Laser Processing for Precise Fabrication of the THz Optics
Focusing of 4.75 Thz (λ = 63 µm) radiation with laser fabricated Fresnel lens

THz imaging in an emerging technology in astronomy, medicine, art conservation, security, materials inspection, etc. Off-axis parabolic mirrors and refractive lenses are available commercially and very often are employed in THz imaging setups. In order to reduce the complexity of the THz systems and make them more compact, diffractive lenses such as multilevel phase Fresnel lenses and Fibonacci lenses have been developed on high-resistivity silicon and in metal. High repetition rate ultrashort (1 MHz, 10 ps, 1064 nm) laser pulses were used to fabricate Fresnel lenses in silicon. Depending on the lens design, laser beam scanning with both galvanometric and polygon scanners were utilised. In batch processing with a polygon scanner, material removal rate up to 1.46 mm3/s was achieved. Using this technology, silicon Fresnel lenses for various THz frequencies, including 0.6 Thz and 4.75 Thz, were fabricated. High focusing performance with a focal spot diameter of only 2.4 times larger than the wavelength was achieved. In general, with this technology, optical components for the 0.1 – 5 THz frequency range can be manufactured. The aperture of the optical element ranges from 10 to 25 mm.

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Laser-Ablated Silicon in the Frequency Range From 0.1 to 4.7 THz

Related products:  Atlantic series Atlantic 5 series

Authors:  S .Indrišiūnas, E. Svirplys, H. Richter, A. Urbanowicz, G. Račiukaitis, T. Hagelschuer, H.W. Hübers, I. Kašalynas

The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1-4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with psor ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.

Published: 2019.   Source: IEEE Transactions on Terahertz Science and Technology, vol. 9, no. 6, pp. 581-586, Nov. 2019.

Laser processing for precise fabrication of the THz optics

Related products:  Atlantic series

Authors:  B. Voisiat, S. Indrišiūnas, R. Šniaukas, L. Minkevičius, I. Kašalynas, G. Račiukaitis

Zone plates with integrated band-pass filters and binary Fresnel lenses designed for the THz spectral range were fabricated by direct laser ablation in metal films and the silicon substrate. Results on the process performance and quality of the products are reviewed. The focusing performance was measured using the THz source that produces the 580 GHz radiation. The beam was directed to the centre of the fabricated optical elements. Zone plates with integrated band-pass filters have shown the double performance in focusing and spectral selection. The dependence of ablation rate and surface roughness on the laser process parameters was thoroughly investigated on the silicon. The depth of the ablated grooves linearly depends on the number of laser scans number with a particular slope for each scanning speed. The process regime with the 125 mm/s scanning speed provided the most precise control over the ablation depth. The topography measurements of the laser fabricated multilevel phase zone plates (Fresnel lenses) with the 10 mm focal length showed good agreement with the calculated topography. The intensity distribution of the focus spots using the laser fabricated 2, 4 and 8 level binary Fresnel lenses showed better focusing performance when more depth levels were applied in the lens production.

Published: 2017.   Source: Proc. SPIE 10091, 100910F (2017)

Fibonacci terahertz imaging by silicon diffractive optics

Related products:  Atlantic series

Authors:  D. Jokubauskis, L. Minkevičius, M. Karaliūnas, S. Indrišiūnas, I. Kašalynas, G. Račiukaitis, G. Valušis

Fibonacci or bifocal terahertz (THz) imaging is demonstrated experimentally employing a silicon diffractive zone plate in continuous wave mode. Images simultaneously recorded in two different planes are exhibited at 0.6 THz frequency with the spatial resolution of wavelength. Multifocus imaging operation of the Fibonacci lens is compared with a performance of the conventional silicon phase zone plate. Spatial profiles and focal depth features are discussed varying the frequency from 0.3 to 0.6 THz. Good agreement between experimental results and simulation data is revealed.

Published: 2018.   Source: Optics Letters. 43(12), 2795-2798 (2018)
Laser-assisted Selective Copper Deposition on Polymers
Electronic circuit traces of capacitive touch button for Fiat 500 gloves box cover. Fabricated using SSAIL technology

Fabrication of circuit traces is the most challenging task in Moulded interconnect devices (MID) production, being both technically difficult to achieve and difficult to make cost effectively. Moulded interconnect devices (MID) – an injection-moulded thermoplastic part with integrated electronics – offer material, weight and cost savings by integrating electronic circuits directly into polymeric components. Selective Surface Activation Induced by Laser (SSAIL) is a new technology for writing electronic circuits directly onto the dielectric material. This is done by modifying the surface properties with a picosecond pulse laser and has been developed at the Center for physical sciences and technology. Lasers can write the circuits directly by modifying the surface of polymers followed by an electroless metal plating. SSAIL is a three-step process. First is surface modification by laser; second is chemical activation of the modified areas; and the last step is metal deposition by electroless plating. The new technology offers laser writing speeds of up to 4m/s, and therefore spatial plating pitch is kept narrow at 25 µm.

Photopolymerization

Photopolymerization is a powerful and versatile light-activated resin solidification process. It is attractive for the fabrication of complex micrometer-size three-dimensional (3D) structures. Many fabrication techniques of polymeric microstructures are based on photopolymerization via photolithography, digital light processing lithography, rapid prototyping, multi-photon polymerization, 3D printing, interference lithography, etc. Polymeric microstructures with a prescribed shape and thickness are desirable for a wide range of applications: tissue engineering, electronics and optics, coating, adhesives, drug delivery, microfluidics and surface science.

Source: E. Stankevičius, E. Daugnoraitė, etc. Mechanism of pillars formation using four-beam interference lithography. Optics and Lasers in Engineering 116, 41-46 (2019).

