Laser-induced Plasma-assisted Ablation Research Articles

Laser-induced plasma-assisted ablation of sapphire microstructures and their wettability

Laser-induced plasma-assisted ablation of sapphire microstructures and their wettability

Effect of temperature on the material removal mechanism of LIPAA process

Laser induced plasma assisted ablation (LIPAA) is a new processing technology for transparent hard and brittle materials. During LIPAA processes, high temperature plasma thermal ablation and ion mechanical removal are coupled in the process of material removal. In this paper, an experimental method to study the effect of temperature on LIPAA process was presented. By using different metal targets (pure copper and pure iron) to carry out LIPAA processing experiments on sapphire C surface, the single-pulse energy threshold, microgroove morphology, microgroove surface roughness, material removal rate and temperature field of the processing area were compared. It was verified that the thermal properties such as the thermal conductivity of the metal target had a great influence on the processing results. The molecular dynamics simulation method was introduced to assist the theoretical analysis. The results showed that the material removal mechanism of laser-induced plasma processing sapphire was mainly thermal ablation. The mechanical energy generated by the shock wave of the plasma plume would assist the thermal energy to remove the material. The research results have guiding significance for exploring the sapphire LIPAA processing mechanisms at different temperatures and different targets.

High aspect ratio sapphire micromachining by ultraviolet laser‐induced plasma‐assisted ablation (LIPAA)

AbstractThe ultraviolet laser‐induced plasma‐assisted ablation performed in this article can attain deep and high‐quality engravings in sapphire without necessitating volatile solutions or expensive equipment such as high‐power ultrashort‐pulsed lasers. The dominant mechanism of ablation is discovered to be from the direct ablation of excited sapphire surfaces and not from the plasma generated from the target material. Only an initial deposition from the target is needed to initiate the direct ablation. Note that 20‐µm wide, 30‐µm deep channel and hole features with a surface roughness (Sa) of .65 µm are achieved at an etching rate of .3 µm per pulse without the need for extensive cleaning. Engravings can reach up to 150‐µm depths at a maximum tapering angle of 5° until the shrinking absorbent surface vanishes, and 500‐µm wide 430‐µm deep topside through‐cutting is achieved. This study characterizes the morphology of direct laser ablation of transient absorbent sapphire surfaces. This method demonstrates the potential for the low‐cost rapid engraving of high aspect ratio features in transparent sapphire substrates.

Effect of target on micromachining of sapphire using laser-induced plasma-assisted ablation

Effect of target on micromachining of sapphire using laser-induced plasma-assisted ablation

Induction and amplification of elastic wave into cementitious material by applied laser ablation technique

To identify the elastic wave excitation behavior by means of laser pulse irradiation on cementitious material surface in this study, the application of pulsed laser irradiation system for laser ablation and spallation technique can be explained and proposed for a method for vibration (elastic wave) excitation used in NDT techniques. Expecting laser-induced-plasma-assisted ablation (LIPAA), laser ablation mechanism based on detecting AE (acoustic emission) signal is clarified as well as vibration amplitude and energy amplification by LIPAA with respect to such cementitious materials as cement paste. Elastic wave excitation into cementitious material due to laser ablation is not only influenced by pulse irradiation condition but also laser-induced-plasma-assisted ablation (LIPAA) process. The proposed technique for LIPAA works to induce and amplify the vibration (energy) generation when pulsed laser irradiation is implemented with predetermined fluence on cementitious material.

Subaquatic indirect laser ablation technique for glass processing.

Subaquatic indirect Laser-Induced Plasma-Assisted Ablation (SLIPAA) is proposed as a laser-based technique for glass processing. In this configuration, a water layer is added between a metallic target and a soda-lime glass substrate, so the processing of the glass is due to a combination of the ablation mechanism, the shock waves, and the cavitation bubbles. Thus, this method makes it possible to produce higher depth structures than those performed up to now by other standard laser techniques based on ablation, achieving structures in glass with rectangular cross-sectional profiles. Channels of 1 mm width are fabricated, reaching an average maximal depth value of almost 1400 µm at 30 passes of the laser beam while keeping the focal position fixed. Furthermore, the difference between processing the material with and without the addition of the water layer is presented. The influence of the processing parameters on the shape and quality of the fabricated structures is studied by optical and confocal microscopy, microcomputed tomography, and scanning electron microscopy. Compositional analysis of the glass is performed by energy dispersive X-ray technique to assess the transference of material from the metallic target to the fabricated channels. Deeper and more complex structures are obtained by refocusing the laser beam on the target and adding a pulsed flowing water film.

