VUV-UV-VIS Laser High-Order Harmonic Generation Phase Matching
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Solution Overview
Problem
Current techniques face challenges in extending high-order harmonic generation into the VUV-EUV-X-ray regions with efficient phase matching, as higher laser intensities lead to ionization, degrading phase matching conditions and reducing coherence, and using longer wavelengths results in lower single-atom yield.
Innovation Solution
Employing shorter wavelength driving lasers in the VUV-UV-VIS region with optimized loose-focus or waveguide geometries to achieve high ionization and balance dispersion contributions from atoms and ions, enhancing macroscopic and microscopic yields for coherent VUV-EUV-X-ray generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If higher laser intensities are used to extend high-order harmonic generation into shorter wavelengths, then the generation of soft x-rays at wavelengths shorter than 10 nm is achieved, but ionization of the gas increases dramatically, degrading phase matching conditions and reducing coherence length
Solution Approach 1:
The patent changes the fundamental parameter of laser wavelength from conventional near-IR (0.8 μm) to VUV-UV-VIS range (200-400 nm). This parameter change enables access to shorter X-ray wavelengths while operating at lower intensities, thereby avoiding excessive ionization and maintaining phase matching conditions. The wavelength shift fundamentally alters the interaction physics, allowing coherent radiation generation at wavelengths below 10 nm without the degradation issues encountered with intensity scaling.
2Length of moving object
If longer wavelength lasers are used to generate shorter wavelength X-rays, then the single-atom yield decreases significantly (scaling as λLaser−3 to λLaser−5.5), but the approach was initially thought to enable extended wavelength range
Solution Approach 1:
The patent inverts the conventional approach by using shorter wavelength lasers (VUV-UV-VIS) instead of longer wavelength lasers (mid-IR) to generate high-order harmonics. This inversion reverses the scaling relationship, causing single-atom yield to increase as λLaser−3 to λLaser−5.5 rather than decrease, thereby simultaneously achieving shorter output wavelengths and higher conversion efficiency.
3Productivity
If higher laser intensities are used to compensate for lower single-atom yield with longer wavelength lasers, then more X-ray photons can be generated, but the coherence length decreases due to ionization and the emission originates from a short region with low density of emitters
Solution Approach 1:
By changing the laser wavelength parameter to VUV-UV-VIS range, the patent achieves higher single-atom yield at lower intensities. This allows for extended coherence lengths while maintaining high X-ray flux, as the lower intensity avoids excessive ionization that would otherwise limit the interaction region length and emitter density.
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 results in high conversion efficiency, achieving quasi-monochromatic and tunable VUV-EUV-X-ray beams with extended coherence length and increased photon energies, overcoming previous limitations in phase matching and coherence.
Implementation Method 1
high-order harmonic generation into the VUV-EUV-X-ray regions of the spectrum
Implementation Method 2
laser intensities that cause substantial ionization of the nonlinear medium
Data Source
AI summary
A method for extending and enhancing bright coherent high-order harmonic generation into the VUV-EUV-X-ray regions of the spectrum involves a way of accomplishing phase matching or effective phase matching of extreme upconversion of laser light at high conversion efficiency, approaching 10−3 in some spectral regions, and at significantly higher photon energies in a waveguide geometry, in a self-guiding geometry, a gas cell, or a loosely focusing geometry, containing nonlinear medium. The extension and enhancement of the coherent VUV, EUV, X-ray emission to high photon energies relies on using VUV-UV-VIS lasers of shorter wavelength. This leads to enhancement of macroscopic phase matching parameters due to stronger contribution of linear and nonlinear dispersion of both atoms and ions, combined with a strong microscopic single-atom yield.