Narrow-Linewidth Laser Monolithic Integration
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Solution Overview
Problem
Traditional DFB or DBR lasers have limited cavity length, making it difficult to achieve ultra-narrow linewidths, and hybrid integration lasers with Si-based photon integrated circuits and III-V SOA suffer from low yield, reliability, and environmental resistance issues due to complex butt-joint coupling.
Innovation Solution
A monolithically integrated narrow-linewidth laser with a passive ring waveguide, gain wavelength-selection unit, and active waveguides for loss compensation, eliminating butt-coupling losses and enhancing stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional DFB or DBR laser structures are used, then the device complexity is reduced, but the linewidth cannot be sufficiently narrowed due to limited cavity length
Solution Approach 1:
The laser is divided into distinct functional segments: a semiconductor gain medium section and a separate ring resonator cavity section. This segmentation allows each part to be optimized independently - the gain medium provides amplification while the extended ring cavity provides the long optical path length needed for narrow linewidth, resolving the contradiction between simple structure and narrow linewidth achievement.
2Manufacturing precision
If hybrid integration with Si-based photon integrated circuit and III-V SOA is used, then the linewidth is narrowed, but the yield and reliability decrease due to complex butt-joint coupling
Solution Approach 1:
The patent merges the gain medium and ring resonator into a monolithically integrated structure where the two components are directly coupled without requiring separate butt-joint assembly. This integration eliminates the unreliable interfaces between different material systems while maintaining the narrow linewidth benefits of the extended cavity, simultaneously achieving both performance and reliability goals.
3Ease of manufacture
If butt-joint coupling scheme is used, then the device can be assembled, but the coupling loss and polarization loss increase, reducing environmental resistance
Solution Approach 1:
The waveguide modes are designed and configured in advance during the monolithic fabrication process to ensure optimal coupling between the gain medium and ring resonator. This preliminary configuration of mode fields eliminates the need for post-assembly alignment and butt-joint coupling, thereby preventing coupling losses and polarization mismatches before the device even operates.
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 narrower linewidth, higher side-mode suppression ratio, and improved resistance to severe environments, ensuring the ring external cavity operates in a critical coupling state with reduced costs and increased reliability.
Implementation Method 1
fully utilize the ring resonator cavity to extend the optical cavity length
Implementation Method 2
a gain waveguide used for providing gain for the laser
Implementation Method 3
a passive ring waveguide; a first passive input/output waveguide, coupled with the passive ring waveguide
Data Source
AI summary
The present disclosure discloses a narrow-linewidth laser. The narrow-linewidth laser comprises a passive ring waveguide, a first passive input/output waveguide which is coupled with the passive ring waveguide, a gain wavelength-selection unit which is used for providing gain for the whole laser and is configured to be capable of selecting the light with a specific wavelength to be coupled into the passive ring waveguide, and a second passive input/output waveguide which is coupled with the passive ring waveguide in order to output lasing light from the laser. The narrow-linewidth semiconductor laser provided by the present disclosure has a simple structure and does not have butt-joint coupling loss between a gain region and a waveguide external cavity region. There is no a linewidth limitation caused by butt-coupling loss in such semiconductor lasers. Moreover, because of the integral formation semiconductor technique, the laser should have low cost, higher stability and reliability, and higher resistance to severe environment. Furthermore, based on a loss compensation structure, a ring external cavity of the laser can work in a critical coupling state under different coupling coefficients. Therefore, the laser with a narrow linewidth and a high side-mode suppression ratio should be achieved.