Transparent superhydrophobic glass prepared by laser-induced plasma-assisted ablation on the surface

Transparent superhydrophobic glass prepared by laser-induced plasma-assisted ablation on the surface

Fabrication of SERS substrates by femtosecond LIPAA for detection of contaminants in foods

Rapid and sensitive detection of contaminants in foods is crucial for minimizing potential health hazards to humans. In this work, we developed a SERS substrate fabricated by femtosecond laser induced plasma assisted ablation (fs LIPAA) for food contaminants detection. By tuning laser fluence, the distribution and size of silicon nanoparticles generated by fs LIPAA are studied. Hotspots with high uniformity can be created for SERS functionalization by decorating the substrate with a layer of silver film. It is found that the SERS performance is well optimized at a laser fluence of 5 J/cm2. The proposed Ag NPs/glass SERS substrate shows good uniformity with an enhancement factor of 2 × 105 via R6G Raman probe as compared to a traditional smooth Ag film. The detection limits of melamine in milk liquid and ciprofloxacin in water are both 1 ppm. The results demonstrate great potential to pave a new way to realize the use of SERS substrates in food safety.

Spatial and temporal thermo-physical analysis of Laser-induced plasma assisted ablation (LIPAA) of polycarbonate

High transmissivity of transparent materials in a wide range of wavelength increases its difficulty of machining using lasers. Laser beam passes through the material, producing no thermal effect on the transparent sheet. Conversely, the technique Laser-Induced Plasma Assisted Ablation (LIPAA) is capable of addressing the challenge of machining transparent materials with the aid of laser-induced plasma. This paper reports a three-dimensional nonlinear transient modeling and simulation of the LIPAA process for microchannel fabrication on transparent materials. The merit of the approach lies in simulating simultaneous ablation of both transparent polycarbonate and aluminium metal target during the process. The effect of plasma energy besides input laser irradiation has also been considered to have a realistic approach to the process and consequently, ablation on rear side of polycarbonate is obtained. The developed model has the potential of estimating spatial-temperature distribution along the traverse direction and direction perpendicular to it. The spatial distribution lent a hand in predicting the width and depth of the microchannel. A good correlation between the simulated and the experimental results was achieved on validation. Temporal-temperature distribution for pulse-on and pulse-off time was also explored. It is witnessed that the heating rate during pulse-on time is more than the cooling rate during pulse-off time. Likewise, it is observed that the temperature generated on aluminium is more than on polycarbonate. Substantially, the model can be employed to demonstrate LIPAA for microchannel fabrication on transparent materials irrespective of its transitivity.

Anisotropy of material removal during laser-induced plasma assisted ablation of sapphire

Sapphire crystals have a special lattice structure, which causes anisotropy in their processing quality due to anisotropy of the physical and mechanical properties. Laser-induced plasma assisted ablation (LIPAA) is a new processing technology used to process transparent, hard, and brittle materials. LIPAA is regarded as a photoelectric composite processing method that makes the material removal and surface generation mechanisms more complicated. In this study, a surface generated by LIPAA processing showed much higher quality than a surface generated by direct laser ablation. Moreover, LIPAA has the advantage of a lower etching energy threshold than that of infrared laser direct ablation. Infrared laser-induced plasma assisted ablation was performed on different sapphire crystal orientations to explore the influence of anisotropy on LIPAA processing. The LIPAA material removal rates for different sapphire planes were presented and compared with results for direct laser ablation-focused ion beam (FIB) processing. The results showed that thermal removal was most dominant during LIPAA processing of sapphire. The material removal rate was highest in the [10 1‾ 0] direction and lowest in the [112‾ 0] direction.

Experimental study on the direct planar metallization on glass by the particle sputtering in laser-induced plasma-assisted ablation

Laser-induced plasma-assisted ablation (LIPAA) is an efficient and low-cost method for processing the metallic pattern on glass. In this study, the metallic sacrificed target was used in the LIPAA process, the feasibility of direct planar metallization on the glass substrate was explored. For this purpose, the morphology and chemical composition of the planar metallization layer on glass substrate, which was fabricated by line-by-line LIPAA, was characterized in detail, and the corresponding metallization regime was clarified. The experimental results indicate that gap distance between the glass specimen and metallic sacrificed substrate has a significant influence on the homogeneity, thickness, compactness, and chemical composition of the metallization layer. In addition, with a small gap distance, the periodic behaviors of generation, accumulation, blockage and spray of the metallic oxide powders between the gap bring about stripes embedded in the metallization layer. Moreover, based on the prepared metallization layer by line-by-line LIPAA, the patterned circuit was fabricated on the glass by laser patterning method and its conductivity was enhanced by successive chemical reduction. The comprehensive performance test for the patterned circuit in terms of morphology, adhesion strength, conductivity demonstrate that the line-by-line LIPAA method presents a great potential for preparing the patterned circuit on glass.

