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In this paper, we investigate the influence of the following parameters: pulse duration, pulse repetition rate, line-to-line and pulse-to-pulse overlaps, and scanning strategy on the ablation of AISI 316L steel and CuZn37 brass with a nanosecond, 1064-nm, Yb fiber laser. The results show that the material removal rate (MRR) increases monotonically with pulse duration up to the characteristic repetition rate (f0) where pulse energy and average power are maximal. The maximum MRR is reached at a repetition rate that is equal or slightly higher as f0. The exact value depends on the correlation between the fluence of the laser pulses and the pulse repetition rate, as well as on the material properties of the sample. The results show that shielding of the laser beam by plasma and ejected material plays an important role in reducing the MRR. The surface roughness is mainly influenced by the line-to-line and the pulse-to-pulse overlaps, where larger overlap leads to lower roughness. Process optimization indicates that while operating with laser processing parameters resulting in the highest MRR, the best ratio between the MRR and surface roughness appears at ~50% overlap of the laser pulses, regardless of the material being processed.

Bor, običajno podan kot borov oksid (B2O3), je ena izmed sestavin borosilikatnega stekla, ki je pomembna komponenta v proizvodnji steklene volne. Ker so surovine, ki vsebujejo bor, zelo drage, se bor vzdržuje na točno določeni koncentraciji, ki se jo preverja s titracijsko metodo. Titracija je časovno zelo potraten proces in je primerna le za vzorce, ki vsebujejo več kot 0.35 masnih odstotkov B2O3. Bolj optimalna rešitev je meritev z masnim spektrometrom z induktivno sklopljeno plazmo (ICP-MS), saj je priprava vzorcev enostavnejša, analizira se lahko več vzorcev hkrati, s tem pa se tudi zmanjša možnost napak in prihrani veliko časa. Ključna komponenta ICP-MS-a je stabilna argonova plazma, ki pri zelo visoki temperaturi molekule razbije na posamezne ione, le - ti pa potujejo naprej skozi kvadrupol in se ločijo na osnovi razmerja med maso in nabojem (m/z). Zaradi občutljivosti naprave, se ICP-MS uporablja predvsem za analizo elementov v sledovih, zato je ta analizna tehnika primerna za določevanje bora v naših vzorcih. V diplomskem delu smo optimizirali obstoječo metodo za določitev koncentracije bora v stekleni ter kameni volni s pomočjo ICP-MS. Rezultate realnih vzorcev smo primerjali s koncentracijami bora v standardnih referenčnih materialih. Rezultati meritev bora so pokazali, da z obstoječo metodo pri stokratni redčitvi vzorca zelo dobro merimo višje koncentracije bora (nad 0.35%) v vzorcih in bi lahko v tem primeru ICP-MS analizo uporabljali namesto časovno zamudne titracije. ICP-MS je primeren tudi za merjenje vzorcev z nizko koncentracijo bora (pod 0.35%). Poleg metode ICP-MS, ki se uporablja za analizo tekočih vzorcev, smo uporabili tudi metodo laserske ablacije, sklopljene z metodo ICP-MS. Vzorci pri tej analizni tehniki so v trdnem stanju, pripravljeni pri dveh različnih temperaturah, in sicer pri 750 ° in 1150 °C. Rezultati so pokazali, da LA-ICP-MS lahko nadomesti tekočinsko ICP-MS pri vzorcih z visoko koncentracijo bora, saj so bile relativne razlike med rezultati, pridobljenimi v internem laboratoriju in rezultati, pridobljenimi na zunanjem inštitutu majhne (do 3.4%). Boron oxide (B2O3) is one of the components of borosilicate glass, which is used as an important raw material in the production of glass mineral wool. Raw materials containing boron are very expensive and this is one of the main reasons that the concentration of boron is maintained at a certain level. For boron determination usually the titration method is used. Since this is a very time-consuming procedure and has high boron detection limit (0.35%), determination of boron by using the inductively coupled plasma-mass spectrometry (ICP-MS) would be a better solution. Furthermore, sample preparation for ICP-MS measurements is easier and more samples can be analysed at the same time. Stable argon plasma is a key component of the ICP-MS. At very high temperatures molecules are ionised. Ions are traveling through quadrupole and are separated according to their mass and charge (m/z) ratio. Due to its high sensitivity, the ICP-MS is mainly used for trace analyses and is appropriate technique for boron determination in our samples. In the diploma thesis, the existing ICP-MS method for boron determination in glass and rock mineral wool was optimised. The results of real samples were compared with boron concentrations in standard reference materials. The results showed that high concentrations of boron (above 0.35%) could be accurately determined by current method and 100-fold dilution of the sample. It can be concluded that the solution mode ICP-MS can be used instead of time-consuming titration. In addition, with that method also concentrations below 0.35% can be determined. Beside the solution mode ICP-MS, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used. Solid state samples were prepared at two different temperatures, 750 °C and 1150 °C. The results showed that LA-ICP-MS can replace the solution mode ICP-MS when boron concentrations are high, since the relative differences between the results obtained in the internal laboratory compared to the results obtained in the external laboratory were low (up to 3.4%).

