Integrated optic vector-matrix multiplier

• US 8,027,587 B1
• Filed: 08/20/2008
• Issued: 09/27/2011
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Watts, Michael R.
• Primary Examiner(s): Phan; Hanh
• Application Number:
  US12/194,646
• Time in Patent Office: 1,133 Days
• Field of Search: 398/48, 398/79, 398/183, 398/83, 398/43, 398/82, 398/85, 398/141, 398/186, 398/200, 398/201, 385/24, 385/37, 385/16, 385/17, 385/18, 385/2, 385/32, 385/50, 359/107, 359/237, 359/245, 359/238, 359/561, 708/831, 708/191, 708/607, 364/736, 364/713, 364/754, 364/845, 364/841, 364/757
• US Class Current: 398/79
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/29343 Cascade of loop resonators
• CPC Class Codes: G02F 1/025 in an optical waveguide structure G02F1/017, G02F1/2257 take precedence
• CPC Class Codes: G02F 1/2257 the optical waveguides being made of semiconducting material
• CPC Class Codes: G02F 2203/055 wavelength filtering
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/58 Multi-wavelength, e.g. operation of the device at a plurality of wavelengths
• CPC Class Codes: G02F 3/00 Optical logic elements; Optical bistable devices
• CPC Class Codes: G06E 1/045 Matrix or vector computation

Abstract

A vector-matrix multiplier is disclosed which uses N different wavelengths of light that are modulated with amplitudes representing elements of an N×1 vector and combined to form an input wavelength-division multiplexed (WDM) light stream. The input WDM light stream is split into N streamlets from which each wavelength of the light is individually coupled out and modulated for a second time using an input signal representing elements of an M×N matrix, and is then coupled into an output waveguide for each streamlet to form an output WDM light stream which is detected to generate a product of the vector and matrix. The vector-matrix multiplier can be formed as an integrated optical circuit using either waveguide amplitude modulators or ring resonator amplitude modulators.

Claims

1. A vector-matrix multiplier for multiplying an N×

1 vector and an M×

N matrix to generate an M×

1 vector-matrix product, comprising;

an optical multiplexer to receive a plurality of N different wavelengths of light corresponding to a number N of rows in the vector and to combine the plurality of N different wavelengths of light into an input wavelength-division-multiplexed (WDM) light stream, with each different wavelength of light being modulated with an amplitude which represents a row element a_i of the vector with i=1, 2 . . . N;

an optical splitter to receive the input WDM light stream from the optical multiplexer and to split the input WDM light stream into a plurality of M light streamlets, with each light streamlet being guided out of the optical splitter into a transfer waveguide;

a plurality of M×

N optical amplitude modulators arranged in M rows, with each row containing N of the optical amplitude modulators, and with each optical amplitude modulator in each of the M rows being coupled to one of the transfer waveguides to receive one of the N different wavelengths of light from the light streamlet in that transfer waveguide and to amplitude modulate that wavelength of light for a second time in response to an input signal which represents a column element b_ji of the matrix which is provided to that optical amplitude modulator; and

a plurality of M output waveguides, with each output waveguide being coupled to each optical amplitude modulator located in one of the M rows to receive each of the N different wavelengths of light from that row which have been amplitude-modulated for the second time and to form therefrom an output WDM light stream having an overall amplitude which represents a row element c_j=Σ

a_ib_ji of the M×

1 vector-matrix product.

2. The apparatus of claim 1 further comprising a plurality of photodetectors, with each photodetector detecting the overall amplitude of one of the output WDM light streams to generate therefrom an output signal that represents one of the row elements c_j of the M×

1 vector-matrix product.

3. The apparatus of claim 2 wherein the output signal corresponding to each row element c_j of the M×

1 vector-matrix product is an analog output signal, and further comprising an analog-to-digital converter to convert the analog output signal into a digital output signal.

4. The apparatus of claim 3 wherein the row elements a_i and the column elements b_ji are both digital elements, and further comprising a plurality of digital-to-analog converters to convert the row elements a_i and the column elements b_ji into analog elements to provide an analog amplitude modulation for the plurality of N different wavelengths of light and for the plurality of M×

N optical amplitude modulators.

5. The apparatus of claim 1 wherein each of the N different wavelengths of light is generated by a laser.

6. The apparatus of claim 5 wherein each laser is amplitude modulated by a modulation signal provided thereto to amplitude modulate the light generated by that laser to represent one of the row elements a_i of the vector.

7. The apparatus of claim 1 herein the optical multiplexer comprises an input waveguide to receive each of the N different wavelengths of light, and an optical filter comprising at least one micro-ring resonator to filter each different wavelength of light.

8. The apparatus of claim 1 wherein the optical multiplexer comprises a plurality of N optical amplitude modulators to provide the amplitude modulation for each different wavelength of light representing one of the row elements a_i of the vector.

9. The apparatus of claim 1 wherein each optical amplitude modulator in the plurality of M×

N optical amplitude modulators comprises at least one micro-ring resonator.

10. The apparatus of claim 9 wherein each optical amplitude modulator in the plurality of M×

N optical amplitude modulators comprises a waveguide amplitude modulator.

