MEMS Diffraction Grating Layout for Compact External Resonance Lasers
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Solution Overview
Problem
Existing external resonance-type laser modules face challenges in reducing size, power consumption, and spectral line width, particularly when using quantum cascade lasers due to large beam diameters and the need for increased diffraction grating areas, leading to higher power consumption and broader spectral line widths.
Innovation Solution
The laser module incorporates a MEMS diffraction grating with a movable portion and a diffraction grating portion arranged such that the normal line of the grating is inclined relative to the quantum cascade laser's end surface, with the grating length in one direction exceeding the other, and disposed along the lamination direction of the quantum cascade laser's structure, ensuring efficient light reception and reducing the grating's size and spectral line width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the diffraction grating is increased to handle the large beam diameter from the quantum cascade laser, then the light reception efficiency is improved, but the power consumption increases due to the larger driving force required
Solution Approach 1:
The diffraction grating is designed with an asymmetric rectangular shape where the length in the first direction (along the lamination direction of the quantum cascade laser) exceeds the length in the second direction. This asymmetric configuration allows the grating to effectively intercept the large beam diameter from the quantum cascade laser while minimizing the area in the direction perpendicular to the beam propagation, thereby reducing the driving force required and lowering power consumption.
2Reliability
If the area of the diffraction grating is increased to handle the large beam diameter, then the light reception efficiency is improved, but the module size increases
Solution Approach 1:
The diffraction grating employs an asymmetric rectangular configuration where the longer dimension aligns with the lamination direction of the quantum cascade laser to maximize light interception, while the shorter dimension minimizes the overall footprint of the module. This allows efficient light reception without proportionally increasing the module size.
Solution Approach 2:
The diffraction grating is positioned at an inclination angle relative to the beam propagation direction. This angular arrangement allows the grating to intercept the large beam diameter effectively while maintaining a compact overall structure, as the light path is optimized to utilize the inclined surface area efficiently.
3Volume of moving object
If the diffraction grating is positioned at an inclination angle to reduce the beam diameter projection, then the module size is reduced, but the light reception efficiency may deteriorate
Solution Approach 1:
The diffraction grating uses an asymmetric rectangular shape with the longer side aligned along the lamination direction of the quantum cascade laser. When positioned at an inclination angle, this asymmetric configuration ensures that the longer dimension provides sufficient light interception area despite the angular orientation, maintaining light reception efficiency while achieving compact module size.
4Use of energy by moving object
If the diffraction grating area is reduced to decrease power consumption, then the power consumption is reduced, but the spectral line width increases due to lower wavelength resolution
Solution Approach 1:
The diffraction grating is designed with asymmetric dimensions where the length in the first direction (along the lamination direction) exceeds the length in the second direction. This configuration optimizes the number of lattice grooves that can be positioned within the beam diameter in the inclined orientation, thereby maintaining high wavelength resolution and narrow spectral line width while using a smaller overall grating area to reduce power consumption.
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 allows for a compact design with reduced power consumption and narrower spectral line widths, enhancing wavelength resolution and reducing stray light, especially effective for mid-infrared light sources like quantum cascade lasers.
Implementation Method 1
the MEMS diffraction grating diffracts and reflects the light emitted from the quantum cascade laser by the diffraction grating portion
Implementation Method 2
the MEMS diffraction grating diffracts and reflects the light emitted from the quantum cascade laser
Implementation Method 3
a lens disposed between the quantum cascade laser and the MEMS diffraction grating
Data Source
AI summary
An external resonance-type laser module includes: a quantum cascade laser; a MEMS diffraction grating including a movable portion capable of swinging around an axis and a diffraction grating portion formed on the movable portion; and a lens. The diffraction grating portion includes a plurality of lattice grooves arranged in a first direction and each of the plurality of lattice grooves extends in a second direction perpendicular to the first direction. The MEMS diffraction grating is disposed such that a normal line of the diffraction grating portion is inclined with respect to an end surface and the first direction is along a lamination direction of a laminated structure when viewed in a direction perpendicular to the end surface. A length of the diffraction grating portion in the first direction exceeds a length of the diffraction grating portion in the second direction.