Circular Diffraction Grating for 2D Laser Beam Combining
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Solution Overview
Problem
Current 2D coherent beam combining techniques face challenges in simplifying geometrical design and implementing self-feedback mechanisms, leading to complex optical or electrical systems for phase locking and spectral overlap, especially when scaling up to high power laser systems.
Innovation Solution
A circular or spiral diffraction grating is used in an intra-cavity laser design to combine all laser sources, providing passive phase locking and eliminating the need for double diffraction gratings, allowing for compact and scalable high power laser systems with improved brightness and beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a first-order grating stack is used to combine multiple wavelengths in 2D configuration, then spatial brightness is improved, but spectral bandwidth increases
Solution Approach 1:
The patent segments the beam combining function into two distinct components: a first diffractive element for spatial beam combining and a second diffractive element for wavelength multiplexing. This segmentation allows independent optimization of each function, enabling high spatial brightness through 2D beam combining while maintaining narrow spectral bandwidth through selective wavelength combination.
Solution Approach 2:
The patent introduces an intermediary wavelength selection mechanism between the multiple wavelength sources and the final combined beam. The second diffractive element acts as a mediator that selectively combines specific wavelengths while rejecting others, thereby controlling the spectral bandwidth of the output beam independent of the spatial combining process.
2Reliability
If feedback systems are used to passively or actively lock phase of laser sources, then coherent beam combining is achieved, but device complexity increases
Solution Approach 1:
The patent implements a self-service phase locking mechanism where the diffractive elements and laser sources are configured to automatically achieve phase coherence without external feedback control. The geometric arrangement and diffractive optics create inherent phase relationships that self-align the combined beam, eliminating the need for complex active or passive feedback systems.
Solution Approach 2:
Instead of using feedback to enforce phase locking, the patent inverts the approach by designing the optical system to naturally produce phase-locked output through its structural configuration. The diffractive elements are designed such that the desired coherent combination is the default state, requiring no additional control mechanisms.
3Power
If the number of combined laser sources is increased, then laser power is scaled up, but spectral bandwidth broadens making phase locking more difficult
Solution Approach 1:
The patent segments the wavelength combination process to handle multiple laser sources independently. Each laser source operates at a distinct wavelength that is processed through the diffractive elements separately, allowing the system to scale to many sources without cumulative spectral broadening. The second diffractive element recombines these independently managed wavelengths.
Solution Approach 2:
The diffractive elements are designed with universal functionality to handle any number of wavelength channels simultaneously. The optical design accommodates scalable addition of laser sources without requiring redesign, as the diffractive structures inherently manage multiple wavelengths through their geometric configuration rather than source-specific tuning.
4Productivity
If two separate diffractive gratings are used for horizontal and vertical beam combining, then 2D coherent combining is achieved, but device complexity increases
Solution Approach 1:
The patent merges the horizontal and vertical beam combining functions into a unified diffractive optical system. Rather than requiring two separate grating stacks oriented at right angles, the invention uses integrated diffractive elements that perform both spatial dimensions of beam combination simultaneously, reducing the number of discrete optical components required.
Solution Approach 2:
The diffractive elements are designed with multi-functionality to perform both spatial beam combining and wavelength multiplexing operations. This universal design consolidates multiple optical functions into single components, eliminating the need for separate horizontal and vertical grating systems while achieving equivalent 2D coherent combining performance.
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 simplifies the design of 2D coherent beam combining, achieving better spectral bandwidth and beam quality compared to existing methods, while maintaining compactness and scalability, and eliminates the need for complex feedback systems.
Implementation Method 1
A circular or spiral diffraction grating is used in an intra-cavity laser design to combine all laser sources
Data Source
AI summary
Examples of combining multiple laser beams into a single laser beam by using a circular or spiral diffraction grating are described. The multiple laser beams can be combined coherently or incoherently depending on the geometrical layout of the laser beams.