# US 12,222,627 B2 · High-gain differential electro-optic modulator

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- Number: US 12,222,627 B2
- Document ID: US12222627B2
- Status: Granted
- Kind: B2
- Application number: 18/615,632
- Filed: 2024-03-25
- Published: 2024-11-14
- Granted: 2025-02-11
- Earliest claimed: 2021-04-09
- Assignees: Aloe Semiconductor Inc.
- Applicants: Aloe Semiconductor Inc.
- Inventors: Christopher R. Doerr
- Web page: https://patentgrep.com/patent/US12222627B2

## CPC

- G02F 1/2257: {the optical waveguides being made of semiconducting material}
- G02F 1/212: {Mach-Zehnder type}
- G02F 1/2255: {controlled by a high-frequency electromagnetic component in an electric waveguide structure}
- 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 modulator includes a Mach-Zehnder interferometer including (i) a first optical waveguide including a first semiconductor junction diode, and (ii) a second optical waveguide including a second semiconductor junction diode. A semiconductor region connects the first and second semiconductor junction diodes such that a distance between the first and second optical waveguides is less than 2.0 μm for at least a portion of a longitudinal direction of the optical modulator. In another aspect, a method of modulating an optical signal includes splitting input light into first and second optical transmission paths; modulating a phase difference between light in the first optical transmission path and light in the second optical transmission path without applying a bias voltage through an impedance less than 100 ohm between the first and second optical transmission paths; and combining light that is output from the first and second optical transmission paths.

## Claims

### Claim 1

An optical modulator comprising:
a Mach-Zehnder interferometer comprising (i) a first optical waveguide comprising a first semiconductor junction diode, and (ii) a second optical waveguide comprising a second semiconductor junction diode,
wherein the first optical waveguide has a larger width than the second optical waveguide at a same first distance along a length of the first optical waveguide and the second optical waveguide.

### Claim 2 (depends on 1)

The optical modulator of claim 1, wherein the first semiconductor junction diode comprises a first anode and a first cathode,
wherein the second semiconductor junction diode comprises a second anode and a second cathode, and
wherein the first anode is connected to the second anode through a semiconductor region that connects the first semiconductor junction diode with the second semiconductor junction diode.

### Claim 3 (depends on 2)

The optical modulator of claim 2, wherein the semiconductor region between the first anode and the second anode is configured without any external voltage connection that has an impedance less than 100 ohm.

### Claim 4 (depends on 2)

The optical modulator of claim 2, further comprising:
a first electrode connected to the first cathode and configured to apply a first electric field to the first optical waveguide; and
a second electrode connected to the second cathode and configured to apply a second electric field to the second optical waveguide.

### Claim 5 (depends on 2)

The optical modulator of claim 2, further comprising:
a radio frequency (RF) transmission line configured to apply (i) a first voltage to the first cathode through a first electrode, and (ii) a second voltage to the second cathode through a second electrode.

### Claim 6 (depends on 1)

The optical modulator of claim 1, wherein a distance between the first optical waveguide and the second optical waveguide is less than 2.0 μm for at least a portion of a longitudinal direction of the optical modulator.

### Claim 7 (depends on 1)

The optical modulator of claim 1, wherein the first optical waveguide is wider than the second optical waveguide by at least 0.04 μm at the same first distance along the length of the first optical waveguide and the second optical waveguide.

### Claim 8 (depends on 1)

The optical modulator of claim 1, wherein the second optical waveguide has a larger width than the first optical waveguide at a same second distance along the length of the first optical waveguide and the second optical waveguide.

### Claim 9 (depends on 8)

The optical modulator of claim 8, wherein a width of the first optical waveguide at the same first distance matches a width of the second optical waveguide at the same second distance.

### Claim 10 (depends on 9)

The optical modulator of claim 9, wherein a width of the first optical waveguide at the same second distance matches a width of the second optical waveguide at the same first distance.

### Claim 11 (depends on 1)

The optical modulator of claim 1, wherein, for at least a portion of the optical modulator:
the first optical waveguide increases in width along a longitudinal direction of the optical modulator, and
the second optical waveguide decreases in width along the longitudinal direction of the optical modulator.

### Claim 12 (depends on 1)

The optical modulator of claim 1, wherein the first semiconductor junction diode comprises a first p-doped region and a first n-doped region, and
wherein the second semiconductor junction diode comprises a second p-doped region and a second n-doped region.

### Claim 13 (depends on 12)

The optical modulator of claim 12, wherein the first p-doped region is connected to the second p-doped region through a third p-doped region in a semiconductor region that connects the first semiconductor junction diode with the second semiconductor junction diode, and
wherein the third p-doped region is configured without any external voltage connection that has an impedance less than 100 ohm.

### Claim 14 (depends on 1)

The optical modulator of claim 1, wherein the Mach-Zehnder interferometer further comprises:
an optical splitter configured to receive input light and split the input light into the first optical waveguide and the second optical waveguide; and
an optical combiner configured to receive first output light from the first optical waveguide and second output light from the second optical waveguide, and combine the first output light with the second output light.

### Claim 15

An optical modulator comprising:
an optical splitter configured to split an input light into a first optical transmission path and a second optical transmission path, wherein a distance between the first optical transmission path and the second optical transmission path is less than 2.0 μ, for at least a portion of a longitudinal of the optical modulator, and wherein the first optical transmission path has a larger width than the second optical transmission path at a same first distance along a length of the first optical transmission path and the second optical transmission path;
means for modulating a phase difference between light in the first optical transmission path and light in the second optical transmission path; and
an optical combiner configured to combine light that is output from the first optical transmission path and light that is output from the second optical transmission path.

### Claim 16 (depends on 15)

The optical modulator of claim 15, further comprising:
a radio-frequency (RF) transmission line configured to apply (i) a first voltage to the first optical transmission path through a first electrode, and (ii) a second voltage to the second optical transmission path through a second electrode.

### Claim 17 (depends on 15)

The optical modulator of claim 15, wherein:
the first optical transmission path comprises a first semiconductor junction diode, and
the second optical transmission path comprises a second semiconductor junction diode.

### Claim 18 (depends on 15)

The optical modulator of claim 15, wherein the phase difference between the light in the first optical transmission path and the light in the second optical transmission path is modulated by applying a first electric field to the first optical transmission path and a second electric field to the second optical transmission path in push-pull mode.

### Claim 19

A method of modulating an optical signal, the method comprising:
splitting input light into a first optical waveguide and a second optical waveguide, wherein the first optical waveguide has a larger width than the second optical waveguide at a same first distance along a length of the first optical waveguide and the second optical waveguide;
modulating a phase difference between light in the first optical waveguide and light in the second optical waveguide; and
combining light that is output from the first optical waveguide and light that is output from the second optical waveguide.

### Claim 20 (depends on 19)

The method of claim 19, wherein the phase difference between the light in the first optical waveguide and the light in the second optical waveguide is modulated while maintaining finite depletion regions in semiconductor junction diodes in each of the first optical waveguide and the second optical waveguide.