Electro-optical modulator flexible coplanar strip line connections

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Solution Overview

Problem

Existing electro-optical modulators face challenges in improving their frequency response due to the inductance of bonding wires, which causes reflection of high-frequency electrical signals and deteriorates the modulators' performance.

Innovation Solution

The use of a flexible coplanar strip line for electrical connections between driver units and electrode arrangements, which are capacitively coupled, allowing for improved high-frequency characteristics and reduced power loss, enabling compact and efficient modulator designs with lower thermal crosstalk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bonding wires are used to connect driver units to travelling wave electrodes, then the electrical connection is simple and easy to manufacture, but the inductance of the bonding wires causes reflection of high frequency electrical signals and deteriorates the frequency response of the modulators

Engineering Contradiction:
Improvefrequency responseVSAvoidelectrical connection structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and removes the bonding wires from the electrical connection structure, replacing them with a coplanar strip line configuration where electrical lines are directly patterned on the substrate. This eliminates the inductive effects of bonding wires while maintaining electrical connectivity between driver units and waveguide electrodes.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical bonding wire connection system with an integrated coplanar strip line system where electrical connections are formed as planar conductive traces on the substrate. This substitution eliminates the three-dimensional inductive structure in favor of a two-dimensional planar structure with controlled impedance characteristics.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If conventional electrical connections are used between driver units and electrode arrangements, then the assembly is simple, but thermal crosstalk between the driver unit and modulator increases

Engineering Contradiction:
Improvethermal crosstalkVSAvoidelectrical connection structure
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent introduces a coplanar strip line configuration with dedicated electrical lines that act as intermediaries between driver units and waveguide electrodes. These controlled-impedance transmission lines provide thermal isolation while maintaining electrical signal integrity, reducing thermal crosstalk compared to direct bonding wire connections.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent transitions from three-dimensional bonding wire connections to a two-dimensional coplanar strip line layout. This dimensional change allows for optimized spacing and thermal management, as the electrical connections are distributed across the substrate plane rather than concentrated in vertical bonding structures, thereby reducing thermal coupling.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Loss of energy

If the optical waveguides are made broader to reduce power loss, then the power efficiency improves, but the device size and complexity increase

Engineering Contradiction:
Improvepower lossVSAvoidwaveguide dimensions
Core Design Contradiction:
Loss of energyVSVolume of moving object

Solution Approach 1:

The patent optimizes the dimensions and geometric parameters of the optical waveguides to achieve low power loss without excessive size increase. By carefully controlling waveguide width, height, and spacing parameters, the design achieves efficient light confinement and low propagation loss while maintaining compact dimensions suitable for integrated photonic circuits.

Inventive Principle:
Principle #35Parameter changes

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

This solution enhances the frequency response and power efficiency of electro-optical modulators, facilitating the development of compact high-frequency modules with reduced thermal issues and increased transmission rates, such as 100 Gbit/s in CFP4 module size.

Implementation Method 1

a plurality of capacitive elements formed by capacitive segments of the second optical waveguide; wherein the waveguide electrodes are capacitively coupled to the driver units via the capacitive segments and the capacitive elements

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 2

each one of the electrical connections between the driver units and the electrode arrangement comprise a flexible coplanar strip line

Methodology Applied
Scientific EffectElectrical signal transmission: Conduction (electrical)

Implementation Method 3

at least one electro-optical phase modulator having a first optical waveguide

Methodology Applied
Scientific EffectOptical waveguide: Waveguide (optics)

Data Source

PatentEP3355111B1Electro-optical modulator devices
Publication Date: 2023.05.17 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
  • EP3355111B1 patent drawingFigure 1A
  • EP3355111B1 patent drawingFigure 1B
  • EP3355111B1 patent drawingFigure 1C

AI summary

The invention relates to an electro-optical modulator device, comprising at least one electro-optical phase modulator (100) having one optically active optical waveguide (112) and an electrode arrangement (1) for applying a voltage across the active optical waveguide (112), wherein the electrode arrangement (1) comprises a plurality of waveguide electrodes (113) arranged on top of capacitive segments (114) formed by the optically active waveguide (112); and a plurality of capacitive elements. According to the invention, the modulator further comprises a plurality of driver units (30, 30a-d) for supplying a voltage to the electrode arrangement (1); and electrical connections between the driver units (30, 30a-d) and the electrode arrangement (1), wherein the waveguide electrodes (113) are capacitively coupled to the driver units (30, 30a-d) via the capacitive segments (114) and the capacitive elements and the electrical connections, wherein each one of the electrical connections between the driver units (30, 30a-d) and the electrode arrangement (1) comprise a flexible coplanar strip line (50, 50a-d).