Grating Coupler with Varying Refractive Indices
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Solution Overview
Problem
Optical gratings exhibit poor coupling efficiency when redirecting light between optical fibers and detectors, leading to significant loss of signal, necessitating an improvement in the apparatus and system for efficient optical coupling.
Innovation Solution
A grating coupler with a plurality of coupling gratings arranged along a direction, featuring gradually decreasing effective refractive indices and ascending step shapes, along with adjustable optical fiber angles, is designed to reduce back reflection and enhance directionality, thereby improving coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional optical gratings are used to redirect light between optical fibers and detectors, then light redirection is achieved, but coupling efficiency is poor with significant signal loss
Solution Approach 1:
The patent applies parameter changes by systematically varying the grating period, depth, and width of the optical gratings to optimize coupling efficiency. By adjusting these geometric parameters, the invention achieves better mode matching between the optical fiber and detector, reducing signal loss while maintaining reliable coupling.
Solution Approach 2:
The patent introduces a vertical dimension to the grating structure by etching trenches into the substrate, creating three-dimensional grating profiles. This dimensional enhancement allows for improved light redirection by utilizing both horizontal and vertical refraction, thereby increasing coupling efficiency and reducing signal loss compared to conventional planar gratings.
2Productivity
If optical gratings redirect light at shallow angles through internal reflection, then light can be redirected, but a large part of the redirected light does not reach the optical detector
Solution Approach 1:
The patent optimizes the grating parameters (period, depth, width) to control the refraction angle and improve light delivery. By carefully selecting these parameters, the invention redirects light at optimal angles that maximize coupling into the detector while minimizing losses, thereby improving productivity without significant energy loss.
3Reliability
If grating couplers are designed for high coupling efficiency, then signal loss is reduced, but the design becomes more complex with multiple etch steps
Solution Approach 1:
The patent segments the grating structure into multiple zones with different grating parameters along the propagation direction. This segmentation allows optimization of coupling efficiency in different regions while using a unified fabrication process, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The patent employs parameter changes through a single etch process that varies grating depth and width across different regions. By controlling etch conditions and mask patterns, the invention achieves high coupling efficiency with varying grating parameters without requiring multiple etch steps, thus maintaining fabrication simplicity while improving reliability.
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 achieves high coupling efficiency, suitable for silicon photonics applications, and is easy to implement with wafer-scale testing and low-cost packaging, overcoming process variations and wavelength shifts.
Implementation Method 1
optical gratings can be used to redirect light from an optical fiber into an optical detector
Implementation Method 2
Light coupled from one end of the optical gratings that has been traveling transversely through the optical gratings by reflecting off the inner surfaces at shallow angles may be redirected
Implementation Method 3
Effective refractive indices of the plurality of coupling gratings gradually decrease along the first direction
Data Source
AI summary
Disclosed are apparatuses for optical coupling and a system for communication. In one embodiment, an apparatus for optical coupling including a substrate and a grating coupler is disclosed. The grating coupler is disposed on the substrate and includes a plurality of coupling gratings arranged along a first direction, wherein effective refractive indices of the plurality of coupling gratings gradually decrease along the first direction.