Integrated polarization converter and frequency shifter

Patent metadata

Field	Value
Publication number	US-10203528-B2
Application number	US-201715821600-A
Country	US
Kind code	B2
Filing date	Nov 22, 2017
Priority date	Nov 23, 2016
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

An optical device is described. This optical device includes an electro-optical material having an X-cut, Y-propagate orientation. In particular, a Y crystallographic direction of the electro-optical material is parallel to an optical waveguide defined in the electro-optic material and an X crystallographic direction of the electro-optical material is parallel to a vertical direction of the optical device. By applying drive signals having an angular frequency to the electro-optic material, the optical device may perform modulation, corresponding to a traveling-wave configuration, of an optical signal based at least in part on the drive signals. where the modulation involves a polarization conversion and a frequency shift. The angular frequency of the drive signals may be selected to approximately cancel electro-optic cross terms in X-Z plane of the electro-optical material. Moreover, an amplitude of the drive signals may be selected so that the optical device emulates a half-wave-plate configuration.

First claim

What is claimed is:

1. An optical device, comprising:
an electro-optic material having a surface;
electrodes, disposed on or above the surface, configured to receive drive signals; and
an optical waveguide defined in the electro-optic material and configured to convey an optical signal, wherein a Y crystallographic direction of the electro-optical material is parallel to the optical waveguide and an X crystallographic direction of the electro-optical material is parallel to a vertical direction of the optical device, which is substantially perpendicular to the surface;
wherein the optical device comprises an integrated polarization converter and frequency shifter; and
wherein an angular frequency of the drive signals is selected to approximately cancel electro-optic cross terms in X-Z plane of the electro-optical material.

2. The optical device of claim 1 , wherein the electro-optic material has a trigonal crystal symmetry of a 3m point group.

3. The optical device of claim 1 , wherein the optical waveguide is configured to approximately null birefringence of the electro-optic material.

4. The optical device of claim 1 , wherein the drive signals have an angular frequency and the electro-optic material is configured to perform modulation, corresponding to a traveling-wave configuration, of the optical signal based at least in part on the drive signals.

5. The optical device of claim 4 , wherein the modulation corresponds to r 13 , r 33 and r 42 coefficients in an electro-optical tensor of the electro-optical material.

6. The optical device of claim 1 , wherein an input of the optical waveguide is configured to receive the optical signal having an input circular polarization and an input frequency, and an output of the optical waveguide is configured to provide the optical signal having an output circular polarization that is orthogonal to the input circular polarization and that has an output frequency corresponding to the input frequency and an angular frequency of the drive signals.

7. The optical device of claim 1 , wherein an amplitude of the drive signals is selected so that the optical device emulates a half-wave-plate configuration.

8. The optical device of claim 1 , wherein the optical device comprises an optical isolator.

9. The optical device of claim 1 , wherein the optical device is configured to modulate the optical signal in a first propagation direction along the optical waveguide and is configured to substantially not modulate the optical signal in a second propagation direction along the optical waveguide, which is opposite to the first propagation direction.

10. The optical device of claim 1 , wherein the drive signals have a common amplitude, an angular frequency and, respectively, a first phase or a second phase; and
wherein the first phase and the second phase are selected so that a magnitude of the electro-optic modulations of the electro-optic material along two orthogonal directions in an X-Z plane of the electro-optic material are approximately equal.

11. A method for modulating an optical signal, comprising:
conveying the optical signal in an optical waveguide in an optical device, wherein the optical waveguide is defined in an electro-optic material, and wherein a Y crystallographic direction of the electro-optical material is parallel to the optical waveguide and an X crystallographic direction of the electro-optical material is parallel to a vertical direction of the optical device;
modulating the optical signal by applying drive signals having an angular frequency to the electro-optic material, wherein the modulation corresponds to a traveling-wave configuration, and wherein the modulation involves a polarization conversion and a frequency shift; and
selecting an angular frequency of the drive signals to approximately cancel electro-optic cross terms in X-Z plane of the electro-optical material.

12. The method of claim 11 , wherein the electro-optic material has a trigonal crystal symmetry of a 3m point group.

13. The method of claim 11 , wherein the optical device comprises an optical isolator.

14. An optical isolator, comprising:
an electro-optic material having a surface;
electrodes, disposed on or above the surface, configured to receive drive signals; and
an optical waveguide defined in the electro-optic material and configured to convey an optical signal, wherein the optical isolator is configured to modulate, based at least in part on the drive signals, the optical signal in a first propagation direction along the optical waveguide and is configured to substantially not modulate the optical signal in a second propagation direction along the optical waveguide, which is opposite to the first propagation direction, and wherein an angular frequency of the drive signals is selected to approximately cancel electro-optic cross terms in X-Z plane of the electro-optical material.

15. The optical isolator of claim 14 , wherein, when the optical signal propagates along the first propagation direction and has an input circular polarization and an input frequency, the optical isolator is configured to output the optical signal having an output circular polarization that is orthogonal to the input circular polarization and that has an output frequency corresponding to the input frequency and an angular frequency of the drive signals.

16. The optical isolator of claim 14 , wherein an amplitude of the drive signals is selected so that the optical isolator emulates a half-wave-plate configuration.

17. The optical isolator of claim 14 , wherein the drive signals have a common amplitude, an angular frequency and, respectively, a first phase or a second phase; and
wherein the first phase and the second phase are selected so that a magnitude of the electro-optic modulation of the electro-optic material along two orthogonal directions of the electro-optic material is approximately equal.

18. The optical isolator of claim 14 , wherein a Y crystallographic direction of the electro-optical material is parallel to the optical waveguide and an X crystallographic direction of the electro-optical material is parallel to a vertical direction of the optical isolator, which is substantially perpendicular to the surface.

19. The optical isolator of claim 14 , wherein a Z crystallographic direction of the electro-optical material is parallel to the optical waveguide and an X crystallographic direction of the electro-optical material is parallel to a vertical direction of the optical isolator, which is substantially perpendicular to the surface.

Assignees

• Univ California

Inventors

• Yoo Sung-Joo Ben
• Qin Chuan
• Ercan Burcu
• Lu Hongbo

Classifications

• G02F2201/127

  travelling wave · CPC title

• G02F1/0353 Primary

  involving an electro-optic TE-TM mode conversion · CPC title

• G02F2203/07

  Polarisation dependent · CPC title

• G02F1/0327

  Operation of the cell; Circuit arrangements (G02F1/05 takes precedence) · CPC title