Prof. Mirosław Sawczak Profile

Prof. Mirosław Sawczak

at Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences

SPIE Involvement:

Author

Publications (36)

Proceedings Article | 3 October 2022 Poster + Paper

The electrical, morphological, and optical properties of heavily boron-doped diamond sheets as a function of methane concentration in the gas phase

Michał Rycewicz, Adrian Nosek, Mirosław Sawczak, Jacek Ryl, Robert Bogdanowicz

Proceedings Volume 12200, 122000B (2022) https://doi.org/10.1117/12.2646108

KEYWORDS: Methane, Diamond, Boron, Optical properties, Raman spectroscopy, Absorbance, Tantalum, Doping, P-type semiconductors, Nanocrystals, Resistance

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Proceedings Article | 18 April 2021

Effect of pH on optical sensing with poly-L-lysine-modified nanodiamonds

Maciej Glowacki, Monika Janik, Mirosław Sawczak, Anna Wcislo, Pawel Niedzialkowski, Mateusz Ficek, Robert Bogdanowicz

Proceedings Volume 11772, 117720D (2021) https://doi.org/10.1117/12.2589306

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Nitrogen-vacancy (NV) centers are crystallographic defects which provide diamonds with unique physical properties. The centers are known for their intensive, time-stable fluorescence, and an electron spin, which exhibits long coherence time and may be manipulated using external stimuli. Nanodiamonds containing the NV centers are promising tools in biolabeling, biosensing, and drug delivery due to the aforementioned properties of the defects combined with a chemical inertness of a core and an easily functionalized surface of the diamond. Many biochemical reactions are pH-sensitive, therefore, in order to utilize the NV centers for monitoring of such processes, the pH-dependency of the properties of the nanodiamonds needs to be well-understood. Functionalization of the nanodiamonds’ surfaces with biological molecules undergoing pH-triggered changes of conformation, e.g. poly-L-lysine, could not only increase the particles’ biocompatibility and promote cell adhesion, but also possibly enhance pH-sensitivity. In the present study, an impact of pH on the fluorescence, a zeta potential, and a contact angle of the NV centers-containing nanodiamonds dispersed in liquid media is examined. The suspensions were made of commercially available, fluorescent diamond particles in an as-received, unmodified state, and after the poly-L-lysine had been attached to their surfaces via two different procedures – in aqueous, and anhydrous environment. Values of pH of dispersion media were specifically chosen to induce diverse conformation of the poly-L-lysine: from a fully relaxed conformation, through a state of being neither wholly extended, nor helical, to a complete α-helix conformation. The intensity of the photoluminescence emitted by the NV centers has been found to depend on the pH-triggered conformation of the poly-L-lysine attached to the surfaces of the nanodiamonds. The impact of the conformation of the poly-L-lysine on the electric charge of the nanoparticles has also been analyzed. This study confirms the potential of the nitrogen-vacancy centers for optical sensing of pH-triggered processes.

Proceedings Article | 29 January 2019

Direct laser writing of Ag nanoparticle-composed structures in glass

N. Nedyalkov, M. Koleva, N. Stankova, R. Nikov, P. Atanasov, L. Aleksandrov, R. Iordanova, G. Sliwinski, M. Sawczak, K. Grochowska, M. Terakawa

Proceedings Volume 11047, 110470J (2019) https://doi.org/10.1117/12.2516518

KEYWORDS: Silver, Glasses, Nanoparticles, Annealing, Laser processing, Optical properties, Composites, Metals, Plasmons, Pulsed laser operation

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In this work results on laser assisted formation of silver nanoparticles in glass are presented. The sample material used in the experiments is Ag doped borosilicate glass fabricated by conventional melt quenching method. The glass samples are irradiated by nanosecond laser pulses at wavelength of 266 nm with a wide range of fluences and number of applied pulses. It is found that the laser radiation can lead to specific yellow coloration of the irradiated areas. The performed analyses show formation of silver nanoparticles in these zones. The optical properties of the irradiated areas are found to depend on the laser processing parameters and the silver concentration. The mechanism of nanoparticle formation is also discussed. The presented method can be used for formation of nanoparticles inside transparent materials and can be used for fabrication of novel materials with application in photonics.

Proceedings Article | 1 September 2017

Preparation of fluorescent nanodiamond suspensions using bead-assisted ultrasonic disintegration

Maciej Głowacki, Mateusz Gardas, Mateusz Ficek, Mirosław Sawczak, Robert Bogdanowicz

Proceedings Volume 10455, 104550E (2017) https://doi.org/10.1117/12.2281681

KEYWORDS: Ultrasonics, Luminescence, Color centers

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Nitrogen-vacancy (N-V) centers are the most widely studied crystallographic defect in the diamond lattice since their presence causes strong and stable fluorescence. The negative charge state of the defect (NV-) is especially desired because of its potential for quantum information processing. In this study, fluorescent suspensions of diamond particles have been produced by microbead-assisted ultrasonic disintegration of commercially obtained diamond powder containing N-V color centers. Zirconium dioxide ZrO₂ was chosen as an abrasive and a mixture of deionized water and dimethyl sulfoxide (DMSO) was used as a solvent. Raman spectrum of the starting material has been obtained and the resulting liquids have been measured in terms of photoluminescence. Moreover, thin layer of the diamond particles has been deposited on a silicon substrate and examined using scanning electron microscopy (SEM). During the course of the experiment a new method, which uses sodium chloride NaCl as an abrasive, has been proposed. The results of fluorescence measurements of the suspension prepared using this technique are highly promising.

