Reverse Taper Waveguide for Optical Combiner Light Loss
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Solution Overview
Problem
Tapered optical waveguides increase the numerical aperture (NA) of light as the cross-sectional area decreases, leading to light loss due to escape from the waveguide, unless the input light is carefully angled to maintain total internal reflection.
Innovation Solution
A waveguide with a progressively varying cross-section from an un-tapered end to a tapered end, where the un-tapered end has a circular cross-section and the tapered end has a pie-shaped cross-section, maintaining a constant effective cross-sectional area and reducing the NA of light as it propagates, thereby minimizing light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the waveguide is tapered to concentrate light into a smaller fiber guide, then the light concentration is improved, but the numerical aperture increases causing light loss
Solution Approach 1:
The patent changes the geometric parameters of the waveguide by implementing a reverse taper configuration where the core diameter increases along the propagation direction. This parameter change allows the numerical aperture to decrease progressively, preventing light loss while still achieving light concentration at the output face through the area reduction from input to output.
2Power
If the waveguide cross-section is reduced to combine power, then the power concentration is improved, but the numerical aperture increases exceeding critical angle
Solution Approach 1:
The patent inverts the conventional taper configuration by making the waveguide core diameter increase rather than decrease along the propagation direction. This inversion causes the numerical aperture to decrease instead of increase, maintaining total internal reflection reliability while achieving power concentration through the overall cross-section reduction from input to output.
3Loss of energy
If the numerical aperture is kept small to prevent light loss, then the light containment is improved, but the light concentration capability is reduced
Solution Approach 1:
The patent implements a dynamic numerical aperture profile that varies along the propagation direction. The reverse taper configuration creates a progressively decreasing numerical aperture that adapts to the light propagation needs, maintaining low NA at the output for good containment while allowing higher NA at the input for better light collection and concentration capability.
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 design allows for the concentration of light with minimal escape from the waveguide, improving brightness and enabling efficient light transfer in high-power applications by maintaining light containment throughout the waveguide.
Implementation Method 1
the NA of the light at an input must be sufficiently small that any eventual increase in the NA does not exceed a critical angle and the waveguide maintains total internal reflection
Data Source
AI summary
A waveguide comprises an un-tapered end and a tapered end. The waveguide progressively varies a numerical aperture (NA) of light as the light propagates from the tapered end to the un-tapered end.