Distributed Reflector Laser with Detuned Loading for Stable 50+ GHz Modulation

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Solution Overview

Problem

Conventional optical transmitters in fiber optic networks face limitations in modulation bandwidth due to the electron-photon resonance frequency, with existing approaches like DBR, DFB, and PFL lasers achieving only up to 55 GHz, and variations in P-P resonance frequency caused by grating phase fluctuations.

Innovation Solution

A distributed reflector (DR) laser structure composed of a DFB and DBR section with optimized cavity lengths and grating coupling coefficients, incorporating a detuned loading effect and photon-photon resonance, and a coplanar electrode structure to reduce parasitic effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the cavity length is reduced to increase relaxation resonance frequency, then modulation bandwidth is improved, but the resonance frequency is fundamentally limited by electron-photon resonance

Engineering Contradiction:

Improvemodulation bandwidthVSAvoidresonance frequency stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The laser cavity is divided into two distinct sections: a DFB laser section for light generation and a DBR section for wavelength selection and feedback. This segmentation allows independent optimization of each section, enabling the DFB section to operate at higher resonance frequencies while the DBR section provides stable feedback, thereby achieving modulation bandwidth exceeding 50 GHz without being fundamentally limited by electron-photon resonance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent optimizes key parameters including the DFB section length (50-200 μm), DBR section length (100-400 μm), grating coupling coefficients (κaLa = 2-6, κpLp = 2-6), and detuning amount (0.01-0.1 nm) to achieve both high modulation bandwidth and stable P-P resonance frequency, breaking the conventional electron-photon resonance limit

Inventive Principle:

Principle #35Parameter changes

2Speed

If DBR laser with detuned loading is used to increase effective differential gain, then modulation bandwidth is improved, but photon-photon resonance frequency varies due to grating phase fluctuations

Engineering Contradiction:

Improvemodulation bandwidthVSAvoidP-P resonance frequency stability

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent introduces a detuning amount (Δλ = 0.01-0.1 nm) between the lasing wavelength and DBR peak reflection wavelength to achieve detuned loading effect, increasing effective differential gain and modulation bandwidth while simultaneously stabilizing the P-P resonance frequency against grating phase fluctuations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The DFB section is designed with specific grating coupling coefficient product (κaLa = 2-6) and length (50-200 μm) to provide stable feedback, while the DBR section uses optimized parameters (κpLp = 2-6, length = 100-400 μm) to achieve both high differential gain and stable P-P resonance frequency, reducing sensitivity to grating phase variations

Inventive Principle:

Principle #3Local quality

3Power

If longer DFB cavity length is used to increase output power, then power is improved, but microwave transmission characteristics deteriorate

Engineering Contradiction:

Improveoutput powerVSAvoidmicrowave transmission characteristics

Core Design Contradiction:

PowerVSSpeed

Solution Approach 1:

The laser is segmented into DFB and DBR sections with optimized individual lengths. The DFB section length is specifically optimized (50-200 μm) to balance output power generation with microwave transmission characteristics, while the DBR section provides additional feedback to enhance modulation bandwidth, achieving both high power and superior microwave characteristics simultaneously

Inventive Principle:

Principle #1Segmentation

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 DR laser achieves a modulation bandwidth exceeding 50 GHz with reduced variation in P-P resonance frequency and improved microwave characteristics, supporting higher output power and superior microwave transmission.

Implementation Method 1

a distributed feedback (DFB) laser section and a distributed Bragg reflector (DBR) section

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Implementation Method 2

the lasing wavelength is chosen to be detuned from the peak of the DBR reflection spectrum (the detuned loading effect)... the enhanced E-P resonance frequency due to the increase of the effective differential gain

Methodology Applied

Scientific EffectDetuned loading effect:

Implementation Method 3

Methodology Applied

Scientific EffectParasitic capacitance and inductance reduction: Parasitic Capacitance

Data Source

PatentUS20260045767A1Distributed reflector laser

Publication Date: 2026.02.12 MAKINO JUNKO

AI summary

The invention provides a distributed reflector (DR) semiconductor laser, comprising two cavity sections which are composed of a distributed feedback (DFB) laser section and a distributed Bragg reflector (DBR) section.