External Resonant Laser Module Layout for Stray Light Suppression
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Solution Overview
Problem
The issue with existing external resonant laser modules is the deterioration of laser quality due to stray light components that are not returned to the quantum cascade laser element, mixing with the emitted laser light and degrading its quality.
Innovation Solution
The laser module is designed with a package configuration where the distance between the top wall and the lens holder is smaller than the thickness of the lens holder, preventing stray light from entering the space where the quantum cascade laser element is located, and the electrode terminal is positioned closer to the top wall than the laser element to minimize interference with the lens holder, while the lens holder surfaces are blackened to absorb stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lens holder is disposed with a larger distance from the top wall to accommodate components, then the ease of manufacture and assembly is improved, but stray light can enter the quantum cascade laser element space and deteriorate laser quality
Solution Approach 1:
The patent positions the electrode terminal closer to the top wall than the quantum cascade laser element, utilizing the vertical dimension (Z-axis) to resolve the spatial conflict. This dimensional reorganization allows the lens holder to be positioned with minimal distance from the top wall while still providing adequate space for wire connection and assembly operations.
Solution Approach 2:
The patent applies local quality by blackening the surface of the lens holder at the space between the top wall and the lens holder. This localized treatment creates a light-absorbing region that prevents stray light from entering the quantum cascade laser element space, while maintaining the overall structural integrity and assembly accessibility of the package.
2Device complexity
If the electrode terminal is positioned closer to the quantum cascade laser element to simplify wiring, then the device complexity is reduced, but the lens holder cannot be positioned close to the top wall allowing stray light contamination
Solution Approach 1:
The patent inverts the conventional arrangement by positioning the electrode terminal closer to the top wall than the quantum cascade laser element. This inversion resolves the contradiction by allowing the lens holder to be positioned close to the top wall (preventing stray light contamination) while still providing accessible space for wire connection and assembly operations.
3Volume of moving object
If the package structure is made compact to reduce size, then the volume is reduced, but stray light suppression becomes difficult
Solution Approach 1:
The patent changes the critical parameter from the absolute distance between the top wall and lens holder to the relationship between this distance and the lens holder thickness. By specifying that the distance be smaller than the lens holder thickness, the patent achieves effective stray light suppression in a compact package volume, as the blackened region occupies the entire gap space.
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 suppresses stray light from mixing with the emitted laser light, thereby securing appropriate laser quality and improving the reliability and workability of the module.
Implementation Method 1
a lens for passing an outgoing light from the quantum cascade laser element and a light returned from the movable diffraction grating to the quantum cascade laser element
Implementation Method 2
light from the quantum cascade laser element is diffracted and reflected by the diffraction grating, and light having a specific wavelength among the light from the quantum cascade laser element is returned to the quantum cascade laser element
Implementation Method 3
light from the quantum cascade laser element is diffracted and reflected by the diffraction grating
Implementation Method 4
the light of the specific wavelength is amplified and output to the outside
Implementation Method 5
the lens holder surfaces are blackened to absorb stray light
Data Source
AI summary
The laser module includes a QCL element, a MEMS diffraction grating, a lens holder for holding a lens disposed between the QCL element and the MEMS diffraction grating, and a package. The package includes a bottom wall, a side wall erected on the bottom wall and formed in an annular shape so as to surround a region in which the QCL element is accommodated, and a top wall closing an opening of the side wall on a side opposite to a side where the bottom wall is disposed. The top wall faces the bottom wall in a direction orthogonal to the optical axis direction of the lens, and the distance between the top wall and a surface of the lens holder on a side where the top wall is disposed is smaller than a thickness of the lens holder along the optical axis direction of the lens.