is applied to the pair of electrodes, alignment of the liquid crystals changes to a second orientation in order to alter the optical phase delay for the TE light traveling through the waveguide, the second orientation characterized by at least a portion of the liquid crystal molecules aligned with their longitudinal axes oriented at an angle of 0 to 90 degrees relative to a plane of the waveguide, and with their longitudinal axis oriented at an angle in the range of approximately 1 to 90 degrees measured relative to the propagation direction.

16. The waveguide of claim 15, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein as the control signal is applied to the pair of electrodes, the optical phase delay changes for the TM polarized light traveling through the waveguide.

17. The waveguide of claim 16, wherein the optical phase delay for the TE polarized light is greater than the optical phase delay for the TM polarized light.

18. The waveguide of claim 15, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein as the control signal is applied to the pair of electrodes, the optical phase delay increases for the TM polarized light traveling through the waveguide and simultaneously the optical phase delay of the TE polarized light traveling through the waveguide decreases.

19. The waveguide of claim 15, further comprising TM polarized light traveling through the waveguide along the propagation direction;

and

wherein as the control signal is applied to the pair of electrodes, the optical phase delay decrease for the TM polarized light traveling through the waveguide and simultaneously the optical phase delay of the TE polarized light traveling through the waveguide increases.

20. The waveguide of claim 15, wherein the electric field is oriented substantially perpendicular to the propagation direction of the TE light traveling through the waveguide.