Polarization Beam Splitter-Polarization Rotator Structure

• US 20080019637A1
• Filed: 07/24/2007
• Published: 01/24/2008
• Est. Priority Date: 09/08/2005
• Status: Active Grant

• Current Assignee: Infinera Corp.
• Original Assignee: Infinera Corp.
• Inventors: Little, Brent, Chen, Wei
• Granted Patent: US 7,702,188 B2
• Time in Patent Office: Days
• US Class Current: 385/28
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/126 using polarisation effects G02B6/1226 takes precedence
• CPC Class Codes: G02B 6/136 by etching
• CPC Class Codes: G02B 6/272 comprising polarisation means for beam splitting and combining
• CPC Class Codes: G02B 6/2766 Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters
• CPC Class Codes: G02B 6/2773 Polarisation splitting or combining

Abstract

A polarization beam splitter-polarization rotator-polarization beam combiner optical structure comprising a pair of polarization rotators having a polarization beam splitter associated with the input ends of the two polarization rotators, and a polarization beam combiner associated with output ends of the two polarization rotators, and a method of purifying a light signal comprising TE and TM modes by disassociating the primary TE and TM modes from first order splitter and rotation error components.

Claims

1. An optical structure, comprising:

a polarization beam splitter comprising an input end, and an output end having a first output and a second output;

a polarization rotator system comprising a first polarization rotator having an input end and an output end, and a second polarization rotator having an input end and an output end; and

a polarization beam combiner comprising an input end having a first and second input, and an output end; and

wherein the first output of the polarization beam splitter is operatively connected to the input end of the first polarization rotator, and the output end of the first polarization rotator is operatively connected to the first input of the polarization beam combiner; and

wherein the second output of the polarization beam splitter is operatively connected to the input end of the second polarization rotator, and the output end of the second polarization rotator is operatively connected to the second input of the polarization beam combiner.

2. The optical structure of claim 1 comprising at least one additional optical element.

3. The optical structure of claim 2 wherein the at least one additional optical element is a filter, polarizer, waveguide, reflector, coupler, interconnect, phase modulator, intensity modulator, frequency shifter transducer, oscillator, power splitter, resonator or photodetector.

4. An optical structure, comprising:

a polarization beam splitter comprising a first splitter waveguide having an input end and an output end, and a second splitter waveguide having an output end;

a polarization rotator system comprising a first polarization rotator having an input end and an output end and a second polarization rotator having an input end and an output end; and

a polarization beam combiner comprising a first combiner waveguide having an input end and an output end, and a second combiner waveguide having an input end and an output end,

wherein the output end of the first splitter waveguide is operatively connected to the input end of the first polarization rotator, and the output end of the first polarization rotator is operatively connected to the input end of the first combiner waveguide, and wherein the output end of the second splitter waveguide is operatively connected to the input end of the second polarization rotator, and the output end of the second polarization rotator is operatively connected to the input end of the second combiner waveguide.

5. The optical structure of claim 4 wherein the first splitter waveguide is operatively connected to the first polarization rotator via a first splitter connector waveguide and the second splitter waveguide is operatively connected to the second polarization rotator via a second splitter connector waveguide.

6. The optical structure of claim 4 wherein the first combiner waveguide is operatively connected to the first polarization rotator via a first combiner connector waveguide, and the second combiner waveguide is operatively connected to the second polarization rotator via a second combiner connector waveguide.

7. The optical structure of claim 4 wherein the first splitter waveguide supports the TM mode and the second splitter waveguide supports the TE mode.

8. The optical structure of claim 4 wherein the first splitter waveguide supports the TE mode and the second splitter waveguide supports the TM mode.

9. The optical structure of claim 4 wherein the first polarization rotator converts TM mode to TE mode and the second polarization rotator converts TE mode to TM mode.

10. The optical structure of claim 4 wherein the first polarization rotator converts TE mode to TM mode and the second polarization rotator converts TM mode to TE mode.

11. The optical structure of claim 4 wherein the TM mode and TE mode are combined into the second combiner waveguide.

12. The optical structure of claim 11 wherein the first order error modes are combined into the first combiner waveguide.

13. The optical structure of claim 4 wherein the TM mode and TE mode are combined into the first combiner waveguide.

14. The optical structure of claim 13 wherein the first order error modes are combined into the second combiner waveguide.

15. The optical structure of claim 4 comprising at least one additional optical element.

16. The optical structure of claim 15 wherein the at least one additional optical element is a filter, polarizer, waveguide, reflector, coupler, interconnect, phase modulator, intensity modulator, frequency shifter transducer, oscillator, power splitter, resonator or photodetector.