In this study we report the influence of laser ablation on the controlled biodegradability of a Fe–Mn alloy developed for medical implants. After texturing by a nanosecond Nd:YAG laser, the surface expressed extreme super-hydrophilic wetting properties, since laser ablation led to micro-channels and chemical modification resulting in nanostructured metal oxides. The influence of functionalized surface properties on corrosion behavior was examined on molecular level by using X-ray photoelectron spectroscopy. Results reveal that the oxide layer after the laser texturing of Fe–Mn alloy consists mainly of Fe2O3 and FeO, with the content of Mn in the oxide layer being significantly higher than in the bulk. The results of the electrochemical measurements clearly demonstrate the superior biodegradability of the Fe–Mn alloy samples functionalized by laser ablation. Here, the laser-triggered corrosion is self-driven by further production of corrosion products that leads to biodegradability of the whole sample.

A Nd:YAG laser with 7-ns pulses and pulse energies up to 10 mJ is used to induce an optical breakdown in the front surface of an aluminum rod, covered by a water layer. The rod is part of a ballistic pendulum. In this way, we study the propulsion effects by means of coupling coefficient and energy-conversion efficiency with respect to different confining geometries, volumes of water applied to the front surface of the rod, and the distance of this surface from the laser-beam focus. Holes with different dimensions are drilled on the target surface and filled with different volumes of water to examine the influence of the confinement by the liquid (a free boundary) and a solid-surface geometry on laser ablation effects. The rod movement and the water ejection after laser ablation are acquired by a high-speed camera with 10k frames per second. The results show that the confinement by cavity substantially increases the propulsion effects by shaping the ejected flow of the liquid; while the cavitation bubble, induced inside the water layer, plays a significant role in propulsion efficiency. From the presented results, it follows that the laser-propelled rod carries below 0.5% of the total mechanical energy after propulsion, while the rest of this energy represents the kinetic energy of the ablated water. As expected, moving the target surface away from the focal position decreases the ablative-propulsion efficiency. When the focus is moved inside the solid target, the decrease occurs due to lower conversion of the pulse energy into the energy of the cavitation bubble. If the focus is moved from the surface outward, the bubble moves towards the liquid–gas interface and it is not able to efficiently eject all the liquid from the target.

Vrtanje mikrometrskih in podmikrometrskih izvrtin z laserskim snopom je pomemben tehnološki izziv, ki ga lahko rešimo z detekcijskim sistemom v povratni zanki. V magistrskem delu smo razvili detekcijski sistem, ki nam je omogočal nadzorovanje prevrtanosti tanke kovinske folije in smo ga vgradili v laserski sistem z nanosekundnim vlakenskim laserjem. Postavili smo laserski sistem, ki vsebuje nanosekundni vlakenski laser (λ = 1060 nm), skenirno glavo in optiko (premer snopa v gorišču znaša 13 um). Eksperimente smo izvajali na foliji iz nerjavnega jekla debeline 28 µm in titana z debelino 32 µm. Odprtozančni sistem za izdelavo mikroizvrtin smo spremenili v zaprtozančni s pomočjo fotodiode, asferične leče in krmilnega vezja, ki smo ga skozi nalogo zasnovali in razvili. Detekcijski sistem deluje tako, da zbere svetlobo na fotodiodi in s tem zazna laserski preboj, hkrati pa prekine nadaljnje lasersko bliskanje za izvrtano luknjo. S sistemom za detekcijo smo poiskali optimalne parametre za izdelavo izvrtin na nerjavnem jeklu v rangu 1.3 µm ± 0.5 µm in pokazali, da jih je mogoče ponovljivo izdelati. Raziskali smo vpliv polarizacije na obliko izhodne luknje in kontrolirano razširili izhodni premer, s pomočjo zakasnitve določenega števila laserskih bliskov, po detekciji preboja skozi material. Za analizo vzorcev smo uporabili optični mikroskop s petstokratno povečavo, nato pa še električni vrstični mikroskop (SEM), kjer smo luknjice izmerili. Na koncu smo