Narrow Linewidth Laser With M-Z External Cavity Wavelength Selection
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Solution Overview
Problem
Traditional monolithically integrated semiconductor lasers face limitations in achieving narrow linewidth due to limited cavity length and complex electrothermal management, resulting in lower output power and side-mode-suppression ratio, which restricts their application in high-precision spectral measurement and coherent communication systems.
Innovation Solution
A narrow linewidth laser is developed using a Mach-Zehnder compound external cavity structure combining a passive ring resonant cavity and an FP resonant cavity, with adjustable refractive index waveguides for wavelength tuning and a second gain region for amplification, and an additional PN or MOS junction region for loss compensation and rapid tuning, enabling broadband tunability and high side-mode suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional DFB or DBR laser with limited cavity length is used, then the structure is compact, but narrow linewidth cannot be obtained
Solution Approach 1:
The patent implements an external cavity structure that extends the laser cavity beyond the semiconductor chip boundaries, effectively nesting the gain medium within a larger optical resonance system. This allows the laser to achieve a long effective cavity length for narrow linewidth while maintaining a compact chip structure, resolving the contradiction between size and linewidth performance
2Adaptability or versatility
If complex grating structure is used for wavelength selection, then wavelength selection capability is improved, but narrow linewidth is still hard to obtain
Solution Approach 1:
The patent combines multiple cavity structures (external cavity and intra-cavity grating) into a unified laser system where the external cavity provides the primary wavelength selection and linewidth narrowing, while the internal grating provides additional spectral filtering. This merged structure achieves both broad wavelength tunability and narrow linewidth simultaneously
3Manufacturing precision
If dielectric photonic integrated circuits with multiple resonant cavities are used, then broadband tuning and narrow linewidth are achieved, but electrothermal management becomes complex and tuning speed slows
Solution Approach 1:
The patent extracts the wavelength selection and linewidth narrowing functions from the complex electrothermal management system by using a passive external cavity structure with grating-based wavelength selection. This separates the optical functions from the thermal management complexity, simplifying the overall system while maintaining narrow linewidth performance and enabling faster tuning through electrical control of the external cavity
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 solution achieves a simple structure with rapid and low-power tunability, high output power, and narrow linewidth, overcoming the limitations of traditional lasers by reducing coupling loss and enhancing stability and reliability.
Implementation Method 1
a passive ring resonant cavity, an FP resonant cavity... the passive ring resonant cavity and the FP resonant cavity are combined to form an M-Z (Mach-Zehnder interference structure) compound external cavity structure... at least used for providing wavelength selection and narrowing laser linewidth
Implementation Method 2
M-Z (Mach-Zehnder interference structure) compound external cavity structure
Implementation Method 3
adjustable refractive index waveguides for wavelength tuning
Implementation Method 4
an additional PN or MOS junction region for loss compensation and rapid tuning
Data Source
AI summary
A narrow linewidth laser includes a passive ring resonant cavity, an FP resonant cavity, and a first gain region. The passive ring resonant cavity and the FP resonant cavity are combined to form an M-Z (Mach-Zehnder interference structure) compound external cavity structure, and the M-Z compound external cavity structure is at least used for providing wavelength selection and narrowing laser linewidth. The first gain region is provided on the outer side of the M-Z compound external cavity structure and is used for providing a gain for the whole laser. The narrow linewidth laser is simple in structure, high in side-mode suppression ratio, narrow in linewidth, and high in output power. By further integrating a PN junction region or MOS junction region, broadband and rapid tuning with low power consumption can also be achieved, and tuning management is simple.