11. The apparatus of claim 1 wherein each optical amplitude modulator in the plurality of M×

N optical amplitude modulators comprises a ring resonator amplitude modulator.

12. The apparatus of claim 1 wherein each optical amplitude modulator in the plurality of M×

N optical amplitude modulators comprises a semiconductor junction.

13. The apparatus of claim 12 wherein the semiconductor junction within each optical amplitude modulator in the plurality of M×

N optical amplitude modulators is a reverse-biased semiconductor junction.

14. A vector-matrix multiplier for multiplying an N×

1 vector and an M×

N matrix to generate an M×

1 vector-matrix product, comprising;

a substrate;

a number (M+1)×

N of micro-ring resonator filter-modulators formed on the substrate, with N of the micro-ring resonator filter-modulators each receiving a different wavelength of light and amplitude modulating the light at each different wavelength in response to a plurality of first input signals provided to the N micro-ring resonator filter-modulators, with each first input signal representing a row element a_i of the vector with i=1, 2 . . . N, and with the remaining M×

N micro-ring resonator filter-modulators amplitude modulating the light at each different wavelength for a second time in response to a plurality of second input signals provided the remaining M×

N micro-ring resonator filter-modulators, with each second input signal representing a column element b_ji of the matrix; and

at least one output waveguide on the substrate to receive the light from the remaining M×

N micro-ring resonator filter-modulators which has been amplitude modulated for the second time, with each output waveguide receiving the light from a set of the remaining M×

N micro-ring resonator filter-modulators which has been modulated by the second input signals which represent the column elements b_ji=b_j1, b_j2 . . . b_jN for a row j of the matrix so that an overall amplitude of the light in each output waveguide represents a row element c_j=Σ

a_ib_ji of the M×

1 vector-matrix product.

15. The apparatus of claim 14 further comprising a photodetector to receive the light from each output waveguide and to generate therefrom an output signal to represent one of the row elements c_j of the M×

1 vector-matrix product.

16. The apparatus of claim 14 further comprising an optical multiplexer on the substrate formed, at least in part, from the N micro-ring resonator filter-modulators, with the optical multiplexer converting the different wavelengths of light into an input wavelength-division-multiplexed (WDM) light stream.

17. The apparatus of claim 14 wherein each of the (M+1)×

N micro-ring resonator filter-modulators comprises at least one micro-ring resonator.

18. The apparatus of claim 17 wherein each micro-ring resonator has a diameter of less than or equal to 20 microns.

19. The apparatus of claim 17 wherein each micro-ring resonator comprises a monocrystalline silicon waveguide core.

20. The apparatus of claim 14 wherein each of the (M+1)×

N micro-ring resonator filter-modulators comprises an amplitude modulator.

21. The apparatus of claim 20 wherein the amplitude modulator comprises a waveguide amplitude modulator.

22. The apparatus of claim 20 wherein the amplitude modulator comprises a ring resonator amplitude modulator.

23. The apparatus of claim 20 wherein the amplitude modulator comprises a semiconductor junction.

24. The apparatus of claim 23 wherein the semiconductor junction comprises a reverse-biased semiconductor junction.

25. The apparatus of claim 14 wherein the different wavelengths of light are spaced apart in frequency with a substantially-equal frequency spacing between each adjacent pair of the different wavelengths of light.

26. The apparatus of claim 14 wherein the different wavelengths of light are infrared wavelengths in a wavelength range of 1-2 microns.

27. The apparatus of claim 14 wherein each different wavelength of light is provided by a laser.

28. A vector-matrix multiplier for multiplying a vector and a matrix to generate a product of the vector and the matrix, comprising:

a substrate;

a plurality of lasers, with each laser providing light at a different wavelength;

a first plurality of optical amplitude modulators on the substrate, with each optical amplitude modulator of the first plurality of optical modulators receiving the light from one of the lasers and, in response to a first input signal representative of a row element a_i of the vector with i=1, 2 . . . N, modulating an amplitude of the light to form a channel of amplitude-modulated light;

a bus waveguide on the substrate to receive each channel of amplitude-modulated light and to combine each channel of amplitude-modulated light to form a wavelength-division-multiplexed (WDM) light stream;

at least one transfer waveguide on the substrate and optically coupled to the bus waveguide, with each transfer waveguide receiving a portion of the WDM light stream from the bus waveguide;

a second plurality of optical amplitude modulators on the substrate proximate to each transfer waveguide, with each optical modulator of the second plurality of optical modulators coupling one of the channels of amplitude-modulated light out of the portion of the WDM light stream and amplitude modulating that channel of amplitude-modulated light in response to a second input signal representative of a column element b_ji of the matrix, thereby forming a doubly-modulated light component;

at least one output waveguide on the substrate to receive the doubly-modulated light components from the optical modulators of each second plurality of optical modulators and to guide the doubly-modulated light components towards an output end of that output waveguide; and

a photodetector located proximate to the output end of each output waveguide to detect the doubly-modulated light components from that output waveguide and to generate therefrom an output signal representative of a row element c_j of the product of the vector and the matrix.