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FemtoLux series – microjoule class industrial grade femtosecond fiber laser
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Thermal control of SZ2080 photopolymerization in four-beam interference lithography

Related products:  Atlantic series

Authors:  Ž. Prielaidas, S. Juodkazis, E. Stankevičius

Photopolymerization by four-beam interference lithography on a preheated SZ2080 sample was explored at different initial temperatures of the sample: 20 °C, 50 °C, 75 °C, 100 °C, 125 °C, and 150 °C, and at exposure times ranging from 0.5 s to 5 s. The average laser power selected was ∼100 mW for the 300 ps duration pulses at a 1 kHz repetition rate. The experimental results demonstrate that the higher initial temperature of the sample positively influences the crosslinking of the patterns. These findings will improve polymerization protocols for multi-beam interference lithography.

Published: 2020.   Source: Phys. Chem. Chem. Phys., 2020,22, 5038-5045

Photo-polymerization differences by using nanosecond and picosecond laser pulses

Related products:  FemtoLux series Atlantic series

Authors:  E. Stankevičius, E. Daugnoraitė, A. Selskis, S. Juodkazis, G. Račiukaitis

Formation of polymeric pillars by using laser interference lithography is compared for nanosecond and picosecond laser pulses. The experimental results are explained by dynamics of laser-excited radicals. The shape of fabricated structures demonstrates that thermal accumulation and oxygen diffusion from the surrounding air make an influence on polymerization when the pulse duration is in the nanosecond range. By using picosecond laser pulses, the thermal accumulation and oxygen diffusion effects are not important for low repetition rate (500 Hz), and they become relevant only at the repetition rates higher than ≥ 1 kHz. It is shown that thermal accumulation is caused by a low-temperature diffusivity and heat accumulation at the polymer-glass interface, and it plays a significant role in the final shape of the structures fabricated using the nanosecond laser pulses.

Published: 2017.   Source: Optics Express, 25(5) 4819- 4830 (2017)

Mechanism of pillars formation using four-beam interference lithography

Related products:  Atlantic series

Authors:  E. Stankevičius, E. Daugnoraitė, G. Račiukaitis

Three different experiments were performed in order to determine the mechanism of pillars formation using four-beam interference lithography. The experimental results demonstrate that pillars, fabricated in argon gas, were wider and higher compared with the pillars fabricated in nitrogen gas, low vacuum or air. It clearly indicates that the pillar bottom widening effect is not affected by the depletion of atmospheric oxygen as in all environments the fabricated pillars have a wider bottom part. Moreover, the shape of the fabricated pillars is not affecting by the back reflection from the positioning stage and by the light irradiation conditions. These results clearly indicate that the photopolymerization process is enhanced by the heat current and it determines the pillar bottom widening effect.

Published: 2019.   Source: Optics and Lasers in Engineering 116, 41-46 (2019)
Generation of Gold Nanoparticles Directly on the Surface
ITO electrode modified with gold nanoparticles

ITO electrodes modified with gold nanoparticles possess faster electron transfer rates and larger current responses than bare ITO electrodes. Therefore such electrodes could be applied for the creation of highly sensitive and selective future sensors. The generation of gold nanoparticles on ITO electrodes using nanosecond lasers has advantages over drop-casting deposition as they do not use colloidal solutions and the generation of gold nanoparticles occurs directly on the desired surface. The main advantages of nanosecond laser processing are submicron treatment accuracy, low thermal impact to the substrate and surrounding areas and selective generation of nanoparticles on desired place and shape of the surface.

Source: E. Stankevičius, M. Garliauskas, etc. Engineering electrochemical sensors using nanosecond laser treatment of thin gold film on ITO glass. Electrochimica Acta 297, 511-522 (2019).

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Nanosecond Lasers
NL230 series – high energy Q-switched DPSS Nd:YAG lasers

Engineering electrochemical sensors using nanosecond laser treatment of thin gold film on ITO glass

Related products:  NL230 series

Authors:  E. Stankevičius, M. Garliauskas, L. Laurinavičius, R. Trusovas, N. Tarasenko, R. Pauliukaitė

Direct generation of gold nanoparticles on ITO glass using a nanosecond laser is presented and the electrochemical properties of the gold modified ITO electrodes for detection of the ascorbic acid are analyzed. Gold nanoparticles were generated by nanosecond laser pulse irradiation of thin, 3–30 nm thick, gold films. It was found that diameters and the number of generated nanoparticles per unit area strongly depends on the thickness of the gold film when it is less than 10 nm. Furthermore, experiments have shown that the influence of laser processing parameters (the laser pulse energy and pulse number) to the size, the distribution and the area density of generated gold nanoparticles on ITO glass is negligible. Characterization of the electrochemical properties of the gold modified ITO electrodes by nanosecond laser showed that the fabricated electrodes could be employed in electrochemical sensing. Therefore, the demonstrated generation of gold nanoparticles on ITO by using the nanosecond laser approach opens new opportunities for the development of highly sensitive and low-cost electrochemical sensors.

Published: 2019.   Source: Electrochimica Acta 297, 511-522 (2019)
Solar Cell Scribing
P3 Type 2 scribe

Climate and environmental concerns led to the rapid growth of renewable power generation. It is forecasted that in the near future, solar photovoltaics (PV) will become one of the major energy sources. Such demand for PV electricity could be satisfied by low cost, low material consuming thin-film devices such as copper indium gallium (di)selenide (CIGS) modules.

Lasers are extensively used in the production lines of flexible CIGS PV for all processing steps, namely P1, P2, and P3 laser scribes (with P3 being the most difficult) to produce monolithic series interconnects between cells.

However, scaling up the manufacturing throughput to several m/s or more is one of the major objectives for the successful development of CIGS thin-film technologies and the implementation of lasers into industrial production lines as a standard tool.