Micro-reactors fabricated by Subaquatic indirect Laser-Induced Plasma-Assisted Ablation on soda-lime glass substrates

Synchronization control of complex systems is a field that emerged with huge interest and aims to study new possible routes to synchronization in networks of non-locally coupled chemical oscillators. Light can be used to stimulate these systems and to be able to synchronize the different micro-reactors involved in the complex system. To this end, transparent reactors with good optical qualities are needed. Glass is the most appropriated material to be used for fabricating the micro-reactors. Subaquatic indirect Laser-Induced Plasma-Assisted Ablation is presented as a laser technique that combines underwater ablation with shock waves as a potential technique for fabricating these micro-reactors by using a Nd:YVO4 laser.

Experimental investigation of deep-hole micro-drilling of glass using LIPAA process

ABSTRACT This paper aims to study the mechanism of glass deep-hole micro-drilling by the Laser-Induced Plasma-Assisted Ablation (LIPAA) process. The Micro-drilling of glass was studied under various laser intensities. Nd:YAG nanosecond pulsed laser with 12 ns pulse duration was used as the laser light source. Copper was used as the metal target for the experiments. It is shown that laser glass micro-drilling is divided into two ablation stages. In the first stage, ablation is done by the brittle failure of glass caused by the collision of plasma plume with the glass surface. Exertion of mechanical pressure is also an important factor in the first few laser shots. Due to mechanical failure, glass microstructure changes in the focal spot. Second stage ablation is directly conducted by the thermal mechanism through absorption of laser by the glass. The hole produced on the glass by thermal mechanism is free of cracks. Cylindricity and roundness of the hole are very desirable. Laser intensity plays a vital role in material removal rate, hole depth and diameter. The process can be used for high-speed deep-hole micro-drilling of transparent materials to laser with good surface integrity and high-aspect ratio.

Low-cost SERS substrate featuring laser-ablated amorphous nanostructure

In this work, we aimed at fast and scalable manufacturing of low-cost SERS substrates using ultrashort-pulse laser-induced plasma-assisted ablation (LIPAA) of soda-lime glass. A two-step approach of amorphous nanostructure formation on the glass surface and subsequent deposition of 170 nm silver layer resulted in homogenous SERS-active substrates covered with nanostructures of around 100 nm in diameter, forming 1–3 μm size dendrimers. The average enhancement factor (EF) evaluated using thiophenol was 3.0 × 105, while the surface activity was found to be consistent at any given point of substrates. Relatively modest EF was explained by amorphous, rounded-shaped features on soda-lime glass formed during the LIPAA-induced melting and subsequent solidification. That resulted in a lesser amount of hot spots but increased surface homogeneity. The use of soda-lime glass to fabricate SERS substrates promises a cheaper and scalable alternative to more widely used sapphire and other material substrates opening prospects for low-cost routine SERS testing with high reproducibility in chemistry, medical, forensic, and environmental sciences.

A comparative study of direct laser ablation and laser-induced plasma-assisted ablation on glass surface

This paper presents a comparative study of direct laser ablation (DLA) and laser-induced plasma-assisted ablation (LIPAA) methods to fabricate single-channel microgrooves on the surface of glass substrate by picosecond laser irradiation. The comparative study focuses on the morphological feature and surface chemical components of the micro-groove generated. For this purpose, optical microscope, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) are utilized to characterize the changes of morphologic and chemical compositions. The influence of laser parameters on the morphology of the glass surface is explored. For DLA, the microgroove with the least quantity and size of cracks is prepared successfully by setting the parameters as: scanning speed of 1 mm/s at laser output power of 3 W. In case of LIPAA, microgroove with no cracks and greater depth is achieved by setting the parameters as: scanning speed of 1 mm/s at laser output power of 1 W and distance between glass substrate and copper target at 0.06 mm. The result of XPS demonstrates that there is no significant change in chemical elements on glass surface after DLA, while there is Cu element deposits on glass surface after LIPAA.

The role of sacrificial target material in micromachining of glass using laser-induced plasma-assisted ablation (LIPAA)

Laser produced metal plasma was used to fabricate micro-craters on the surface of the soda lime glass. The glass micro-crater machined by a single laser pulse is the first step towards the fabrication of a complex optical component and an elongated channel for the microfluidic devices. In this study, the role of the type of sacrificial material plasma on the structure of glass micro-craters was explored. For this purpose, aluminum and tungsten were used as the sacrificial target materials. The laser fluence and the gap distance between glass and metal target were varied in the range of 27–970 J/cm2 and 0–500 μm, respectively. The optical microscope and surface profilometer were used to analyze the structure of micro-craters. The size of glass micro-crater was observed to depend on the laser fluence for both Al and W plasmas. However, the size of glass micro-crater fabricated by Al plasma was much bigger than that of the W plasma. Moreover, the structure of the micro-crater also depends on the gap distance. The measured ablation yield of the metal targets, size of the expanding plasma and physical processes occurring at the plasma–glass interface were used to explain the observed difference in the structure of glass micro-craters fabricated by Al and W plasmas.

