Misaligned Fast-Axis Collimating Lenses for Laser Diode Power Scaling
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Solution Overview
Problem
Semiconductor laser diodes face limitations in scaling power while maintaining beam quality, leading to inadequate power levels and beam quality for applications like material processing and telecommunications, as increasing the lasing stripe width results in optical facet damage and reduced beam quality.
Innovation Solution
A system comprising a stack of laser diode bar arrays and a multimode optical fiber, with fast-axis collimating lenses misaligned relative to the laser diode bar arrays to improve the coupling efficiency of light into the fiber, allowing for higher power levels with maintained beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the lasing stripe width of semiconductor laser diodes is increased to achieve higher power levels, then the available power increases, but the beam quality deteriorates and optical facet damage occurs
Solution Approach 1:
The patent divides a single wide-stripe laser diode into multiple narrow-stripe laser diodes arranged in an array. Each narrow-stripe diode maintains high beam quality with stripe widths of 3-5 microns, while the array configuration enables power scaling to 10 Watts or more by combining the output of multiple diodes through optical coupling elements.
Solution Approach 2:
The patent combines the output beams from multiple individual laser diodes using optical coupling elements (lenses, mirrors, or fiber optic couplers) to create a unified high-power beam. The optical elements merge the separate beams while maintaining the quality characteristics of individual narrow-stripe diodes, achieving both high power and high beam quality simultaneously.
2Reliability
If the lasing stripe width is kept small to maintain beam quality near the diffraction limit, then the beam quality remains high, but the available power is limited to less than 500 mW
Solution Approach 1:
The patent uses multiple narrow-stripe laser diodes (each 3-5 microns wide) arranged in arrays rather than a single wide-stripe diode. This segmentation allows each diode to operate in the high-quality TEM00 mode while the collective array output provides the required high power levels through optical combining.
Solution Approach 2:
The patent transitions from a single-dimensional (single diode) approach to a multi-dimensional array configuration. By arranging multiple narrow-stripe diodes in two-dimensional arrays and using optical elements to combine their outputs in different spatial dimensions, the system achieves power scaling without compromising beam quality.
3Power
If broad area diode lasers with stripe width of about 100 microns are used to achieve powers in excess of ten Watts, then the power level increases, but the beam quality is substantially reduced with significant asymmetries
Solution Approach 1:
The patent replaces broad area diodes (100 microns wide) with arrays of narrow-stripe diodes (3-5 microns wide). This segmentation maintains the high beam quality of narrow stripes while achieving the high power levels of broad area diodes through the combined output of multiple elements in the array.
Solution Approach 2:
The patent applies different stripe widths to different elements within the array, with each element optimized for high beam quality. The local quality of each narrow-stripe diode is preserved, and the overall system quality is maintained through proper optical combining, avoiding the asymmetries and quality degradation of broad area diodes.
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 significantly increases the efficiency of light coupling into multimode optical fibers, achieving higher power levels with improved beam quality, reducing energy loss and preserving laser beam power, thus addressing the limitations of semiconductor laser diodes in high-power applications.
Implementation Method 1
efficiently couple the outputs of two-dimensional laser diode arrays into optical fibers
Implementation Method 2
fast-axis collimating (FAC) lenses, wherein at least one FAC lens of the plurality of FAC lenses corresponds to each laser diode bar array
Data Source
AI summary
A system is provided for combining laser light sources. The system includes: a stack of laser diode bar arrays, comprising two or more laser diode bar arrays, each laser diode bar array having multiple laser diodes; a multimode optical fiber; and a plurality of optical elements disposed between the stack of laser diode bar arrays and the multimode optical fiber, configured to direct light from the stack of laser diode bar arrays to the multimode optical fibers, the plurality of optical elements further including: a plurality of fast-axis collimating (FAC) lenses, wherein at least one FAC lens of the plurality of FAC lenses corresponds to each laser diode bar array. At least one FAC lens of the plurality of FAC lenses is misaligned with respect to the corresponding laser diode bar array. At least one misaligned FAC lens has at least one of a translational position and a orientation relative to its corresponding laser diode bar array different from another FAC lens of the plurality of FAC lenses relative to its corresponding laser diode bar array.