A modern ultra-short Atlantic series laser, offering high average power at the laser pulse repetition rate of 1 MHz, showed outstanding results in scaling up the throughput of P3 Type 2 scribing in a fully functional CIGS solar cell. High pulse repetition rate enabled  the P3 scribing speed of 50 m/s. The laser-induced conductivity of P3 Type 2 scribes was extremely low, ensuring minimum solar module efficiency losses. Furthermore, channels were cleanly exposed, with insignificant melting of the CIGS absorber layer and were highly repeatable.

Source: P. Gečys, E. Markauskas, etc. CIGS thin-film solar module processing: case of high-speed laser scribing. Scientific Reports. 7, 40502 (2017)

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Atlantic series – high power industrial picosecond lasers
Atlantic 5 series – compact air cooled industrial picosecond laser

Picosecond Laser Modification of CIGS Active Layer

Related products:  Atlantic series

Authors:  P. Gečys, E. Markauskas, A. Žemaitis, G. Račiukaitis

Cu-chalcopyrite based solar cells such as Cu(In,Ga)Se2 (CIGS) have been established as the most efficient thin-film technology in converting sunlight into electricity. Laser scribed monolithic interconnects are one of the key technologies which will play a significant role in future develop-ments of CIGS technology. Laser scribing is needed to maintain module efficiency by dividing large scale device to smaller cells interconnected in series. CIGS layer is a thermally sensitive material, and laser modification can induce local structural changes of the active layer and significantly modi-fy the electrical properties. Therefore, the laser modified region can act as series interconnect be-tween the adjacent cells. In this study, we investigated the laser modification of the CIGS active layer with picosecond laser. The EDS analysis revealed the increase of Cu/(In+Ga) ratio in laser treated areas while Raman measurements indicated changes in main CIGS peak and formation of the Cu-rich CuGaSe2 phase. Therefore, this resulted in significant electrical conductivity increase in laser-treated areas. Electrical testing of the laser performed P2 micro-welds showed scribe conduc-tivities up to 9.3 Ω·cm which are acceptable for the cell serial interconnection.

Published: 2016.   Source: J. of Laser Micro/Nanoengineering, 11(2) 257-260 (2016)

CIGS thin-film solar module processing: case of high-speed laser scribing

Related products:  Atlantic series Atlantic 5 series

Authors:  P. Gečys, E. Markauskas, S. Nishiwaki, S. Buecheler, R. De Loor, A. Burn, V. Romano, G. Račiukaitis

In this paper, we investigate the laser processing of the CIGS thin-film solar cells in the case of the high-speed regime. The modern ultra-short pulsed laser was used exhibiting the pulse repetition rate of 1 MHz. Two main P3 scribing approaches were investigated – ablation of the full layer stack to expose the molybdenum back-contact, and removal of the front-contact only. The scribe quality was evaluated by SEM together with EDS spectrometer followed by electrical measurements. We also modelled the electrical behavior of a device at the mini-module scale taking into account the laser-induced damage. We demonstrated, that high-speed process at high laser pulse repetition rate induced thermal damage to the cell. However, the top-contact layer lift-off processing enabled us to reach 1.7 m/s scribing speed with a minimal device degradation. Also, we demonstrated the P3 processing in the ultra-high speed regime, where the scribing speed of 50 m/s was obtained. Finally, selected laser processes were tested in the case of mini-module scribing. Overall, we conclude, that the top-contact layer lift-off processing is the only reliable solution for high-speed P3 laser scribing, which can be implemented in the future terawatt-scale photovoltaic production facilities.

Published: 2017.   Source: Scientific Reports. 7, 40502 (2017)
Fast Periodic Microstructuring of Large Area Surfaces
The scanning microscope image of direct laser interference patterning example

A number of applications, such as fabrication of plasmonic devices, control of surface wettability or reflectance requires a fast and reliable microstructuring approach. To produce fine periodic microstructures with lasers, Direct Laser Interference Patterning (DLIP) can be used. Interference patterning allows the distribution of  laser energy over large areas and produces subwavelength features in this area with a single exposition. As if patterning was done with thousands of very tightly focused laser spots. The main drawback of this method is the limited variety of available pattern shapes. Therefore, a confocal six-beam interference optical module with polarization control for each separate beam was developed. The DLIP method works most efficiently with high pulse energy lasers. Furthermore, for precise patterning, shorter  pulse duration has to be selected to avoid material melting due to thermal diffusion between the high intensity interference spots. Therefore, a high pulse energy sub-nanosecond laser (1 kHz, 300 ps, 532 nm) was used to provide high quality patterning with a relatively simple and inexpensive laser source. Using this approach, a number of patterns were obtained experimentally for the first time using the interference patterning technique. Patterning rate up to 1 m2/h was available.

Source: M. Gedvilas, S. Indrišiūnas, etc. Nanoscale thermal diffusion during the laser interference ablation using femto-, pico-, and nanosecond pulses in silicon. Phys. Chem. Chem. Phys., 2018, 20, 12166-12174.

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Atlantic series – high power industrial picosecond lasers
Atlantic 5 series – compact air cooled industrial picosecond laser

Nanoscale thermal diffusion during the laser interference ablation using femto-, pico-, and nanosecond pulses in silicon

Related products:  Atlantic series Atlantic 5 series

Authors:  M. Gedvilas, S. Indrišiūnas, B. Voisiat, E. Stankevičius, A. Selskisa, G. Račiukaitis

Laser interference ablation in silicon using femto-, pico-, and nanosecond pulses was investigated. The experimental and computational results provide information about nanoscale thermal diffusion during the ultra-short laser–matter interaction. The temperature modulation depth was introduced as a parameter for quality assessment of laser interference ablation. Based on the experiments and calculations, a new semi-empirical formula which combines the interference period with the laser pulse duration, the thermal modulation depth and the thermal diffusivity of the material was derived. This equation is in excellent agreement with the experimental and modelling results of laser interference ablation. This new formula can be used for selecting the appropriate pulse duration for periodical structuring with the required resolution and quality.

