QCL Window Sealing Structure to Protect AR Film During Brazing
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Solution Overview
Problem
The existing semiconductor laser devices face issues with damage to the anti-reflection film on the light-emitting window due to high heat during brazing and require high airtightness to maintain a vacuum or inert gas atmosphere, which is challenging to achieve.
Innovation Solution
The semiconductor laser device employs a light-emitting window with a first anti-reflection film region and a metallized second region separated by a solder member, joined to the package with a lower melting point, preventing stress transmission and ensuring airtightness, while using a lens externally attached for beam shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brazing material with high melting point is used to join the light-emitting window to the package, then airtightness is improved, but the anti-reflection film on the light-emitting window is damaged by heat
Solution Approach 1:
The incident surface of the window member is divided into two distinct regions: a first region with an anti-reflection film for optical performance, and a second metallized region for mechanical joining. This segmentation allows the window member to be joined to the package using soldering in the second region without exposing the anti-reflection film in the first region to damaging heat, while still achieving adequate airtightness through the sealed connection.
Solution Approach 2:
Different regions of the window member are given different properties: the first region has an anti-reflection film optimized for optical performance, while the second region is metallized for mechanical strength and joining capability. This local differentiation allows each region to fulfill its specific function without compromising the other, enabling low-temperature soldering that protects the anti-reflection film while maintaining package sealing.
2Manufacturing precision
If the anti-reflection film is formed on the light-emitting window to improve extraction efficiency, then optical performance is improved, but the film is damaged during brazing process
Solution Approach 1:
The incident surface is segmented into a first region with the anti-reflection film for optimal light extraction and a second metallized region for joining. This allows the anti-reflection film to be formed only where needed for optical performance, while the metallized region provides a heat-resistant area for soldering that protects the film during the joining process.
Solution Approach 2:
The metallized second region acts as an intermediary between the window member and the soldering process, providing a heat-resistant interface that absorbs the thermal stress of joining without transmitting it to the anti-reflection film. This mediator layer enables the soldering process to proceed at lower temperatures that do not damage the optical coating.
3Ease of manufacture
If the package size is reduced to improve workability, then ease of manufacture is improved, but maintaining airtightness becomes more difficult
Solution Approach 1:
The joining method is changed from high-temperature brazing to low-temperature soldering, which enables the use of smaller, more compact packages without compromising airtightness. The soldering process provides adequate sealing at lower temperatures, allowing for reduced package dimensions while maintaining the required vacuum or inert gas atmosphere.
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 effectively prevents damage to the anti-reflection film and maintains high airtightness, allowing for reduced package size and improved workability, especially for laser light with large beam radiation angles.
Implementation Method 1
The second region is joined to the counterbore surface through a solder member
Implementation Method 2
a first anti-reflection film is provided
Data Source
AI summary
A quantum cascade laser device includes a QCL element and a package. A light-emitting window through which laser light emitted from the QCL element passes is provided on a side wall of the package. The light-emitting window includes a small-diameter hole, a large-diameter hole larger than the small-diameter hole, a counterbore surface having an annular shape that connects the small-diameter hole and the large-diameter hole, and a window member disposed inside the large-diameter hole. An incident surface of a window member includes a first region in which an anti-reflection film is provided, and a second region metallized and formed in an annular shape to be separated from the first region and to surround the first region. The second region is joined to the counterbore surface through a solder member.