Prism-Based Light Separation for Laser-Pumped Plasma Sources
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Solution Overview
Problem
Current laser-sustained plasma light sources face challenges in efficiently separating pump light and collected light, particularly in the vacuum ultraviolet range, due to the limitations of cold mirror coatings, which are difficult to manufacture and not transparent to typical pump laser wavelengths below 200 nm.
Innovation Solution
A system that uses prism-based illumination separation elements, such as total internal reflection elements, dispersion elements, and evanescent field coupling elements, positioned between the pump source and the plasma collector, to spatially separate pumping illumination from the emitted broadband radiation without the need for cold mirrors, utilizing materials like CaF2 and MgF2 that are transparent to both wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cold mirror coatings are used to separate pump light and collected light, then light separation is achieved, but manufacturing complexity increases and transparency to pump laser wavelengths below 200 nm is lost
Solution Approach 1:
The patent changes the material parameters by using VUV-transparent materials (such as LiF, MgF2, CaF2, Al2O3, or SiO2) instead of conventional broadband dielectric mirror materials. This parameter change enables the optical elements to transmit VUV wavelengths below 200 nm while maintaining the light separation function through alternative optical designs that do not rely on cold mirror coatings.
Solution Approach 2:
The patent introduces VUV-transparent windows or optical elements as intermediary components between the pump source and the plasma region. These intermediaries allow pump light to pass through to excite the plasma while enabling separate collection of emitted light, replacing the need for cold mirror coatings that block VUV transmission.
2Adaptability or versatility
If broadband dielectric mirrors are used for light separation, then visible and near-UV light can be separated, but the system becomes complex and cannot handle wavelengths below 200 nm
Solution Approach 1:
The patent extends the spectral adaptability by selecting materials with appropriate optical properties for VUV transmission. By changing the material parameters to use VUV-transparent substances, the system achieves versatility across UV, VUV, and soft X-ray ranges without requiring complex cold mirror coatings, thereby reducing device complexity while expanding spectral coverage.
Solution Approach 2:
The patent creates universal optical elements (windows, lenses, mirrors) made from VUV-transparent materials that can handle multiple wavelength ranges including VUV, UV, and visible light. These multi-functional elements replace the need for specialized cold mirror coatings for different spectral ranges, simplifying the overall system design while maintaining broad spectral adaptability.
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
Effectively separates pump light and collected light across various spectral ranges, including VUV, UV, and visible light, enhancing the efficiency of light source systems used for inspection and metrology without the complexity of cold mirror coatings.
Implementation Method 1
one or more illumination separation prism elements positioned between a reflective surface of the collector and the pump source and arranged to spatially separate the pumping illumination including the first wavelength and the emitted broadband radiation including at least a second wavelength
Implementation Method 2
A system that uses prism-based illumination separation elements, such as total internal reflection elements
Implementation Method 3
an optical fiber optically coupling the pump source and the homogenizing element, wherein the optical fiber is configured to deliver pumping illumination to the homogenizing element at an off-axis location of the homogenizing element
Implementation Method 4
the plasma emits broadband radiation including at least a second wavelength
Implementation Method 5
laser-sustained plasma source
Data Source
AI summary
A system for separating plasma pumping light and collected broadband light includes a pump source configured to generate pumping illumination including at least a first wavelength, a gas containment element for containing a volume of gas, a collector configured to focus the pumping illumination from the pumping source into the volume of gas to generate a plasma within the volume of gas, wherein the plasma emits broadband radiation including at least a second wavelength and an illumination separation prism element positioned between a reflective surface of the collector and the pump source and arranged to spatially separate the pumping illumination including the first wavelength and the emitted broadband radiation including at least a second wavelength emitted from the plasma.