Cascaded Mach-Zehnder Modulators for Low-Loss Intensity Modulation

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Solution Overview

Problem

Existing modulators in photonic chips, such as Mach-Zehnder modulators, face challenges in efficiently translating input power into optical modulation amplitude and suffer from issues like insertion loss, attenuation, and impedance matching, while maintaining a high extinction ratio and compact footprint.

Innovation Solution

A modulator structure incorporating cascaded Mach-Zehnder interference filters with active and passive delay sections, featuring optical phase shifters with p-n junctions and semi-circular bends, and a lumped modulator design that includes optical phase shifters to enhance phase and intensity modulation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional Mach-Zehnder modulator structures are used, then intensity modulation is achieved, but insertion loss and transmission penalty increase

Engineering Contradiction:

Improveinsertion lossVSAvoidtransmission penalty

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The modulator is divided into multiple cascaded Mach-Zehnder interferometer stages, each contributing to the overall modulation function. This segmentation allows for optimized phase shifting in each stage, reducing the total insertion loss while maintaining reliable transmission through the combined effect of multiple stages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Optical phase shifters are strategically positioned at specific locations within the waveguide arms of each Mach-Zehnder interferometer stage. This local placement of phase-shifting elements optimizes the modulation efficiency at critical points, reducing overall insertion loss while maintaining transmission reliability through localized phase control.

Inventive Principle:

Principle #3Local quality

2Reliability

If larger modulator structures are used to improve modulation efficiency, then extinction ratio improves, but device footprint increases

Engineering Contradiction:

Improveextinction ratioVSAvoidfootprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The modulator functionality is distributed across multiple compact Mach-Zehnder interferometer stages rather than requiring a single large structure. Each stage contributes to the extinction ratio, and their cascaded arrangement achieves high overall extinction ratio while maintaining a compact total footprint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple Mach-Zehnder interferometer stages are cascaded in series, utilizing the temporal dimension of light propagation rather than only spatial expansion. This allows achievement of high extinction ratio through multiple modulation events along the propagation path while maintaining a compact device footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If more optical phase shifters are added to improve modulation efficiency, then intensity modulation efficiency improves, but device complexity increases

Engineering Contradiction:

Improvemodulation efficiencyVSAvoidstructure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The modulation function is divided into multiple stages, each with its own optical phase shifters. This segmentation distributes the complexity across identical modular units, making the overall system more manageable while achieving high modulation efficiency through the cumulative effect of multiple stages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each Mach-Zehnder interferometer stage serves multiple functions: it provides both phase modulation through its optical phase shifters and intensity modulation through its interference output. This multi-functionality of each stage contributes to overall modulation efficiency while avoiding the need for separate dedicated components, thereby controlling device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 proposed modulator structure achieves improved transmission penalty, reduced insertion loss, high extinction ratio, and efficient intensity modulation with a smaller footprint, while maintaining comparable bandwidth and lower driving voltage compared to conventional modulators.

Implementation Method 1

An optical phase shifter includes a p-n junction in a portion of the delay section of the first waveguide core

Methodology Applied

Scientific EffectElectro-optic effect: Electro-Optic Effects

Implementation Method 2

A phase difference may be introduced between the light propagating in the different arms to provide intensity modulation and different switched conditions

Methodology Applied

Scientific EffectInterference: Interference

Data Source

PatentUS20250328055A1Modulators based on cascaded mach-zehnder interferometers

Publication Date: 2025.10.23 GLOBALFOUNDRIES US INC

AI summary

Structures for a modulator and methods of forming a structure for a modulator. The structure comprises a first waveguide core including a delay section, and a second waveguide core including a delay section. The delay section of the second waveguide core has a shorter length than the delay section of the first waveguide core. The structure further comprises an optical phase shifter including a p-n junction in a portion of the delay section of the first waveguide core.