17. An optical structure comprising:

a first polarization rotator comprising an input end, an output end and a midsection having a length extending between the input end and the output end, the midsection having a varying cross sectional geometry along the length of the midsection that induces rotation of a polarization mode of an electromagnetic signal as the electromagnetic signal propagates along the length of the midsection;

a second polarization rotator comprising an input end, an output end and a midsection having a length extending between the input end and the output end, the midsection having a varying cross sectional geometry along the length of the midsection that induces rotation of a polarization mode of an electromagnetic signal as the electromagnetic signal propagates along the length of the midsection;

a polarization beam splitter comprising;

a first splitter waveguide having an input end and an output end and supporting at least one guided TE polarized mode and at least one guided TM polarized mode; and

a second splitter waveguide having an input end and an output end and supporting at least one of a guided TE polarized mode and a guided TM polarized mode, the first splitter waveguide and second splitter waveguide cooperating to form an adiabatic region in which light having one of the TE and TM polarized modes remains within the first splitter waveguide and exits therefrom via the output end thereof into the first polarized rotator and light having the other one of the TE and TM polarized modes evanescently couples into the second splitter waveguide and exits therefrom via the output end thereof into the second polarization rotator; and

a polarization beam combiner comprising;

a first combiner waveguide having an input end and an output end and supporting at least one of the guided TE polarized mode and the guided TM polarized mode from one of the first polarization rotator or second polarization rotator; and

a second combiner waveguide having an input end and an output end and supporting at least one of the guided TE polarized mode and the guided TM polarized mode from the other one of the first polarization rotator or second polarization rotator, the first combiner waveguide and second combiner waveguide cooperating to form an adiabatic region in which light having one of the TE and TM polarized modes substantially remains within the first combiner waveguide, and substantially all of the light having the other one of the TE and TM polarized modes within the second combiner waveguide evanescently couples into the first combiner waveguide thereby substantially combining the TE and TM modes into one of the first combiner waveguide and the second combiner waveguide.

18. The optical structure of claim 17 comprising at least one additional optical element.

19. The optical structure of claim 18 wherein the at least one additional optical element is a filter, polarizer, waveguide, reflector, coupler, interconnect, phase modulator, intensity modulator, frequency shifter transducer, oscillator, power splitter, resonator or photodetector.

20. A method of purifying a light signal, comprising:

providing an optical structure comprising;

a polarization beam splitter comprising a first splitter waveguide having an input end and an output end, and a second splitter waveguide having an input end;

a polarization rotator system comprising a first polarization rotator having an input end and an output end and a second polarization rotator having an input end and an output end; and

a polarization beam combiner comprising a first combiner waveguide having an input end and an output end, and a second combiner waveguide having an input end and an output end,

wherein the output end of the first splitter waveguide is operatively connected to the input end of the first polarization rotator, and the output end of the first polarization rotator is operatively connected to the input end of the first combiner waveguide, and wherein the output end of the second splitter waveguide is operatively connected to the input end of the second polarization rotator, and the output end of the second polarization rotator is operatively connected to the input end of the second combiner waveguide;

inputting a light signal comprising TM and TE modes into the polarization beam splitter wherein the light signal is split into separate TM and TE modes, and wherein one of the TM and TE modes is rotated via the first polarization rotator and the other of the TM and TE modes is rotated via the second polarization rotator, and combining the rotated TM and TE modes into one of the first and second combiner waveguides while first order TM and TE error components are combined into the other of the first and second combiner waveguides, thereby separating the primary TM and TE modes from the first order TM and TE error components.

21. The method of claim 20 wherein the optical structure comprises at least one additional optical element.

22. The method of claim 21 wherein the at least one additional optical element is a filter, polarizer, waveguide, reflector, coupler, interconnect, phase modulator, intensity modulator, frequency shifter transducer, oscillator, power splitter, resonator or photodetector

23. A method for making a combined polarization beam splitter, polarization rotator, and polarization beam combiner, comprising:

providing an optical structure comprising a first waveguide, and a second waveguide positioned adjacent to the first waveguide, the waveguide structure comprising a core material disposed within a cladding material;

disposing a resist layer on the waveguide structure, the resist layer leaving exposed an exposed area of the first waveguide and an exposed area of the second waveguide; and

etching the exposed area of the first waveguide and the exposed area of the second waveguide such that a first polarization rotator is formed in an intermediate portion of the first waveguide and a second polarization rotator is formed in an intermediate portion of the second waveguide, and a polarization beam splitter is formed in a first terminal portion of the waveguide structure, and a polarization beam combiner is formed in a second terminal portion of the waveguide structure.

24. The method of claim 23 wherein the combined polarization beam splitter, polarization rotator, and polarization beam combiner comprise an additional optical element.

25. The method of claim 24 wherein the at least one additional optical element is a filter, polarizer, waveguide, reflector, coupler, interconnect, phase modulator, intensity modulator, frequency shifter transducer, oscillator, power splitter, resonator or photodetector