Published: 2018.   Source: Phys. Chem. Chem. Phys., 2018, 20, 12166-12174

In situ formation and photo patterning of emissive quantum dots in organic small molecules

Related products:  Atlantic series

Authors:  A. K Bansal, M. T. Sajjad, F. Antolini, L. Stroea, P. Gečys, G. Raciukaitis, P. André, A. Hirzer, V. Schmidt, L. Ortolani, S. Toffanin, S. Allard, U. Scherf, I. Samuel

Nanostructured composites of inorganic and organic materials are attracting extensive interest for electronic and optoelectronic device applications. Here we report a novel method for the fabrication and patterning of metal selenide nanoparticles in organic semiconductor films that is compatible with solution processable large area device manufacturing. Our approach is based upon the controlled in situ decomposition of a cadmium selenide precursor complex in a film of the electron transporting material 1,3,5-tris(N-phenyl-benzimidazol-2-yl)-benzene (TPBI) by thermal and optical methods. In particular, we show that the photoluminescence quantum yield (PLQY) of the thermally converted CdSe quantum dots (QDs) in the TPBI film is up to 15%. We also show that laser illumination can form the QDs from the precursor. This is an important result as it enables direct laser patterning (DLP) of the QDs. DLP was performed on these nanocomposites using a picosecond laser. Confocal microscopy shows the formation of emissive QDs after laser irradiation. The optical and structural properties of the QDs were also analysed by means of UV-Vis, PL spectroscopy and transmission electron microscopy (TEM). The results show that the QDs are well distributed across the film and their emission can be tuned over a wide range by varying the temperature or irradiated laser power on the blend films. Our findings provide a route to the low cost patterning of hybrid electroluminescent devices.

Published: 2015.   Source: Nanoscale, 7(25), 11163-11172 (2015)

Fluorescence Microscopy Study of CdS quantum dots Obtained by Laser Irradiation from a Single Source Precursor in Polymeric Film

Related products:  Atlantic series

Authors:  F. Antolini, M. Lanzi, G. Raciukaitis

Recently the quantum dots (QDs) synthesis from single source precursors (SSPs) showed a potential interest for patterning formation of nano-composites. In this approach the SSPs have to be mixed with a matrix that afterwards is treated selectively to obtain the desired nanocomposite. The study of the generation of the QDs from the SSPs is, therefore, crucial for the definition of its behaviour within the polymeric matrix.

The formation of the CdS QDs via thermolysis of the cadmium diethyldithiocarbamate (CdDDTC) was performed and studied in the presence of a non coordinating solvent such as octadecene (ODE) in presence of myristic acid (MA) as ligand.

The precursor is then studied in combination with the poly(methyl methacrylate) (PMMA) polymer for the generation of the CdS QDs under the laser irradiation within a film. The effect of the laser has been studied both on neat PMMA and on the polymer/precursor blend film with the aid of the fluorescence microscope.

The results are used to identify the optimal laser parameters to obtain the decomposition of the precursor and to evaluate the effect of the laser irradiation on the polymer.

Published: 2017.   Source: Materials Today: Proceedings, 4, Supplement 1, s19-s26 (2017)
Direct Laser Writing
Scanning electron microscope micrograph of thin metal film removed by direct laser writing

Metal films on glass are widely used in industry and science and cover diverse applications. Chromium film on glass is an important material in photo mask production for lithography, as well as in the production of diffraction gratings and linear optical encoders for metrology. Aluminum and silver are used as mirrors, titanium for diffractive optical elements and gold films are widely applied in biomedicine as a substrate for bio-chip production. Lasers are frequently applied for patterning metal film instead of wet chemical or plasma etching. When performing micromachining using lasers, multiple bursts of lower-power irradiation are employed to minimize heating. Metal thin films are ablated without damaging the glass substrate using nanosecond, picosecond and femtosecond laser pulses. Film thickness and drawing shape can be controlled depending on the application.

Source: V.P. Veiko, R.A. Zakoldaev, etc. Thermochemical writing with high spatial resolution on Ti films utilising picosecond laser. Optical Materials Express 9, 2729-2737 (2019).

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Atlantic series – high power industrial picosecond lasers
Atlantic 5 series – compact air cooled industrial picosecond laser

Thermochemical writing with high spatial resolution on Ti films utilising picosecond laser

Related products:  Atlantic series Atlantic 5 series

Authors:  V.P. Veiko, R.A. Zakoldaev, E.A. Shakhno, D.A. Sinev, Z.K. Nguyen, A.V. Baranov, K.V. Bogdanov, M. Gedvilas, G. Račiukaitis, L.V. Vishnevskaya, E.N. Degtyareva

In this paper, we investigate the local oxidation of titanium thin films under the action of picosecond laser pulses. Periodical structures were recorded by the multi-beam interference scheme utilizing various numbers of laser beams, and the relationship between spatial resolution and the contrast of the structures was studied. The Raman spectra of the laser processing regions confirmed the oxidation even under the action of a single picosecond pulse. An analytical simulation of titanium film oxidation in the interference field was provided, and obtained results are correlated with the experimental data. The results of theoretical modeling show that the thermochemical effects of picosecond laser pulses allow recording periodic structures with a period of 0.65 lines per μm. The demonstrated results are important in the adaptation of technological laser systems for the manufacture of diffractive optical elements.

