Universal Optical Coupler Tapered Structure Out-of-Plane Fiber
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Solution Overview
Problem
Current optical coupling structures for photonics integrated circuits (PICs) face challenges in efficiently coupling waveguides to external optical fibers, particularly due to modal mismatch and the difficulty in designing compact, cost-effective systems that handle out-of-plane fiber orientations, leading to significant beam power loss.
Innovation Solution
The development of an optical interconnect device featuring a universal coupler with a tapered structure that expands the light beam spot size to match the external optical fiber, combined with a surface lens for efficient coupling, and a method for fabricating this device using CMOS-compatible processes, allowing for both in-plane and vertical fiber orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If grating couplings are used to couple out-of-plane optical fibers to waveguides, then coupling between waveguide and external optical fiber is achieved, but significant loss of beam power occurs and design and manufacture become difficult
Solution Approach 1:
The patent introduces a tapered structure as an intermediary component between the waveguide and external optical fiber. This taper acts as a mode transformer that gradually transitions the optical mode from the waveguide to a larger spot size, enabling efficient coupling to out-of-plane fibers without the significant power loss associated with grating couplings
Solution Approach 2:
The tapered structure changes the spatial parameters of the optical mode by gradually increasing the spot size from the waveguide output to a larger diameter at the fiber interface. This parameter transformation enables mode matching between the waveguide and external fiber, reducing coupling loss while supporting out-of-plane orientations
2Reliability
If traditional coupling structures (butt coupling, cylindrical lenses, graded index rod lenses) are used, then coupling efficiency between laser and single mode fiber is improved, but the systems become bulky and assembly cost increases
Solution Approach 1:
The patent merges the coupling function and mode transformation function into a single integrated tapered structure on the waveguide surface. This eliminates the need for separate cylindrical lenses, graded index rod lenses, or complex alignment mechanisms, thereby reducing system bulkiness and assembly complexity while maintaining high coupling efficiency
Solution Approach 2:
The invention transitions from three-dimensional bulk optical components (lenses, rod lenses) to a two-dimensional surface-based tapered structure. This dimensional reduction integrates the coupling function directly into the waveguide surface, eliminating the need for separate optical components and simplifying the overall system architecture
3Volume of moving object
If waveguide-optical fiber interface is not perpendicular to propagation direction (out-of-plane coupling), then compact integration is achieved, but modal mismatch increases and coupling efficiency decreases
Solution Approach 1:
The tapered structure serves as a mediator that bridges the modal mismatch between the waveguide and out-of-plane optical fiber. By gradually transforming the mode profile, it enables efficient coupling even when the fiber is positioned out-of-plane, thus maintaining coupling efficiency while achieving compact integration
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 enhances coupling efficiency by matching the light beam spot size with the fiber core, reducing losses and enabling more compact, cost-effective optical interconnect systems that can handle various fiber orientations, thereby improving the integration of PICs with external optical fibers.
Implementation Method 1
the tapered structure expands the first spot size of the light beam to a second spot size, wherein the second spot size is larger than the first spot size
Implementation Method 2
an external optical fiber attached to a surface lens, wherein the surface lens receives the expanded light beam from the universal coupler and focuses the light beam to the external optical fiber
Data Source
AI summary
An optical interconnect device and the method of fabricating it are described. The device includes an in-plane laser cavity transmitting a light beam along a first direction, a Franz Keldysh (FK) optical modulator transmitting the light beam along the first direction, a mode-transfer module including a tapered structure disposed after the FK optical modulator along the first direction to enlarge the spot size of the light beam to match an external optical fiber and a universal coupler controlling the light direction. The tapered structure can be made linear or non-linear along the first direction. The universal coupler passes the laser light to an in-plane external optical fiber if the fiber is placed along the first direction, or it is a vertical coupler in the case that the external optical fiber is placed perpendicularly to the substrate surface. The coupler is coated with highly reflective material.