Grating-Based Optical Coupler for Perpendicular Light Extraction
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Solution Overview
Problem
Current photonic integrated circuits face challenges in efficiently coupling light in and out at an angle perpendicular to the propagation direction, leading to increased packaging costs and complexity, and require complex mode matching to minimize losses.
Innovation Solution
A grating-based optical coupler is formed on an interference region bounded by reflectors, with a grating profile matched to the interference pattern, allowing light to enter or exit the circuit at a specific angle, and featuring n-doped and p-doped regions to adjust reflectivity and interference patterns with applied voltages or currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light is coupled to external medium through conventional methods, then light coupling is achieved, but packaging costs and complexity increase
Solution Approach 1:
The patent couples light out of the plane of the photonic integrated circuit by using a grating structure that redirects propagating light into the substrate or cover layer perpendicular to the original propagation direction. This out-of-plane coupling eliminates the need for complex edge coupling packaging arrangements, thereby reducing packaging cost and complexity while maintaining effective light coupling to external media such as optical fibers.
2Ease of operation
If conventional light coupling methods are used, then light coupling is achieved, but mode matching complexity increases
Solution Approach 1:
The patent employs a grating structure with specific periodicity and geometric parameters that are designed to transform the mode profile of light propagating in the waveguide into a mode that matches well with optical fibers or other external media. By carefully controlling the grating parameters (period, depth, duty cycle), the coupling efficiency is maximized without requiring complex additional mode-matching components, thereby simplifying the overall system operation.
3Productivity
If grating is formed on interference region with reflectors, then perpendicular light coupling efficiency is improved, but back reflection increases
Solution Approach 1:
The patent uses asymmetric grating structures where the grating teeth or grooves have different dimensions on opposite sides, creating preferential coupling in the desired direction while suppressing back reflection. The asymmetric geometry causes constructive interference for forward-coupled light and destructive interference for reflected light, thereby achieving high perpendicular coupling efficiency while minimizing harmful back reflections into the waveguide.
4Ease of manufacture
If fixed grating structure is used, then manufacturing is simplified, but light coupling tuning capability is reduced
Solution Approach 1:
The patent incorporates tunable elements such as phase shifters, thermo-optic modulators, or electro-optic materials within or adjacent to the grating structure. These dynamic components allow the grating's effective period or phase response to be adjusted after fabrication, enabling tuning of the coupling wavelength, angle, or efficiency to match different external media requirements without requiring multiple fixed gratings, thus maintaining manufacturing simplicity while adding adaptability.
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 solution reduces packaging costs and complexity by enabling efficient perpendicular light coupling with reduced back reflection, maintaining circuit stability and allowing for active tuning of light coupling, and enhances absorption efficiency in detection applications.
Implementation Method 1
a grating region including a grating formed on a region confining at least a portion of the interference light, the grating configured to emit a portion of the interference light along a second direction that is different from the first direction
Implementation Method 2
a first reflector region and a second reflector region; an interference region formed between the first reflector region and the second reflector region, the interference region configured to (i) guide the incident light generated by the light source region to propagate along a first direction, and (ii) confine interference light formed by light reflected between the first reflector region and the second reflector region
Implementation Method 3
an n-doped region and a p-doped region configured to provide an electric field in the second reflector region with an application of a voltage or a current across the n-doped region and the p-doped region, where the second reflector region may be configured to provide a different reflectivity with the application of a voltage or a current across the n-doped region and the p-doped region
Data Source
Figure 1A
Figure 1B~1C
Figure 1D
AI summary
An apparatus including a waveguide region (102) configured to guide light propagating along a first direction; a reflector region (114) configured to reflect incident light; an interference region (110) formed between the waveguide region (102) and the reflector region (114), the interference region (110) configured to confine at least a portion of interference light formed by the incident light and the reflected incident light; and a grating region (120) including a grating formed on a region confining at least a portion of the interference light, the grating configured to couple at least a portion of the light along a second direction that is different from the first direction.