Proceedings Article | 22 August 2017

Organic semiconductor rubrene thin films deposited by pulsed laser evaporation of solidified solutions

N. Majewska, M. Gazda, R. Jendrzejewski, S. Majumdar, M. Sawczak, G. Śliwiński

Proceedings Volume 10453, 104532H (2017) https://doi.org/10.1117/12.2276250

KEYWORDS: Organic semiconductors, Thin films, Pulsed laser operation, Spintronics, Crystals, Thin film deposition, Raman spectroscopy

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Organic semiconductor rubrene (C₄₂H₂₈) belongs to most preferred spintronic materials because of the high charge carrier mobility up to 40 cm²(V·s)^-1. However, the fabrication of a defect-free, polycrystalline rubrene for spintronic applications represents a difficult task. We report preparation and properties of rubrene thin films deposited by pulsed laser evaporation of solidified solutions. Samples of rubrene dissolved in aromatic solvents toluene, xylene, dichloromethane and 1,1-dichloroethane (0.23-1% wt) were cooled to temperatures in the range of 16.5-163 K and served as targets. The target ablation was provided by a pulsed 1064 nm or 266 nm laser. For films of thickness up to 100 nm deposited on Si, glass and ITO glass substrates, the Raman and AFM data show presence of the mixed crystalline and amorphous rubrene phases. Agglomerates of rubrene crystals are revealed by SEM observation too, and presence of oxide/peroxide (C₄₂H₂₈O₂) in the films is concluded from matrix-assisted laser desorption/ionization time-of-flight spectroscopic analysis.

Proceedings Article | 17 February 2017

Gold nanoparticles evaluation using functional optical coherence tomography

Marcin Strąkowski, Maciej Głowacki, Aleksandra Kamińska, Mirosław Sawczak

Proceedings Volume 10053, 1005336 (2017) https://doi.org/10.1117/12.2254912

KEYWORDS: Nanoparticles, Gold, Optical coherence tomography, Tissue optics, Polarization, Spectroscopy, Medical diagnostics, Scattering, Particles, Statistical analysis

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The main object of this research was to assess the ability to characterize the gold nanoparticles using optical modalities like optical coherence tomography. Since the nanoparticles, especially gold one, have been very attractive for medical diagnosis and treatment the amount of research activities have been growing rapidly. The nanoparticles designed for different applications like contrast agents or drugs delivery change the optical features of tissue in different way. Therefore, the expanded analysis of scattering optical signal may lead to obtain much more useful information about the tissues health and the treatment efficiency. The noninvasive measurements of the concentration and distribution of the nanoparticles, as well as their size in the media have been taken under consideration. For this purpose the polarization sensitive optical coherence tomography system with spectroscopic analysis (PS-SOCT) has been designed and used. In this contribution we are going to present the PS-SOCT measurement data obtained for the gold nanoparticles. The measurements have been taken for the liquid (gold nanoparticles in water) samples changing the particles concentrations in time.

SPIE Journal Paper | 26 January 2017

Application of the laser diode with central wavelength 975 nm for the therapy of neurofibroma and hemangiomas

Jacek Szymańczyk, Mirosław Sawczak, Witold Cenian, Katarzyna Karpienko, Małgorzata Jędrzejewska-Szczerska, Adam Cenian

JBO, Vol. 22, Issue 01, 010502, (January 2017) https://doi.org/10.1117/12.10.1117/1.JBO.22.1.010502

KEYWORDS: Laser therapeutics, Semiconductor lasers, Skin, Laser tissue interaction, Laser development, Continuous wave operation, Nd:YAG lasers, Fiber lasers, Optical fibers, Gas lasers

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This paper presents a newly developed dermatological laser (with a central wavelength 975 nm) for application in therapies requiring deep penetration of tissue, e.g., cutaneous (dermal) neurofibroma (von Recklinghausen disease) and hemangiomas. This laser can work either in pulses or continues wave mode. Laser radiation is transmitted toward the application region by optical fiber with a diameter of 0.6 mm. The compact design of the laser facilitates its transport and increases the comfort of use.

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Proceedings Article | 5 January 2017

Nanoparticle Over Mirror plasmonic structures prepared with use of Au colloid produced by laser ablation in water

Mirosław Sawczak, Marcin Zyskowski, Jakub Karczewski, Petar A. Atanasov, Nikolay N. Nedyalkov, Rumen Nikov, Nadya A. Stankova, Gerard Śliwiński

Proceedings Volume 10226, 102260G (2017) https://doi.org/10.1117/12.2261918

KEYWORDS: Gold, Nanoparticles, Aluminum, Nano opto mechanical systems, Neptunium, Absorption, Glasses, Laser ablation, Plasmonics, Scanning electron microscopy

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Recently, an intensive research is carried out on plasmonic structures due to their potential application in many areas such as sensing, light harvesting and energy conversion and storage. In particular, a growing interest is observed in the Nanoparticle Over Mirror (NOM) structures for which the lithography and surface chemical functionalization represent the most popular production routes¹. However, the application of those techniques is limited by the low efficacy, process complexity and chemical contamination of nanoparticles (NP). In this work, we report the contamination-free and low cost fabrication method of NOMs based on wet coating and ultrasonic-assisted nanocolloid drying process. The glass plates covered with magnetron sputtered 100 nm thick Au film and subsequently with Al₂O₃ layers (6 – 36 nm) by means of pulsed laser deposition are used as substrates. Au NPs are produced in the form of colloidal suspension by means of laser ablation in water using the 1064 nm, 6 ns Nd:YAG laser. The NOM synthesis is finalized by imposing of the Au NP suspension onto the as prepared Au-Al₂O₃/glass substrates and dried. To avoid NP agglomeration, the wet coated substrates are sonicated using 20W, 20 kHz ultrasound generator. SEM inspection of the obtained NOM structures confirms the positive sonication effect, i.e. the presence of agglomerate-free, homogenous layers. These consist of NPs (36 nm average diameter) which are characterized by the resonance absorption band at 528 nm. For NOM structures the UV-vis spectra reveal increased infrared activity and peak shift in agreement with theoretical modeling². The NOM structure characterization is completed by analysis of the SEM and profilometry measurement results.

