Two-Stage Beam Expansion for Alignment-Tolerant Fiber Coupling
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Solution Overview
Problem
Conventional fiber optic connections to silicon-based photonic integrated circuits face challenges in achieving high bandwidth, ease of manufacturing, misalignment tolerance, and compatibility with wafer-level packaging due to the complexity of integrating edge couplers and curved mirrors, which are difficult to manufacture and integrate with other planar processes.
Innovation Solution
A two-stage beam expansion process is implemented, comprising a first in-plane optical element for initial beam expansion and a second out-of-plane optical element for further expansion and deflection, using non-grating based optics to facilitate high bandwidth and alignment tolerance, with the second element being integrated into the silicon-based substrate to reduce complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If edge coupler with 2D curved mirror is used to expand and collimate light beam, then alignment tolerance is improved, but manufacturing difficulty and device complexity increase
Solution Approach 1:
The patent segments the beam expansion process into two independent stages: first expanding the beam width using an edge coupler, then collimating the expanded beam using a separate collimating lens. This segmentation allows each component to be optimized independently and manufactured using standard planar processes, avoiding the need for complex 2D curved mirrors while achieving the same alignment tolerance improvement.
Solution Approach 2:
The patent transitions from using 2D curved mirrors (requiring high-precision direct-laser lithography) to using planar 1D grating structures combined with separate collimating lenses. This dimensional simplification enables manufacturing using standard semiconductor fabrication processes while maintaining the beam expansion and collimation functionality.
2Reliability
If 2D curved mirror is integrated into photonic chip, then beam collimation is achieved, but integration complexity and height profile increase
Solution Approach 1:
The patent separates the collimation function from the beam expansion function, implementing them as distinct components: an edge coupler for expansion and a separate collimating lens for beam parallelization. This segmentation reduces integration complexity compared to integrating a 2D curved mirror that combines both functions, while achieving the same beam collimation reliability.
Solution Approach 2:
Instead of using a 2D curved mirror to simultaneously expand and collimate the beam in a single component, the patent inverts the approach by using a planar edge coupler for expansion followed by a separate collimating lens. This inverted architecture simplifies integration with other planar processes and reduces the height profile while maintaining beam collimation performance.
3Manufacturing precision
If grating coupler with micro-lens is used for beam expansion, then alignment tolerance is improved, but operational bandwidth is limited
Solution Approach 1:
The patent changes the operational parameters by using an edge coupler instead of a grating coupler. The edge coupler design enables broadband operation across multiple wavelengths, unlike grating couplers that are limited to specific wavelength ranges. This parameter change maintains alignment tolerance improvement while significantly expanding the operational bandwidth for high data rate WDM applications.
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 enables high bandwidth, improved manufacturability, increased alignment tolerance, and compatibility with wafer-level packaging, allowing for efficient integration with other planar processes and module components.
Implementation Method 1
a first optical element, which is configured to expand the light beam in a first direction, in-plane of the photonic chip
Implementation Method 2
a first optical element, which is configured to expand the light beam in a first direction, in-plane of the photonic chip
Implementation Method 3
a second optical element, which is configured to deflect, and at the same time further expand, the expanded light beam in a second direction, out-of-plane of the photonic chip
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
The present disclosure relates to silicon-based photonic chips, in particular, for optically coupling to an optical fiber or optical fiber assembly, and a method for fabricating the same. The photonic chip of the disclosure comprises a single-mode waveguide configured to guide light and provide a light beam. Further, the photonic chip comprises a first optical element configured to expand the light beam in a first direction in-plane of the photonic chip, in order to provide an expanded light beam. The photonic chip also comprises a second optical element configured to deflect and at the same time further expand the expanded light beam in a second direction, in order to provide an output light beam from the photonic chip.