SC-PCF and HC-PCF Radiation Source Assembly
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Solution Overview
Problem
Existing radiation source assemblies for generating broadband radiation face challenges such as large volume, alignment issues due to long beam paths, and potential damage from high peak intensities, which affect integration and performance.
Innovation Solution
A radiation source assembly comprising a solid core photonic crystal fiber (SC-PCF) and a hollow core photonic crystal fiber (HC-PCF) filled with a gaseous working medium, where the SC-PCF broadens the spectrum of pulses through normal group-velocity dispersion and the HC-PCF generates broadband radiation through nonlinear interaction with the gas medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a femtosecond pump source is used to generate broadband radiation via Modulational Instability in a gas-filled hollow core photonic crystal fiber, then a high-power spectrum with good flatness is achieved, but substantial pulse-to-pulse variations and undesirably high intensity noise occur
Solution Approach 1:
The patent changes the physical parameters of the system by switching from Modulational Instability to Soliton Self-Compression mechanism, and by using a solid core photonic crystal fiber instead of a gas-filled hollow core fiber. This parameter change transforms the radiation generation mechanism to achieve both high-power spectrum flatness and low intensity noise simultaneously
Solution Approach 2:
The solid core photonic crystal fiber acts as an intermediary component that enables Soliton Self-Compression of the femtosecond pump pulses. This intermediary structure facilitates the transformation of pulse characteristics to reduce intensity noise while maintaining spectrum quality
2Volume of stationary object
If the required volume of the femtosecond pump source is reduced, then integration into metrology tools becomes easier, but the beam path length through free-space decreases making alignment more sensitive to angular pointing changes
Solution Approach 1:
The patent merges the pump source and fiber input into a integrated assembly where the beam delivery optics are combined with the fiber coupling structure. This merging reduces the overall volume while maintaining alignment stability by eliminating the separate free-space beam path
Solution Approach 2:
The patent nests the fiber input structure within the pump source housing, creating a compact integrated assembly. The fiber is positioned and coupled within the pump source structure itself, reducing the overall volume while maintaining precise alignment through the nested configuration
3Illumination intensity
If the laser beam is focused into a high-pressure gas environment to generate broadband radiation, then spectral broadening is achieved, but heating and ionization of materials occur causing damage and decreased lifetime
Solution Approach 1:
The patent replaces the expensive and fragile high-pressure gas environment with a solid core photonic crystal fiber structure that is more durable and long-lasting. The solid fiber structure achieves the same spectral broadening effect without the harmful heating and ionization issues of high-pressure gas
Solution Approach 2:
The patent uses a composite photonic crystal fiber structure combining solid materials with photonic bandgap properties to achieve spectral broadening. This composite structure provides both the spectral broadening function and enhanced mechanical durability, eliminating material damage issues
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 proposed assembly enhances white-light conversion efficiency by up to 100% and reduces intensity noise, while also improving stability and reducing the size of the radiation source assembly, making it more integratable and efficient.
Implementation Method 1
the SC-PCF is configured to broaden a spectrum of the pulses of radiation by providing nonlinearity at normal group-velocity dispersion
Implementation Method 2
the HC-PCF is configured to generate broadband radiation by nonlinear interaction of the pulses of radiation with the gaseous working medium
Implementation Method 3
A proven way to reduce these variations is addressing Soliton Self-Compression (SSC) instead of MI: this nonlinear scheme offers two orders-of-magnitude lower intensity noise
Implementation Method 4
ultimately to a single several-femtosecond-long spike with a broad spectrum
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Radiation source assembly and method for generating broadband radiation. The radiation source assembly comprises a solid core photonic crystal fiber, SC-PCF, having an input end and an output end, wherein the input end is configured to receive pulses of radiation from a pump source; a hollow core photonic crystal fiber, HC-PCF, that is filled with a gaseous working medium and arranged to receive pulses of radiation at an input end of the HC-PCF that are output from the output end of the SC-PCF; and wherein the SC-PCF is configured to broaden a spectrum of the pulses of radiation by providing nonlinearity at normal groupvelocity dispersion, and the HC-PCF is configured to generate broadband radiation by nonlinear interaction of the pulses of radiation with the gaseous working medium, and output the broadband radiation at an output end of the HC-PCF.