# US 7,411,724 B2 · Electro-optic crystal, diffraction-based, beam-steering element

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- Number: US 7,411,724 B2
- Document ID: US7411724B2
- Status: Granted
- Kind: B2
- Application number: 11/005,124
- Filed: 2004-12-06
- Published: 2006-06-08
- Granted: 2008-08-12
- Earliest claimed: 2004-12-06
- Assignees: Northrop Grumman Corporation
- Inventors: James M. Cicchiello; Curtis J. Harkrider; Kenneth E. Kreischer; David A. Gallagher
- Web page: https://patentgrep.com/patent/US7411724B2

## CPC

- G02F 1/292: {by controlled diffraction or phased-array beam steering (controlled diffraction for optical switching G02F1/31)}
- G02F 2201/12: electrode
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

A beam-steering element made of a more optically-active material, potassium tantalate niobate, with an improved diffraction efficiency, having a plurality of electrode layers and one electro-optic crystal layer interposed between every two adjacent electrode layers. Each electro-optic crystal layer and the electrode layer adjacent thereto have an aspect ratio of about 1:1. The electrode layers and the electro-optic crystal layers are interposed between two substrates. Preferably, the substrates are transparent to an incoming beam to be modulated by the electro-optic crystal layer.

## Claims

### Claim 1

A beam-steering element, comprising a plurality of electrode layers and one electro-optic crystal layer made of potassium tantalate niobate interposed between every two adjacent electrode layers, the electrode layers being transparent to an incoming beam to be modulated by the electro-optic crystal layer, wherein each electro-optic layer includes a surface figure that is a function of the wavelength of an incoming beam.

### Claim 2 (depends on 1)

The element of claim 1, wherein each electro-optic crystal layer and the electrode layer adjacent thereto have an aspect ratio of about 1:1.

### Claim 3 (depends on 1)

The element of claim 1, further comprising two substrates on which two outermost electrode layers are respectively formed.

### Claim 4 (depends on 3)

The element of claim 3, wherein the substrates are transparent to an incoming beam to be modulated by the electro-optic crystal layer.

### Claim 5 (depends on 4)

The element of claim 4, further comprising a reflective layer coated on one of the substrate.

### Claim 6 (depends on 4)

The element of claim 4, wherein the incoming beam includes at least one optical beam having a wavelength of about 1.55 microns.

### Claim 7 (depends on 1)

The element of claim 1, wherein the electrode layers have a surface figure of about 1/50 of the wavelength of the incoming beam.

### Claim 8 (depends on 1)

The element of claim 1, wherein the incoming beam includes at least one optical beam having a wavelength of about 1.55 microns.

### Claim 9 (depends on 1)

The element of claim 1, wherein each of the electrode layers includes a plurality of electrodes spaced from each other by a gap.

### Claim 10 (depends on 9)

The element of claim 9, wherein the gap has a width of about 0.5 microns.

### Claim 11 (depends on 9)

The element of claim 9, wherein the electrodes are fabricated from indium tin oxide.

### Claim 12 (depends on 9)

The element of claim 9, wherein the gaps are filled with an insulation material.

### Claim 13 (depends on 11)

The element of claim 11, wherein the insulation material includes silicon oxide.

### Claim 14 (depends on 9)

The element of claim 9, wherein each of the electrodes has a width of about 1.0 microns.

### Claim 15 (depends on 9)

The element of claim 9, wherein the electrodes of each electrode layer are aligned with the respective electrodes of the other electrode layers.

### Claim 16 (depends on 1)

The element of claim 1, wherein each of the electrode layers includes ten electrodes.

### Claim 17 (depends on 16)

The element of claim 16, wherein the electrodes of each electrode layers are aligned in at least one row.

### Claim 18 (depends on 1)

The element of claim 1, wherein the electro-optical crystal layer is about 1.5 microns thick.

### Claim 19

An electro-optic crystal beam-steering element, comprising:
a first module and a second module, each comprising:
a first substrate and a second substrate;
at least three electrode layers interposed between the first and second substrates; and
at least two electro-optic crystal layers interposed between each pair of the adjacent electrode layers, each electro-optic layer having a surface figure that is a function of the wavelength of an incoming optical beam to be modulated by the electo-optic crystal layers; wherein
the second substrate of the first module is attached to the second substrate of the second module.

### Claim 20 (depends on 19)

The element of claim 19, wherein the second substrates are thinner than the first substrates.

### Claim 21 (depends on 19)

The element of claim 19, wherein the second substrates of the first and second module have a thickness substantially the same as that of each electrode layer.