preverili, kolikšna je najmanjša možna razdalja med luknjicami za izdelavo največje možne matrike izvrtin. Ugotovili smo, da je čas za vrtanje ene izvrtine 0.3 ms in 6 min 48 s za matriko 40000 izvrtin/cm2 . Najmanjša izhodna luknja, ki smo jo uspeli izvrtati, znaša 0.8 µm. Drilling micrometer and sub-micrometer holes with a laser beam is an important technological challenge that can be solved with a feedback loop detection system. In this master's thesis, we have developed a detection system that allows us to control perforation of a thin metal foil and installed it into a laser system with a nanosecond fiber laser. We set up a laser system containing a nanosecond fiber laser (λ = 1060 nm) , scanning head an optics (the beam diameter in focus equals 13 um). The experiments were performed on stainless steel foil with a thickness of 28 µm and titanium with a thickness of 32 µm. The open-loop system for micro-holes drilling, was transformed into the closed-loop system by using a photodiode, an aspherical lens and a control circuit, which we designed and developed within this thesis. The detection system works by collecting light on the photodiode, thereby detecting a laser-induced breakdown, while interrupting further laser pulses for the drilled hole. With the detection system, we found the optimal parameters for the production of holes in a stainless steel foil in range of 1.3 µm ± 0.5 µm and showed that they can be reproduced. The effect of polarization on the shape of the output hole was investigated and the output diameter controlled by delaying a certain number of laser pulses, after detecting a brakdown through the material. An optical microscope, with a five hundred times magnification, was used to analyze the samples, followed by characterization with a scanning electron microscope (SEM), where the holes were measured. Finally, we checked the minimum distance between the holes to produce the largest array of perforated holes. We found that the drilling time of one hole was 0.3 ms, while it takes 6 min 48 s for a matrix of 40000 holes per cm2. The exit diameter of the smallest hole we were able to drill equalled 0.8 um.

Učinkovitost laserske ablacije je pomemben parameter pri graviranju. Ta je v našem primeru definirana kot razmerje med teoretično energijo, ki je potrebna za odstranitev materiala, in energijo, ki smo jo dovedli v obliki svetlobe obdelovalnega laserja. Uporabili smo nanosekundni (12˗240 ns) Yb vlakenski vir z valovno dolžino 1060 nm. Obravnavana materiala na preizkusih sta bila v našem primeru nerjavno jeklo in aluminij. Z uporabo različnih kombinacij obdelovalnih parametrov, kot so frekvenca ter časovni potek moči, vršna in povprečna moč laserskih bliskov, smo dobili različne globine ablacije materiala. Iz dobljenih vrednosti smo lahko izračunali spreminjanje učinkovitosti laserske ablacije in izvedli analizo. Tako smo ugotovili, da se učinkovitost spreminja z različnimi pogoji in se posledično osredotočili na optimalne parametre, kjer je bila učinkovitost največja. Učinkovitost smo še dodatno povečali z optimizacijo dodatnih parametrov, kot so: hitrost potovanja laserskega snopa po površini, število prehodov, razmik vzporednih poti potovanja laserskega snopa ter s spremembo strategije graviranja. Efficiency of laser ablation is a very important parameter in engraving. In our case it is defined as the ratio between the energy that is theoretically needed for vaporizing a volume of material and the energy of the light radiated by the excitation laser. We used a nanosecond (12-240 ns) Yb fiber laser with a wavelength of 1060 nm. The used materials in our experiment were stainless steel and aluminium. With the use of different parameter combinations like frequency, pulse shape, peak and average power we obtained different material ablation depths. From the acquired data we calculated and analyzed the laser ablation efficiency of the engraving process. We then examined out how the efficiency changes with different conditions and focused on the optimum parameters, that give us the best results. The efficiency we then further increased with optimization of additional parameters, such as scanning speed, number of scans, spacing of scanning lines and scanning strategies.

