Stepped BAL Wavelength Combining for Fast-Axis Divergence and Heat
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Solution Overview
Problem
Broad area laser diodes (BALs) in optical modules face challenges with fast axis wavelength beam combining due to high fast axis divergence angles and thermal management issues, limiting the power and efficiency of the laser beams.
Innovation Solution
An optical module design featuring a stepped structure with distributed laser diodes, fast axis collimators, a transform lens, and a grating for wavelength beam combining, which allows for improved thermal conductivity and enhanced beam combining efficiency by spacing diodes apart and using a grating positioned at the focal length of the transform lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If broad area laser diodes are used to emit laser beams, then high power output is achieved, but fast axis divergence angle increases
Solution Approach 1:
The patent segments the laser diodes onto multiple steps of a stepped structure, with each step positioned at a different lateral distance from the transform lens. This segmentation allows each laser diode to be independently positioned to optimize its beam combining characteristics, resolving the divergence issue while maintaining high power output.
Solution Approach 2:
The patent introduces a lateral distance dimension by positioning laser diodes at different lateral distances from the transform lens along the optical axis. This dimensional arrangement enables wavelength beam combining to compensate for fast axis divergence, transforming the problem from a two-dimensional beam propagation issue into a three-dimensional spatial-frequency mapping problem that can be solved through grating-based wavelength combining.
2Productivity
If multiple laser diodes are closely spaced to combine beams, then beam combining efficiency improves, but thermal management deteriorates
Solution Approach 1:
The stepped structure segments the laser diodes spatially, distributing them across multiple lateral distances from the transform lens. This segmentation maintains beam combining efficiency through wavelength beam combining while simultaneously improving thermal management by distributing heat generation across a larger spatial volume, preventing thermal accumulation that would occur with closely spaced diodes.
Solution Approach 2:
The transform lens and grating act as intermediaries that enable beam combining without requiring physical proximity of the laser diodes. The transform lens performs spatial-to-spectral mapping, and the grating combines beams based on wavelength, allowing efficient beam combining while maintaining thermal separation between diodes through the stepped structure.
3Adaptability or versatility
If laser diodes are positioned at different lateral distances from transform lens, then wavelength beam combining is enabled, but device complexity increases
Solution Approach 1:
The stepped structure provides a systematic segmentation approach where each step corresponds to a specific lateral distance from the transform lens. This segmentation enables wavelength beam combining by allowing precise positioning of laser diodes at different lateral distances, while the modular stepped design keeps the overall device complexity manageable through structured organization.
Solution Approach 2:
The patent changes the lateral distance parameter of laser diodes relative to the transform lens to enable wavelength beam combining. By systematically varying this parameter across different steps of the stepped structure, the patent achieves adaptable wavelength combining capability while maintaining reasonable device complexity through controlled parameter variation rather than arbitrary positioning.
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 design increases the power and brightness of the combined laser beam, improves numerical aperture, and enhances dollar per watt efficiency, while also improving thermal management and reliability by dispersing heat across the stepped structure.
Implementation Method 1
the grating is configured to receive the plurality of laser beams from the transform lens, to combine the plurality of laser beams into a single laser beam
Implementation Method 2
the transform lens is configured to receive the plurality of laser beams from the plurality of FACs and to direct the plurality of laser beams to the grating positioned at the focal length of the transform lens
Implementation Method 3
each FAC, of the plurality of FACs, is disposed between a corresponding laser diode, of the plurality of laser diodes, and the transform lens
Data Source
AI summary
An optical module includes a stepped structure that includes a plurality of steps, a plurality of laser diodes (e.g., broad area laser diodes (BALs)), a transform lens; a grating; and an output coupler (OC). At least one laser diode, of the plurality of laser diodes, is disposed on each step of the plurality of steps of the stepped structure. The transform lens is configured to receive a plurality of laser beams emitted by the plurality of laser diodes and to direct the plurality of laser beams to the grating. The grating is configured to receive and to combine the plurality of laser beams into a single laser beam, and to direct the single laser beam to the OC. The OC is configured to receive the single laser beam from the grating and to direct a portion of the of the single laser beam out of the optical module.