Heat input and accumulation for ultrashort pulse processing with high average power

2018 ◽  
Vol 7 (3) ◽  
pp. 145-155 ◽  
Author(s):  
Johannes Finger ◽  
Benedikt Bornschlegel ◽  
Martin Reininghaus ◽  
Andreas Dohrn ◽  
Markus Nießen ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Heat Input ◽  
Ultrashort Pulse ◽  
Average Power ◽  
High Repetition Rate ◽  
Materials Processing ◽  
Heat Accumulation ◽  
Absorbed Energy ◽  
Pulse Processing ◽  
Ultrashort Laser

Abstract Materials processing using ultrashort pulsed laser radiation with pulse durations <10 ps is known to enable very precise processing with negligible thermal load. However, even for the application of picosecond and femtosecond laser radiation, not the full amount of the absorbed energy is converted into ablation products and a distinct fraction of the absorbed energy remains as residual heat in the processed workpiece. For low average power and power densities, this heat is usually not relevant for the processing results and dissipates into the workpiece. In contrast, when higher average powers and repetition rates are applied to increase the throughput and upscale ultrashort pulse processing, this heat input becomes relevant and significantly affects the achieved processing results. In this paper, we outline the relevance of heat input for ultrashort pulse processing, starting with the heat input of a single ultrashort laser pulse. Heat accumulation during ultrashort pulse processing with high repetition rate is discussed as well as heat accumulation for materials processing using pulse bursts. In addition, the relevance of heat accumulation with multiple scanning passes and processing with multiple laser spots is shown.

scholarly journals The challenges of productive materials processing with ultrafast lasers

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Rudolf Weber ◽  
Thomas Graf
Keyword(s):  
Ultrafast Lasers ◽  
Average Power ◽  
Processing System ◽  
Processing Parameters ◽  
Materials Processing ◽  
High Tech ◽  
X Rays ◽  
Heat Accumulation ◽  
Physical Limitations ◽  
Air Breakdown

Abstract Materials processing with ultrafast lasers with pulse durations in the range between about 100 fs and 10 ps enable very promising and emerging high-tech applications. Moreover, the average power of such lasers is steadily increasing; multi kilowatt systems have been demonstrated in laboratories and will be ready for the market in the next few years, allowing a significantly increase in productivity. However, the implementation of ultrafast laser processes in applications is very challenging due to fundamental physical limitations. In this paper, the main limitations will be discussed. These include limitations resulting from the physical material properties such as the ablation depth and the optimal fluence, from processing parameters such as air-breakdown and heat accumulation, from the processing system such as thermal focus shift, and from legal regulations due to the potential emission of soft X-rays.

scholarly journals Sequences of Sub-Microsecond Laser Pulses for Material Processing: Modeling of Coupled Gas Dynamics and Heat Transfer

2019 ◽  
Vol 9 (22) ◽  
pp. 4785
Author(s):  
Gusarov ◽  
Kovalev
Keyword(s):  
Heat Transfer ◽  
Laser Radiation ◽  
Laser Processing ◽  
Gas Dynamics ◽  
Optical Breakdown ◽  
Single Pulse ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
Heat Accumulation ◽  
Pulse Separation

Multipulse laser processing of materials is promising because of the additional possibilities to control the thickness of the treated and the heat-affected zones and the energy efficiency. To study the physics of mutual interaction of pulses at high repetition rate, a model is proposed where heat transfer in the target and gas-dynamics of vapor and ambient gas are coupled by the gas-dynamic boundary conditions of evaporation/condensation. Numerical calculations are accomplished for a substrate of an austenitic steel subjected to a 300 ns single pulse of CO2 laser and a sequence of the similar pulses with lower intensity and 10 μs inter-pulse separation assuring approximately the same thermal impact on the target. It is revealed that the pulses of the sequence interact due to heat accumulation in the target but they cannot interact through the gas phase. Evaporation is considerably more intensive at the single-pulse processing. The vapor is slightly ionized and absorbs the infrared laser radiation by inverse bremsstrahlung. The estimated absorption coefficient and the optical thickness of the vapor domain are considerably greater for the single-pulse regime. The absorption initiates optical breakdown and the ignition of plasma shielding the target from laser radiation. The multipulse laser processing can be applied to avoid plasma ignition.

scholarly journals Targets with cone-shaped microstructures from various materials for enhanced high-intensity laser–matter interaction

2021 ◽  
Vol 9 ◽  
Author(s):  
Tina Ebert ◽  
René Heber ◽  
Torsten Abel ◽  
Johannes Bieker ◽  
Gabriel Schaumann ◽  
...  
Keyword(s):  
Laser Pulse ◽  
High Intensity ◽  
Ultrashort Laser Pulse ◽  
Process Chain ◽  
Pulse Processing ◽  
High Intensity Laser ◽  
Matter Interaction ◽  
Different Characteristics ◽  
Ultrashort Laser ◽  
Intensity Laser

Abstract Targets with microstructured front surfaces have shown great potential in improving high-intensity laser–matter interaction. We present cone-shaped microstructures made out of silicon and titanium created by ultrashort laser pulse processing with different characteristics. In addition, we illustrate a process chain based on moulding to recreate the laser-processed samples out of polydimethylsiloxane, polystyrol and copper. With all described methods, samples of large sizes can be manufactured, therefore allowing time-efficient, cost-reduced and reliable ways to fabricate large quantities of identical targets.

scholarly journals Sputtering of Neutral Molecules and Molecular Ions From the Adenine Crystal Surface Induced by the UV Picosecond Laser Pulse

1982 ◽  
Vol 1 (1) ◽  
pp. 37-43 ◽  
Author(s):  
V. S. Antonov ◽  
V. S. Letokhov ◽  
Yu. A. Matveyets ◽  
A. N. Shibanov
Keyword(s):  
Laser Radiation ◽  
Kinetic Energy ◽  
Crystal Surface ◽  
Picosecond Laser ◽  
Laser Pulses ◽  
Molecular Ions ◽  
Laser Radiation Intensity ◽  
Ion Sputtering ◽  
Absorbed Energy ◽  
Picosecond Laser Pulse

This paper presents the results of observation of sputtering of neutral molecules and ions from the crystal adenine surface induced by fourth-harmonic Nd:YAG laser radiation with a pulse duration of 30 ps. The energy fluence of laser pulses was in the region (1–3) × 10−4 J/cm2. The kinetic energy distribution of the sputtered molecules spreads up to 0.7 eV. The experiment shows that the threshold of adenine molecular ion sputtering is connected with absorbed energy density in upper layers of the crystal surface but not by laser radiation intensity.

Results of Comparisons of the Russian and German Standards of the Unit of Average Power of Laser Radiation at Wavelengths of 0.532, 1.064, and 10.6 μm

2013 ◽  
Vol 56 (8) ◽  
pp. 942-948
Author(s):  
A. A. Liberman ◽  
S. A. Moskalyuk ◽  
M. V. Ulanovskii ◽  
B. B. Khlevnoi
Keyword(s):  
Laser Radiation ◽  
Average Power
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