The intermediate pulse duration regime between typical ultra-short and nanosecond pulses has been investigated using MHz-range bursts of 70 ps pulses emitted from a custom-made fiber laser source. The goal of this study was to observe and understand the processes involved during laser ablation on the timescales from picoseconds to nanoseconds, relevant due to pulses in bursts. We developed material processing approaches that enable similar behaviour as single 70 ps pulse ablation to ultra-short pulses in terms of quality and burst-mode behaviour like nanosecond pulses in terms of efficiency. The variability of the fiber laser operation modes was studied and compared to both ultra-short and nanosecond pulses from standard laser sources.

Antropogeni vplivi na morske organizme so številni in vključujejo večanje količin strupenih elementov ali spojin, spremembe habitatov, neposredne spremembe nekaterih vrst, motnje naravnih ciklov hranil idr. Intenzivni razvoj industrije, infrastruktur in turizma povzroča kopičenje snovi v vodnem stolpcu in sedimentih. Kot rezultat so morski organizmi izpostavljeni vedno višjim koncentracijam snovi v okolju. V magistrski nalogi smo ugotavljali geokemične in izotopske značilnosti velikih leščurjev P. nobilis (Linne, 1758), morske trave P. oceanica (Linne, 1758), čokatih volekov H. trunculus (Linne, 1758) in sedimentov. Vzorci so bili zbrani v okviru bilateralnega sodelovanja med Slovenijo in Hrvaško, na območju Nacionalnega parka Kornati. Izbrali smo pet lokacij, ki se med seboj razlikujejo glede na večjo, manjšo in najmanjšo možnost antropogenega vpliva na morske sedimente in posledično morske organizme. Določili smo izotopske značilnosti različnih delov mehkega tkiva velikih leščurjev (mišica, škrge, želodec) in morske trave pozejdonke (koreninski in nadkoreninski del). Spremembe izotopskih profilov v mehkem tkivu velikega leščurja in pozejdonke so posledica naravnih procesov in ne kažejo na antropogeno onesnaženje. Z geokemičnimi analizami smo v velikem leščurju, čokatem voleku in sedimentih ugotovili obseg antropogenih vplivov na izbranih lokacijah. V velikem leščurju in čokatem voleku, nas je zanimala predvsem vsebnost izbranih potencialno strupenih elementov PTE, redkih zemelj REE ter elementov skupine platine PGE. V površinskih sedimentih smo ugotavljali vsebnost REE. Rezultati geokemičnih analiz v mehkem tkivu velikega leščurja, čokatega voleka in sedimenta kažejo na antropogeno onesnaženje na lokacijah Mana, Piškera in Vrulje. Koncentracije so v mehkem tkivu velikega leščurja za večino PTE, REE in PGE višje, kot v mehkem tkivu čokatega voleka. V primerjavi z organizmi so koncentracije REE v sedimentih višje. Z metodo laserske ablacije smo po najdaljšem delu lupine in v prirastnicah velikega leščurja določili variabilnost izbranih PTE (As, Cd, Cu, Ni, Pb, Sb, Se) in REE (La, Ce) v času rasti organizma. V ta namen smo izrezali prečne profile skeletov velikega leščurja iz lokacije Piškera (P-PN1) in izdelali polirane preparate. S primerjavo analiz z metodo LA-ICP-MS, smo ugotovili večje antropogeno onesnaženje v zadnjih 10–20 letih. Anthropogenic effects on marine organisms are numerous and include the increase in quantities of toxic elements or compounds, changes in habitats, direct changes in certain species, disruption of natural nutrient cycles, etc. The intensive development of industry, infrastructure and tourism causes accumulation of substances in the water column and sediments. As a result, marine organisms are exposed to ever-higher concentrations of substances in the environment. In the master's thesis we have determined the geochemical and isotopic characteristics of noble pen shell P. nobilis (Linne, 1758), seagrass P. oceanica (Linne, 1758), sea snail H. trunculus (Linne, 1758) and sediments. The samples were collected in the framework of bilateral cooperation between Slovenia and Croatia, in the area of the National Park Kornati. Selected sampling locations differ from each other in view of the larger, smaller and smallest possible anthropogenic impacts on marine sediments and marine organisms. We determined the isotopic characteristics of various parts of soft tissue from noble pen shell (muscle, gills, stomach) and seagrass (root and leaves). Changes of the isotope value in the soft tissue of the noble pen shell and sea snail are the result of natural processes and do not indicate anthropogenic contamination. With geochemical analyzes of noble pen shell, sea snail and sediments we determined the extent of anthropogenic impacts at selected sampling locations. In noble pen shell sea snail, we were particularly interested in the content of selected potentially toxic elements PTE, rare earth metals REE and platinum group elements PGE. In sediments we were interested in content of REE. The results of the geochemical analysis of noble pen shell, sea snail and sediments show anthropogenic pollution at locations Mana, Piškera and Vrulje. The concentrations in the soft tissue of noble pen shell are higher for most PTE, REE and PGE than in the soft tissue of sea snail. Compared to organisms, concentrations of REE in sediments are higher. Using the laser ablation method, we tried to determine the variability of PTE (As, Cd, Cu, Ni, Pb, Sb, Se) and REE (La, Ce) during the growth of the organism. For this purpose we made thin section of noble pen shell from the Piškera location (P-PN1). By comparing LA-ICP-MS analyzes, we determined major anthropogenic pollution over the past 10-20 years.