### Claim 22 (depends on 19)

The element of claim 19, further comprising an anti-reflection coating coated to the second substrate of at least one the first and second modules.

### Claim 23 (depends on 19)

The element of claim 19, wherein the electrode layers and the first and second substrates are transparent to at least one incoming optical beam to be modulated by the electro-optic crystal layer.

### Claim 24 (depends on 23)

The element of claim 23, wherein the incoming optical beam has a wavelength of about 1.55 microns.

### Claim 25 (depends on 23)

The element of claim 23, wherein each of the electro-optic crystal layers has an aspect ratio of modulator thickness to electrode thickness of 1:1.

### Claim 26 (depends on 19)

The element of claim 19, wherein each of the electrode layers includes an array of electrodes spaced from each other by a gap.

### Claim 27 (depends on 26)

The element of claim 26, wherein the gaps are filled with an insulation material.

### Claim 28 (depends on 19)

The element of claim 19, wherein both the electrode layers and the electro-optic layers are planarized to a surface flatness of about one fiftieth of the wavelength of an incoming optical beam to be modulated by the electro-optic crystal layers.

### Claim 29 (depends on 19)

The element of claim 19, wherein the electro-optic crystal layers are fabricated from potassium tantalate niobate.

### Claim 30

A method of fabricating an electro-optic, agile beam-steering device, comprising forming an electro-optic modulation layer and a plurality of electrodes having an aspect ratio of about 1:1, wherein each electro-optic layer includes a surface figure that is a function of the wavelength of an incoming beam.

### Claim 31 (depends on 30)

The method of claim 30, wherein the electro-optic modulation layer includes potassium tantalate niobate. optic modulation layer includes potassium tantalate niobate.

### Claim 32

An electro-optic, agile beam-steering device, comprising an electro-optic modulation layer and a plurality of electrodes having an aspect ratio of about 1:1, wherein each electro-optic layer includes a surface figure that is a funtion of the wavelength of an incoming beam.

### Claim 33 (depends on 32)

The method of claim 32, wherein the electro-optic modulation layer includes a potassium tantalate niobate layer. layer includes a potassium tantalate niobate layer.

### Claim 34

A beam-steering element, comprising:
a plurality of electrode layers;
one electro-optic crystal layer made of potassium tantalite niobate interposed between every two adjacent electrode layers; and
two substrates on which two outmost electrode layers are respectively formed, the substrates being transparent to an incoming beam to be modulated by the electro-optic crystal layer, wherein a reflective layer is coated on a surface of one of the substrates opposite the electrode layer.

### Claim 35 (depends on 34)

The element of claim 34, wherein each electro-optic crystal layer and the electrode layer adjacent thereto have an aspect ratio of about 1:1.

### Claim 36 (depends on 34)

The element of claim 34, wherein the electrode layers are transparent to an incoming beam to be modulated by the electro-optic crystal layers.

### Claim 37 (depends on 34)

The element of claim 34, wherein each of the electrode layers includes a plurality of electrodes spaced from each other by a gap.

### Claim 38 (depends on 34)

The element of claim 34, wherein the gaps are filled with an insulation material.

### Claim 39

An electro-optic crystal beam-steering element, comprising:
a first module and a second module, each comprising:
a first substrate and a second substrate, wherein an anti-reflective coating is
coated on at least one of the substrates;
at least three electrode layers interposed between the first and second substrates; and
at least two electro-optic crystal layers interposed between each pair of the
adjacent electrode layers; wherein
the second substrate of the first module is attached to the second substrate of the second module.

### Claim 40 (depends on 39)

The element of claim 39, wherein the second substrates of the first and second module have a thickness substantially the same as that of each electrode layer.

### Claim 41 (depends on 39)

The element of claim 39, wherein each of the electro-optic crystal layers has an aspect ratio of modulator thickness to electrode thickness of 1:1.

### Claim 42 (depends on 39)

The element of claim 39, wherein each of the electrode layers includes an array of electrodes spaced from each other by a gap.

### Claim 43 (depends on 42)

The element of claim 42, wherein the gaps are filled with insulation material.

### Claim 44

An electro-optic, agile beam-steering device, comprising an electro-optic modulation layer, a plurality of electrodes having an aspect ratio of about 1:1, the electrodes being formed on a substrate, wherein an anti-reflective coating is coated on a surface of the substrate opposite the electrodes.

### Claim 45 (depends on 44)

The device of claim 44, wherein the electro-optic modulation layer includes a potassium tantalate niobate layer.