Time-resolved emission and scattering imaging of plume dynamics and nanoparticle ejection in femtosecond laser ablation of silver thin films

Park, Minok; Jeun, Jinhong; Han, Gyoowan; Grigoropoulos, Costas P.

doi:10.1063/5.0009227

Cited by 10 publications

(9 citation statements)

References 20 publications

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“…Previous work on femtosecond laser irradiation, has shown that the presence of pressurized plasma plumes may drive the motion of NPs to oblique angles due to the Gaussian spatial distribution of the laser, with a higher local laser intensity in the center as compared to the peripheral areas. 10 Likewise, in the case of temporally modulated CW pulses we observed extended emitting plumes at 0.4 μs after the pulse in Fig. 2 (b-i), with the purple dotted line showing the outline of the expanding plasma.…”

supporting

confidence: 55%

“…2. Interestingly, the emission persistence (lifetime) of these plasmas is much longer (500 μs) than those typical produced by pulsed lasers at atmospheric pressure (~1 μs for femtosecond laser 10,13 and ~10 μs for nanosecond laser 20,21 ). We anticipate that such AlO formation would be suppressed under vacuum or inert conditions due to the lack of ambient oxygen.…”

mentioning

confidence: 92%

“…In addition to interdepended physical processes 9,10 (plasma plumes, nano-/micro-particles, liquid phase expulsion 9 ), chemical transformations and new species formation in the laser-induced plasma state may play a pivotal role in the ablation process. Therefore, a fundamental-level understanding of the complex underlying physical and chemical mechanisms is needed to control and optimize processes for aforementioned applications.…”

mentioning

confidence: 99%

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Spatio-temporal ablation dynamics and plasma chemistry of aluminum induced by temporally modulated ytterbium fiber laser

Park

Balkey

Mao

et al. 2021

Applied Physics Letters

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In this work, we studied single-pulse ablation dynamics of temporally modulated continuous wave laser-material interaction with Al using in situ multimodal time-resolved diagnostics, that describe in detail the associated physical and chemical processes. Timeresolved scattering, emission imaging, and optical emission spectroscopy unveiled a sequence of events spread out across three distinct phases: (i) early phase ablation process, associated with particle generation and liquid Al columns formation (< 20 μs), (ii) secondary detonation when sufficient ejected material is accumulated over the surface (20-50 μs), and (iii) molten liquid Al pool oscillation on the surface, followed by large droplet ejection from the liquid pool (100-500 μs). Atomic Al and AlO were observed with optical emission spectroscopy at different ratios during the entire lifetime of the event, verifying the formation of oxidized Al vapor upon its interaction with air. Morphological and compositional characterization confirmed surface oxidation and material resolidification in the form of protrusions produced during the irradiation process. This work provides insights into the complex physical and chemical mechanisms of single-pulse ablation in the sub-millisecond laser pulse regime, which are critically important for parameter optimization in a variety of laser processing, microfabrication, and deposition applications.

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supporting

confidence: 55%

mentioning

confidence: 92%

mentioning

confidence: 99%

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Spatio-temporal ablation dynamics and plasma chemistry of aluminum induced by temporally modulated ytterbium fiber laser

Park

Balkey

Mao

et al. 2021

Applied Physics Letters

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“…Previous work reported vertical ejection of nanoparticles (NPs) with velocities of 200 m/s under single-pulse fs laser irradiation and suggested that they would be generated via spallation due to ultrafast thermodynamic phase changes ( 23 , 26 , 27 ). Likewise, taking in account (i) the ablation depth of 500 nm ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…A detailed description of the experimental system is given in Materials and Method, while information on the Mie theory modeling (21) used to design the scattering imaging system is included in figs. S2 and S3 (22,23).…”

Section: Resultsmentioning

confidence: 99%

Mechanisms of ultrafast GHz burst fs laser ablation

Park

Mao

et al. 2023

Sci. Adv.

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Gigahertz (GHz) femtosecond (fs) lasers have opened possibilities for enhancing and controlling the laser machining quality to engineer the physicochemical properties of materials. However, fundamental understanding of laser-material interactions by GHz fs laser has remained unsolved due to the complexity of associated ablation dynamics. Here, we study the ablation dynamics of copper (Cu) by GHz fs bursts using in situ multimodal diagnostics, time-resolved scattering imaging, emission imaging, and emission spectroscopy. A combination of probing techniques reveals that GHz fs bursts rapidly remove molten Cu from the irradiated spot due to the recoil pressure exerted by following fs pulses. Material ejection essentially stops right after the burst irradiation due to the limited amount of remnant matter, combined with the suppressed heat conduction into the target material. Our work provides insights into the complex ablation mechanisms incurred by GHz fs bursts, which are critical in selecting optimal laser conditions in cross-cutting processing, micro/nano-fabrication, and spectroscopy applications.

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Inverse Design of Photonic Surfaces via High throughput Femtosecond Laser Processing and Tandem Neural Networks

Park,

Grbčić,

Motameni

et al. 2024

Advanced Science

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This work demonstrates a method to design photonic surfaces by combining femtosecond laser processing with the inverse design capabilities of tandem neural networks that directly link laser fabrication parameters to their resulting textured substrate optical properties. High throughput fabrication and characterization platforms are developed that generate a dataset comprising 35280 unique microtextured surfaces on stainless steel with corresponding measured spectral emissivities. The trained model utilizes the nonlinear one‐to‐many mapping between spectral emissivity and laser parameters. Consequently, it generates predominantly novel designs, which reproduce the full range of spectral emissivities (average root‐mean‐squared‐error < 2.5%) using only a compact region of laser parameter space 25 times smaller than what is represented in the training data. Finally, the inverse design model is experimentally validated on a thermophotovoltaic emitter design application. By synergizing laser‐matter interactions with neural network capabilities, the approach offers insights into accelerating the discovery of photonic surfaces, advancing energy harvesting technologies.

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Time-resolved emission and scattering imaging of plume dynamics and nanoparticle ejection in femtosecond laser ablation of silver thin films

Cited by 10 publications

References 20 publications

Spatio-temporal ablation dynamics and plasma chemistry of aluminum induced by temporally modulated ytterbium fiber laser

Spatio-temporal ablation dynamics and plasma chemistry of aluminum induced by temporally modulated ytterbium fiber laser

Mechanisms of ultrafast GHz burst fs laser ablation

Inverse Design of Photonic Surfaces via High throughput Femtosecond Laser Processing and Tandem Neural Networks

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