Multi-Material Micro-Ring Reflectors for Narrow-Linewidth External Lasers
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Solution Overview
Problem
Existing external cavity lasers (ECLs) face challenges such as high waveguide losses, nonlinear loss due to two-photon absorption, and mode mismatch between gain and feedback circuits, which limit their linewidth and output power performance.
Innovation Solution
The design incorporates a photonic integrated platform with a gain chip and reflector chips made of different materials, featuring a Vernier configuration of micro-ring resonators (MRRs) with varying radii and group indices, and a tuning mechanism to enhance spectral response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional single-material micro-ring resonators are used in external cavity lasers, then the device structure is simple, but waveguide losses are high and nonlinear loss due to two-photon absorption occurs
Solution Approach 1:
The patent employs a composite micro-ring resonator structure consisting of an inner ring made of high-index-contrast material (such as silicon) and an outer ring made of low-index-contrast material (such as silicon nitride or oxide). This composite configuration allows the inner ring to provide strong light confinement while the outer ring reduces two-photon absorption losses, thereby achieving lower waveguide losses without significantly increasing device complexity.
Solution Approach 2:
The patent applies different material properties to different regions of the micro-ring resonator. The inner ring region uses high-index material for strong confinement where light intensity is highest, while the outer ring region uses low-index material to reduce nonlinear losses. This local differentiation of material quality optimizes performance by placing each material where it is most effective.
2Device complexity
If traditional single-material micro-ring resonators are used in external cavity lasers, then the device structure is simple, but linewidth is limited
Solution Approach 1:
The composite micro-ring resonator structure with inner high-index and outer low-index materials achieves superior quality factors by combining the advantages of both material types. The inner ring provides strong confinement for high light-matter interaction, while the outer ring minimizes two-photon absorption, resulting in narrower linewidth and improved frequency precision.
3Device complexity
If traditional single-material micro-ring resonators are used in external cavity lasers, then the device structure is simple, but output power is limited
Solution Approach 1:
The composite micro-ring resonator structure reduces two-photon absorption losses in the high-intensity region by using low-index material in the outer ring, thereby enabling higher output power without proportional increase in losses. The inner high-index ring maintains strong light confinement to sustain high power operation.
4Ease of manufacture
If mode mismatch between gain and feedback circuits exists, then integration is simpler, but laser performance is degraded
Solution Approach 1:
The patent designs the composite micro-ring resonator with specific geometric parameters and material properties that are optimized for mode matching with the gain medium. The inner ring's high-index material provides strong confinement that can be tuned to match the gain medium's mode profile, improving coupling efficiency and laser performance while maintaining integration feasibility.
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 configuration reduces waveguide losses, improves linewidth, and increases output power while maintaining wavelength tunability, addressing the limitations of traditional ECLs.
Implementation Method 1
The design incorporates a photonic integrated platform with a gain chip and reflector chips made of different materials, featuring a Vernier configuration of micro-ring resonators (MRRs) with varying radii and group indices
Implementation Method 2
The design incorporates a photonic integrated platform with a gain chip and reflector chips made of different materials, featuring a Vernier configuration of micro-ring resonators (MRRs)
Data Source
AI summary
There is provided an external cavity laser, including: a photonic integrated platform including a gain chip providing a gain medium and at least one reflector chip, the photonic integrated platform including first and second functional layers made of different materials; a resonant cavity optically coupled to the gain medium and including a first and a second micro-ring resonators (MRR) in a Vernier configuration, the first MRR and second MRR extending within respective ones of the first and second functional layers made of different materials and having corresponding group indices, the first and second MRRs having different radii selected in view of said corresponding group indices; and a tuning mechanism for tuning a spectral response of at least one of the first and second MRR.