Optical Resonator With Through Opening For High Harmonic Generation
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Solution Overview
Problem
Current optical resonators face challenges in achieving high harmonic generation with low power losses and efficient coupling of radiation, particularly for fs radiation, due to limitations in geometric access and dispersion effects, which hinder scalability and intensity enhancement.
Innovation Solution
The proposed optical resonator design features a stable configuration with through openings in mirrors, allowing direct geometric access and minimizing losses by exploiting degeneracy of transverse eigenmodes, creating a quasi-imaging resonator with a Gouy phase that enables intensity maxima on the optical axis and reduced power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a through opening or input/output element is placed on the optical axis for direct geometric access, then radiation can be coupled in or out efficiently, but the through opening represents an obstacle to the circulating radiation causing power losses
Solution Approach 1:
The patent applies local quality by creating a localized intensity minimum precisely at the position of the through opening on the optical axis. The field distribution is engineered such that the intensity is minimal where the obstacle is located, while maintaining high intensity elsewhere in the beam path. This allows the through opening to be positioned without causing significant power losses, as the circulating radiation naturally avoids this region.
Solution Approach 2:
The patent changes the field distribution parameters of the circulating radiation by exciting specific transverse modes (such as higher-order Gaussian modes or Laguerre-Gaussian modes) that have intensity minima on the optical axis. By adjusting the mode composition and Gouy phase, the field distribution is optimized to minimize overlap with the through opening, thereby reducing power losses while maintaining geometric access.
2Loss of energy
If the hole radius is reduced to minimize power losses for Gaussian beams, then the obstacle size decreases, but the fraction of transmitted high harmonic power through the hole is also reduced
Solution Approach 1:
The patent exploits the local quality of different transverse modes by selecting modes that have intensity minima at the hole location. Higher-order modes such as GH(1,0) or Laguerre-Gaussian modes with azimuthal index l>0 naturally have zero or minimal intensity on the optical axis, allowing the hole to be positioned without blocking significant power. This enables the hole to be sized appropriately for high harmonic extraction while minimizing losses in the fundamental beam.
Solution Approach 2:
The patent transitions from considering only the fundamental Gaussian mode (single dimension) to utilizing higher-order transverse modes (multiple dimensions). By exciting modes with different spatial distributions in the transverse plane, the system gains an additional degree of freedom to position the hole in regions of low intensity, thereby resolving the trade-off between hole size and power transmission efficiency.
3Loss of energy
If dichroic mirrors are used for coupling radiation in or out, then major losses to circulating radiation can be avoided, but geometric access is limited and not available for all wavelengths
Solution Approach 1:
The patent extracts the coupling function from the mirrors themselves (dichroic mirrors) and places it on the optical axis through a through opening or separate input/output element. This separates the wavelength-selective coupling function from the beam path obstruction, allowing radiation to be coupled in or out at the optical axis without requiring dichroic mirrors. The through opening geometry can then be optimized for each wavelength independently, providing versatility across different wavelengths while maintaining low losses.
Solution Approach 2:
The patent creates a universal coupling mechanism that can handle different wavelengths without requiring wavelength-specific dichroic mirrors. By using a through opening on the optical axis with appropriately engineered field distributions, the same resonator structure can couple various wavelengths efficiently, making the system adaptable and versatile for different applications including fs radiation and high harmonics.
4Illumination intensity
If the resonator is designed to maximize intensity for non-linear processes, then the interaction intensity increases, but the field distribution becomes more sensitive to interference and losses
Solution Approach 1:
The patent changes the field distribution parameters by utilizing higher-order transverse modes that have characteristic intensity patterns with minima on the optical axis. This allows the resonator to be designed with through openings without significantly increasing sensitivity to interference, as the field naturally avoids the obstacle regions. The intensity enhancement for non-linear processes is maintained in the regions away from the optical axis where the field is strongest.
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 achieves high finesse and large power enhancements with minimal losses, enabling efficient coupling and scalability for high harmonic generation, particularly for fs radiation, while maintaining a simple and stable structure.
Implementation Method 1
the mirrors are arranged in such a way that a degeneracy of several transverse eigenmodes of the resonator occurs without an obstacle, through the combination of which an intensity minimum is achieved at the location of the through opening or the coupling-in or out-coupling element in the resonator with an obstacle
Implementation Method 2
creating a quasi-imaging resonator with a Gouy phase that enables intensity maxima on the optical axis and reduced power losses
Implementation Method 3
The direct geometric access to the optical axis enables the use of such a resonator for other applications, for example Thomson backscattering of electrons to generate coherent X-rays, pump-probe experiments or the detection of vacuum polarization
Data Source
Figure 1a~1e
Figure 2
Figure 3~4
AI summary
The invention relates to a stable optical resonator in which an obstacle is formed or arranged on the optical axis in the form of a through-opening (6) in one of the mirrors (1-4, 7, 8) or in the form of an incoupling or outcoupling element in order to allow a direct geometric access to the optical axis. The mirrors (1-4, 7, 8) of the resonator are arranged such that multiple transverse eigenmodes of the resonator decompose without an obstacle, and an intensity minimum is achieved by means of the combination of said eigenmodes at the location of the through-opening or the incoupling or outcoupling element in the resonator with an obstacle. Using this design, an optical resonator of high finesse, said resonator having a location with an intensity maximum on the optical axis, can be implemented in a simple manner, for example comprising only two curved mirrors with a design freedom with respect to the resonator length and the focus diameter.