Stacking-Dimension Wavelength Beam Combining for Diode Laser Arrays
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Solution Overview
Problem
Conventional external-cavity one-dimensional wavelength beam combining techniques for diode laser arrays are limited by tight tolerances and high costs due to sensitivity to 'smile' and pointing errors, which degrade beam quality and efficiency.
Innovation Solution
Performing wavelength beam combining along the stacking dimension instead of the array dimension, using a configuration that includes a cylindrical telescope, transform lens, and diffraction grating to image and overlap beams from multiple diode bars, thereby reducing the impact of 'smile' and pointing errors and allowing the use of low-cost, off-the-shelf diode bars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wavelength beam combining is performed along the array dimension using conventional external-cavity techniques, then beam combining is achieved, but tight tolerances and high costs result due to sensitivity to smile and pointing errors
Solution Approach 1:
The patent performs wavelength beam combining along the stacking dimension (vertical dimension) rather than the conventional array dimension (horizontal dimension). This dimensional change fundamentally alters the optical path geometry, allowing beams from multiple diode bars to be combined while significantly reducing sensitivity to smile and pointing errors that plague conventional array-dimension combining approaches
2Reliability
If conventional wavelength beam combining is performed along the array dimension, then beam combining is achieved, but high costs result due to sensitivity to smile and pointing errors
Solution Approach 1:
By switching from array-dimension combining to stacking-dimension combining, the patent enables the use of lower-cost, off-the-shelf diode bars that are less stringent regarding smile and pointing error specifications, thereby reducing overall system cost while maintaining beam combining efficiency
Solution Approach 2:
The patent enables the use of standard, commercially available diode bars with relaxed specifications rather than requiring custom-manufactured, high-precision components, effectively substituting expensive precision components with cheaper, readily available alternatives
3Reliability
If wavelength beam combining is performed along the stacking dimension, then robustness and efficiency become independent of smile and pointing errors, but new optical configuration is required
Solution Approach 1:
The patent implements wavelength beam combining along the stacking dimension using a specific optical configuration involving cylindrical telescopes and transform lenses arranged to image and overlap beams vertically, creating a geometry inherently insensitive to smile and pointing errors that plagues horizontal array combining
Solution Approach 2:
The patent introduces cylindrical telescopes and transform lenses as intermediary optical elements that facilitate the stacking-dimension beam combining process, these components serve as mediators to image and overlap beams from different diode bars while maintaining the desired insensitivity to manufacturing errors
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 approach results in a higher-power laser source with improved efficiency and manufacturability, achieving superior performance and lower costs compared to conventional methods, with enhanced output spectrum, beam quality, and size characteristics.
Implementation Method 1
The cylindrical lens 120 is placed at a distance equal to one focal length between the laser stack 110 and the diffraction grating 130. The cylindrical lens 120 converges the optical beams from the laser diode elements of each diode bar in the stack such that the beams are spatially overlapped
Implementation Method 2
The cavity also comprises a cylindrical lens 120, diffraction grating 130, and a partially reflecting output coupler 140. The partially reflecting output coupler 140 is placed on the path of the first-order diffracted beams from the diffraction grating 130
Implementation Method 3
The volume Bragg grating 160 is placed as close as possible (e.g., about 1 mm) to the laser stack 110. The cylindrical lens 120 and the diffraction grating 130 match the wavelength spread of the volume Bragg grating 160
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An external-cavity one-dimensional multi-wavelength beam combiner that performs wavelength beam combining along a stacking dimension of a laser stack formed of a plurality of laser arrays, each laser array configured to generate optical radiation having a unique wavelength, and each of the plurality of laser arrays including a plurality of laser emitters arranged along an array dimension of the laser stack. The multi-wavelength beam combiner includes a cylindrical telescope configured to image each of the laser emitters along a slow axis of the laser emitters, a transform lens arranged to intercept the optical radiation from each of the plurality of laser arrays and combine the optical radiation along a stacking dimension of the laser stack to form a multi- wavelength optical beam, and a diffraction element positioned at a region of overlap of the optical radiation to receive and transmit the multi-wavelength optical beam.