Split Transmitter Optical Sub-Assembly for Coupling and Heat Dissipation
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Solution Overview
Problem
Existing optical transceiver technologies face challenges in high relative placement accuracy and heat management due to the assembly of multiple micro-optical components, leading to low process yield and thermal issues, particularly in silicon photonics integrated circuits with high-power continuous wave laser diodes.
Innovation Solution
A TOSA structure comprising a light source sub-assembly and an optical sub-assembly, both actively aligned on a silicon chip or an electrical substrate, with a direct heat dissipation path through the substrate or chip, allowing flexible assembly and improved thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple high-power CW laser diodes are co-packaged on top of the PIC to maximize transmission data rate, then the optical power and data rate are improved, but the heat generation increases significantly leading to thermal accumulation and reduced laser lifetime
Solution Approach 1:
The patent segments the TOSA into two independent sub-assemblies: a light source sub-assembly containing the laser diode and an optical sub-assembly containing the grating coupler and waveguide. This segmentation allows independent thermal management for each sub-assembly, enabling the light source to be positioned where heat dissipation is most effective while maintaining optimal optical coupling.
2Manufacturing precision
If active alignment is performed on multiple optical components on the PIC to achieve required coupling efficiency, then the optical coupling efficiency is improved, but the process yield becomes extremely low due to the challenging alignment process
Solution Approach 1:
By dividing the TOSA into two sub-assemblies that are actively aligned simultaneously, the patent reduces the complexity of aligning multiple individual components separately. The light source sub-assembly and optical sub-assembly are aligned as units, significantly reducing the alignment steps and improving process yield while maintaining high coupling efficiency.
Solution Approach 2:
The patent combines the alignment of the light source and optical components into a single simultaneous active alignment process. This merging of alignment operations reduces the cumulative alignment errors and simplifies the manufacturing process, thereby improving both coupling efficiency and process yield.
3Device complexity
If the CW LD is assembled on top of the PIC directly to form a TOSA, then the integration is simplified, but the relative placement accuracy between micro-optical components and the waveguide becomes difficult to control
Solution Approach 1:
The patent segments the TOSA into a light source sub-assembly and an optical sub-assembly, each with its own mounting structure. This segmentation allows each sub-assembly to be independently fabricated and pre-aligned, then combined through a single active alignment step, thereby maintaining simple integration while achieving high relative placement accuracy.
4Strength
If bonding interfaces are used to connect the laser sub-mount, PIC, and PIC sub-mount, then the structural integrity is improved, but the thermal resistance increases leading to heat accumulation
Solution Approach 1:
The patent extracts the thermal management function from the bonding interfaces by introducing dedicated heat dissipation structures (heat sinks and thermal vias) in the light source sub-assembly. This separation allows the bonding interfaces to maintain structural integrity while the dedicated thermal paths handle heat dissipation, minimizing thermal resistance.
Solution Approach 2:
The patent introduces thermal vias and heat sink structures as intermediary elements between the laser diode and the substrate. These intermediaries provide low thermal resistance paths for heat flow while maintaining the structural integrity of the bonding interfaces, effectively decoupling the mechanical and thermal functions.
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
Enhances optical coupling efficiency and thermal management by optimizing the alignment and distance between sub-assemblies, reducing thermal resistance and extending laser lifetime while maintaining high tolerances.
Implementation Method 1
a light source component emitting a light
Implementation Method 2
the light source bench and the optical bench are thermally conductive to dissipate, individually or together, heat generated from the light source component
Data Source
AI summary
Structures and active alignment methods thereof of a Transmitter Optical Sub-Assembly (TOSA) Structure are provided, that includes a light source sub-assembly including a light source component assembled on a light source bench; an optical sub-assembly including an optical component assembled on an optical bench; and a silicon chip including a coupler. A light emitted by the light source component is received by the coupler via the optical component along an optical path, the light source bench and the optical bench are thermally conductive to dissipate heat. The light source sub-assembly and the optical sub-assembly are actively aligned at the same time to optimize optical coupling between the light source sub-assembly and the optical sub-assembly by optimizing positions and a distance of the light source sub-assembly and the optical sub-assembly, the positions and the distance are flexibly adjusted during the active alignment process.