One-step fabrication of metal nanoparticles on polymer film by femtosecond LIPAA method for SERS detection

Flexible transparent SERS substrates have aroused great interest as a rapid and in situ detection method for trace chemicals. We demonstrate a one-step and environmentally friendly method to fabricate flexible fluorinated ethylene propylene (FEP) surface plasmon resonance film by femtosecond laser induced plasma assisted ablation (LIPAA) for in situ SERS detection. By tuning laser fluence, the distributions and sizes of silver and gold nanoparticles generated by femtosecond LIPAA are studied. Using a Rhodamine 6G (R6G) Raman probe with a 532 nm laser excitation, the proposed Ag NPs/FEP and Au NPs/FEP substrates show enhancement factors of 5.6 × 107 and 2.4 × 106, respectively, as compared to a bare FEP film without the metallic nanoparticles. The Raman signals show good uniformity and a linear relationship with the concentration of R6G solution. In addition, the detection limit of thiram on an apple for in situ measurement is 0.1 mg/Kg, corresponding to 7.96 ng/cm2. The proposed SERS detection approach has great potential to pave a new way in food safety applications, such as detecting pesticides in harvested fruits.

Nanosecond laser induced glass particle deposition over steel mesh for long-term superhydrophilicity and gravity driven oil water separation

In this report we show that the laser textured stainless steel meshes which serve as excellent oil water separator immediately after laser processing, lose their oil water separation capability after storage in ambient air. This was possibly due to the reactive nature of the metal oxides formed during laser processing which resulted in transition of the wettability of processed metallic meshes from superhydrophilic to superhydrophobic during storage. To overcome this issue, we show that by using a glass cover plate over the metal mesh during laser processing, micron/submicron sized glass particles can be deposited on to the mesh via a process known as laser induced plasma assisted ablation. Since the glass is inherently hydrophilic and inert, and therefore the glass particles coating produced a stable superhydrophilic/underwater-superoleophobic surface which was observed to maintain its superhydrophilicity for the tested duration of ~8 months and perform oil/water separation with an efficiency of ~96% for various oils. Further, the glass particles coated mesh was found to sustain several cycles of sandpaper abrasion before losing its oil water separation capability.

Femtosecond Laser Precision Engineering: From Micron, Submicron, to Nanoscale

As a noncontact strategy with flexible tools and high efficiency, laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication, especially to achieve novel functional photoelectric structures and devices. For the microscale creation, several femtosecond laser fabrication methods, including multiphoton absorption, laser-induced plasma-assisted ablation, and incubation effect have been developed. Meanwhile, the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales. Down to nanoscale feature sizes, advanced processing strategies, such as near-field scanning optical microscope, atomic force microscope, and microsphere, are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to ~25 nm due to near-field effect. The most fascinating femtosecond laser precision engineering is the possibility of large-area, high-throughput, and far-field nanofabrication. In combination with special strategies, including dual femtosecond laser beam irradiation, ~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air. The challenges and perspectives in the femtosecond laser precision engineering are also discussed.

Numerical modelling and simulation of microchannel fabrication on polycarbonate using Laser-Induced Plasma Assisted Ablation (LIPAA)

Microchannel fabrication on transparent materials using lasers is difficult for a wide range of wavelength. Laser-Induced Plasma Assisted Ablation (LIPAA) is a novel process for machining of microchannels on the transparent materials. LIPAA overcomes the challenges faced due to its transparency over a wide range of wavelength. Here, transparent materials are ablated with the aid of laser-induced plasma on its rear side. This paper presents a two-dimensional transient numerical model to understand the physics of material removal during the LIPAA process. A realistic model is developed considering assumptions like moving Gaussian heat source, temperature dependent properties and combined convection-radiation effect. Extensive numerical analysis is performed concerning the effect of plasma along with the effect of input laser irradiation. The results predicted have been validated with the experimental results and found in good agreement. The numerical analysis provides some useful observations like increase in pulse power density, pulse repetition rate and pulse duration, enhances the channel dimensions. Similarly, considering the effect of moving heat flux, it is witnessed that the peak temperature attains a constant value on reaching a certain distance, thus assuring a channel of uniform dimension. The developed model can be utilized effectively to establish LIPAA in practice.