# US 2018/0026723 A1 · Inherently Broadband Linearized Electro-Optic Modulator with Customizable Performance

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2018/0026723 A1
- Document ID: US20180026723A1
- Status: Published application
- Kind: A1
- Application number: 15/655,277
- Filed: 2017-07-20
- Published: 2018-01-25
- Earliest claimed: 2016-07-22
- Assignees: Photonic Systems, Inc.
- Applicants: Photonic Systems, Inc.
- Inventors: Edward I. Ackerman; Gary E. Betts; Charles H. Cox
- Web page: https://patentgrep.com/patent/US20180026723A1

## CPC

- H04B 10/50575: {to control the modulator DC bias}
- G02F 1/0123: {Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops}
- G02F 1/225: in an optical waveguide structure
- H04B 10/506: {Multiwavelength transmitters}
- H04B 10/54: Intensity modulation
- H04B 10/564: Power control
- H04B 10/588: in external modulation systems
- H04B: TRANSMISSION
- 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 linearized electro-optic modulator includes a substrate comprising a first Mach Zehnder interferometer comprising a first and second optical waveguide and a second Mach Zehnder interferometer comprising a first and a second optical waveguide. A signal electrode is positioned on the substrate to receive a modulation signal. First and second ground electrodes are positioned on the substrate and are electrically connected to ground potential. The signal electrode and the first and second ground electrodes are positioned so that an electric field generated by the signal electrode modulates both the first and second Mach Zehnder interferometers to generate a first and a second linearized modulated optical signal.

## Claims

### Claim 1

A linearized electro-optic modulator comprising:
a) a substrate comprising a first Mach Zehnder interferometer comprising a first and second optical waveguide and a second Mach Zehnder interferometer comprising a first and a second optical waveguide;
b) a signal electrode positioned on the substrate to receive a modulation signal; and
c) a first and second ground electrode positioned on the substrate that are electrically connected to ground potential,
wherein the signal electrode and the first and second ground electrodes are positioned so that an electric field generated by the signal electrode modulates both the first and second Mach Zehnder interferometer to generate a first and a second modulated optical signal.

### Claim 2 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the substrate comprises a lithium niobate substrate.

### Claim 3 (depends on 2)

The linearized electro-optic modulator of claim 2 wherein the lithium niobate substrate comprises X-cut lithium niobate.

### Claim 4 (depends on 2)

The linearized electro-optic modulator of claim 2 wherein the lithium niobate substrate comprises Z-cut lithium niobate.

### Claim 5 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the substrate comprises a semiconductor material.

### Claim 6 (depends on 5)

The linearized electro-optic modulator of claim 5 wherein the semiconductor material comprises silicon.

### Claim 7 (depends on 5)

The linearized electro-optic modulator of claim 5 wherein the semiconductor material comprises gallium arsenide.

### Claim 8 (depends on 5)

The linearized electro-optic modulator of claim 5 wherein the semiconductor material comprises a quarternary semiconductor material.

### Claim 9 (depends on 8)

The linearized electro-optic modulator of claim 8 wherein the quarternary semiconductor material comprises InGaAsP.

### Claim 10 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the substrate comprises an inorganic material.

### Claim 11 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the substrate comprises a polymer.

### Claim 12 (depends on 1)

The linearized electro-optic modulator of claim 1 further comprising a bias electrode.

### Claim 13 (depends on 12)

The linearized electro-optic modulator of claim 12 wherein the bias electrode is configured to multiplex a bias signal with a time-varying modulation signal.

### Claim 14 (depends on 1)

The linearized electro-optic modulator of claim 1 further comprising a first bias electrode that biases the first Mach Zehnder interferometer and a second bias electrode that biases the second Mach Zehnder interferometer.

### Claim 15 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the linearized electro-optic modulator performs linear-electro-optic-effect modulation.

### Claim 16 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the linearized electro-optic modulator performs carrier injection.

### Claim 17 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the signal electrode is positioned over the first optical waveguide of one of the first or second Mach-Zehnder interferometers and one of the first and second ground electrodes is positioned over the second arm of the one of the first or second Mach-Zehnder interferometer.

### Claim 18 (depends on 17)

The linearized electro-optic modulator of claim 17 wherein the other of the first and second ground electrodes is positioned over the optical waveguide of the other of the at least one of the first or second Mach-Zehnder interferometer.

### Claim 19 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the signal electrode is positioned over the first optical waveguide of one of the first and the second Mach-Zehnder interferometers, and one of the first and second ground electrodes is positioned over the second optical waveguide of the one of the first and the second Mach-Zehnder interferometers.