Proceedings Article | 5 January 2017

Gold nanostructures for detection of pesticides, nitrates and drugs using Surface Enhanced Raman spectroscopy

N. Nedyalkov, Ru. Nikov, Ro. Nikov, A. Nikolov, P. Atanasov, Y. Nakajima, M. Terakawa, M. Sawczak, K. Grochowska, G. Sliwinski

Proceedings Volume 10226, 102260B (2017) https://doi.org/10.1117/12.2261674

KEYWORDS: Gold, Nanostructures, Raman spectroscopy, Nanoparticles, Nanolithography, Surface enhanced Raman spectroscopy, Glasses, Ceramics, Metals, Laser ablation

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In this work laser-assisted methods for metal nanostructures formation and their application as active substrates in Surface Enhanced Raman Spectroscopy are presented. The nanostructures are fabricated by laser processing of gold thin films deposited on low cost substrates as glass, ceramic, polymer and paper. The films are deposited by classical PLD technology. The produced films are then processed by nanosecond pulses delivered by nanosecond Nd:YAG laser system. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. Femtosecond Pulsed Laser Deposition in air is also applied for direct deposition of gold nanostructure. In another set of experiments gold nanoparticle colloids are fabricated by laser ablation of gold target in chloroform. The fabricated structures are then tested as active systems in SERS, as detection of pesticides (DDT), nitrates (NH₄NO₃), and drugs (Methylene blue) is demonstrated. The obtained results show that these nanostructures can be efficiently used in the detection and monitoring of materials with a high social impact.

Proceedings Article | 8 December 2016

Introductory investigations of dermatologic diode laser with wavelengths 975 nm: clinical therapy of Recklinghausen disease and of hemangiomas

J. Szymańczyk, W. Cenian, L. Piechowski, M. Sawczak, M. Jędrzejewska-Szczerska, A. Cenian

Proceedings Volume 10159, 101590H (2016) https://doi.org/10.1117/12.2263511

KEYWORDS: Semiconductor lasers, Laser therapeutics, Nd:YAG lasers, Continuous wave operation, Skin, Laser tissue interaction, Laser development, Gas lasers, Laser induced plasma spectroscopy, Distortion

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The newly developed pulsed/cw dermatological laser (with wavelengths 975 nm) is applied for therapies requiring deep penetration of tissue e.g. cutaneous (dermal) neurofibroma (Recklinghausen disease) or hemangiomas. As the selected eight patients had been treated previously using pulsed a Nd:YAG laser a comparison of these therapies was possible. The results of cutaneous neurofibroma therapy using diode laser show an improvement compared with the case of Ho:YAG and Nd:YAG laser therapies - however this should be checked for a larger number of patients.

SPIE Journal Paper | 11 August 2015

Use of optical skin phantoms for preclinical evaluation of laser efficiency for skin lesion therapy

Maciej Wróbel, Malgorzata Jedrzejewska-Szczerska, Stanislaw Galla, Leszek Piechowski, Miroslaw Sawczak, Alexey Popov, Alexander Bykov, Valery Tuchin, Adam Cenian

JBO, Vol. 20, Issue 08, 085003, (August 2015) https://doi.org/10.1117/12.10.1117/1.JBO.20.8.085003

KEYWORDS: Skin, Laser therapeutics, Tissue optics, Tissues, Absorption, Temperature metrology, Scattering, Semiconductor lasers, Laser scattering, Laser irradiation

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Skin lesions are commonly treated using laser heating. However, the introduction of new devices into clinical practice requires evaluation of their performance. This study presents the application of optical phantoms for assessment of a newly developed 975-nm pulsed diode laser system for dermatological purposes. Such phantoms closely mimic the absorption and scattering of real human skin (although not precisely in relation to thermal conductivity and capacitance); thus, they can be used as substitutes for human skin for approximate evaluation of laser heating efficiency in an almost real environment. Thermographic imaging was applied to measure the spatial and temporal temperature distributions on the surface of laser-irradiated phantoms. The study yielded results of heating with regard to phantom thickness and absorption, as well as laser settings. The methodology developed can be used in practice for preclinical evaluations of laser treatment for dermatology.

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Proceedings Article | 8 January 2015

Pulsed laser deposition of organic semiconductor rubrene thin films

K. Grochowska, S. Majumdar, P. Laukkanen, H. Majumdar, M. Sawczak, G. Śliwiński

Proceedings Volume 9447, 94470F (2015) https://doi.org/10.1117/12.2176009

KEYWORDS: Glasses, Thin films, Raman spectroscopy, Crystals, Spintronics, Organic semiconductors, Organic materials, Pulsed laser deposition, Pulsed laser operation, Aluminum

