Optical Modulator Carrier Diffusion Blocking

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Solution Overview

Problem

In photonic neural networks, electrical crosstalk between adjacent phase shifters in silicon modulators distorts modulated signals due to carrier diffusion along the waveguide propagation direction, limiting the performance and reliability of photonic integrated systems.

Innovation Solution

A carrier-injection-based optical modulator with a blocking structure, such as a PN junction or space, is implemented at the ends of the intrinsic region to prevent carrier diffusion between phase shifters, ensuring consistent phase behavior and reducing electrical crosstalk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple phase shifters are employed in the silicon modulator to achieve high-bit resolution control of optical intensity, then the modulation precision is improved, but electrical crosstalk occurs between adjacent phase shifters due to carrier diffusion

Engineering Contradiction:

Improvemodulation precisionVSAvoidelectrical crosstalk

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

A blocking structure (PN junction or space) is introduced as an intermediary element between adjacent phase shifters to prevent carrier diffusion. This mediator blocks the harmful carrier flow while allowing the optical signal to pass through, thus eliminating electrical crosstalk without affecting the modulation precision of the phase shifters.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful effect of carrier diffusion into a beneficial design feature by strategically placing blocking structures that utilize the natural carrier behavior to define precise boundaries between phase shifters, thereby maintaining modulation precision while preventing crosstalk.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If a blocking structure is added to prevent carrier diffusion, then electrical crosstalk is suppressed, but the device complexity increases

Engineering Contradiction:

Improvesignal integrityVSAvoidmodulator structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the structural parameters of the phase shifter by integrating blocking structures directly into the waveguide design. By changing the physical configuration to include PN junctions or spaced regions as inherent parts of the phase shifter structure, the solution maintains signal integrity while minimizing additional complexity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The blocking structure is merged with the phase shifter structure itself rather than being added as a separate component. This integration combines the phase modulation function with the carrier blocking function into a single unified structure, reducing overall device complexity while maintaining signal integrity.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The blocking structure effectively suppresses carrier diffusion and electrical crosstalk, enhancing the precision and reliability of photonic integrated systems by maintaining consistent phase shifter performance and preventing signal distortion.

Implementation Method 1

there would be electrical crosstalk between adjacent phase shifters since the carriers in the waveguide core region of PIN junction could diffuse along the waveguide propagation direction

Methodology Applied

Scientific EffectCarrier diffusion: Diffusion

Implementation Method 2

a blocking structure is provided at at least one end of the intrinsic region or close to the at least one end to block the diffusion of carriers from the intrinsic region along the waveguide propagation direction

Methodology Applied

Scientific EffectPN junction blocking: Diffusion Barrier

Implementation Method 3

carrier-injection-based silicon modulator could provide large changes of refraction index and high modulation depths in a compact footprint

Methodology Applied

Scientific EffectCarrier injection:

Implementation Method 4

the carriers in the waveguide core region of PIN junction could diffuse along the waveguide propagation direction

Methodology Applied

Scientific EffectRefraction index change: Refraction

Data Source

PatentUS20220334418A1Optical modulators and photonic integrated systems

Publication Date: 2022.10.20 SHANGHAI XIZHI TECH CO LTD

AI summary

The invention relates to the field of photonic integrated circuits and provides an optical modulator and a photonic integrated system, which can suppress phase deviation caused by carrier diffusion. The optical modulator includes at least one phase shifter including a waveguide channel for transmitting optical signal, and a P-type doped region and a N-type doped region located on opposite sides of the waveguide channel. In the waveguide channel, an undoped intrinsic region is located between the P-type doped region and the N-type doped region. At least one end of the intrinsic region or close to the at least one end is provided with a blocking structure for blocking the diffusion of carriers from the intrinsic region along the waveguide propagation direction, so that the phase deviation caused by the diffusion of carriers can be suppressed, and the electrical crosstalk between adjacent phase shifters can be suppressed, thereby avoiding modulation signal distortion caused by the electrical crosstalk. As a result, the reliability and precision of the photonic integrated system can be improved.