Optical Waveguide Phase Grating Coupling
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Solution Overview
Problem
Existing optical waveguide and arrayed waveguide connections face challenges such as large circuit size, difficult circuit design and manufacturing, and high insertion loss when light transitions between slab and arrayed waveguides due to complex transition regions and optimized tapered shapes.
Innovation Solution
A configuration of multiple phase gratings with alternating interference regions is used, where the end of the arrayed waveguide is connected to the slab waveguide at a constructive interference portion of the self-image formed by the phase gratings, leveraging the Talbot effect to concentrate light and reduce insertion loss without increasing circuit size or complicating manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a transition region with gradually changing refractive index is disposed, then light coupling between slab waveguide and arrayed waveguide is improved, but circuit size becomes large
Solution Approach 1:
The waveguide structure is segmented into distinct regions: a slab waveguide region, an arrayed waveguide region, and intermediate transition regions. Multiple phase gratings are segmented and arranged alternately with interference regions, creating discrete functional zones that manage light coupling without requiring a large continuous transition region.
Solution Approach 2:
Phase gratings serve as intermediary elements between the slab waveguide and arrayed waveguide. These gratings, combined with interference regions, act as mediators that facilitate light coupling through diffraction and interference effects, eliminating the need for large gradual refractive index transitions.
2Loss of energy
If a slope portion is disposed between slab waveguide and arrayed waveguide, then light coupling is improved, but circuit manufacturing becomes difficult
Solution Approach 1:
The coupling structure is divided into discrete, manufacturable elements: multiple phase gratings separated by interference regions. Each element can be independently designed and fabricated using standard waveguide fabrication processes, avoiding the manufacturing complexities of continuous slope portions.
Solution Approach 2:
The solution uses discrete parameter changes through phase gratings with specific duty cycles and periods rather than continuous parameter changes via slope portions. The phase grating parameters (depth, width, period) can be precisely controlled during fabrication to achieve the desired coupling effect.
3Loss of energy
If tapered shape and position of island-shaped region are optimized, then light concentration on arrayed waveguide is improved, but circuit design becomes difficult
Solution Approach 1:
The complex light concentration function is segmented into multiple simple phase grating elements arranged in a periodic pattern. Each phase grating is a simple rectangular structure, but their collective arrangement creates the desired light concentration effect without requiring complex optimized tapered shapes or island-shaped regions.
Solution Approach 2:
Instead of optimizing complex geometric parameters of island-shaped regions and tapered shapes, the solution uses systematic parameter changes in phase grating properties (phase depth, grating period, duty cycle) to achieve light concentration. These parameters are easier to design and manufacture.
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 reduces insertion loss and simplifies design and manufacturing by concentrating light as a propagation mode, maintaining low radiation loss and avoiding complex refractive index differences, thus enhancing optical waveguide performance.
Implementation Method 1
a plurality of phase gratings diffracting light propagated in a slab waveguide
Implementation Method 2
a plurality of interference regions where the light diffracted by the plurality of phase gratings is interfered
Implementation Method 3
leveraging the Talbot effect to concentrate light and reduce insertion loss
Data Source
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AI summary
This invention provides a technique which does not increase the circuit size, does not make difficult the circuit design and manufacturing, and can reduce insertion loss when light enters from a slab waveguide toward an arrayed waveguide or when the light enters from the arrayed waveguide toward the slab waveguide. This invention provides an optical waveguide provided with a slab waveguide 1, which has a plurality of phase gratings GP1 arranged at a distance from each other in a direction substantially parallel to a light propagation direction and diffracting propagated light and a plurality of interference regions IF arranged alternately to the plurality of phase gratings GP1 in the direction substantially parallel to the light propagation direction and interfering the light diffracted by the plurality of phase gratings GP1, and an arrayed waveguide 2 whose end is connected to an end of the slab waveguide 1 at a position of a constructive interference portion of a self-image formed by the plurality of phase gratings GP1 as an integrated phase grating.