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Pulsed Laser Deposition (PLD) technique is applied to produce organic semiconductor (OS) rubrene thin film for spintronics applications. The use of organic material for spintronics is motivated by the advantages such as long spin diffusion length due to low spin-orbit and hyperfine coupling^1,2, chemical tuning of electronic functionality, easy structural modifications, ability of self-assembly and mechanical flexibility³ etc. However, a major drawback of OS is its low mobility compared to inorganic semiconductors. The PLD growth of rubrene aims on fabricating OS films under more controlled environment to achieve higher crystalline order to improve its mobility and spin coherence length. Among organic materials, rubrene reveals the highest hole mobility - up to 40 cm²/(V∙s) and can be exploited in organic light-emitting diodes (OLEDs) or field-effect transistors (OFETs) ^4. In this work the rubrene thin films are produced from hardened pellets in vacuum using Nd:YAG pulsed laser operated at 1064 nm, 2 Hz and energy fluence around 0.2 J/cm². For the reference rubrene samples on SiO₂ glass the AFM data reveal continuous 5-7 nm thick films. The amorphous structures are confirmed by XRD measurements and also Raman spectra which show signatures of both tetracene and phenyl bands and a broadband at 1373 cm^-1. The obtained results indicate that continuous, defect-free rubrene films can be prepared by means of PLD for investigation of the spin polarization properties of organic-inorganic hybrids. Further studies are on the way to improve crystalline qualities of the rubrene films for less grain boundary related defects and improved mobility and spin diffusion length.

Proceedings Article | 9 March 2014

Characterisation of CFRP surface contamination by laser induced fluorescence

Pawel Malinowski, Miroslaw Sawczak, Tomasz Wandowski, Wieslaw Ostachowicz, Adam Cenian

Proceedings Volume 9064, 90640E (2014) https://doi.org/10.1117/12.2042864

KEYWORDS: Luminescence, Contamination, Laser induced fluorescence, Adhesives, Nondestructive evaluation, Silicon, Composites, Analytical research, Spectroscopy, Manufacturing

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The application of Carbon Fibre Reinforced Polymers (CFRP) in aeronautics has been increasing. The CFRP elements are joint using rivets and adhesive bonding. The reliability of the bonding limits the use of adhesive bonding for primary aircraft structures, therefore it is important to assess the bond quality. The performance of adhesive bonds depends on the physico-chemical properties of the adhered surfaces. This research is focused on characterization of surfaces before bonding. In-situ examination of large surface materials, determine the group of methods that are preferred. The analytical methods should be non-destructive, enabling large surface analysis in relatively short time. In this work a spectroscopic method was tested that can be potentially applied for surface analysis. Four cases of surface condition were investigated that can be encountered either in the manufacturing process or during aircraft service. The first case is related to contamination of CFRP surface with hydraulic fluid. This fluid reacts with water forming a phosphoric acid that can etch the CFRP. Second considered case was related to silicone-based release agent contamination. These agents are used during the moulding process of composite panels. Third case involved moisture content in CFRP. Moisture content lowers the adhesion quality and leads to reduced performance of CFRP resulting in reduced performance of the adhesive bond. The last case concentrated on heat damage of CFRP. It was shown that laser induced fluorescence method can be useful for non-destructive evaluation of CFRP surface and some of the investigated contaminants can be easily detected.

Proceedings Article | 15 March 2013

Time-resolved LIPS of molecular bands for reliable identification of calcite in historical materials

Iwona Żmuda-Trzebiatowska, Mirosław Sawczak, Panagiotis Siozos, Demetrios Anglos, Olga Kokkinaki, Gerard Śliwiński

Proceedings Volume 8770, 87700B (2013) https://doi.org/10.1117/12.2014231

KEYWORDS: Calcium, Laser induced plasma spectroscopy, Nitrogen, Calcite, Carbonates, Laser induced fluorescence, Plasma, Minerals, Raman spectroscopy, Absorption

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In this work the time-resolved Laser-Induced Plasma Spectroscopy (LIPS) is applied for investigation of samples containing calcium carbonate (CaCO₃) which represents a marker in the identification of historical stone and pigment materials. The relatively broad bands in the range of 547-560 nm and between 580 nm and 650 nm ascribed to the CaO molecular emission are clearly observed together with the collection of sharp peaks characteristic for the atomic Ca I and ionic Ca II lines. For suppressed oxide formation processes by means of recording the spectra in the N₂ environment a marked change in the time evolution of the CaO bands is observed and reaction kinetics different from that observed in air is concluded. This supports the CaO assignment and is confirmed by values of the decay time constant of 2,49 μs for nitrogen and 0,81μs for air derived from fitting of the experimental decay curves of the molecular emission. The case of CaO confirms that the time-resolved LIPS analysis provide useful supplementary data and contribute to reliability of the material identification.

Proceedings Article | 22 January 2013

Pulsed dermatologic 20W diode-laser emitting at 975-nm

L. Piechowski, W. Cenian, M. Sawczak, A. Cenian

Proceedings Volume 8703, 870304 (2013) https://doi.org/10.1117/12.2014998

KEYWORDS: Pulsed laser operation, Laser applications, Semiconductor lasers, Laser therapeutics, Nd:YAG lasers, Laser development, Skin, Fiber lasers, Beam controllers, Pulsed fiber lasers

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The pulsed dermatologic laser for photothermolysis is constructed basing on technology of 975 nm diode lasers developed for fiber-laser excitation. In near future these lasers can replace ND:YAG ones for dermatologic applications, especially therapy of deep skin diseases.

