Segmented P-i-N Waveguides with High-Impedance Lines for EAM Bandwidth

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Solution Overview

Problem

The bandwidth of electroabsorption modulators and electroabsorption modulator lasers is limited by the length of the modulator and impedance mismatch, leading to high parasitic inductance and microwave reflection.

Innovation Solution

A segmental p-i-n active waveguide structure is introduced, connected with high-impedance transmission lines to reduce microwave reflection, and impedance-controlled transmission lines are used to shorten gold wire lengths and reduce parasitic inductance, thereby increasing bandwidth without requiring a new wafer etching and growth process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the length of the electroabsorption modulator is increased, then the optical absorption is improved, but the bandwidth is reduced due to increased parasitic inductance

Engineering Contradiction:

Improveoptical absorptionVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The electroabsorption modulator is divided into multiple segmented p-i-n active waveguides connected in series. Each segment has its own electrodes and active region, allowing the total optical absorption to be distributed across multiple shorter sections rather than one long section, thereby reducing parasitic inductance while maintaining absorption performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

High-impedance transmission lines are introduced as intermediary elements to connect the segmented p-i-n active waveguides. These transmission lines have characteristic impedances greater than 50 ohms and are designed to minimize signal reflection and loss while maintaining electrical connectivity between segments, effectively acting as mediators that reduce parasitic inductance

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the impedance mismatch between EAM (∼20Ω) and source/load (50Ω) is not addressed, then the structure is simple, but microwave reflection increases reducing bandwidth

Engineering Contradiction:

Improvestructure simplicityVSAvoidbandwidth

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The characteristic impedance of the transmission lines connecting the segmented waveguides is changed to greater than 50 ohms. This parameter change in impedance creates a gradual transition that reduces reflection at the interfaces between the 20-ohm EAM and the 50-ohm source/load, thereby improving bandwidth without significantly increasing structural complexity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system uses a composite transmission line structure combining low-impedance p-i-n active waveguide sections with high-impedance transmission line sections. This composite approach creates an impedance transformation network that bridges the mismatch between the EAM and external circuits, reducing microwave reflection

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If conventional packaging with long gold wires is used, then the packaging process is simple, but parasitic inductance increases reducing bandwidth

Engineering Contradiction:

Improvepackaging simplicityVSAvoidbandwidth

Core Design Contradiction:

Ease of manufactureVSSpeed

Solution Approach 1:

The high-impedance transmission lines are integrated into the device structure during wafer fabrication before packaging. This preliminary action creates built-in impedance-matched connections that extend the electrical pathways, allowing for shorter gold wire bonds during packaging while maintaining low parasitic inductance and good impedance matching

Inventive Principle:

Principle #10Preliminary action

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 approach effectively increases the bandwidth of electroabsorption modulators by reducing microwave reflection and parasitic inductance, enhancing the frequency bandwidth of the electroabsorption modulator laser device without the need for additional processing steps.

Implementation Method 1

the high-impedance transmission lines are used in series to connect the p-i-n active waveguide sections to reduce the microwave reflection and then increase the device bandwidth

Methodology Applied

Scientific EffectMicrowave reflection reduction through impedance matching: Reflection

Implementation Method 2

an electroabsorption modulator (EAM) or an electroabsorption modulator laser (EML)

Methodology Applied

Scientific EffectElectroabsorption: Absorption (EM radiation)

Data Source

PatentUS11374382B2Method for increasing EAM bandwidth, component structure and manufacturing process thereof using plural p-i-n waveguides serially connected by high-impedance transmission lines

Publication Date: 2022.06.28 LUXNET CORP

AI summary

A method for increasing the bandwidth of an electroabsorption modulator (EAM) includes the following steps. First, a plurality of p-i-n active waveguides for the EAM are defined on a p-i-n optical waveguide forming an EAM having a shorter p-i-n active waveguide length. Then, the bandwidth of the EAM can be increased. Second, the high-impedance transmission lines are used in series to connect the EAM sections to reduce the microwave reflection and then increase the device bandwidth. Finally, the impedance-controlled transmission lines for the signal input and output can not only reduce the parasitic effects resulting from packaging, but also reduce the microwave reflection resulting from the impedance mismatch at the device input and load.