Published: 2019.   Source: Optical Materials Express 9, 2729-2737 (2019)

Compact diffractive optics for THz imaging

Related products:  Atlantic series

Authors:  L. Minkevičius, S. Indrišiūnas, R. Šniaukas, G. Račiukaitis, V. Janonis, V. Tamošiūnas, I. Kašalynas, G. Valušis

We present a compact diffractive silicon-based multilevel phase Fresnel lens (MPFL) with up to 50 mm in diameter and a numerical aperture up to 0.86 designed and fabricated for compact terahertz (THz) imaging systems. The laser direct writing technology based on a picosecond laser was used to fabricate diffractive optics on silicon with a different number of phase quantization levels P reaching an almost kinoform spherical surface needed for efficient THz beam focusing. Focusing performance was investigated by measuring Gaussian beam intensity distribution in the focal plane and along the optical axis of the lens. The beam waist and the focal depth for each MPFL were evaluated. The influence of the phase quantization number on the focused beam amplitude was estimated, and the power transmission efficiency reaching more than 90% was revealed. The THz imaging of less than 1 mm using a robust 50 mm diameter multilevel THz lens was achieved and demonstrated at 580 GHz frequency.

Published: 2018.   Source: Lith. J. Phys. 58, 99-107 (2018)
Bio-inspired Shark-skin-like Surface Structuring
Top view (a) and cross-sectional (b) scanning electron microscope micrographs of laser ablated shark-skin-like riblet structures on pre-heated Teflon

Bio-inspired surfaces decrease friction with gases and the most recognizable textures are shark-skin-like riblets. Such surfaces can be formed using  direct laser ablation with high flexibility options. The bio-inspired riblet surfaces were formed using picosecond ultraviolet laser ablation on pre-heated Teflon at various sample temperatures. The ablation of hot Teflon was found to be 30% more efficient than the conventional laser structuring at room temperature. The functional properties and surface morphologies of the laser-fabricated textures were found to be close to the simplified geometry of shark-skin. The friction of structured Teflon surfaces with the flowing air was investigated using a drag measurement setup.

Source: A. Žemaitis, J. Mikšys, etc. High-efficiency laser fabrication of drag reducing riblet surfaces on pre-heated Teflon. Materials Research Express 6, 065309 (2019).

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Industrial Lasers
Atlantic series – high power industrial picosecond lasers
Atlantic 5 series – compact air cooled industrial picosecond laser

Laser-Ablated Silicon in the Frequency Range From 0.1 to 4.7 THz

Related products:  Atlantic series Atlantic 5 series

Authors:  S .Indrišiūnas, E. Svirplys, H. Richter, A. Urbanowicz, G. Račiukaitis, T. Hagelschuer, H.W. Hübers, I. Kašalynas

The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1-4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with psor ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.

Published: 2019.   Source: IEEE Transactions on Terahertz Science and Technology, vol. 9, no. 6, pp. 581-586, Nov. 2019.

Irradiation of Diamond-Like Carbon Films by Picosecond Laser Pulses

Related products:  Atlantic series

Authors:  L. Marcinauskas, A. Grigonis, L. Vigricaitė, Ž. Rutkūnienė, M. Gedvilas, G. Račiukaitis

The picosecond laser irradiation of diamond-like carbon (DLC) film on the silicon wasinvestigated. The DLC films were irradiated by Nd:YVO4 laser with the infrared (1064 nm, fluency 1.02 J/cm2) and ultraviolet (355 nm, fluency 0.79 J/cm2) wavelengths with 1, 10, and 100 pulse numbers per spot. The energy dispersive X-ray spectroscopy and microRaman spectroscopy measurements indicated that the full ablation area of the DLC was narrower than laser beam radius of the 1064 nm wavelength with 10 and 100 pulses. The increase of the oxygen concentration was obtained near the ablation areas after irradiation with the first harmonic. The microRaman and SEM measurements demonstrated that the DLC film was fully ablated in the laser spot when the third harmonic was used. The formation of silicon carbide (SiC) in the center of the irradiated spot was found after 100 pulses.

Published: 2014.   Source: Journal of Laser Micro/Nanoengineering, 10(1), 43-48 (2015)

Laser processing for precise fabrication of the THz optics

Related products:  Atlantic series

Authors:  B. Voisiat, S. Indrišiūnas, R. Šniaukas, L. Minkevičius, I. Kašalynas, G. Račiukaitis

Zone plates with integrated band-pass filters and binary Fresnel lenses designed for the THz spectral range were fabricated by direct laser ablation in metal films and the silicon substrate. Results on the process performance and quality of the products are reviewed. The focusing performance was measured using the THz source that produces the 580 GHz radiation. The beam was directed to the centre of the fabricated optical elements. Zone plates with integrated band-pass filters have shown the double performance in focusing and spectral selection. The dependence of ablation rate and surface roughness on the laser process parameters was thoroughly investigated on the silicon. The depth of the ablated grooves linearly depends on the number of laser scans number with a particular slope for each scanning speed. The process regime with the 125 mm/s scanning speed provided the most precise control over the ablation depth. The topography measurements of the laser fabricated multilevel phase zone plates (Fresnel lenses) with the 10 mm focal length showed good agreement with the calculated topography. The intensity distribution of the focus spots using the laser fabricated 2, 4 and 8 level binary Fresnel lenses showed better focusing performance when more depth levels were applied in the lens production.

Published: 2017.   Source: Proc. SPIE 10091, 100910F (2017)

Rapid high-quality 3D micro-machining by optimised efficient ultrashort laser ablation

Related products:  Atlantic series Atlantic 5 series

Authors:  A. Žemaitis, M. Gaidys, P. Gečys, G. Račiukaitis, M. Gedvilas

Solid-state lasers with pulse duration of 10 ps and radiation wavelength of 1064 nm were used to investigate the laser ablation efficiency dependence on processing parameters: laser fluence (pulse energy and beam spot size), beam scanning speed, pulse repetition rate, and scanned line (hatch) distance for the copper sample. Utilising a 40 W power laser, the highest ablation efficiency of 2.5 µm3/µJ and the ablation rate of 100 µm3/µs with the smallest surface roughness of 0.2 µm was obtained. Three-dimensional (3D) fabrication using a galvanometer scanner and layer-by-layer removal technique with optimal parameters defined for efficient ablation were demonstrated at a rate of 6 mm3/min. Combination of high material removal rate with excellent quality and complex 3D structure formation is in a high interest for mimicking bio-inspired surfaces, micro-mould fabrication and decorative applications.

