Universal Linear Components

• US 20140299743A1
• Filed: 11/27/2013
• Published: 10/09/2014
• Est. Priority Date: 11/27/2012
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Miller, David A.B.
• Granted Patent: US 10,534,189 B2
• Time in Patent Office: Days
• US Class Current: 250/204
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/212 Mach-Zehnder type
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence

Abstract

Universal linear components are provided. In general, a P input and Q output wave combiner is connected to a Q input and R output wave mode synthesizer via Q amplitude and/or phase modulators. The wave combiner and wave mode synthesizer are both linear, reciprocal and lossless. The wave combiner and wave mode synthesizer can be implemented using waveguide Mach-Zehnder modulator technology. This device can provide any desired linear transformation of spatial modes between its inputs and its outputs. This capability can be generalized to any linear transformation at all by using representation converters to convert other quantities (e.g., polarization, frequency) to spatial mode patterns. The wave combiner and wave mode synthesizer are also useful separately, and can enable applications such as self-adjusting mode coupling, optimal multi-mode communication, and add-drop capability in a multi-mode system. Control of the wave combiner and wave mode synthesizer can be implemented with simple single-variable optimizations.

Claims

1. A coherent N to one wave combiner having N≧

2 inputs and a single output, the apparatus comprising;

a coherent wave superposition network that is substantially linear, reciprocal and lossless, and which includes one or more series-connected 2×

2 wave splitters configured such that the contribution of each of the N inputs to the output is adjustable in both amplitude and relative phase;

wherein the coherent wave superposition network provides N−

1 control ports at which waves not coupled to the output are emitted; and

N−

1 detectors disposed at the control ports;

wherein amplitude splits and phase shifts of the coherent wave superposition network are determined in operation by adjusting them in sequence to sequentially null signals from the N−

1 detectors.

2. The wave combiner of claim 1 wherein the 2×

2 wave splitters comprise one or more waveguide Mach-Zehnder interferometers.

3. A coherent P input to Q output wave combiner having P≧

2 and Q≦

P, the apparatus comprising;

Q combiners indexed by an integer i (1≦

i≦

Q), wherein each combiner i for 1≦

i≦

min(Q, P−

1) is a P+1−

i to one combiner according to claim 1;

wherein inputs of combiner i for i≧

2 are provided by the control ports of combiner i−

1; and

wherein the detectors of combiner i for i<

Q are tap detectors that absorb less than 50% of the incident light and transmit the remainder.

4. The wave combiner of claim 3, wherein the tap detectors absorb less than 10% of the incident light and transmit the remainder.

5. A coherent N to one wave combiner having N inputs and a single output, the apparatus comprising:

a coherent wave superposition network that is substantially linear, reciprocal and lossless, and which includes one or more series-connected 2×

2 wave splitters configured such that the contribution of each of the N inputs to the output is adjustable in both amplitude and relative phase;

wherein the coherent wave superposition network provides N−

1 control ports at which waves not coupled to the output are emitted; and

an output detector disposed at the output;

wherein amplitude splits and phase shifts of the coherent wave superposition network are determined in operation by adjusting them in sequence to maximize a signal from the output detector.

6. The wave combiner of claim 5, wherein the output detector is a tap detector that absorbs less than 50% of the incident light and transmits the remainder.

7. A coherent P input to Q output wave combiner having P≧

2 and Q≦

P, the apparatus comprising;

Q combiners indexed by an integer i (1≦

i≦

Q), wherein each combiner i for 1≦

i≦

min(Q, P−

1) is a P+1−

i to one combiner according to claim 5;

wherein inputs of combiner i for i≧

2 are provided by the control ports of combiner i−

1.

8. A coherent one to N wave mode synthesizer having one input and N≧

2 outputs, the apparatus comprising;

a coherent wave superposition network that is substantially linear, reciprocal and lossless, and which includes one or more series-connected 2×

2 wave splitters configured such that the contribution of the input to each of the N outputs is adjustable in both amplitude and relative phase;

wherein the coherent wave superposition network provides N−

1 control ports at which waves incident on the outputs can be emitted; and

N−

1 detectors disposed at the control ports;

wherein amplitude splits and phase shifts of the coherent wave superposition network are determined in operation by adjusting them in sequence to sequentially null signals from the N−

1 detectors when the N outputs are illuminated with a phase-conjugated version of a desired output mode.

9. The wave mode synthesizer of claim 8 wherein the 2×

2 wave splitters comprise one or more waveguide Mach-Zehnder interferometers.

10. A coherent Q input to R output wave mode synthesizer having Q≧

2 and Q≦

R, the apparatus comprising;

Q mode synthesizers indexed by an integer i (1≦

i≦

Q), wherein each mode synthesizer i for 1≦

i≦

min(Q, R−

1) is a one to R+1−

i mode synthesizer according to claim 8;

wherein outputs of mode synthesizer i for i≧

2 are provided to the control ports of mode synthesizer i−

1 as inputs; and

wherein the detectors of mode synthesizer i for i<

R are tap detectors that absorb less than 50% of the incident light and transmit the remainder.

11. The wave mode synthesizer of claim 10, wherein the tap detectors absorb less than 10% of the incident light and transmit the remainder.

12. A coherent one to N wave mode synthesizer having one input and N≧

2 outputs, the apparatus comprising;

a coherent wave superposition network that is substantially linear, reciprocal and lossless, and which includes one or more series-connected 2×

2 wave splitters configured such that the contribution of the input to each of the N outputs is adjustable in both amplitude and relative phase;

wherein the coherent wave superposition network provides N−

1 control ports at which waves incident on the outputs can be emitted; and

an input detector disposed at the input and capable of detecting radiation incident on the outputs that is coupled to the input;

wherein amplitude splits and phase shifts of the coherent wave superposition network are determined in operation by adjusting them in sequence to maximize a signal from the input detector when the N outputs are illuminated with a phase-conjugated version of a desired output mode.

13. The wave combiner of claim 12, wherein the input detector is a tap detector that absorbs less than 50% of the incident light and transmits the remainder.

14. A coherent Q input to R output wave mode synthesizer having Q≧

2 and Q≦

R, the apparatus comprising;

Q mode synthesizers indexed by an integer i (1≦

i≦

Q), wherein each mode synthesizer i for 1≦

i≦

min(Q, R−

1) is a one to R+1−

i mode synthesizer according to claim 12;

wherein outputs of mode synthesizer i for i≧

2 are provided to the control ports of mode synthesizer i−

1 as inputs.

15. A universal linear component comprising:

a linear, reciprocal and lossless wave combiner having P inputs and Q outputs with 2≦

Q≦

P configured such that the contribution of each of the P inputs to each of the Q outputs of the wave combiner is adjustable in both amplitude and relative phase;

a linear, reciprocal and lossless wave mode synthesizer having Q inputs and R outputs with Q≦

R configured such that the contribution of each of the Q inputs to each of the R outputs of the wave mode synthesizer is adjustable in both amplitude and relative phase; and

Q amplitude and/or phase modulators connected between outputs of the wave combiner and inputs of the wave mode synthesizer.

16. The universal linear component of claim 15, further comprising:

an input transformer of polarization modes to spatial modes configured to provide inputs to the wave combiner; and

an output transformer of spatial modes to polarization modes configured to receive the outputs of the wave mode synthesizer.

17. The universal linear component of claim 15, further comprising one or more three-port optical circulators connected to an input of the wave combiner and to an output of the wave mode synthesizer, whereby a universal non-reciprocal linear component is provided.