Proceedings Article | 22 January 2013

Influence of laser modification of TiO2 films for its photocatalytic properties

Mirosław Sawczak, Michał Górski, Hubert Rachubiński, Adam Cenian

Proceedings Volume 8703, 87030M (2013) https://doi.org/10.1117/12.2014621

KEYWORDS: Absorption, Raman spectroscopy, Glasses, Statistical analysis, Laser irradiation, Scanning electron microscopy, Calibration, Crystals, Nd:YAG lasers, Titanium dioxide

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The photocatalytic activity of TiO₂ layer modified by laser radiation is discussed in the paper. Commercially available nanopowder P25(Degussa) was used, which consists of a mixture of anatase and rutile - two crystallographic forms of TiO₂ . The spin-coating technique was applied to produce thin layers on glass. After drying and calcination the layer was thermally modified using a pulsed (6 ns) Nd:YAG laser (FHG 266 nm). This caused a clearly visible surface darkening effect. The XRD spectra show that phase change transition (from anatase to rutile) took place partially. This was also confirmed by Raman spectra. The main peak of Raman-spectra shifts from 142,84 to 145,22 cm^-1, probably due to decreasing size of TiO₂ nanoparticles or more probably due to a defects generation in nanocrystallite structure. Defects have been reported in the literature as surface oxygen depletion and generation valance states Ti³⁺ and Ti⁴⁺. Eventually, kinetics of methylene-blue decay and CO₂ to methane conversion were examined. In both cases an increase of catalytic activity was observed.

Proceedings Article | 13 March 2007

Laser techniques for cultural heritage research case studies

G. Sliwiński, M. Jasińska, J. Bredal-Jørgensen, A. Kamińska, K. Komar, M. Sawczak

Proceedings Volume 6604, 66040T (2007) https://doi.org/10.1117/12.726906

KEYWORDS: Calcium, Iron, Laser induced plasma spectroscopy, Aluminum, Silicon, Laser irradiation, Resistance, Spectroscopy, Scanning electron microscopy, Barium

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Results of the recent application studies of laser-based techniques for conservation practice, carried out in the frames of research and conservation projects are presented and discussed. The Gotland Sandstone Project covers laser cleaning, spectroscopic techniques of the process monitoring and materials analysis. The post-processing effect is investigated by means of LIBS, colorimetry, SEM and XEDS in order to answer questions regarding encrustation removal, discoloration and alteration due to environmental pollution and laser interaction, respectively. The cleaning is monitored acoustically. Slight differences in stone yellowing are revealed when applying laser in air or pure N₂ environment which is ascribed to material oxidation and partial combustion of surface remnants due to presence of O₂ contributing to the final effect of laser cleaning. Results of microscopic observation are supported by the presence of elements S, Al, Ca, and C which prevail in crust. In case of restoration of the historical documents on paper the ablative cleaning and the nearly nondestructive identification and composition analysis of surface layers such as contaminants, substrate and pigments are performed. Spectra obtained by means of the LIPS technique for historical, originally contaminated and also artificially soiled model samples reveal reach structures. The emission lines of Ca, Na, K, Al and Fe are ascribed to contaminants because of intensities decreasing with prolonged surface irradiation during laser cleaning. Bands of Ti and Ba correspond to white pigments (TiO₂ and BaSO₄) in the paper and are confirmed by the Raman spectra as well. For identification of historical pigments the reference measurements on model substrates are performed, too.

Proceedings Article | 1 February 2007

Method for the CO2 laser beam wavefront control

M. Sawczak, G. Rabczuk

Proceedings Volume 6599, 65990M (2007) https://doi.org/10.1117/12.726660

KEYWORDS: Mirrors, Sensors, Deformable mirrors, Transmission electron microscopy, Wavefronts, Signal detection, Gas lasers, Carbon monoxide, Beam controllers, Wavefront sensors

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The results of experimental tests concerning the wavefront sensor designed for control of the cw CO₂ laser beam transformed by the deformable multichannel bimorph mirror are presented in the paper. Wave-front curvature sensing is realised by measuring the radiation intensity distribution in the defocused beam and comparing it with the distribution recorded for a reference, undisturbed beam. The characteristics of the sensor are analysed versus the controlled deformation introduced to the tested beam by a deformable mirror. The experimental tests show that the curvature signal, measured by the designed array detector is proportional to the local distortions of the wavefront of the laser beam.

Proceedings Article | 23 January 2007

Langmuir probe diagnostics of plasma generated by means of pulsed Nd:YAG laser interaction with Si-based targets

Adam Cenian, Miroslaw Sawczak, Gerard Sliwinski

Proceedings Volume 6598, 65980Z (2007) https://doi.org/10.1117/12.726591

KEYWORDS: Plasma, Laser ablation, Ions, Silicon, Plasma generation, Nd:YAG lasers, Ionization, Pulsed laser operation, Diagnostics, Plasma diagnostics

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Investigations of laser ablation plume aimed at applications for the SiO nano-film deposition are reported. The plasma formation and propagation through experimental chamber was investigated by means of Langmuir probe. The effects related to plume splitting and acceleration are discussed.

Proceedings Article | 12 October 2005

The effect of laser drilling on surface and material properties of AlN ceramic

N. Nedialkov, M. Sawczak, M. Jadraque, P. Atanasov, M. Martin, G. Sliwinski

Proceedings Volume 5958, 595836 (2005) https://doi.org/10.1117/12.622706

KEYWORDS: Aluminum nitride, Laser drilling, Ceramics, Aluminum, Ions, Plasma, Laser ablation, Scanning electron microscopy, Absorption, Photon transport