Antropogeni vplivi na morske organizme so številni in vključujejo večanje količin strupenih elementov ali spojin, spremembe habitatov, neposredne spremembe nekaterih vrst, motnje naravnih ciklov hranil idr. Intenzivni razvoj industrije, infrastruktur in turizma povzroča kopičenje snovi v vodnem stolpcu in sedimentih. Kot rezultat so morski organizmi izpostavljeni vedno višjim koncentracijam snovi v okolju. V magistrski nalogi smo ugotavljali geokemične in izotopske značilnosti velikih leščurjev P. nobilis (Linne, 1758), morske trave P. oceanica (Linne, 1758), čokatih volekov H. trunculus (Linne, 1758) in sedimentov. Vzorci so bili zbrani v okviru bilateralnega sodelovanja med Slovenijo in Hrvaško, na območju Nacionalnega parka Kornati. Izbrali smo pet lokacij, ki se med seboj razlikujejo glede na večjo, manjšo in najmanjšo možnost antropogenega vpliva na morske sedimente in posledično morske organizme. Določili smo izotopske značilnosti različnih delov mehkega tkiva velikih leščurjev (mišica, škrge, želodec) in morske trave pozejdonke (koreninski in nadkoreninski del). Spremembe izotopskih profilov v mehkem tkivu velikega leščurja in pozejdonke so posledica naravnih procesov in ne kažejo na antropogeno onesnaženje. Z geokemičnimi analizami smo v velikem leščurju, čokatem voleku in sedimentih ugotovili obseg antropogenih vplivov na izbranih lokacijah. V velikem leščurju in čokatem voleku, nas je zanimala predvsem vsebnost izbranih potencialno strupenih elementov PTE, redkih zemelj REE ter elementov skupine platine PGE. V površinskih sedimentih smo ugotavljali vsebnost REE. Rezultati geokemičnih analiz v mehkem tkivu velikega leščurja, čokatega voleka in sedimenta kažejo na antropogeno onesnaženje na lokacijah Mana, Piškera in Vrulje. Koncentracije so v mehkem tkivu velikega leščurja za večino PTE, REE in PGE višje, kot v mehkem tkivu čokatega voleka. V primerjavi z organizmi so koncentracije REE v sedimentih višje. Z metodo laserske ablacije smo po najdaljšem delu lupine in v prirastnicah velikega leščurja določili variabilnost izbranih PTE (As, Cd, Cu, Ni, Pb, Sb, Se) in REE (La, Ce) v času rasti organizma. V ta namen smo izrezali prečne profile skeletov velikega leščurja iz lokacije Piškera (P-PN1) in izdelali polirane preparate. S primerjavo analiz z metodo LA-ICP-MS, smo ugotovili večje antropogeno onesnaženje v zadnjih 10–20 letih. Anthropogenic effects on marine organisms are numerous and include the increase in quantities of toxic elements or compounds, changes in habitats, direct changes in certain species, disruption of natural nutrient cycles, etc. The intensive development of industry, infrastructure and tourism causes accumulation of substances in the water column and sediments. As a result, marine organisms are exposed to ever-higher concentrations of substances in the environment. In the master's thesis we have determined the geochemical and isotopic characteristics of noble pen shell P. nobilis (Linne, 1758), seagrass P. oceanica (Linne, 1758), sea snail H. trunculus (Linne, 1758) and sediments. The samples were collected in the framework of bilateral cooperation between Slovenia and Croatia, in the area of the National Park Kornati. Selected sampling locations differ from each other in view of the larger, smaller and smallest possible anthropogenic impacts on marine sediments and marine organisms. We determined the isotopic characteristics of various parts of soft tissue from noble pen shell (muscle, gills, stomach) and seagrass (root and leaves). Changes of the isotope value in the soft tissue of the noble pen shell and sea snail are the result of natural processes and do not indicate anthropogenic contamination. With geochemical analyzes of noble pen shell, sea snail and sediments we determined the extent of anthropogenic impacts at selected sampling locations. In noble pen shell sea snail, we were particularly interested in the content of selected potentially toxic elements PTE, rare earth metals REE and platinum group elements PGE. In sediments we were interested in content of REE. The results of the geochemical analysis of noble pen shell, sea snail and sediments show anthropogenic pollution at locations Mana, Piškera and Vrulje. The concentrations in the soft tissue of noble pen shell are higher for most PTE, REE and PGE than in the soft tissue of sea snail. Compared to organisms, concentrations of REE in sediments are higher. Using the laser ablation method, we tried to determine the variability of PTE (As, Cd, Cu, Ni, Pb, Sb, Se) and REE (La, Ce) during the growth of the organism. For this purpose we made thin section of noble pen shell from the Piškera location (P-PN1). By comparing LA-ICP-MS analyzes, we determined major anthropogenic pollution over the past 10-20 years.

