Multimode Optical Fiber Supercontinuum Generation
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Solution Overview
Problem
Current polychromatic laser sources using micro-structured optical fibers face limitations in achieving high energy output and spectral continuity due to small core diameters and non-continuous generation of the conversion spectrum, which restricts their application in multiplex CARS micro-spectroscopy and other fields.
Innovation Solution
A device employing a pulsed laser source and a very multimodal optical fiber capable of delivering high-energy pulses, where the pump energy is relocated by nonlinear effects into the fundamental mode, generating a highly spatially coherent supercontinuum with a continuous spectrum across the visible and infrared domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a micro-structured optical fiber with small core diameter is used to achieve high energy confinement, then the light-matter interaction is increased and conversion efficiency is improved, but the damage threshold is quickly reached and high output energies cannot be delivered
Solution Approach 1:
The patent divides the optical fiber into two distinct sections: a first section with a small core diameter optimized for high nonlinearity and supercontinuum generation, and a second section with a large core diameter optimized for high damage threshold and energy delivery. This segmentation allows each section to perform its specialized function without compromise.
Solution Approach 2:
The first optical fiber section (small core) is effectively nested within the overall fiber structure, followed by the second section (large core). The pump beam propagates through both sections in sequence, with the small-core section generating the supercontinuum that is then carried by the large-core section to the output.
2Power
If a multimode optical fiber with large core diameter is used to deliver high energies, then higher energies can be guided, but the output radiation is distributed over several modes which greatly reduces the brightness
Solution Approach 1:
The patent separates the functions of brightness generation and energy delivery into two fiber sections. The first section (small core, single-mode or few-mode) generates the supercontinuum with high spatial coherence and brightness, while the second section (large core, multimode) carries the high energy output without compromising the spatial coherence established in the first section.
3Adaptability or versatility
If a micro-structured optical fiber is pumped in the normal dispersion domain, then the conversion spectrum is generated, but the generation is non-continuous due to stimulated Raman effect so true spectral continuity cannot be achieved
Solution Approach 1:
The patent changes the dispersion parameter of the optical fiber by using an anomalous dispersion regime instead of normal dispersion. This parameter change fundamentally alters the nonlinear dynamics, enabling soliton formation and soliton fission processes that generate continuous spectral broadening without the discontinuous Raman effect dominant in normal dispersion.
4Power
If the core diameter is increased to deliver high energies, then higher energies can be guided, but the capacity to modify dispersion is reduced and brightness is greatly reduced
Solution Approach 1:
The patent segments the fiber structure into two parts with different core diameters and dispersion characteristics. The first section has small core diameter enabling strong dispersion control and nonlinear effects, while the second section has large core diameter optimized for low loss and high energy delivery, with each section's dispersion properties tailored to its specific function.
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
The solution enhances the brightness and spectral continuity of the polychromatic beam, enabling its use in applications like multiplex CARS micro-spectroscopy and other analysis methods by achieving a quasi-monomode output with high brilliance and continuous spectral coverage.
Implementation Method 1
each optical fiber has at least ten modes, including one called fundamental and between which the pump energy of the primary photons is initially distributed, and is suitable for relocating this pump energy by Kerr effect in the fundamental mode
Implementation Method 2
generating the secondary photons of different wavelengths by conversions of wavelengths from the wavelength of the primary photons which are in the mode fundamental
Data Source
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Figure 4~6B
Figure 7
AI summary
The invention relates to a generation device (DG) which comprises: at least one pulsed laser source (SL) outputting primary photons having at least one wavelength in a single spatial mode and in pulses having high pump energy; shaping means (MM) acting on the primary photons in order to output an input beam (FE); and at least one optical fibre (FO) having at least ten modes between which the pump energy is initially distributed and suitable for relocating the latter by non-linear effect in a fundamental mode, before generating secondary photons with different wavelengths by converting wavelengths from the wavelength of the primary photons in the fundamental spatial mode.