### Claim 20 (depends on 19)

The linearized electro-optic modulator of claim 19 wherein the other of the first and second ground electrodes is positioned over an optical waveguide of the other one of the first and the second Mach-Zehnder interferometers.

### Claim 21 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein each of the first and second Mach-Zehnder interferometers have a different Vπ.

### Claim 22 (depends on 21)

The linearized electro-optic modulator of claim 21 wherein a ratio of a Vπ of the first Mach-Zehnder interferometer to a Vπ of the second Mach-Zehnder is substantially invariant with RF frequency.

### Claim 23 (depends on 22)

The linearized electro-optic modulator of claim 22 wherein the ratio of the Vπ of the first Mach-Zehnder interferometer to the Vπ of the second Mach-Zehnder that is substantially invariant with RF frequency is chosen to impart a predetermined performance to an RF photonic link.

### Claim 24 (depends on 23)

The linearized electro-optic modulator of claim 23 wherein the predetermined performance comprises an optimum performance.

### Claim 25 (depends on 22)

The linearized electro-optic modulator of claim 22 wherein the ratio of the Vπ of the first Mach-Zehnder interferometer to the Vπ the second Mach-Zehnder is approximately equal to two.

### Claim 26 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein each of the first and second Mach-Zehnder interferometers has a different efficiency.

### Claim 27 (depends on 1)

The linearized electro-optic modulator of claim 1 wherein the signal electrode comprises a plurality of electrode segments.

### Claim 28 (depends on 27)

The linearized electro-optic modulator of claim 27 wherein at least some of the plurality of electrode segments comprises a gain element.

### Claim 29

An RF photonic link comprising:
a) an optical source;
b) a linearized electro-optic modulator comprising:
i. a substrate comprising a first Mach Zehnder interferometer comprising a first and second optical waveguide having an input that is optically coupled to an output of the optical source and a second Mach Zehnder interferometer comprising a first and a second optical waveguide that is optically coupled to an output of the optical source;
ii. a signal electrode positioned on the substrate to receive a modulation signal; and
iii. a first and second ground electrode positioned on the substrate that are electrically connected to ground potential,
wherein the signal electrode and the first and second ground electrodes are positioned so that an electric field generated by the signal electrode modulates both the first and second Mach Zehnder interferometer to generate a first modulated optical signal at a first output and a second modulated optical signal at a second output; and
c) an optical receiver having a first input that is coupled to the first optical output of the linearized electro-optic modulator and a second input that is coupled to the second output of linearized electro-optic modulator, the optical receiver generating a substantially linear RF signal.

### Claim 30 (depends on 29)

The RF photonic link of claim 29 wherein the optical source comprises a single optical source.

### Claim 31 (depends on 29)

The RF photonic link of claim 29 wherein the optical source comprises a first laser having an output that is coupled to the input of the first Mach Zehnder interferometer and a second laser having an output that is coupled to the input of the second Mach Zehnder interferometer.

### Claim 32 (depends on 31)

The RF photonic link of claim 31 wherein the first laser emits light at a first wavelength and the second laser emits light at a second wavelength that is different from the first wavelength.

### Claim 33 (depends on 29)

The RF photonic link of claim 29 wherein the optical receiver comprises a single photodetector.

### Claim 34 (depends on 29)

The RF photonic link of claim 29 wherein the optical receiver comprises a first optical detector that is optically coupled to the first output of the linearized electro-optic modulator and a second optical detector that is optically coupled to the second output of the linearized electro-optic modulator.

### Claim 35 (depends on 29)

The RF photonic link of claim 29 wherein the optical receiver comprises a balanced photodetector with a single differential output.

### Claim 36 (depends on 29)

The RF photonic link of claim 29 wherein the optical receiver comprises a wavelength-division multiplexer combiner that generates a wavelength-division multiplexed signal.

### Claim 37 (depends on 29)

The RF photonic link of claim 29 wherein the linearized electro-optic modulator is configured to achieve quadrature bias points to reduce even-order distortion products.

### Claim 38 (depends on 29)

The RF photonic link of claim 29 wherein the linearized electro-optic modulator is configured to minimize 3rd-order distortion products.

### Claim 39 (depends on 29)

The RF photonic link of claim 29 wherein the linearized electro-optic modulator is configured to minimize 2nd-order distortion products.

### Claim 40 (depends on 29)

The RF photonic link of claim 29 wherein at least one of the first and the second Mach-Zehnder interferometric modulators are configured so that the linearized electro-optic modulator achieves non-quadrature bias points.

### Claim 41 (depends on 29)

The RF photonic link of claim 29 wherein the signal electrode comprises a plurality of electrode segments.

### Claim 42 (depends on 41)

The RF photonic link of claim 41 wherein at least some of the plurality of electrode segments comprises a gain element.