Corner-Coupled PIC Optical Interface for Low-Loss Fiber Coupling
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Solution Overview
Problem
Coupling light into and out of photonic integrated circuits (PICs) from optical fibers or other media is challenging due to complex fabrication methods and high optical losses, particularly when using CMOS fabrication techniques.
Innovation Solution
A corner-coupled optical coupler is fabricated with optical waveguide cores adjacent to the substrate surface at an acute angle, allowing direct coupling to photonic integrated circuits without significant substrate propagation, reducing optical losses and fabrication complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional CMOS fabrication techniques are used to fabricate photonic integrated circuits, then manufacturing scalability is improved, but optical coupling complexity and optical losses increase
Solution Approach 1:
The optical coupling interface is segmented into distinct functional regions: a first region for receiving optical waves from an optical fiber, a second region for directing waves into the photonic integrated circuit, and a third region for emitting waves. This segmentation allows each region to be optimized independently while maintaining compatibility with CMOS fabrication processes.
Solution Approach 2:
Different regions of the optical coupling interface are assigned different functional properties and geometries. The first region has specific curvature and size for fiber coupling, the second region has acute angle orientation for wave direction, and the third region has specific dimensions for emission. This local differentiation reduces overall coupling complexity while maintaining manufacturing scalability.
2Reliability
If traditional optical coupling methods are used, then coupling functionality is achieved, but optical losses increase
Solution Approach 1:
The optical coupling interface incorporates curved surfaces with specific radii of curvature in the first and third regions. These curved geometries enable evanescent mode coupling, which significantly reduces optical losses compared to flat interface coupling while maintaining reliable wave transfer functionality.
Solution Approach 2:
The optical coupling interface transitions from traditional planar coupling to a three-dimensional structure with varying depths and angles. The second region extends at an acute angle from the substrate surface, creating a volumetric coupling path that reduces optical losses by minimizing evanescent mode interactions with the substrate.
3Adaptability or versatility
If complex substrate propagation is used for optical coupling, then coupling coverage is improved, but fabrication complexity increases
Solution Approach 1:
The invention extracts the optical coupling functionality from the bulk substrate and concentrates it into a thin-film interface structure. By removing the need for complex substrate propagation and focusing coupling in a localized thin-film region, the solution reduces fabrication complexity while maintaining broad coupling coverage through the evanescent mode mechanism.
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
Facilitates wafer-level testing, reduces optical losses, and simplifies fabrication, enabling more compact and cost-effective photonic circuit designs with customizable optical functionality.
Implementation Method 1
The first optical waveguide core is optically coupled to at least one passive optical element... The first optical waveguide core is optically coupled to a wavelength-dependent optical element
Implementation Method 2
a substrate comprising an optically transmissive material... The third portion between the first and second portions that is separated from the first surface of the substrate by a thickness of the optically transmissive material
Data Source
AI summary
An apparatus for coupling an external optical interface to a first optical interface of a photonic integrated circuit comprises: a substrate comprising an optically transmissive material; and a first optical waveguide core formed in proximity to a first surface of the substrate. The first optical waveguide core comprises: a first portion comprising the external optical interface, a second portion that is (1) adjacent to the first surface of the substrate, and (2) adjacent to a second surface of the substrate at an acute angle with the first surface of the substrate, and a third portion between the first and second portions that is separated from the first surface of the substrate by a thickness of the optically transmissive material.