# US 2013/0155485 A1 · Acousto-optic device with electrode having different transverse edge positions

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- Number: US 2013/0155485 A1
- Document ID: US20130155485A1
- Status: Published application
- Kind: A1
- Application number: 13/325,777
- Filed: 2011-12-14
- Published: 2013-06-20
- Earliest claimed: 2011-12-14
- Assignees: Gooch and Housego PLC
- Inventors: CHRISTOPHER N. PANNELL
- Web page: https://patentgrep.com/patent/US20130155485A1

## CPC

- G02F 1/116: {using an optically anisotropic medium, wherein the incident and the diffracted light waves have different polarizations, e.g. acousto-optic tunable filter [AOTF] (G02F1/125 takes precedence)}
- G02F 1/11: based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves (acousto-optical deflection G02F1/33)
- G02F 2201/122: having a particular pattern
- Y10T 29/42: Piezoelectric device making
- 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
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An acousto-optic (AO) device includes an AO interaction crystal for receiving and propagating a light ray along an optical propagation direction (OPD). A piezoelectric transducer is on at least one surface of the AO interaction crystal for receiving an electrical signal and emitting an acoustic wave into the AO interaction crystal. An electrode is on the piezoelectric transducer for coupling the electrical signal to the piezoelectric transducer. The electrode is a patterned electrode that includes a plurality of different transverse edge positions. The plurality of different transverse edge positions span a position range of at least five percent of an average height (Havg) of the electrode.

## Claims

### Claim 1

An acousto-optic (AO) device, comprising:
an AO interaction crystal for receiving and propagating a light ray along an optical propagation direction (OPD);
a piezoelectric transducer on at least one surface of said AO interaction crystal for receiving an electrical signal and emitting an acoustic wave into said AO interaction crystal, and
an electrode on said piezoelectric transducer for coupling said electrical signal to said piezoelectric transducer,
wherein said electrode is a patterned electrode that includes a plurality of different transverse edge positions, and
wherein said plurality of different transverse edge positions span a position range of at least five percent of an average height (Havg) of said electrode.

### Claim 2 (depends on 1)

The AO device of claim 1, wherein said plurality of different transverse edge positions follow a pre-defined linear function.

### Claim 3 (depends on 1)

The AO device of claim 1, wherein said plurality of different transverse edge positions follow a non-linear function.

### Claim 4 (depends on 3)

The AO device of claim 3, wherein non-linear function comprises a pre-defined non-deterministic function.

### Claim 5 (depends on 4)

The AO device of claim 4, wherein said non-deterministic function comprises a Gaussian random variable.

### Claim 6 (depends on 1)

The AO device of claim 1, wherein said patterned electrode in said OPD further includes:
an electrically continuous region proximate to its center and
a discontinuous region, comprising:
a plurality of spaced apart features oriented in said ODP that are electrically connected to said continuous region,
wherein feature sizes of said features are sufficiently small to provide a fine structure far field condition for said acoustic wave in said AO interaction crystal underlying said discontinuous region beginning <10 mm measured from an interface between said piezoelectric transducer and said AO interaction crystal,
wherein said plurality of spaced apart features enhance suppression of out-of-band light.

### Claim 7 (depends on 1)

The AO device of claim 1, wherein said patterned electrode is representable by a plurality of electrically contiguous rectangles oriented along a transverse direction.

### Claim 8 (depends on 1)

The AO device of claim 1, wherein a peak-to-peak length-averaged in length-averaged average acoustic intensity at a midway position in said AO interaction crystal between a center of said patterned electrode and its edges and transverse positions proximate thereto are reduced by at least 50 percent as compared to a variance in said average acoustic intensity for a reference rectangular electrode having an area equal to said patterned electrode.

### Claim 9 (depends on 1)

The AO device of claim 1, wherein said AO device comprises an Acousto-Optic Modulator (AOM), Acousto-Optic Beam Deflector (AOBD), Bragg Cell (BC), Acousto-Optic Tunable Filter (AOTF), Acousto-Optic Frequency Shifter (AOFS) or an Acousto-Optic Correlator (AOC).

### Claim 10

A method of fabricating an electrode for coupling to a piezoelectric transducer of an acousto-optic (AO) device, comprising:
designing an electrode pattern for said electrode that includes a plurality of different transverse edge positions, wherein said plurality of different transverse edge positions span a position range of at least five percent of an average height (Havg) of said electrode, and
forming said electrode pattern on a face of said piezoelectric transducer using a process comprising lithography.

### Claim 11 (depends on 10)

The method of claim 10, wherein said plurality of different transverse edge positions follow a linear function.

### Claim 12 (depends on 10)

The method of claim 10, wherein said plurality of different transverse edge positions follow a non-linear function.

### Claim 13 (depends on 12)

The method of claim 12, wherein non-linear function comprises a non-deterministic function.

### Claim 14 (depends on 10)

The method of claim 10, wherein said designing said electrode pattern comprises dividing an initial rectangular pattern having an initial rectangular outline into a plurality of smaller rectangles, and
displacing said plurality of smaller rectangles with respect to one another from said initial rectangular outline in a direction perpendicular to an optical propagation direction (OPD) for said AO device so that a main body of said electrode is continuous and no gaps in said electrode pattern are introduced.

### Claim 15 (depends on 14)

The method of claim 14, wherein said displacing comprises random displacing.

### Claim 16

A telecentric-confocal AOTF-based imaging system, comprising:
an acousto-optic tunable filter (AOTF), comprising:
an AO interaction crystal for receiving and propagating a light ray along an optical propagation direction (OPD);
a piezoelectric transducer on at least one surface of said AO interaction crystal for receiving an electrical signal and emitting an acoustic wave into said AO interaction crystal, and
an electrode on said piezoelectric transducer for coupling said electrical signal to said piezoelectric transducer,
wherein said electrode is a patterned electrode that includes a plurality of different transverse edge positions, and
wherein said plurality of different transverse edge positions span a position range of at least five percent of an average height (Havg) of said electrode,
an aperture stop positioned at an input (S1) and a beam stop (S2) positioned at an output of said system at a distance from respective lenses equal to focal lengths f1 and f2 associated with said respective lenses, and
a photodetector positioned to detect a beam transmitted through said beam stop.

### Claim 17 (depends on 16)

The system of claim 16, wherein said patterned electrode in said OPD further includes:
a continuous region proximate to its center and
a discontinuous region, comprising:
a plurality of spaced apart features oriented in said ODP that are electrically connected to said continuous region,
wherein feature sizes of said features are sufficiently small to provide a fine structure far field condition for said acoustic wave in said AO interaction crystal underlying said discontinuous region beginning <10 mm measured from an interface between said piezoelectric transducer and said AO interaction crystal,
wherein said plurality of spaced apart features enhance suppression of out-of-band light.