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For the laser drilling of aluminum nitride (AlN) ceramic the influence of the laser parameters and material properties on the drilling rate, quality of the holes and the effects related to plasma formation are investigated. The ablation is performed by pulsed irradiation of Nd:YAG laser at wavelengths of 1064, 532 and 355 nm, at pulse duration of 6 ns (FWHM) in air. The SEM scans of the processed surface reveal regular, cylindrically shaped holes of diameter of about 100 μm obtained under conditions of constant fluence at all wavelengths applied. Holes are surrounded by circular zones which are colored different than the non-processed surface, and of a much larger diameter. Comparison of the original material composition with that of the processed one made by EDX shows a decrease of the N concentration in the affected area. The zones are identified as heat-affected due to the high thermal conductivity of the ceramic material and change of the photon distribution due to multiple reflections into the material. In the LIBS spectra recorded in order to obtain the composition of the ablated material the presence of ions and neutrals depends on the laser intensity applied. At intensity values close to the ablation threshold the ejected material consists mainly of neutrals and doubling the intensity results in appearance of single-ionized Al species. The ionized species dominate over neutrals under conditions of higher drilling rate (15 GW/cm² at 532 nm). Their existence in the plasma plume together with clusters is confirmed by the TOF-MS spectra. It also corresponds to the characteristic spatial structure of the plume. The investigation of the decomposition reactions of AlN in dependence on the applied laser intensity is based on numerical solving of the three dimensional heat-transfer equation. A solution consistent with the experimental observation indicates that at threshold the ceramic decomposes into gaseous nitrogen and solid Al particulates, while at higher fluences the Al vaporizes and influences the drilling quality.

Proceedings Article | 22 April 2005

Curvature sensor for a laser beam wavefront control

M. Sawczak, Grazyna Rabczuk, W. Warszawski

Proceedings Volume 5830, (2005) https://doi.org/10.1117/12.618748

KEYWORDS: Mirrors, Sensors, Wavefronts, Deformable mirrors, Beam controllers, Wavefront sensors, Wavefront distortions, Signal detection, Helium neon lasers, Optical testing

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Results of the experimental tests concerning the wavefront sensor designed for control of the laser beam transformed by the deformable multichannel bimorph mirror are presented in the paper. The sensor developed on the base of the curvature sensing method consists of the vibrating mirror of a membrane type and a multi-element detector for the beam intensity measurements. The characteristics of the sensor are analysed versus the controlled deformation introduced to the tested beam by a deformable mirror. The measurements prove that the curvature signal measured by the detector is proportional to the local distortions of the wavefront of the laser beam.

Proceedings Article | 23 March 2005

Laser drilling of AIN ceramics using nanosecond pulses

Nikolay Nedialkov, Peter Atanasov, M. Sawczak, Gerard Sliwinski

Proceedings Volume 5777, (2005) https://doi.org/10.1117/12.611043

KEYWORDS: Ceramics, Laser drilling, Plasma, Pulsed laser operation, Aluminum, Laser ablation, Aluminum nitride, Absorption, Scanning electron microscopy, Ions

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Laser drilling of aluminum nitride (AIN) ceramics by 6 ns SHG (λ=532 nm) Nd:YAG laser pulses is studied. The drilling rate, quality of the holes, and the effects related to plasma formation are investigated. Numerical model based on the heat-transfer equation is developed to describe the drilling process. Different mechanisms of material decomposition are found to be realized, which depend on the laser fluence. They determine the quality of the holes produced. Below 5 GW/cm² the material ejection is realized by decomposition of ceramics into solid or liquid Al and gaseous N₂. The letter blows away culsters and flakes from the irradiated area and the holes drilled have irregular shape. At higher laser intensities, the decomposition into gaseous Al and N₂ or direct evaporation of the ceramics results in good hole quality. A saturation of the ablation rate as a function of the laser intensity is observed above 15 GW/cm². The calculated depths of the holes drilled are in agreement with the experimental data when absorption of the laser radiation from the plasma plume is taken into account.

Proceedings Article | 23 March 2005

Investigation of the laser cleaning effect on historical wood-pulp paper documents

Aleksandra Kaminska, M. Sawczak, Gerard Sliwinski

Proceedings Volume 5777, (2005) https://doi.org/10.1117/12.611323

KEYWORDS: Resistance, Laser irradiation, Ultraviolet radiation, Pulsed laser operation, Statistical modeling, Polymerization, Chemical analysis, Humidity, Kinematics, Laser damage threshold

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The pulsed laser cleaning of wood-pulp paper samples systematically investigate for renovation of historical documents indicates on negative effects of the irradiation at 266 and 355 nm on the mechanical and chemical paper properties whenever application of the 532 nm laser and fluence below 0,6 J/cm² reveal satsifactory performance.

Proceedings Article | 23 March 2005

Control of a high-power cw CO2 laser output beam properties by using an adaptive intracavity mirror

Grazyna Rabczuk, M. Sawczak

Proceedings Volume 5777, (2005) https://doi.org/10.1117/12.611027

KEYWORDS: Mirrors, Resonators, Deformable mirrors, Laser resonators, Continuous wave operation, Carbon dioxide lasers, Laser processing, High power lasers, Actuators, Electrodes

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Results of the experimental analysis concerning the output beam characteristics of the industrial cw CO₂ laser with an intracavity deformable mirror are presented. The mirror used is a bimorph piezoelectric adaptive mirror developed at Turn Ltd (Russia). The mirror shape is controlled by supplying the voltage to the mirror electrodes. The performed analysis proves that the use of the deformable mirror with a variable radius of curvature in the laser cavity enables controlled and dynamic changes of the resonator properties that result in the modification and optimization of the laser output characteristics decisive for the laser material processing effects.

