Laser-Pumped Plasma Light Source Stability
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Solution Overview
Problem
Existing laser-pumped plasma light sources face instability due to turbulence of convective gas flows, which affects the brightness and stability of the light source, despite efforts to optimize geometry and collection methods.
Innovation Solution
Achieving high stability and brightness by maintaining a high-pressure gas environment with a density of 50-100 bar, minimizing gas density and refraction through temperature control, and using a focused CW laser to sustain plasma at 600-900 K, thereby reducing turbulence and increasing plasma density without increasing volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the power of a continuous wave laser is increased to increase plasma temperature, then the plasma temperature increases, but the plasma volume increases and additional power is released by radiation and thermal conductivity, stabilizing the temperature
Solution Approach 1:
The patent employs pulsed lasers with high repetition rate instead of continuous wave lasers to heat the plasma. This periodic heating approach allows the plasma to be heated to high temperatures during the pulse duration while having time to cool and contract between pulses, thus avoiding the volume expansion that occurs with continuous heating. The pulsed nature of the laser enables temperature increases without the stabilizing feedback mechanism that limits continuous wave laser heating.
Solution Approach 2:
The patent dynamically adjusts the laser parameters including pulse duration, repetition rate, and power to optimize plasma temperature while controlling volume. By making the heating process dynamic rather than static, the system can achieve higher temperatures without the plasma volume expanding to release excess energy, thus resolving the contradiction between temperature increase and volume stabilization.
2Illumination intensity
If pulsed lasers with high repetition rate are used to increase brightness, then the brightness increases, but the stability of the light source deteriorates due to turbulence of convective gas flows
Solution Approach 1:
The patent optimizes multiple parameters including pulse duration, repetition rate, and laser power to achieve a balance between brightness and stability. By carefully selecting these parameters, the system generates sufficient brightness while minimizing the intensity and duration of convective flows that cause instability. The optimized parameter set reduces turbulence effects while maintaining high brightness output.
Solution Approach 2:
The patent uses pulsed laser heating that exceeds the minimum required energy input during the pulse duration, creating a temporary high-brightness state. The excessive heating during the pulse is followed by a cooling period between pulses, which allows the system to reset and maintain stability. This partial action approach enables high brightness achievement without continuous excessive heating that would cause sustained turbulence.
3Quantity of substance
If the density of gas particles is increased to increase plasma density, then the plasma density increases, but the refraction increases leading to brightness instability
Solution Approach 1:
The patent changes the gas density parameter to an optimal value that is lower than conventional approaches. This reduced gas density decreases the refraction effects that cause brightness instability while still providing sufficient gas atoms to sustain the plasma discharge. The optimized gas density parameter achieves a balance between maintaining plasma density and minimizing refraction-induced instability.
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 approach results in ultra-high brightness with ultra-low brightness instability, achieving spectral brightness over 50 mW/(mm2·sr) and relative instability less than 0.1%, optimizing conditions for broadband radiation generation.
Implementation Method 1
a temperature of an inner surface of the chamber is in a range from 600 to 900 K or optionally higher
Implementation Method 2
a gas pressure in the chamber is provided close to 50 bar or more
Implementation Method 3
a region of radiating plasma sustained in the chamber by a focused beam of a continuous wave (CW) laser
Implementation Method 4
COD-based light sources with a plasma temperature of about 15,000 K are among the highest brightness continuous light sources
Implementation Method 5
produce high-brightness light in the ultra-violet (UV), visible and near infrared (NIR) spectral bands
Implementation Method 6
a plasma temperature of about 15,000 K are among the highest brightness continuous light sources in a wide spectral range between about 0.1 μm and 1 μm
Implementation Method 7
The problem of increasing the stability and control of convective gas flows, the turbulent flow of which leads to instability of the brightness of the light source
Implementation Method 8
minimizing the gas density and the refraction, associated with this density, in turn, provides highly efficient suppression of the light source brightness instability, associated with the turbulence of convective gas flows
Data Source
AI summary
The invention relates to plasma light sources with a continuous optical discharge (COD). The light source contains a gas filled chamber with a region of radiating plasma sustained by a focused beam of a CW laser. A density of gas particles in the chamber is less than 90·1019 cm−3 and a temperature of the chamber is in a range from 600 to 900 K or optionally higher. Preferably the density of gas particles is as low as possible and the temperature of the inner surface of the chamber at operation is as high as possible under providing a gas pressure in the chamber of about 50 bar or more. The technical result of the invention consists in providing COD sustaining conditions, which are optimal for achieving high stability and high brightness of the radiating plasma, in the creation on this basis of broadband light sources with ultra-high brightness and stability.