Published: 2018.   Source: Optics and Lasers in Engineering 114 (2019) 83–89

High-efficiency laser fabrication of drag reducing riblet surfaces on pre-heated Teflon

Related products:  Atlantic series Atlantic 5 series

Authors:  A. Žemaitis, J. Mikšys, M. Gaidys, P. Gečys, M. Gedvilas

Bio-inspired surfaces are able to decrease friction with fluids and gases. The most recognizable are shark-skin-like riblet surface structures. Such bio-inspired surfaces can be formed by the laser ablation technique. In this work, bio-inspired riblet surfaces with grooves were formed using picosecond ultraviolet laser ablation on pre-heated polytetrafluoroethylene (PTFE) at various sample temperatures. The ablation of hot PTFE was found to be 30% more efficient than the conventional laser structuring at the room temperature. The friction of structured PTFE surfaces with the flowing air was investigated by using drag a measurement setup. Results show the decrease of friction force by 6% with dimensionless riblet spacing around 14–20.

Published: 2019.   Source: Materials Research Express 6, 065309 (2019)

Picosecond Pulsed Laser Ablation for the Surface Preparation of Epoxy Composites

Related products:  Atlantic series

Authors:  F. Palmieri, R. Ledesma, T. Fulton, A. Arthur, K. Eldridge, S. Thibeault, Y. Lin, C. Wohl, J. Connell

As part of a technical challenge under the Advanced Composites Program, methods for improving pre-bond process control for aerospace composite surface treatments and inspections, in conjunction with Federal Aviation Administration guidelines, are under investigation. The overall goal is to demonstrate high fidelity, rapid and reproducible surface treatment and surface characterization methods to reduce uncertainty associated with the bonding process. The desired outcomes are reliable bonded airframe structure, and reduced timeline to certification. In this work, laser ablation was conducted using a q-switched Nd:YVO4 laser capable of nominal pulse durations of 8 picoseconds (ps). Aerospace structural carbon fiber reinforced composites with an epoxy resin matrix were laser treated, characterized, processed into bonded assemblies and mechanically tested. The characterization of ablated surfaces were conducted using scanning electron microscopy (SEM), water contact angle (WCA) goniometry, micro laser induced breakdown spectroscopy (μLIBS), and electron spin resonance (ESR). The bond performance was assessed using a double cantilever beam (DCB) test with an epoxy adhesive. The surface characteristics and bond performance obtained from picosecond ablated carbon fiber reinforced plastics (CFRPs) are presented herein.

Published: 2017.   Source: https://ntrs.nasa.gov/search.jsp?R=20170006187
3D Laser Milling Technology
Examples of 3D laser milling

The high interest of scientific and industrial societies in additive manufacturing has shown that fabrication of three-dimensional (3D) objects is needed. Mostly, 3D printing technology is based on matter melting and solidification, which changes the physical properties of the material, giving an undesirable layer-by-layer appearance, and void formation. The opposite technology to additive is subtractive manufacturing, where ultrashort pulse laser ablation can be utilised. The ultrafast lasers are the number one choice for laser milling technology due to confined laser-matter interaction during very short pulse duration. Minimal heat affected zone and melt-free treatment are achieved with ultrashort pulse lasers leading to advanced processing precision. To form a 3D object, with the help of laser pulses, the unwanted material has to be removed layer-by-layer . For this, the 3D stereolithographic file is divided into the required number of slices along the z-axis. Ultrashort pulse lasers ensure rapid micro-machining and  high quality, which are the most important characteristics for industry-orientated applications.

Source: A. Žemaitis, M. Gaidys, etc. Rapid high-quality 3D micro-machining by optimised efficient ultrashort laser ablation. Optics and Lasers in Engineering 114 (2019) 83–89.

Publications

Found total :
6 articles, 6 selected
Product selected :
All Products
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Industrial Lasers
Atlantic series – high power industrial picosecond lasers
Atlantic 5 series – compact air cooled industrial picosecond laser

Laser-Ablated Silicon in the Frequency Range From 0.1 to 4.7 THz

Related products:  Atlantic series Atlantic 5 series

Authors:  S .Indrišiūnas, E. Svirplys, H. Richter, A. Urbanowicz, G. Račiukaitis, T. Hagelschuer, H.W. Hübers, I. Kašalynas

The optical performance of high-resistivity silicon with a laser-ablated surface was studied in the transmission mode in the frequency range of 0.1-4.7 THz. A reciprocal relationship between the transmission brightness and the surface roughness was observed at discrete THz frequencies. The measured dispersion was reproduced by the THz wave scattering theory using an effective refractive index model. No significant differences between the samples processed either with psor ns-duration laser pulses in ambient air or in argon enriched atmosphere were found in the THz regime. It was demonstrated that the majority of optical losses of the silicon with the laser modified surface were due to the scattering of THz waves and not due to the absorption in silicon-compounds formed during the laser ablation.

Published: 2019.   Source: IEEE Transactions on Terahertz Science and Technology, vol. 9, no. 6, pp. 581-586, Nov. 2019.

