Distributed Reflector Laser Layout for High-Bandwidth Optical 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 limit, with existing approaches like DBR, DFB, and PFL lasers achieving only up to 55 GHz, and requiring precise control of grating phases to stabilize photon-photon resonance.
Innovation Solution
A distributed reflector (DR) laser structure composed of a DFB laser section and a DBR section with optimized cavity lengths and grating coupling coefficients, incorporating a coplanar electrode structure to enhance modulation bandwidth beyond conventional limits, utilizing photon-photon resonance and detuned loading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cavity length is reduced to increase relaxation resonance frequency, then the modulation bandwidth is improved, but the output power decreases
Solution Approach 1:
The laser cavity is divided into two functional sections: a DFB section (100-200 μm) for generating high-frequency modulation and a DBR section (200-400 μm) for providing optical feedback and enhancing differential gain. This segmentation allows each section to be optimized for its specific function, enabling high modulation bandwidth while maintaining sufficient output power through the longer DBR section.
2Speed
If detuned loading is applied to enhance differential gain, then the modulation bandwidth is improved, but the lasing wavelength stability deteriorates
Solution Approach 1:
The DBR section provides strong optical feedback to the DFB section, creating a photon-photon resonance that stabilizes the lasing wavelength. This feedback mechanism compensates for the wavelength detuning required for enhanced differential gain, allowing the system to maintain wavelength stability while operating at the detuned condition for maximum modulation bandwidth.
3Speed
If photon-photon resonance is used to increase modulation bandwidth, then the bandwidth is improved, but the device complexity increases due to precise grating phase control requirements
Solution Approach 1:
The invention optimizes specific parameters of the DFB and DBR gratings (coupling coefficients, lengths, and pitch) to achieve photon-photon resonance. By carefully selecting these parameters, the system achieves high modulation bandwidth while reducing the sensitivity to grating phase variations, thereby simplifying fabrication and control requirements.
4Power
If a longer DFB cavity is used to increase output power, then the output power is improved, but the modulation bandwidth is reduced due to increased parasitic effects
Solution Approach 1:
The laser is segmented into a short DFB section (100-200 μm) optimized for high-frequency modulation with low parasitic effects, and a longer DBR section (200-400 μm) that provides optical feedback and contributes to output power. This segmentation allows the system to achieve high output power without sacrificing modulation bandwidth.
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 modulation bandwidths exceeding 50 GHz with reduced parasitic effects and improved microwave performance, offering flexibility in design and fabrication, and higher output power.
Implementation Method 1
a distributed feedback (DFB) laser section (11, 26) having a gain region (13, 28)
Implementation Method 2
a distributed Bragg reflector (DBR) section (12, 27) coupled end to end with the DFB laser section
Implementation Method 3
incorporating a coplanar electrode structure to enhance modulation bandwidth beyond conventional limits
Implementation Method 4
utilizing photon-photon resonance and detuned loading effects
Implementation Method 5
The P-P resonance frequency is much higher than the E-P resonance frequency, due to the external optical feedback from the DBR section
Data Source
AI summary
The invention provides a distributed reflector (DR) semiconductor laser, comprising a distributed feedback (DFB) laser and a distributed Bragg reflector (DBR).