Compact VUV Plasma Light Source With Noble-Gas Long-Pass Filtering
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Solution Overview
Problem
Existing laser-sustained plasma (LSP) light sources face limitations in generating vacuum ultraviolet (VUV) light efficiently due to damage to optical components from short-wavelength radiation and the challenge of maintaining compact size under high pressure, with limited choices for materials that can withstand VUV wavelengths and structural integrity.
Innovation Solution
A compact laser-sustained plasma light source using a gas mixture of noble gases and a filter tube to absorb harmful wavelengths, creating a reverse vortex flow pattern that protects downstream optical elements and allows for efficient VUV light generation with long-pass filtering, reducing damage and enabling smaller, more durable optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If MgF2 or CaF2 windows are used to transmit VUV light, then light transmission is achieved, but the windows degrade rapidly due to short-wavelength radiation damage
Solution Approach 1:
A filter tube filled with noble gas (xenon, krypton, or argon) is introduced as an intermediary substance between the plasma source and the optical windows. The noble gas absorbs harmful short-wavelength radiation (below 125 nm) through its absorption lines, protecting the MgF2 or CaF2 windows from degradation while allowing useful VUV light transmission
Solution Approach 2:
The harmful short-wavelength radiation that causes window damage is converted into a beneficial filtering mechanism. The noble gas in the filter tube absorbs the harmful wavelengths below 125 nm, and this absorption characteristic is used to protect the optical system while maintaining VUV light generation efficiency
2Productivity
If the window is placed close to the plasma to improve light collection, then collection efficiency increases, but the window damages rapidly from plasma radiation
Solution Approach 1:
The filter tube filled with noble gas serves as a protective intermediary positioned between the plasma and the optical windows. It allows the windows to be placed closer to the plasma for improved light collection efficiency while the noble gas absorbs harmful plasma radiation, preventing window damage
Solution Approach 2:
The harmful short-wavelength radiation component is extracted from the broadband plasma radiation through selective absorption by the noble gas in the filter tube. This separation allows the useful VUV light to reach the windows while the harmful radiation is removed
3Reliability
If the window is placed far from the plasma to reduce damage, then window durability improves, but the window must be larger and thicker which increases device size
Solution Approach 1:
The filter tube with noble gas acts as a protective intermediary that enables the optical windows to be positioned closer to the plasma source. This eliminates the need for larger, thicker windows that would be required if the windows were placed far from the plasma, thus maintaining a compact device size while ensuring window durability
4Illumination intensity
If aluminum mirrors protected by MgF2 coating are used for VUV reflection, then reflection efficiency is achieved, but the mirrors damage rapidly by light less than 125 nm
Solution Approach 1:
The filter tube filled with noble gas is positioned upstream of the aluminum mirrors with MgF2 coating. The noble gas absorbs harmful radiation below 125 nm before it reaches the mirrors, protecting them from rapid damage while allowing efficient VUV light reflection to occur
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 effectively protects optical components from damage, allows for smaller and more durable design, and enhances the efficiency of VUV light generation, reducing noise and heat load on windows and mirrors.
Implementation Method 1
a laser pump source configured to generate an optical pump, wherein the laser pump source is configured to direct the optical pump through the input optical window to sustain a plasma within the filter tube
Implementation Method 2
to sustain a plasma within the filter tube, wherein the plasma generates broadband light
Implementation Method 3
wherein the first noble gas absorbs a portion of the broadband light within a first wavelength band and a second wavelength band
Implementation Method 4
wherein the filter tube is configured to absorb a portion of the broadband light having a wavelength below a selected wavelength threshold, wherein absorption of broadband light by the first noble gas and the filter tube provide long-pass filtering
Data Source
AI summary
A compact LSP broadband light includes a gas containment structure containing a mixture of a first noble gas and a second noble gas, a filter tube positioned within the gas containment structure, an input window, and a pump source. The laser pump source directs an optical pump through the input window to sustain a plasma within the filter tube. The first noble gas absorbs broadband light within a first and a second wavelength band. The filter tube absorbs broadband light having a wavelength below a selected threshold. The absorption of broadband light by the first noble gas and the filter tube provide long-pass filtering to protect one or more downstream optical elements. The gas containment structure includes an output optical window for transmission of filtered broadband light. The gas containment structure includes a gas inlet and outlet for generating a reverse vortex flow pattern within the filter tube.