Devices and methods for polarization splitting

Patent metadata

Field	Value
Publication number	US-11733460-B2
Application number	US-201917290779-A
Country	US
Kind code	B2
Filing date	Oct 31, 2019
Priority date	Nov 2, 2018
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

The invention relates to devices and methods for polarization splitting, where a first optical coupler having at least one input port which receives an input light beam, and at least two output ports at which said light beam, is split into at least a first and a second arms at a first end of said arms. At least one total internal reflection mirror is coupled to the second arm for inducing polarization-dependent phase shifts to the light beam propagating in the second arm, and a polarization-dependent phase difference between the second and the first arm. A second optical coupler having input ports is coupled to the second and opposite ends of the arms. The second coupler has at least one first output port at which light is coupled from said arms, so that the polarization-dependent phase shift of the at least one total internal reflection mirror causes polarization-dependent coupling of light from said input port to said output port.

First claim

The invention claimed is:

1. A polarization splitter, comprising:
a first optical coupler having at least one input port which receives an input light beam, and at least two output ports at which said light beam is split into at least a first arm and a second arm, wherein first ends of said first and second arms are coupled to the at least two output ports of the first optical coupler,
a series of at least two total internal reflection mirrors coupled to at least said second arm for inducing polarization-dependent phase shifts in the light beam propagating in said second arm, and
a second optical coupler having input ports coupled to second ends of said first and second arms, wherein said second ends of said first and second arms are opposite ends compared to said first ends of said first and second arms, and the light beams of the first and second arms have a polarization-dependent phase difference of 90 or 180 degrees induced by said phase shifts, which causes a polarization-dependent coupling of light from said input port to at least one output port of the second coupler, wherein said series of total internal reflection mirrors is used to achieve a targeted polarization-dependent phase difference between said first and second arms.

2. The polarization splitter according to claim 1 , wherein the series of total internal reflection mirrors are coupled to said second arm to achieve a polarization-dependent phase difference between said first and second arms, and identical waveguide bends or total internal reflection mirrors are coupled to each arm to optimize the total optical path length of said first and second arms.

3. The polarization splitter according to claim 1 , wherein a series of metallic mirrors are coupled to said first arm.

4. The polarization splitter according to claim 3 , wherein said series of metallic mirrors and said series of total internal reflection mirrors are processed as identical total internal reflection mirrors from the same silicon substrate, and wherein the mirror forming said series of metallic mirrors are metallized total internal reflection mirrors.

5. The polarization splitter according to claim 1 , wherein said series of total internal reflection mirrors coupled to said second arm comprises four mirrors, each mirror causing a 45 degree phase shift between the s and p polarizations of the light beam propagating in said second arm.

6. The polarization splitter according to claim 1 , wherein the total optical path length difference between the two arms is no more than 360 degrees.

7. The polarization splitter according to claim 1 , wherein the polarization splitter is a 1×2 or a 2×2 Mach-Zehnder interferometer where two polarization modes, a parallel (p) polarized mode and a perpendicular (s) polarized mode, are coupled from the same input port to two different output ports.

8. The polarization splitter according to claim 1 , wherein at least one of the first arm or the second arm comprises at least one phase modulator to adjust or calibrate the phase difference between the arms for at least one polarization.

9. The polarization splitter according to claim 1 , wherein the polarization splitter further comprises optical waveguides that form a photonic integrated circuit.

10. The polarization splitter according to claim 1 , wherein at least one tapered waveguide section is included in at least one arm to at least partly compensate for fabrication imperfections on the total internal reflection mirrors and the resulting impact on path length differences between different arms of the polarization splitter.

11. A method for splitting polarization, comprising the steps of:
feeding an input light beam to at least one input port of a first optical coupler having at least two output ports at which said light beam is split into at least a first and a second arm, wherein first ends of the first and second arms are coupled to the at least two output ports of the first optical coupler,
inducing polarization-dependent phase shifts to the light beam propagating in said second arm by a series of at least two total internal mirrors in said second arm, and
receiving light beams coupled from second ends of said first and second arms to input ports of a second optical coupler, wherein said second ends of said first and second arms are opposite ends compared to said first ends of said first and second arms, said light beams having a polarization-dependent phase difference of 90 or 180 degrees induced by said phase shifts causing a polarization-dependent coupling of light from said input ports to at least one output port of the second coupler,
wherein said series of total internal reflection mirrors is used to achieve a targeted polarization-phase difference between said first and second arms.

12. The method according to claim 11 , wherein said series of total internal reflection mirrors are coupled to said second arm, and identical waveguide bends or total internal reflection mirrors are coupled to each arm to optimize the total optical path length of said first and second arms.

13. The method according to claim 11 , wherein a series of metallic mirrors is coupled to said first arm.

14. The method according to claim 13 , wherein said series of metallic mirrors and said series of total internal reflection mirrors are processed as identical total internal reflection mirrors from the same silicon substrate, and wherein the mirror forming said series of metallic mirrors are metallized total internal reflection mirrors.

15. The method according to claim 11 , wherein said series of total internal reflection mirrors comprises four total internal reflection mirrors coupled to said second arm, each mirror causing a 45 degree phase shift between the s and p polarizations of the light beam propagating in said second arm.

16. The method according to claim 11 , wherein the total optical path length difference between the arms is selected to be no more than 360 degrees.

17. The method according to claim 11 , wherein two polarization modes, a parallel (p) polarized mode and a perpendicular (s) polarized mode, are coupled from the same input port to two different output ports of a 1×2 or a 2×2 Mach-Zehnder interferometer.

Assignees

• Teknologian Tutkimuskeskus Vtt Oy

Inventors

• Aalto Timo

Classifications

• G02B6/29302 Primary

  based on birefringence or polarisation, e.g. wavelength dependent birefringence, polarisation interferometers · CPC title

• G02B6/105 Primary

  having optical polarisation effects · CPC title

• G02B6/126

  using polarisation effects {(G02B6/1226 takes precedence)} · CPC title

• G02B6/29352

  in a light guide · CPC title

• G02F1/225

  in an optical waveguide structure · CPC title