# US 2017/0285437 A1 · Silicon modulators and related apparatus and methods

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- Number: US 2017/0285437 A1
- Document ID: US20170285437A1
- Status: Published application
- Kind: A1
- Application number: 15/472,946
- Filed: 2017-03-29
- Published: 2017-10-05
- Earliest claimed: 2016-03-29
- Assignees: Acacia Communications, Inc.
- Applicants: Acacia Communications, Inc.
- Inventors: Christopher Doerr; Long Chen; Ricardo Aroca
- Web page: https://patentgrep.com/patent/US20170285437A1

## CPC

- G02F 1/2257: {the optical waveguides being made of semiconducting material}
- G02F 1/025: in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence)
- G02F 1/2255: {controlled by a high-frequency electromagnetic component in an electric waveguide structure}
- G02F 1/212: {Mach-Zehnder type}
- 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

An optical Mach Zehnder modulator is described. The optical Mach Zehnder modulator may comprise a plurality of segments separated by curved waveguides. For example, an optical Mach Zehnder modulator may comprise a first waveguide arm having a first pn-junction formed therein, a second waveguide arm having a second pn-junction formed therein, a third waveguide arm coupled to the first waveguide arm via a first curved waveguide and a fourth waveguide arm coupled to the second waveguide arm via a second curved waveguide. The segments may have the same polarities. Alternatively, the segments may have opposite polarities. The different segments may be driven using different RF signals. The RF signals may be delayed from one another.

## Claims

### Claim 1

A Mach Zehnder modulator comprising:
a first waveguide arm having a first pn-junction formed therein;
a second waveguide arm having a second pn-junction formed therein;
a third waveguide arm having a third pn-junction formed therein, the third waveguide arm being coupled to the first waveguide arm via a first curved waveguide;
a fourth waveguide arm having a fourth pn-junction formed therein, the fourth waveguide arm being coupled to the second waveguide arm via a second curved waveguide;
an input waveguide coupled to both the first waveguide arm and second waveguide arm; and
an output waveguide coupled to both the third waveguide arm and fourth waveguide arm.

### Claim 2 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first and third waveguide arms are substantially parallel to each other and the second and fourth waveguide arms are substantially parallel to each other.

### Claim 3 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first and second curved waveguides are U-shaped.

### Claim 4 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first and second curved waveguides are at least partially undoped.

### Claim 5 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first and third waveguide arms are separated by an odd number of U-shaped curved waveguides, one of the odd number of curved waveguides being the first curved waveguide.

### Claim 6 (depends on 5)

The Mach Zehnder modulator of claim 5, wherein the first and second pn-junctions form a first segment, the first segment having a first polarity, and wherein the third and fourth pn-junctions form a second segment, the second segment having the first polarity.

### Claim 7 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first curved waveguide has a fifth pn-junction formed therein and the second curved waveguide has a sixth pn-junction formed therein.

### Claim 8 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first and third waveguide arms are separated by an even number of U-shaped curved waveguides, one of the even number of curved waveguides being the first curved waveguide.

### Claim 9 (depends on 8)

The Mach Zehnder modulator of claim 8, wherein the first and second pn-junctions form a first segment, the first segment having a first polarity, and wherein the third and fourth pn-junctions form a second segment, the second segment having a second polarity.

### Claim 10 (depends on 1)

The Mach Zehnder modulator of claim 1, further comprising driver circuitry configured to drive the first and the second pn-junctions with a first RF signal and the third and fourth pn-junctions with a second RF signal.

### Claim 11 (depends on 10)

The Mach Zehnder modulator of claim 10, further comprising a delay unit configured to delay the second RF signal with respect to the first RF signal.

### Claim 12 (depends on 11)

The Mach Zehnder modulator of claim 11, wherein the delay unit is configured to delay the second RF signal with respect to the first RF signal by an amount approximately equal to an optical delay between the first pn-junction and the third pn-junction.

### Claim 13 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first, second, third and fourth pn-junctions are lateral pn-junctions.

### Claim 14 (depends on 1)

The Mach Zehnder modulator of claim 1, wherein the first, second, third and fourth waveguide arms are formed on a silicon substrate.

### Claim 15

A method of operating a Mach Zehnder modulator, the method comprising:
coupling an optical signal to first and second waveguide arms of the Mach Zehnder modulator;
coupling the optical signal from the first waveguide arm to a third waveguide arm of the Mach Zehnder modulator and from the second waveguide arm to a fourth waveguide arm of the Mach Zehnder modulator, the third waveguide arm being coupled to the first waveguide arm via a first curved waveguide and the fourth waveguide arm being coupled to the second waveguide arm via a second curved waveguide; and
modulating the optical signal by driving, with an RF signal, a first pn-junction formed in the first waveguide arm and a second pn-junction formed in the second waveguide arm.

### Claim 16 (depends on 15)

The method of claim 15, wherein the optical signal travels along the first waveguide arm in a first direction and along the third waveguide arm in a second direction opposite the first direction.

### Claim 17 (depends on 15)

The method of claim 15, wherein the optical signal travels along the first waveguide arm and the third waveguide arm in a same direction.

### Claim 18 (depends on 15)

The method of claim 15, wherein the RF signal is a first RF signal, and wherein modulating the optical signal further comprises driving, with a second RF signal, a third pn-junction formed in the third waveguide arm and a fourth pn-junction formed in the fourth waveguide arm.

### Claim 19 (depends on 18)

The method of claim 18, further comprising delaying the second RF signal with respect to the first RF signal.

### Claim 20 (depends on 19)

The method of claim 19, wherein delaying the second RF signal with respect to the first RF signal comprises delaying the second RF signal with respect to the first RF signal by an amount approximately equal to an optical delay between the first pn-junction and the third pn-junction.