Proceedings Article | 21 June 2004

Conditions for the dynamic control of the focusing properties of the high-power CW CO₂ laser beam in a system with an adaptive mirror

Grazyna Rabczuk, M. Sawczak

Proceedings Volume 5449, (2004) https://doi.org/10.1117/12.563124

KEYWORDS: Mirrors, Continuous wave operation, Control systems, Laser processing, High power lasers, Carbon dioxide lasers, Laser optics, Deformable mirrors, Thermal effects, Optical testing

Read Abstract +

A mirror with a controllable focal length designed for the high power cw CO₂ industrial laser was integrated into the laser beam guiding system in order to verify conditions for the dynamic control of the laser beam focusing properties. The ability of the mirror to correct the thermal distortions in the laser output window was investigated by measuring the beam characteristics versus the mirror shape at different conditions of the laser operation defined by the output power level. The experimental tests prove that the mirror enables dynamic adjustments of the laser beam diameters at the focusing optics and in consequence the control of the focused beam parameters.

Proceedings Article | 15 March 2004

High-power cw CO2 laser beam properties in a system with a variable focal length mirror

Grazyna Rabczuk, M. Sawczak

Proceedings Volume 5481, (2004) https://doi.org/10.1117/12.558280

KEYWORDS: Mirrors, High power lasers, Continuous wave operation, Carbon dioxide lasers, Laser resonators, Laser development, Carbon monoxide, Gas lasers, Resonators, Beam delivery

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The system of a mirror with a variable focal length, controlled by pressure variations generated in a cooling medium behind the mirror plate, was developed and investigated for the high power cw CO₂ industrial laser. The mirror was tested under condition of the laser operation as inter and outer cavity mirror. The results of the experimental analysis confirm that the use of the controllable curvature mirror in the laser resonator allows the dynamic changes in the resonator configuration and corresponding modification of the lasers output characteristics. Measurements performed for the variable focal length mirror, integrated into the beam delivery system prove the possibility for the controllable dynamic adjustment of the focus position as well as the focus size in the range, which is dependent on the mirror location relatively to the focusing optics.

Proceedings Article | 10 November 2003

Ablation of ceramics with ultraviolet, visible, and infrared nanosecond laser pulses

Nikolay Nedialkov, P. Atanasov, M. Sawczak, G. Sliwinski

Proceedings Volume 5120, (2003) https://doi.org/10.1117/12.515847

KEYWORDS: Ceramics, Laser ablation, Laser energy, Absorption, Laser drilling, Plasma, Ultraviolet radiation, Infrared radiation, Silicon, Visible radiation

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Laser ablation of alumina (Al₂O₃), aluminum nitride (AIN) and silicon nitride (Si₃N₄) ceramics by 6 ns Nd:YAG laser operating at wavelengths of 1064 nm, 532 nm and 355 nm is studied. For all materials the maximum ablation rate is observed at wavelength 1064 nm, and the smallest one for irradiation at 532 nm in the case of Si3N4 and AIN. The numerical model, based on the heat-transfer equation describes the temperature distribution in the material and the evaporation process. The calculated depths of the drilled holes are in agreement with experiment.

Proceedings Article | 10 November 2003

Influence of the intracavity perturbations on laser output beam characteristics

Grazyna Rabczuk, S. Labuda, M. Sawczak, G. Sliwinski

Proceedings Volume 5120, (2003) https://doi.org/10.1117/12.515485

KEYWORDS: Pulsed laser operation, Laser resonators, Absorption, Modulation, Carbon dioxide lasers, Optical testing, Mirrors, Q switches, Modulators, Resonators

Read Abstract +

Dynamic properties of the output intensity profiles of the CO₂ laser beam are studied under conditions of the loss modulation caused by a freely expanding stream of an absorber gas injected into the laser cavity. The temporal and spatial output beam characteristics are measured under various experimental conditions specified by the operational parameters of gas-dynamic modulator.

Proceedings Article | 10 November 2003

Experimental tests of an intracavity deformable mirror designed for a cw CO2 laser

M. Sawczak, G. Rabczuk

Proceedings Volume 5120, (2003) https://doi.org/10.1117/12.515507

KEYWORDS: Mirrors, Deformable mirrors, Continuous wave operation, Carbon dioxide lasers, Laser resonators, Reflectivity, Resonators, High power lasers, Optical testing, Diffraction

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The experimental preliminary results concerning the operation conditions of a cw CO₂ laser with a variable focus, concave mirror are presented in the paper. The mirror is introduced as a rear mirror into a stable cavity of the laser. The contour of the mirror is changed by adjusting the pressure of the cooling medium. The laser output properties are investigated versus the parameters describing the deformable mirror shape.

Proceedings Article | 4 November 2003

The effect of wavelength and fluence on the cellulose degradation of laser-cleaned paper

A. Kaminska, M. Sawczak, Gerard Sliwinski

Proceedings Volume 5226, (2003) https://doi.org/10.1117/12.519520

KEYWORDS: Scanning electron microscopy, Pulsed laser operation, Ultraviolet radiation, Laser therapeutics, Contamination, Nd:YAG lasers, Statistical modeling, Optical filters, Laser damage threshold, Chemical analysis

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The effect of a Q-switched Nd:YAG laser irradiation applied for ablative cleaning of the surface contaminants on cellulose samples and aimed on conservation of historical paper documents is investigated. The removal effectiveness of an artificial graphite contamination from model samples is investigated in dependence on the laser wavelength (532, 355 and 266 nm) and fluence (0.3 to 0.9J/cm²) and also the surface color changes are measured. Damages of cellulose fibers due to laser interaction are examined by means of the SEM technique. For irradiation at 266 nm only partial removal of the contamination and a distinct cellulose degradation, and also the yellowing of paper surface are observed. For the 355 nm wavelength and energy fluence below 0.6 J/cm² the degradation of cellulose fibers does not occur. However, a slight yellowness of the surface is observed. The optimal cleaning wavelength of 532 nm and safe energy fluence below 0.6 J/cm² found experimentally agree with literature.

