Continuous-Wave Laser Plasma Illumination Source
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Solution Overview
Problem
Current laser-sustained plasma illumination sources face limitations in generating broadband light due to operating temperature constraints and inefficient energy conversion, particularly for small device feature inspection, where high-power broadband light is needed.
Innovation Solution
A continuous-wave laser-sustained plasma system is developed, utilizing a chamber with a solid or liquid plasma-forming material and a buffer material, where continuous-wave pump illumination is focused to generate or maintain a plasma, allowing for broadband radiation emission across various pressure ranges, including high pressures, and enabling cooler plasma formation compared to pulsed lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If pulsed laser irradiation is used to generate plasma, then broadband radiation can be produced, but the operating temperature becomes too high and energy conversion efficiency decreases
Solution Approach 1:
The patent applies periodic pulsed laser irradiation to generate plasma in a frozen plasma-forming material. By using periodic pulses rather than continuous irradiation, the system can maintain plasma formation while allowing cooling intervals, thus reducing overall plasma temperature and improving energy conversion efficiency compared to continuous high-power laser operation.
Solution Approach 2:
The patent utilizes phase transitions of the plasma-forming material (specifically frozen xenon or other noble gases) to enable plasma generation at lower temperatures. The frozen target absorbs laser energy efficiently and transforms into plasma through phase transition, reducing the need for extreme heating and improving energy conversion efficiency.
2Loss of energy
If continuous-wave pump illumination is focused to generate plasma, then broadband radiation is produced with improved energy efficiency, but the system complexity increases due to precise focusing requirements
Solution Approach 1:
The patent introduces a frozen plasma-forming material target as an intermediary between the continuous-wave laser and the plasma. This target serves as a mediator that absorbs the laser energy and facilitates plasma formation, simplifying the optical system by eliminating the need for extremely precise direct focusing while maintaining high energy conversion efficiency.
Solution Approach 2:
The patent changes the physical state parameter of the plasma-forming material to frozen phase, which dramatically improves laser absorption efficiency. This parameter change allows the use of continuous-wave lasers with less complex focusing optics while achieving the same or better energy conversion efficiency compared to more complex pulsed systems.
3Adaptability or versatility
If a sealed lamp containing working material is used, then plasma can be sustained, but the operating temperature limits the possible species that can be contained
Solution Approach 1:
The patent extracts the working material from a sealed lamp environment and places it as a frozen target in an open or controlled atmosphere. This extraction eliminates the temperature constraints of sealed lamps, allowing the use of various species including those that would decompose or react at lamp operating temperatures, thus expanding species selection flexibility.
Solution Approach 2:
The patent uses an inert atmosphere (vacuum or noble gas environment) to contain the plasma, replacing the sealed lamp approach. This inert environment allows for lower operating temperatures while preventing unwanted chemical reactions, enabling the use of temperature-sensitive species that would be incompatible with traditional high-temperature sealed lamp operation.
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 system effectively generates broadband radiation with improved energy conversion efficiency and operational flexibility, suitable for inspecting ever-shrinking device features by producing cooler plasmas and accommodating high pressures, enhancing the capabilities of existing illumination sources.
Implementation Method 1
An optical system for generating broadband light via light-sustained plasma formation is disclosed
Implementation Method 2
to generate a plasma by excitation of at least the plasma-forming material... to receive broadband radiation emanated from the plasma
Implementation Method 3
a set of focusing optics configured to focus the continuous-wave pump illumination through the buffer material to an interface between the buffer material and the plasma-forming material
Data Source
Figure 1
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AI summary
An optical system for generating broadband light via light-sustained plasma formation includes a chamber, an illumination source, a set of focusing optics, and a set of collection optics. The chamber is configured to contain a buffer material in a first phase and a plasma-forming material in a second phase. The illumination source generates continuous-wave pump illumination. The set of focusing optics focuses the continuous-wave pump illumination through the buffer material to an interface between the buffer material and the plasma-forming material in order to generate a plasma by excitation of at least the plasma-forming material. The set of collection optics receives broadband radiation emanated from the plasma.