We investigate the overall temporal behavior of the bubbles produced by 20-ns- and 100-ns-pulse-duration laser ablations in water using a laser-beam-transmission probe (LBTP). This technique gives the transmission signal attributed to the whole bubble dynamics, including the secondary oscillations, with a single laser shot. Comparing the signals obtained for both pulse durations, the periods of the first oscillation of the bubble are almost the same. Nevertheless, the periods of the subsequent oscillations are significantly different depending on the pulse duration. Such results are obtained by virtue of the LBTP technique.

A nitrogen laser beam (337 nm, 6 ns (FWHM), (3.2 [plus minus] 0.2) mJ) was focused with a quartz lens (f = 100 mm) onto an aluminium target in air at normal pressure. The laser irradiation and plasma explosion caused a modification to the Al surface and the deposition of a thin film (droplets) onto a glassy carbon plate. The irradiated target and the deposited material were studied with a scanning electron microscope (SEM) and a focused-ion-beam (FIB) device. A crater surrounded by a rim was produced on the spot of maximum irradiation on the aluminium target. The crater, very deep in comparison to its width and thickness, was presumably caused by the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities. The temperatures of the electron and the massive particles were explained. Žarek laserske svetlobe (337 nm, 6 ns ((FWHM), (3.2 [plus minus] 0.2) mJ) smo s kremenovo lečo (f = 100 mm) fokusirali na aluminijevo tarčo, ki je bila na zraku pri normalnem zračnem tlaku. Obsevanje z laserjem in eksplozija plazme sta povzročila spremembo površine aluminija ter nanos tanke plasti in kapljic na steklasto ogljikovo ploščico. Obsevano tarčo in nanesen material smo raziskali z vrstičnim elektronskim mikroskopom (SEM) in s fokusiranim ionskim curkom (FIB). Na aluminijevi tarči je na najbolj obsevanem mestu nastal krater, ki je bil zelo globok v primerjavi z njegovo širino in debelino. Krater je bil povzročen zaradi Kelvin-Helmholtzove in Rayleigh-Taylorjeve nestabilnosti. V delu smo razložili tudi temperaturo elektronov in temperaturo masivnih delcev.

