Wedge-on-Mirror Output Coupler for Harmonic Extraction
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Solution Overview
Problem
Current methods for output coupling high-harmonic radiation from enhancement cavities face limitations due to high intra-cavity losses, dispersion, and nonlinear effects, particularly with conventional Brewster plate output couplers, which restrict circulating powers to below 15 kW and compromise optical quality and heat dissipation.
Innovation Solution
A method utilizing a wedge-on-mirror output coupler with a refractive plate element and a deflection mirror, where the primary radiation beam is split based on wavelength-selective reflection, allowing for efficient separation and combination of fundamental and higher harmonic radiation components, enhancing output coupling efficiency while minimizing losses and dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional Brewster plate output coupler is used, then the setup is simple and easy to operate, but the circulating power is limited to below 15 kW and heat dissipation is compromised
Solution Approach 1:
The output coupler is segmented into two distinct functional layers: a Brewster plate layer for fundamental wavelength transmission and a diffraction grating layer for harmonic wavelength diffraction. This segmentation allows each layer to be optimized independently for its specific function, enabling high circulating power while maintaining manageable structural complexity.
Solution Approach 2:
The patent merges two previously separate optical components (Brewster plate and diffraction grating) into a single integrated output coupler structure. This combining allows the fundamental beam to pass through the Brewster plate while harmonics are diffracted by the grating layer, achieving both functions in one element and enabling higher circulating powers.
2Reliability
If a conventional Brewster plate output coupler is used, then the device structure is simple, but optical quality deteriorates and heat dissipation is compromised
Solution Approach 1:
By segmenting the output coupler into separate functional layers (Brewster plate and diffraction grating), each layer can be independently optimized for its specific optical function. The Brewster plate is optimized for fundamental wavelength transmission with minimal dispersion, while the grating layer is optimized for harmonic diffraction, thereby maintaining high optical quality.
Solution Approach 2:
The output coupler uses a composite structure combining different optical materials and functions: a Brewster plate material optimized for fundamental wavelength and a diffraction grating structure optimized for harmonic wavelengths. This composite approach allows each material to be selected for its optimal performance characteristics, improving overall optical quality.
3Productivity
If intra-cavity power is increased to improve HHG efficiency, then conversion efficiency increases, but intra-cavity losses and nonlinear effects increase
Solution Approach 1:
The diffraction grating layer extracts harmonic wavelengths from the circulating beam by diffracting them out of the cavity at a different angle than the fundamental wavelength. This extraction mechanism allows harmonics to be coupled out efficiently without requiring the fundamental beam to experience additional losses, thereby improving conversion efficiency while minimizing intra-cavity losses.
Solution Approach 2:
The output coupler provides local quality optimization by having different optical properties at different wavelengths: the Brewster plate layer provides minimal loss and dispersion for the fundamental wavelength, while the diffraction grating layer provides efficient coupling out for harmonic wavelengths. This local optimization allows high circulating power with minimal overall losses.
4Productivity
If intra-cavity power is increased, then HHG efficiency improves, but dispersion affects the circulating electric field
Solution Approach 1:
The Brewster plate layer is specifically designed to provide minimal group delay dispersion for the fundamental wavelength, ensuring that the circulating electric field maintains its temporal and spatial profile. This local optimization at the fundamental wavelength ensures precise overlap with the seeding field even at high circulating powers, while the diffraction grating layer handles harmonic extraction without affecting the fundamental field quality.
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 enables robust, efficient heat transport and control of dispersion, allowing for higher circulating powers and improved optical quality, potentially exceeding 5000 times the power enhancement factor compared to conventional methods.
Implementation Method 1
The plate element and the deflection mirror are configured such that the fundamental radiation is transmitted through the plate element and reflected on the deflection mirror, while the higher harmonic radiation is reflected at a plate surface of the plate element
Implementation Method 2
a refractive plate element onto different reflected beam paths
Implementation Method 3
the radiation components are reflected in a wavelength-selective manner at different interfaces of an optical device having a deflection mirror and a refractive plate element
Data Source
AI summary
A method of spatially splitting a primary radiation beam (1) with a first radiation component (2) including an optical wavelength and a second radiation component (3) having a wavelength shorter than the first radiation component wavelength, said second radiation component (3) having a second or higher harmonic wavelength relative to the optical wavelength, comprises directing the primary radiation beam (1) onto a deflection mirror (10) having a reflective mirror surface (12) and carrying a refractive plate element (20), reflecting the first radiation component (2) at the reflective mirror surface (12) and reflecting the second radiation component (3) at an exposed plate surface (22) of the refractive plate element (20), wherein the reflected radiation components (4, 5) travel along different beam paths. Furthermore, a method of spatially combining a first beam path of a first radiation component (2) and a second beam path of a second radiation component (3) is described, wherein the beam splitting method is reversed. Further more, an optical device for implementing the above methods and applications of the methods are described.