Two-Submount Light Module for Thermal Stress Reduction
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Solution Overview
Problem
In light modules with optical elements like laser diodes, reducing the size of the sub-mount to minimize thermal stress while maintaining impedance and mechanical strength is challenging due to differences in thermal expansion coefficients between the optical element and the metal block.
Innovation Solution
A two-sub-mount structure is employed, where a first sub-mount is fixed to the metal block, and a second sub-mount with a high-frequency line path is mounted on the first sub-mount, with the lower surface of the second sub-mount electrically connected to the metal block through a metal layer, allowing for reduced size and stress on the optical element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the sub-mount is reduced to minimize size, then the impedance control becomes difficult and mechanical strength decreases, but the stress acting on the optical element from the metal block becomes larger
Solution Approach 1:
The invention divides the sub-mount into two separate sub-mounts (first sub-mount and second sub-mount) with different functional requirements. The first sub-mount provides mechanical support and stress buffering with larger dimensions, while the second sub-mount provides electrical connection and impedance control with smaller dimensions. This segmentation allows each sub-mount to be optimized for its specific function without compromise.
Solution Approach 2:
The first sub-mount acts as an intermediary between the metal block and the second sub-mount. It buffers the thermal stress from the metal block before it reaches the optical element, while allowing the second sub-mount to maintain its smaller size for impedance control. The intermediary structure decouples the conflicting requirements of stress buffering and impedance control.
2Volume of moving object
If the line path width of the high frequency line path is reduced for miniaturization, then the size of the sub-mount is reduced, but the impedance control becomes more difficult
Solution Approach 1:
The invention separates the impedance control function to the second sub-mount, which can be optimized for electrical performance with precise line path width control. The first sub-mount handles mechanical and thermal functions, allowing the second sub-mount to focus on electrical characteristics without being constrained by mechanical size requirements.
3Device complexity
If a single sub-mount structure is used, then the device complexity is reduced, but the ability to simultaneously control impedance and suppress thermal stress is compromised
Solution Approach 1:
The invention divides the sub-mount into two specialized components, each optimized for specific functions. This segmentation improves reliability by ensuring that impedance control and thermal stress suppression are both adequately addressed, even though it increases structural complexity.
Solution Approach 2:
The two-sub-mount structure provides multi-functionality: the first sub-mount handles mechanical support and thermal stress buffering, while the second sub-mount handles electrical connection and impedance control. This multi-functional design ensures reliable performance across multiple requirements.
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 configuration enables miniaturization of the light module by reducing the size of the sub-mount while effectively suppressing thermal stress on the optical element, ensuring impedance matching and mechanical strength.
Implementation Method 1
the lower surface being fixed to the first sub-mount via a metal layer, and the metal layer being electrically connected to the metal block
Implementation Method 2
a difference in a coefficient of thermal expansion exists between the laser chip and the stage, as a result of which a stress is created in a laser chip due to the difference in the coefficient of thermal expansion
Data Source
AI summary
Included are a metal block, a first sub-mount fixed to the metal block, and a second sub-mount having an upper surface and a lower surface which is fixed to the first sub-mount via a metal layer. Also included are an optical element mounted on the upper surface of the second sub-mount and a high frequency line path which is formed on the upper surface of the second sub-mount and electrically connected to the optical element so as to cause a signal such as a high-frequency signal to be input to or output from the optical element. In addition, the metal layer is electrically connected to the metal block.