Fundamentalna istraživanja interakcija laserskog zračenja i materije su naročito intenzivirana pojavom impulsnih lasera, čije je vreme trajanja svakom decenijom postajalo sve kraće. Impulsi Nd:YAG lasera, nanosekundnog trajanja, su pored brojnih primena, naročito pogodni za kreiranje plazme materijala, čije se karakteristike mogu ispitivati metodama optičke emisone spektroskopije. U ovoj disertaciji su eksperimentalno ispitivane karakteristike laserski-indukovane plazme stvorene ablacijom bakra i indijuma u zaostaloj atmosferi vazduha, vodoniku, helijumu i argonu. Primenom metoda emisione spektroskopije dijagnostikovani su plazmeni parametri; kao što su elektronska koncentracija i ekscitaciona temperatura. Na osnovu ovih podataka je sagledana dinamika prostorno-vremenskog razvoja plazme. Određeni su prostorno-vremenski intervali, u funkciji gustine snage laserskog zračenja, vrste materijala mete, vrste i pritiska ambijentalnog gasa, u kojima je optimalno posmatrati oblik i intenzitet spektralnih linija sa ciljem nalaženja atomskih parametara. Posebna pažnja je posvećena sagledavanju efekata samoapsorpcije i uslova njene minimalizacije, pa i korekciji samoapsorpcijom deformisanih profila. U cilju određivanja lokalnih vrednosti parametara u laserski-indukovanoj plazmi, korišćena je metoda zasnovana na inverznoj Abel-ovoj transformaciji. Rezonantne spektralne linije su, zbog svojih karakteristika, bile od posebnog interesa. Širenje rezonantnih spektralnih linija atoma bakra (Cu I 324.7 nm i 327.4 nm) je istraživano u spektru laserski-indukovane plazme u zaostaloj atmosferi vazduha na pritisku od 8 Pa. Na optimalnim uslovima su određeni Stark-ovi parametri ovih liniija i upoređeni sa teorijskim vrednostima. Uloga doprinosa komponenata hiperfine strukture i izotopskog efekta, rezultantnom obliku ovih spektralnih linija, je prvi put uzeta u razmatranje. Pokazano je da hiperfina struktura i izotopski efekat dodatno proširuju profile rezonantnih Cu I linija, što je značajno pri korišćenju ovih linija u dijagnostičke svrhe. Istraživanja u laserski-indukovanoj plazmi indijuma su sprovedena u zaostaloj atmosferi vazduha, vodoniku i argonu. Utvrđeno je da je ambijent argona, zbog manje izraženih prostornih i vremenskih gradijenata, izuzetno pogodan za određivanje temodinamičkih parametara plazme. Pomenuti ambijent je omogućio utvrđivanje uslova koji podrazumevaju minimalne efekte samoapsorpcije. Pod ovim uslovima su, po prvi put, eksperimentalno određeni parametri Stark-ovog širenja rezonantnih In I (410.2 nm i 451.1 nm) i jedne In II (294.1 nm) linije i upoređeni sa postojećim teorijskim vrednostima. Utvrđena je saglasnost sa dosada jedinim postojećim eksperimentalnim podacima koji se tiču pomeraja rezonantnih linija. Pokazano je da hiperfina struktura i izotopski efekat dodatno proširuju profile rezonantnih In I linija, naročito na 410.2 nm. Utvrđeno je da se doprinos hiperfine strukture na elektronskim koncentracijama iznad 1022 m-3 može zanemariti, što je značajno pri korišćenju ovih linija u dijagnostičke svrhe. Pored uzoraka metala ispitivane su karakteristike laserski-indukovane plazme hidratnih jedinjenja (CuSO4·5H2O i CaSO4·2H2O) u vidu presovanih tableta. Ovakav vid uzoraka je imao za cilj pouzdano određivanje elektronske koncentracije korišćenjem karakteristika profila vodonikovih linija iz Balmer-ove serije, za koje postoje veoma pouzdani teorijski proračuni. Pored pomenutih dijagnostičkih pogodnosti, efekat samoapsorpcije spektralnih linija je manje izražen, zbog manje koncentracije isptitivanog elementa u stvorenoj LIBS plazmi. Utvrđeno je da su hidratna jedinjenja veoma pogodna za pouzdano dijagnostikovanje parametara plazme, te je ovakav pristup predložen i za određivanje Stark-ovih parametara. U tezi su predstavljeni i rezultati istraživanja akustičkih efekata koji nastaju sa formiranjem laserski-indukovane plazme. Ispitivani su akustički odzivi proboja u vazduhu, korišćenjem različitih metala kao mete (aluminijum, bakar i zlato). Pored detaljne statističke analize opto-akustičkih signala, izvršena je vremenski integralna i vremenskirazložena analiza njihovih dominantnih učestnosti. Utvrđeno je da se ovim pristupom mogu dobiti informacije o anizotropiji i dinamici plazme, te ukazano na mogućnost korelisanja akustičkog odziva sa količinom ablirane mase. Pokazana je različitost akustičkog odziva u zavisnosti od korišćenog metala mete i sugerisane mogućnosti potencijalnih primena. Ispitivan je prag, kao i okolnosti pojavljivanja, efekata ekraniranja laserskiindukovane plazme u zavisnosti od gustine snage i talasne dužine laserskog zračenja. Utvrđeno je da pojava ekraniranja zavisi od kompleksne sprege različitih procesa, koji rezultuju apsorpcijom dela laserskog-impulsa u plazmi. Određena je vrednost praga značajnije apsorpcije za bakarni uzorak u redukovanim pristiscima helijuma, preciznim utvrđivanjem razlika mase mete pre i posle ablacije. Dobijena vrednost praga je potvrđena i metodama emisione