Clothoid Tapered Waveguide Bend for Compact Low-Loss Optical Circuits
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Solution Overview
Problem
In large-scaled optical circuits, the circuit excess loss is dominated by bend radiation loss and different-curvature waveguide connection loss, which are trade-offs with the allowable curvature radius and circuit area, making it challenging to reduce both losses simultaneously while maintaining a compact circuit design.
Innovation Solution
The implementation of a clothoid tapered waveguide bend, where the waveguide width and curvature are optimized independently at the connection points of waveguides with different widths and curvatures, using a configuration that gradually changes the waveguide width and curvature, such as in a clothoid tapered waveguide bend, to minimize losses and maintain a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the curvature radius of a waveguide is reduced to decrease the circuit area, then the circuit becomes more compact, but the bend radiation loss increases
Solution Approach 1:
The patent applies parameter changes by varying the waveguide width along the propagation direction in the bent region. Specifically, the waveguide width is made narrower in the bent portion compared to the straight portion, which modifies the mode field distribution to reduce bend radiation loss. This allows using a smaller curvature radius without excessive loss increase, thus achieving compact circuit area while maintaining low loss.
Solution Approach 2:
The patent implements local quality by creating a non-uniform waveguide structure where the waveguide width changes locally in the bent region. The waveguide has a narrower width in the curved portion and a wider width in the straight portions, optimizing the local field distribution to minimize radiation loss at the bend while maintaining overall circuit compactness.
2Speed
If the waveguide width is narrowed to reduce the coupling length in a directional coupler, then the coupling speed increases, but the waveguide becomes more sensitive to manufacturing variations and loss
Solution Approach 1:
The patent applies parameter changes by optimizing the waveguide width profile in the bent region. The waveguide width is specifically designed to be narrower in the bent portion, which increases the coupling strength and reduces the coupling length, thereby improving coupling speed while the overall structure maintains low loss characteristics through proper width transition design.
3Loss of energy
If offset connection or clothoid connection is used to reduce different-curvature waveguide connection loss, then the connection loss decreases, but the circuit area increases
Solution Approach 1:
The patent applies parameter changes by using a clothoid-shaped waveguide with continuously varying curvature radius and width. This smooth transition from straight to bent waveguide eliminates abrupt curvature changes, significantly reducing different-curvature connection loss while maintaining a compact footprint by avoiding the need for extended offset connection regions.
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 approach results in a low-loss waveguide bend with reduced circuit excess loss and compact circuit area, while minimizing waveguide connection loss when connecting waveguides of varying widths and curvatures, effectively addressing the trade-offs in existing technologies.
Implementation Method 1
The propagation loss is a loss due to optical scattering caused by optical absorption by a waveguide material itself, refraction fluctuation of the waveguide, or rough core surface
Implementation Method 2
The propagation loss is a loss due to optical scattering caused by optical absorption by a waveguide material itself, refraction fluctuation of the waveguide
Implementation Method 3
a waveguide bend having a curvature radius 1 mm is used... the allowable minimum curvature radius is roughly determined by a specific refractive index difference Δ between the core and the clad
Data Source
AI summary
In a waveguide having a given Δ, a low-loss waveguide bend is realized while the curvature radius is kept small. In an optical waveguide in which a first waveguide and a second waveguide are connected, a clothoid tapered waveguide bend is inserted between the first waveguide and the second waveguide. In the clothoid tapered waveguide bend, the waveguide width continuously changes from a first waveguide width at a connection point of the first waveguide to a second waveguide width at a connection point of the second waveguide, the curvature radius continuously changes from a first curvature radius at the connection point of the first waveguide to a second curvature radius at the connection point of the second waveguide, the first waveguide width and the second waveguide width are different from each other, and the first curvature radius and the second curvature radius are different from each other.