Irradiation of Diamond-Like Carbon Films by Picosecond Laser Pulses

Related products:  Atlantic series

Authors:  L. Marcinauskas, A. Grigonis, L. Vigricaitė, Ž. Rutkūnienė, M. Gedvilas, G. Račiukaitis

The picosecond laser irradiation of diamond-like carbon (DLC) film on the silicon wasinvestigated. The DLC films were irradiated by Nd:YVO4 laser with the infrared (1064 nm, fluency 1.02 J/cm2) and ultraviolet (355 nm, fluency 0.79 J/cm2) wavelengths with 1, 10, and 100 pulse numbers per spot. The energy dispersive X-ray spectroscopy and microRaman spectroscopy measurements indicated that the full ablation area of the DLC was narrower than laser beam radius of the 1064 nm wavelength with 10 and 100 pulses. The increase of the oxygen concentration was obtained near the ablation areas after irradiation with the first harmonic. The microRaman and SEM measurements demonstrated that the DLC film was fully ablated in the laser spot when the third harmonic was used. The formation of silicon carbide (SiC) in the center of the irradiated spot was found after 100 pulses.

Published: 2014.   Source: Journal of Laser Micro/Nanoengineering, 10(1), 43-48 (2015)

Laser processing for precise fabrication of the THz optics

Related products:  Atlantic series

Authors:  B. Voisiat, S. Indrišiūnas, R. Šniaukas, L. Minkevičius, I. Kašalynas, G. Račiukaitis

Zone plates with integrated band-pass filters and binary Fresnel lenses designed for the THz spectral range were fabricated by direct laser ablation in metal films and the silicon substrate. Results on the process performance and quality of the products are reviewed. The focusing performance was measured using the THz source that produces the 580 GHz radiation. The beam was directed to the centre of the fabricated optical elements. Zone plates with integrated band-pass filters have shown the double performance in focusing and spectral selection. The dependence of ablation rate and surface roughness on the laser process parameters was thoroughly investigated on the silicon. The depth of the ablated grooves linearly depends on the number of laser scans number with a particular slope for each scanning speed. The process regime with the 125 mm/s scanning speed provided the most precise control over the ablation depth. The topography measurements of the laser fabricated multilevel phase zone plates (Fresnel lenses) with the 10 mm focal length showed good agreement with the calculated topography. The intensity distribution of the focus spots using the laser fabricated 2, 4 and 8 level binary Fresnel lenses showed better focusing performance when more depth levels were applied in the lens production.

Published: 2017.   Source: Proc. SPIE 10091, 100910F (2017)

Rapid high-quality 3D micro-machining by optimised efficient ultrashort laser ablation

Related products:  Atlantic series Atlantic 5 series

Authors:  A. Žemaitis, M. Gaidys, P. Gečys, G. Račiukaitis, M. Gedvilas

Solid-state lasers with pulse duration of 10 ps and radiation wavelength of 1064 nm were used to investigate the laser ablation efficiency dependence on processing parameters: laser fluence (pulse energy and beam spot size), beam scanning speed, pulse repetition rate, and scanned line (hatch) distance for the copper sample. Utilising a 40 W power laser, the highest ablation efficiency of 2.5 µm3/µJ and the ablation rate of 100 µm3/µs with the smallest surface roughness of 0.2 µm was obtained. Three-dimensional (3D) fabrication using a galvanometer scanner and layer-by-layer removal technique with optimal parameters defined for efficient ablation were demonstrated at a rate of 6 mm3/min. Combination of high material removal rate with excellent quality and complex 3D structure formation is in a high interest for mimicking bio-inspired surfaces, micro-mould fabrication and decorative applications.

Published: 2018.   Source: Optics and Lasers in Engineering 114 (2019) 83–89

High-efficiency laser fabrication of drag reducing riblet surfaces on pre-heated Teflon

Related products:  Atlantic series Atlantic 5 series

Authors:  A. Žemaitis, J. Mikšys, M. Gaidys, P. Gečys, M. Gedvilas

Bio-inspired surfaces are able to decrease friction with fluids and gases. The most recognizable are shark-skin-like riblet surface structures. Such bio-inspired surfaces can be formed by the laser ablation technique. In this work, bio-inspired riblet surfaces with grooves were formed using picosecond ultraviolet laser ablation on pre-heated polytetrafluoroethylene (PTFE) at various sample temperatures. The ablation of hot PTFE was found to be 30% more efficient than the conventional laser structuring at the room temperature. The friction of structured PTFE surfaces with the flowing air was investigated by using drag a measurement setup. Results show the decrease of friction force by 6% with dimensionless riblet spacing around 14–20.

Published: 2019.   Source: Materials Research Express 6, 065309 (2019)

Picosecond Pulsed Laser Ablation for the Surface Preparation of Epoxy Composites

Related products:  Atlantic series

Authors:  F. Palmieri, R. Ledesma, T. Fulton, A. Arthur, K. Eldridge, S. Thibeault, Y. Lin, C. Wohl, J. Connell

As part of a technical challenge under the Advanced Composites Program, methods for improving pre-bond process control for aerospace composite surface treatments and inspections, in conjunction with Federal Aviation Administration guidelines, are under investigation. The overall goal is to demonstrate high fidelity, rapid and reproducible surface treatment and surface characterization methods to reduce uncertainty associated with the bonding process. The desired outcomes are reliable bonded airframe structure, and reduced timeline to certification. In this work, laser ablation was conducted using a q-switched Nd:YVO4 laser capable of nominal pulse durations of 8 picoseconds (ps). Aerospace structural carbon fiber reinforced composites with an epoxy resin matrix were laser treated, characterized, processed into bonded assemblies and mechanically tested. The characterization of ablated surfaces were conducted using scanning electron microscopy (SEM), water contact angle (WCA) goniometry, micro laser induced breakdown spectroscopy (μLIBS), and electron spin resonance (ESR). The bond performance was assessed using a double cantilever beam (DCB) test with an epoxy adhesive. The surface characteristics and bond performance obtained from picosecond ablated carbon fiber reinforced plastics (CFRPs) are presented herein.

