Grating Coupler Anti-Phase Reflection Coating for Single-Mode Fiber
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Solution Overview
Problem
Existing grating couplers face challenges in achieving high optical coupling efficiency with single-mode optical fibers due to the limitations of existing anti-phase reflection coating (APRC) methods, which often result in increased beam size and reduced emission efficiency, making it difficult to align with the smaller core diameter of single-mode fibers.
Innovation Solution
A grating coupler design incorporating a high refractive index layer and a buffer layer with attributes that gradually decrease along the propagation direction, optimizing the anti-phase reflection coating to enhance upward directionality and beam profile matching the single-mode fiber's mode profile, thereby improving optical coupling efficiency without requiring a back mirror or thick core layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If existing anti-phase reflection coating methods are used to improve upward directionality, then the beam size increases and emission efficiency decreases, but optical coupling efficiency with single-mode fibers remains insufficient
Solution Approach 1:
The patent applies parameter changes by gradually varying the thickness of the high refractive index layer along the light propagation direction. This continuous parameter variation optimizes the anti-phase reflection effect to improve upward directionality while controlling beam size expansion, resolving the contradiction between directionality and beam size control
Solution Approach 2:
The patent implements local quality by creating non-uniform thickness distribution of the high refractive index layer, where different regions have different thicknesses optimized for their specific functions. The thicker regions provide stronger reflection while thinner regions control beam expansion, achieving both high directionality and beam size control
2Illumination intensity
If a back mirror is added to increase upward directionality, then optical coupling efficiency improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the back mirror component by replacing it with an optimized anti-phase reflection coating structure. This removes the need for additional reflective elements while achieving the same upward directionality enhancement, thereby reducing device complexity and manufacturing cost
Solution Approach 2:
The patent uses composite material structures by combining high refractive index materials with buffer layers in a multi-layer coating system. This composite structure provides the necessary optical reflection properties without requiring a separate back mirror, simplifying the overall device structure
3Illumination intensity
If the core layer is made thicker to improve grating coupling, then upward directionality increases, but alignment precision with single-mode fibers becomes more difficult
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness profile of the high refractive index layer rather than simply increasing core layer thickness. This parameter optimization achieves high upward directionality while maintaining a thinner effective optical path, thereby preserving alignment precision with single-mode fibers
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 optimized grating coupler achieves high upward directionality and optical coupling efficiency with single-mode fibers, reducing production costs and simplifying the manufacturing process by using standard wafers, while maintaining beam size compatibility with single-mode fiber cores.
Implementation Method 1
a grating is provided with a reflection mirror on the back, and the reflection mirror reflects light emitted from the back of the grating into the top side
Implementation Method 2
A grating coupler changes the propagation direction of a signal light supplied via a waveguide on an optical chip by diffracting the light with its grating
Implementation Method 3
a grating is provided with a multilayer anti-phase reflection coating (APRC) on top, by which a part of a light emitted upward is returned to the substrate side and the returned light is superimposed in anti-phase to the light emitted to the back side so as to cancel each other
Data Source
AI summary
A grating coupler includes a grating including a core and an anti-phase reflection coating provided on at least one part of the grating. The anti-phase reflection coating includes a high refractive index layer and a buffer layer. The high refractive index layer has at least one selected from a plurality of attributes characterizing the high refractive index layer. The at least one selected attribute gradually deceases along a propagation direction of light in the core of the grating.