Photonic Integrated Circuit Mode Conversion for High-Power Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photonic integrated circuits (PICs) using silicon face challenges in achieving high-power operations due to silicon's indirect bandgap, requiring precise alignment of dissimilar materials, which increases packaging costs and limits scalability, and inefficient power transfer between materials with large refractive index differences.
Innovation Solution
The development of heterogeneously integrated PICs with optimized mode-size at the output facet region, utilizing mode conversion and butt-coupling schemes to enhance optical coupling between dissimilar materials, allowing for high-power operations without narrow tapers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heterogeneous integration is used to overcome silicon's indirect bandgap, then laser functionality is achieved, but precise alignment is required which increases packaging costs and limits scalability
Solution Approach 1:
The patent segments the PIC fabrication process into two independent stages: first bonding dissimilar material wafers together, then subsequently defining waveguides and components through processing. This eliminates the need for precise alignment during bonding while maintaining component functionality.
Solution Approach 2:
The dissimilar materials are bonded together in advance before any precise alignment or component definition is required. This preliminary bonding action allows subsequent processing steps to be performed independently without alignment constraints.
2Loss of energy
If tapers are used to transfer optical signals between dissimilar materials, then power transfer efficiency is improved, but taper tip dimensions become prohibitively narrow when refractive index difference is large
Solution Approach 1:
The patent introduces an intermediate waveguide layer with refractive index matched to both the passive waveguide material and the active material. This intermediary enables efficient optical coupling between dissimilar materials with large refractive index differences without requiring prohibitively narrow tapers.
3Loss of energy
If mode area is reduced to support efficient coupling to low-loss passive waveguide material, then coupling efficiency is improved, but output power is limited to below 30 mW due to high intensity in quantum well region
Solution Approach 1:
The patent applies different mode sizes to different regions: a smaller mode area in the coupling region for efficient coupling to passive waveguides, and a larger mode area in the output region for high power operation. This local differentiation resolves the contradiction between coupling efficiency and output power.
Solution Approach 2:
The patent uses a vertical stack configuration where the active region with quantum wells is positioned below the passive waveguide layer. This vertical arrangement allows the optical mode to be confined vertically for efficient coupling while expanding horizontally in the output region for high power, effectively using the vertical dimension to resolve the mode area contradiction.
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
Enables scalable manufacturing of PICs with higher performance and the ability to handle high output optical power, while facilitating efficient power transfer and monitoring through integrated photodetectors.
Implementation Method 1
utilizing mode conversion and butt-coupling schemes to enhance optical coupling between dissimilar materials
Implementation Method 2
utilizing mode conversion and butt-coupling schemes to enhance optical coupling between dissimilar materials
Implementation Method 3
The approach utilizes butt-coupling assisted optical coupling between materials with large refractive index difference and generally has at least one etched facet as a part of the laser structure
Data Source
AI summary
A device has first, second, third and fourth elements, realized in combination as a photonic integrated circuit fabricated on a common substrate. The first has a first interface and a second interface of larger cross-section than the first and supports a first optical mode. The second element at least partly butt-coupled to the first interface at a first butt-coupled interface, has a first intermediate waveguide structure supporting a first intermediate optical mode. The third element at least partly butt-coupled to the second interface at a second butt-coupled interface, has an output facet and a second intermediate waveguide structure supporting a second intermediate optical mode. The fourth element has a first passive waveguide structure supporting a second optical mode. At least one of the second and fourth elements has a tapered waveguide structure facilitating efficient adiabatic transformation between the second optical mode and the first intermediate optical mode.