Published: 2017.   Source: https://ntrs.nasa.gov/search.jsp?R=20170006187
Sapphire Stealth Dicing

Single crystal sapphire offers superior physical, chemical, and optical properties, which make it an excellent material for wide range of applications. However, the high cost of sapphire machining precludes its use in all but the highest value applications. Stealth dicing technique using Atlantic 6 laser is a solution that ensures the best quality and cost minimization. Using this method, laser induced modifications are created inside the volume of sapphire without damaging the top and bottom surfaces of the substrate, even in thick wafers. The modifications create a crack plane and sapphire is cleaved by applying external force, resulting in a clean process with almost no material loses because of effectively zero kerf width. Some applications include: high-speed integrated circuit chips, thin-film GaN-based light emitting diode substrates, wristwatch crystals and movement bearings, scratch resistant display and camera covers, and high durability optical windows for extreme applications.

Publications

Found total :
1 article, 1 selected
Product selected :
All Products
All Products
Industrial Lasers
Atlantic series – high power industrial picosecond lasers

Multi-photon absorption enhancement by dual-wavelength double-pulse laser irradiation for efficient dicing of sapphire wafers

Related products:  Atlantic series

Authors:  M. Gedvilas, J. Mikšys, J. Berzinš, V. Stankevič, G. Račiukaitis

The evidence of multi-photon absorption enhancement by the dual-wavelength double-pulse laser irradiation in transparent sapphire was demonstrated experimentally and explained theoretically for the first time. Two collinearly combined laser beams with the wavelengths of 1064 nm and 355 nm, inter-pulse delay of 0.1 ns, and pulse duration of 10 ps were used to induce intra-volume modifications in sapphire. The theoretical prediction of using a particular orientation angle of 15 degrees of the half-wave plate for the most efficient absorption of laser irradiation is in good agreement with the experimental data. The new innovative effect of multi-photon absorption enhancement by dual-wavelength double-pulse irradiation allowed utilisation of the laser energy up to four times more efficiently for initiation of internal modifications in sapphire. The new absorption enhancement effect has been used for efficient intra-volume dicing and singulation of transparent sapphire wafers. The dicing speed of 150 mm/s was achieved for the 430 μm thick sapphire wafer by using the laser power of 6.8 W at the repetition rate of 100 kHz. This method opens new opportunities for the manufacturers of the GaN-based light-emitting diodes by fast and precise separation of sapphire substrates.

Published: 2017.   Source: Scientific Reports, 7, 5218 (2017)
Metal Black/Color Marking

Medical tools and other devices made of stainless steel (SS) require laser markings for unique device identification (UDI). These markings need to be corrosion resistant in order to withstand numerous autoclave cycles. The Atlantic 6 laser shows excellent results in color modifications of stainless steel. The shade of stainless steel can be lightened or darkened by controlling laser power and scanning speed of the beam. The resistance of the laser marked areas to the corrosion was tested by using the salt spray test according to the international standard (ISO 9227), and the marking can withstand extreme environmental conditions, and is absolutely rust-proof.

Publications

Found total :
1 article, 1 selected
Product selected :
All Products
All Products
Industrial Lasers
Atlantic series – high power industrial picosecond lasers

Corrosion Resistive Laser Marking of Stainless Steel by Atlantic Series Picosecond Laser

Related products:  Atlantic series

Authors:  M. Gedvilas, G, Račiukaitis

Medical tools and other devices made of stainless steel (SS) require laser markings for unique device identification (UDI). These markings need to be corrosion resistant in order to withstand numerous autoclave cycles. EKSPLA with FTMC has developed a picosecond laser marking system – for reliable UDI marks on surgical and spring grade of stainless steel for corrosion resistive applications.

Published: 2017.   Source: Ekspla Application notes.
Glass Processing
Laser milling

The glass is an important engineering material for a number of different applications. Laser machining of transparent materials, such as flat glass, is a fast growing market, driven by new developments in displays, optoelectronics and medical device technology. Conventional glass processing techniques such as diamond drilling and dicing, water-jet drilling, sand blasting or ultrasonic processing are still commonly used in mass production, although limitations of these techniques in flexibility, processing speed and quality require a search for novel technological solutions. Laser-based techniques such as rear side glass processing can offer high quality and throughput, which can be used for glass drilling, cutting and milling applications. Typical kerf widths with such technique can be extremely reduced compared to mechanical diamond tool processing. Therefore, laser milled feature sizes can be reduced to 150 µm. Furthermore, laser cuts are taper–less, therefore, extremely high aspect ratio features can be fabricated. Glass surface chipping during processing is another important issue. However, laser-based processing with Atlantic series picosecond laser can maintain high throughput with the highest processing quality keeping surface chipping bellow 100 µm.

  • Materials: soda lime glass (SLG), fused silica, BK7 glass, borosilicate glass;
  • Quality: Surface chipping <100 µm, sidewall roughness <2 µm;
  • Cutting throughput: 0.6 m/min (1 mm SLG glass), 0.12 m/min (5 mm SLG glass);
  • Via drilling Ø 0.2-1 mm: 1 s/via (1 mm SLG), 5 s/via (5 mm SLG);
  • Material removal rate: 90 mm3/min.

Publications

Found total :
1 article, 1 selected
Product selected :
All Products
All Products
Industrial Lasers
Atlantic series – high power industrial picosecond lasers

Glass dicing with elliptical Bessel beam

Related products:  Atlantic series

Authors:  J. Dudutis, R. Stonys, G. Račiukaitis, P. Gečys

In this paper the possibility to optimize the glass dicing process by controlling the axicon-generated Bessel beam ellipticity is presented. Single-shot intra-volume modifications in soda-lime glass followed by dicing experiments of 1 mm-thick samples are performed. The Bessel beam ellipticity is essential for glass dicing process. Such beam generates intra-volume modifications with transverse crack propagation in dominant direction. Orientation of these modifications parallel to the dicing direction gives significant advantages in terms of processing speed, glass breaking force and cutting quality.

Published: 2019.   Source: Optics & Laser Technology, 111, 331-337 (2019)