Multi-Core Waveguide Laser Stabilizing Output Wavelength
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Solution Overview
Problem
Conventional wavelength-tunable laser diodes experience destabilization of output wavelength due to non-linear optical effects in silicon waveguides, particularly two-photon absorption and free carrier absorption, which limits the trade-off between spectral line-width narrowing and increasing output power.
Innovation Solution
A laser device incorporating a branch waveguide and a multi-core waveguide with adjacent waveguide cores to excite a super mode, suppressing non-linear optical effects and stabilizing the output wavelength by increasing the effective core cross-sectional area and preventing higher-order super mode excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a silicon waveguide with strong light confinement is used to narrow spectral line-width, then the spectral line-width is narrowed, but non-linear optical effects (two-photon absorption and free carrier absorption) occur causing wavelength destabilization
Solution Approach 1:
The waveguide is segmented into multiple cores (first waveguide core and second waveguide core) within a single waveguide structure. This segmentation allows the light to be distributed across multiple cores, increasing the effective area and reducing the intensity in each core, thereby suppressing non-linear optical effects while maintaining the overall light confinement needed for narrow spectral line-width.
Solution Approach 2:
The invention transitions from a single-core waveguide to a multi-core waveguide structure, adding spatial dimensionality to the light propagation path. By arranging multiple cores side-by-side and enabling optical coupling between them, the effective modal area is increased without compromising the confinement strength, thus resolving the contradiction between line-width narrowing and wavelength stability.
2Power
If output optical power is increased in a silicon waveguide, then output power increases, but two-photon absorption and free carrier absorption intensify causing refractive index changes and wavelength destabilization
Solution Approach 1:
The high-power light signal is segmented and distributed across multiple waveguide cores. This reduces the power density in each individual core, suppressing two-photon absorption and free carrier absorption effects that cause refractive index changes and wavelength instability, while still achieving high total output power through the combined effect of multiple cores.
Solution Approach 2:
Multiple waveguide cores are merged into a single multi-core waveguide structure with optical coupling between them. This allows the individual cores to work together as a unified system, distributing the high power load across multiple pathways and reducing non-linear effects in each core while maintaining high overall output power.
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 effectively suppresses non-linear optical effects, achieving both higher optical output power and a narrower spectral line-width without requiring phase adjustment, thereby stabilizing the output wavelength.
Implementation Method 1
a semiconductor optical amplifier (SOA) serving as a gain medium that produces stimulated emission
Implementation Method 2
the N waveguide cores are placed in proximity to one another to enable optical coupling between adjacent waveguide cores of the N waveguide cores
Implementation Method 3
two-photon absorption (TPA), which is one type of the non-linear optical effect, is likely to occur for high output optical power
Implementation Method 4
a phenomenon called free carrier absorption (FCA) occurs where free carriers generated from the TPA absorb light
Data Source
AI summary
A laser device (1) includes: a branch waveguide (23) configured to split light propagating from an optical amplifier (10) into a plurality of light beams and output the plurality of light beams; a multi-core waveguide (27) including a plurality of waveguide cores (24 to 26) configured to carry the plurality of light beams input from the branch waveguide (23); and a light reflector (31) optically coupled to a light input/output end of the multi-core waveguide (27). The waveguide cores (24 to 26) are configured to extend along the same direction, and placed in proximity to one another to enable optical coupling between adjacent waveguide cores of the waveguide cores (24 to 26).