Proceedings Article | 6 October 2003

Output characteristics of a high-power cw CO2 laser with a dynamic control of the optical cavity configuration

Grazyna Rabczuk, M. Sawczak

Proceedings Volume 5230, (2003) https://doi.org/10.1117/12.532237

KEYWORDS: Mirrors, Deformable mirrors, Carbon dioxide lasers, Resonators, Laser resonators, Continuous wave operation, High power lasers, Metals, Optical resonators, Laser applications

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The design properties and preliminary tests of a deformable mirror with a shape controlled by adjusting the pressure of the cooling medium are presented in the paper. The mirror, used as a rear mirror of a stable cavity, was tested under conditions of a transverse flow cw CO₂ laser operation. The tests proved that the use of the variable focal length mirror in the laser cavity allows the dynamic changes in the resonator configuration and thus the dynamic and controllable changes in the laser output characteristics.

Proceedings Article | 9 April 2001

Investigation of a copper-doped sol-gel glass for laser applications

M. Sawczak, Gerard Sliwinski, Marek Grinberg, Benedykt Kuklinski

Proceedings Volume 4397, (2001) https://doi.org/10.1117/12.425116

KEYWORDS: Absorption, Copper, Glasses, Luminescence, Sol-gels, Ions, Laser applications, Nd:YAG lasers, Quantum efficiency, Spectroscopy

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For SiO₂ glass samples doped with Cu⁺ ions at 150 - 500 ppm and prepared by the sol-gel method the absorption, excitation and emission spectra are recorded. Due to excitation in the broad absorption band (250 - 350 nm) a strong luminescence at 540 nm and of FWHM equals 100 nm is observed. Dependencies of the spectral characteristics of this emission on the excitation indicate on the ASE and a possible lasing potential.

Proceedings Article | 25 January 2001

Spatial and temporal characteristics of an industrial cw CO2 laser beam

Grazyna Rabczuk, M. Sawczak, Gerard Sliwinski

Proceedings Volume 4184, (2001) https://doi.org/10.1117/12.413975

KEYWORDS: Resonators, Carbon dioxide lasers, Beam shaping, Continuous wave operation, Optical testing, Laser processing, High power lasers, Laser beam propagation, Laser resonators, Laser stabilization

Read Abstract +

The spatial and temporal characteristics of the laser beam extracted from the industrial high power cw CO2 laser are investigated experimentally and analysed. The beam properties are compared for two optical stable cavity configurations characterised by the different values of the Fresnel number. It is found that the beam shape fluctuations, observed for both cavities, are mainly due to the mechanical vibrations of the laser construction. The cavity of the lower Fresnel number emits the beam ofbetter quality and provides better focussing condition in the processing zone.

Proceedings Article | 4 October 2000

Diagnostic instrument for measurements of a high power CO2 laser beam

Grazyna Rabczuk, M. Sawczak, Gerard Sliwinski

Proceedings Volume 4237, (2000) https://doi.org/10.1117/12.402878

KEYWORDS: Carbon dioxide lasers, High power lasers, Diagnostics, Data processing, Measurement devices, Control systems, Scanners, Sensors, Signal detection, Laser beam propagation

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A measuring device based on a rotating pinhole method was designed and developed at IF-FM for recording the spatial structure of high power cs CO₂ laser beams in the near and far field region. The main performance parameters of the device are presented together with the measurement results concerning the beam propagation characteristics of the 1.2 kW technological laser.

Proceedings Article | 4 October 2000

Luminescence of copper-doped sol-gel matrices for laser applications

M. Sawczak, Gerard Sliwinski, Benedykt Kuklinski, Marek Grinberg

Proceedings Volume 4237, (2000) https://doi.org/10.1117/12.402887

KEYWORDS: Copper, Sol-gels, Annealing, Luminescence, Absorption, Ions, Solids, Liquids, Matrices, Glasses

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Luminescence and absorption spectra of the silica samples prepared by a sol-gel technique and originally doped with Cu solutions in the range of 500/1-3000/1 are recorded. For alternatively applied CuCl₂ or Cu(AA)₂ dopants the same spectral profiles of dry solids are observed. A slightly structured emission band centered at 330 nm and ascribed to the 3d⁹4s¹ yields 3d¹⁰ transition of the Cu⁺ ion is recorded for excitation around 300 nm of samples previously dried and annealed below 455 K. The band shows a red shift for annealing at higher temperatures, and vanishes completely at 1173 K. Instead of broad emission band of more than double half width and of about 25 times higher intensity in the line center at 560 nm occurs most probably due to temperature dependent structural transition accompanied by the Cu⁺-Cu²⁺ change of the dopant valence.

Proceedings Article | 4 October 2000

Experimental study of the high-power CO2 laser beam stability

Grazyna Rabczuk, Sergei Labuda, M. Sawczak

Proceedings Volume 4237, (2000) https://doi.org/10.1117/12.402877

KEYWORDS: Carbon dioxide lasers, Beam shaping, Laser stabilization, High power lasers, Laser processing, Optical testing, Continuous wave operation, Carbon dioxide, Laser resonators, Shape analysis

Read Abstract +

Influence of the discharge current oscillations, mechanical vibrations of the laser construction as well as the on- uniformity of the active medium properties on the output beam characteristics were studied experimentally for a high power, transverse flow, cs CO₂ industrial laser. The factors influencing the laser output power stability were investigated together with the temporal behavior of the spatial beam profiles.

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