# US 2021/0278738 A1 · Phase shifter employing transparent electrodes

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- Number: US 2021/0278738 A1
- Document ID: US20210278738A1
- Status: Published application
- Kind: A1
- Application number: 17/189,025
- Filed: 2021-03-01
- Published: 2021-09-09
- Earliest claimed: 2020-03-03
- Assignees: Psiquantum, Corp.
- Applicants: PsiQuantum, Corp.
- Inventors: Nikhil Kumar
- Web page: https://patentgrep.com/patent/US20210278738A1

## CPC

- G02F 1/035: in an optical waveguide structure
- G02F 1/225: in an optical waveguide structure
- G02F 1/0305: {Constructional arrangements (G02F1/0327 - G02F1/05 take precedence)}
- G02F 1/212: {Mach-Zehnder type}
- G02F 2201/063: ridge; rib; strip loaded
- G02F 2201/12: electrode
- G02F 2202/42: Materials having a particular dielectric constant
- G02F 2203/50: Phase-only modulation
- 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

Electro-optical devices and methods for constructing electro-optical devices such as a switch or phase shifter. An electrode layer is deposited on a substrate layer, a waveguide structure is deposited on the electrode layer, a first cladding layer is deposited on the waveguide structure, and the first cladding layer is planarized and bonded to a wafer. The substrate layer is removed and the electrode layer is etched to split the electrode layer into a first electrode separated from a second electrode. A second cladding layer is deposited on the etched electrode layer. The first and second electrodes may be composed of a material with a large dielectric constant, or they may be composed of a material with a large electron mobility. The device may exhibit a sandwich waveguide architecture where an electro-optic layer is disposed between two strip waveguides.

## Claims

### Claim 1

A device, comprising:
a first cladding layer;
a first electrode;
a first metallic lead electrically connected to the first electrode;
a second electrode;
a second metallic lead electrically connected to the second electrode;
a second cladding layer,
a waveguide structure composed of barium titanate, wherein the waveguide structure is coupled to the first electrode and the second electrode, wherein the waveguide structure is disposed between the first and second cladding layers; and
wherein the first electrode and the second electrode are composed of a first material with an electron mobility higher than silicon.

### Claim 2 (depends on 1)

The device of claim 1,
wherein the first material is transparent to visible light.

### Claim 3

A device, comprising:
a first cladding layer;
a first electrode;
a second electrode;
a waveguide structure composed of a first material, wherein the waveguide structure is coupled to the first electrode and the second electrode; and
a second cladding layer,
wherein the first electrode and the second electrode are composed of a second material with an electron mobility higher than silicon.

### Claim 4 (depends on 3)

The device of claim 3,
wherein the second material has a band gap larger than an operating frequency of the device.

### Claim 5 (depends on 3)

The device of claim 3,
wherein the second material comprises one of:
gallium arsenide (GaAs);
an aluminum gallium arsenide/GaAs heterostructure;
an indium gallium arsenide (InGaAs)/GaAs heterostructure;
zinc oxide (ZnO);
zinc sulfide (ZnS);
indium oxide (InO);
doped silicon;
a two-dimensional electron gas; or
doped strontium titanate.

### Claim 6 (depends on 5)

The device of claim 5,
wherein the doped strontium titanate is either:
niobium doped;
lanthanum doped; or
vacancy doped.

### Claim 7 (depends on 3)

The device of claim 3,
wherein the second material is transparent to visible light.

### Claim 8 (depends on 3)

The device of claim 3,
wherein the first material comprises one of:
barium titanate;
barium strontium titanate;
lead zirconium titanate;
lead lanthanum zirconium titanate; or
strontium barium niobate.

### Claim 9 (depends on 3)

The device of claim 3,
wherein the first cladding layer and the second cladding layer are composed of silicon nitride.

### Claim 10 (depends on 3)

The device of claim 3,
wherein the waveguide structure comprises a ridge portion and a slab layer, wherein the ridge portion is coupled to the slab layer, wherein the ridge portion is disposed between the first electrode and the second electrode.

### Claim 11 (depends on 10)

The device of claim 10,
wherein the ridge portion is disposed on a first side of the slab layer and extends into the first cladding layer, and
wherein the first electrode and the second electrode are coupled to the slab layer on the first side of the slab layer and abut the ridge portion of the waveguide structure.

### Claim 12 (depends on 10)

The device of claim 10,
wherein the ridge portion is disposed on a first side of the slab layer and extends into the first cladding layer,
wherein the first electrode and the second electrode are coupled to the slab layer on a second side of the slab layer opposite the first side.

### Claim 13 (depends on 3)

The device of claim 3,
wherein the first cladding layer is disposed on a first side of the first electrode, second electrode, and waveguide structure, and
wherein the second cladding layer is disposed on a second side of the first electrode, second electrode, and waveguide structure opposite the first side.

### Claim 14 (depends on 3)

The device of claim 3,
wherein the first electrode and the second electrode are configured to generate an electric field along an x-direction in the waveguide structure, and
wherein the waveguide structure is characterized by an electro-optic coefficient having a nonzero value aligned along the x-direction.

### Claim 15 (depends on 1)

The device of claim 1,
wherein the waveguide structure comprises a slab layer, a first strip waveguide portion, and a second strip waveguide portion,
wherein the first and second strip waveguide portions are composed of a second and a third material, respectively, and
wherein the slab layer is disposed between the first strip waveguide portion and the second strip waveguide portion.

### Claim 16 (depends on 15)

The device of claim 15,
wherein the second and third materials are silicon nitride.

### Claim 17 (depends on 3)

The device of claim 3,
wherein the waveguide structure comprises a slab layer, and
wherein the first electrode and the second electrode comprise a second layer coplanar to the slab layer and disposed adjacent to a first side of the slab layer.

### Claim 18 (depends on 3)

The device of claim 3,
wherein the first electrode and the second electrode are separated by a gap region.

### Claim 19 (depends on 3)

The device of claim 3, wherein the first material comprises a transparent material having an index of refraction that is larger than an index of refraction of the first and second cladding layers.

### Claim 20

An optical switch, comprising:
at least one input port;
at least one output port;
a Mach-Zehnder interferometer coupled to a beam splitter, wherein the Mach-Zehnder interferometer comprises a first arm and a second arm;
a photonic phase shifter comprised within the first arm of the Mach-Zehnder interferometer, the photonic phase shifter comprising:
a first cladding layer;
a first electrode;
a second electrode;
a waveguide structure composed of a first material, wherein the waveguide structure is coupled to the first electrode and the second electrode; and
a second cladding layer,
wherein the first electrode and the second electrode are composed of a second material with an electron mobility higher than silicon.