Femtosecond Plasma Grating Spectroscopy for LIBS Signal Enhancement
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Solution Overview
Problem
Existing double-pulse laser-induced breakdown spectroscopy (LIBS) techniques face challenges such as strong background spectral lines in the early stage of plasma generation, high cost due to the requirement of two lasers, and complex device structures.
Innovation Solution
A multipulse-induced spectroscopy method based on a femtosecond plasma grating, where a femtosecond pulse is used to pre-excite the sample and form a plasma grating, followed by a post-pulse at an angle to excite the sample and generate a plasma, with the post-pulse including one or more femtosecond pulses and a time interval less than the lifetime of the plasma grating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a nanosecond pulse is used to heat the plasma, then the heating effect is improved, but the background spectral line intensity increases and detection sensitivity deteriorates
Solution Approach 1:
The patent changes the pulse width parameter from nanosecond to femtosecond scale, which fundamentally alters the plasma generation mechanism. The femtosecond pulse duration (10^-15 seconds) is so short that it ionizes the sample before significant thermalization occurs, avoiding the formation of strong background continuum radiation while still achieving sufficient plasma temperature for atomic emission.
Solution Approach 2:
The patent employs multiple femtosecond pulses with specific time intervals between them. The first pulse creates a plasma grating structure, and subsequent pulses interact with this grating to enhance atomic line emission. This periodic pulsed action allows controlled plasma formation and excitation while maintaining low background levels.
2Power
If two lasers are used to provide femtosecond and nanosecond pulses, then the plasma heating and excitation are improved, but the device complexity and cost increase
Solution Approach 1:
The patent merges the functions of two separate lasers (femtosecond and nanosecond) into a single femtosecond laser system. By using multiple pulses from one femtosecond laser source with different temporal and spatial characteristics, the system achieves both plasma formation and excitation capabilities that previously required two different laser types, thereby reducing device complexity and cost.
Solution Approach 2:
The single femtosecond laser is designed to perform multiple functions: creating the initial plasma grating, providing subsequent excitation pulses, and enabling both heating and atomic line emission enhancement. This multi-functional approach replaces the need for specialized nanosecond and femtosecond lasers, simplifying the overall system architecture.
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 method improves the signal-to-noise ratio and detection sensitivity by enhancing the optical power density and electron density within the plasma channel, allowing for effective analysis of elemental composition without the need for two lasers, thus simplifying the device structure and reducing costs.
Implementation Method 1
Laser-induced breakdown spectroscopy (LIBS) is an elemental composition analysis technique used in elemental detection for samples of different applications. With the LIBS, a high-energy and short-pulse-width laser pulse is used as an excitation source and is focused on a sample.
Implementation Method 2
the angle is a first-order or high-order Bragg angle
Implementation Method 3
receiving and analyzing a fluorescence emitted from the plasma to determine element information of the sample
Data Source
AI summary
A multipulse-induced spectroscopy method based on a femtosecond plasma grating includes: pre-exciting a sample on a stage by providing a femtosecond pulse to form the femtosecond plasma grating; providing a post-pulse on the sample at an angle to excite the sample to generate a plasma, wherein the post-pulse comprises one or more femtosecond pulses, there is a time interval between the femtosecond pulse and the post-pulse, and the time interval is less than a lifetime of the femtosecond plasma grating; and receiving and analyzing a fluorescence emitted from the plasma to determine element information of the sample.