Femtosecond Laser Pulse Trains for Sub-130 Nm Surface Nanostructures
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Solution Overview
Problem
Current methods for nanostructuring surfaces using femtosecond lasers struggle to achieve regular patterns with spatial periodicities less than 130 nm and often result in structures with low spatial periodicity or require lengthy processes.
Innovation Solution
A process involving irradiation of a solid material's surface with a femtosecond laser beam using pulse trains, where each pulse train consists of at least two pulses with specific peak fluences and temporal separations, allowing for the formation of regular patterns of nanostructures with spatial periodicities less than 130 nm, including multiple axes of symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a femtosecond laser beam is used to create laser-inscribed surface structures by focusing, then the equipment is simplified and no vacuum or white room is needed, but the characteristic size of the structures is greater than or equal to the diameter of the laser beam, making it impossible to obtain very small nanostructures
Solution Approach 1:
The patent uses a pulse train consisting of multiple periodic laser pulses with specific temporal spacing (500 fs to 150 ps between consecutive pulses) to create self-organized nanostructures. This periodic action allows the formation of LIPSS with spatial periodicity much smaller than the laser beam diameter, resolving the contradiction between equipment simplicity and manufacturing precision.
Solution Approach 2:
The patent changes the temporal parameters of laser pulses by using a pulse train with controlled peak-to-peak duration (ΔT between 500 fs and 150 ps) and specific fluence summation (10% to 70% of ablation threshold). This parameter change enables the formation of nanostructures with spatial periodicity below 130 nm while maintaining the simplicity of laser-based equipment.
2Ease of operation
If a femtosecond laser beam is used to create laser-inscribed surface structures, then contactless processing is achieved and various surface shapes can be worked on, but the manufacturing process is long since each cavity must be created individually
Solution Approach 1:
The pulse train with periodic pulses creates multiple nanostructures simultaneously through self-organization, rather than creating each cavity individually. This periodic action with controlled temporal spacing enables rapid formation of regular nanostructure patterns, significantly improving productivity while maintaining contactless processing capabilities.
Solution Approach 2:
The laser-induced periodic surface structures form through self-organization of the material under the pulse train, without requiring individual positioning or control of each nanostructure. This self-service mechanism accelerates the manufacturing process while preserving the ease of operation associated with contactless laser processing.
3Manufacturing precision
If a femtosecond laser beam is used with self-organisation to obtain nanostructures of very small size, then spatial periodicity below 100 nm can be achieved, but the structures obtained are limited to ripples with specific periodicity ranges (200 nm to 1000 nm) and low spatial periodicity
Solution Approach 1:
The patent achieves high spatial periodicity (below 130 nm, preferably below 100 nm) by precisely controlling the temporal spacing between pulses (ΔT between 500 fs and 150 ps) and the sum of peak fluences (10% to 70% of ablation threshold). This parameter control enables the formation of diverse nanostructure types including pits, holes, bumps, and gratings, enhancing both precision and adaptability.
Solution Approach 2:
The patent uses dynamic control of the pulse train parameters, including variable peak-to-peak duration and adjustable fluence summation, to adapt the nanostructure formation process to different materials and desired structures. This dynamic approach enables the creation of various nanostructure types with high spatial periodicity, resolving the limitation of fixed ripple patterns.
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 process effectively creates regular patterns of nanostructures with spatial periodicities as low as less than 100 nm, enabling the production of large-sized, symmetrical nanostructures on various materials without the need for vacuum conditions or complex equipment setups.
Implementation Method 1
irradiating a portion of the surface by a femtosecond laser beam... obtaining of a regular pattern of nanostructures on said portion of surface
Implementation Method 2
threshold fluence corresponding to a material ablation threshold for one pulse for said material
Data Source
AI summary
The invention relates to a process for nanostructuring the surface of a solid material in order to form a regular pattern of nanostructures on said surface, comprising:irradiating the surface by a plurality of pulse trains (20) of a femtosecond laser beam:each pulse train (20) comprises at least two pulses (21, 22),each pulse has a peak fluence, and a sum of the peak fluences of the pulses of a pulse train is between 10% and 70% of a threshold fluence corresponding to a material ablation threshold for one pulse for said material,two consecutive pulses of a pulse train are separated by a peak-to-peak duration ΔT between 500 fs and 150 ps,two consecutive pulse trains are separated by a duration greater than 10 ΔT,obtaining a regular pattern of nanostructures on said portion of surface, having a spatial periodicity lower than 130 nm.