spektroskopije na osnovu ponašanja intenziteta linija. Postignuti rezultati u ovoj tezi predstavljaju originalan doprinos proširenju postojećih rezultata u oblastima vezanim za interakciju laserskog zračenja sa materijom, kao i interakciju laserskog zračenja sa plazmom. Ovaj doprinos se ogleda i na polju atomske emisione spektroskopije, utvrđivanja atomskih parametara, ispitivanju oblika spektralnih linija, kao i prostorno-vremenske evolucije laserski-indukovane plazme. Pomenuti rezultati su i od značaja za predstojeća sveobuhvatna modeliranja u domenu kompleksnih procesa pre, tokom i posle formiranja ovakve vrste plazme. Fundamental investigations concerning laser-matter interactions have been extensively conducted ever since the invention of the pulsed laser source. Consequently, the laser pulse durations have had a constant trend of reduction in a last couple of decades. Among many other applications, Nd:YAG nanosecond pulses are frequently used for the purpose of laser-induced breakdown spectroscopy (LIBS). This thesis mainly covers the various aspects of laser induced plasma of copper and indium, created in the residual atmosphere ambient, hydrogen, helium and argon buffer gas. By using methodologies of optical emission spectroscopy, the essential thermodynamic parameters were deduced; electron density and excitation temperature. These data served as a basis for constructing a more general picture about plasma dynamics and its spatiotemporal evolution. The spatiotemporal intervals, strongly dependent on irradiance, sample structure and ambient conditions, were optimally determined with the aim of investigating spectral line shapes and corresponding atomic parameters. Special care was taken in order to detect, minimize or correct the undesirable effects of self-absorption. In order to infer local values of the mentioned plasma parameters, a method based on an inverse Abel transform, was employed. The resonance spectral lines were of a particular interest, mainly because of their unique characteristics. Spectral line broadening of the resonance copper atom lines (Cu I 324.7 nm and 327.4 nm) was investigated in the laser-induced spectrum under reduced atmospheric pressure of 8 Pa. After finding the optimal set of experimental parameters, the Stark broadening coefficients were deduced and compared to the existing theoretical values. The contributions of the hyperfine structure components and isotope effect to the resonance lines shape formation were, for the first time, taken into consideration. It is shown that the hyperfine structure and isotope effect additionally broad resonance line profiles, which is of particular interest when using these lines in various diagnostic purposes. Investigations of laser-induced indium plasma were performed under different ambient environments; reduced pressures of air, hydrogen and argon. Due to less pronounced spatiotemporal gradients and effects of self-absorption, the argon buffer gas was chosen as the most adequate environment for determination of thermodynamic plasma parameters. Under those conditions, the Stark coefficients of two resonance In I (410.2 nm and 451.1 nm) spectral lines and one ionic In II (294.1 nm) line were also determined and compared to the existing theoretical values. In terms of the estimated Stark shift directions, agreement was found with the results of one experimental work, dealing with indium resonance lines. It is shown that the hyperfine structure and isotope effect additionally broad resonance line profiles, especially in the case of 410.2 nm line. This remark is of particular interest when the electron densities exceed 1022 m-3, where HFS contributions can be safely neglected. Beside metallic samples, the characteristics of the laser-induced plasma of hydrogen containing samples (CuSO4·5H2O and CaSO4·2H2O) in the form of a pressed pellets, were also studied. This kind of matrix was chosen in order to increase reliability of electron number density determination using Stark broadened hydrogen Balmer lines, extensively investigated, both theoretically and experimentally. The effects of self-absorption are also less pronounced, due to smaller concentrations of investigated element in the sample. It is concluded that these compounds are suitable for the reliable diagnosis of plasma parameters and therefore, recommended for determination of the Stark broadening coefficients, as well. This thesis also contains results of the investigations of the laser-induced plasma acoustical response, inevitably present during the plasma formation process. The acoustical response was monitored in case of an air breakdown and also for plasmas of various metals (aluminum, copper and gold). Beside detailed statistical analysis of these opto-acoustic signals, the time-integrated and time-resolved analysis of dominant frequency components, were also performed. It is determined that this approach could be used for obtaining information about plasma anisotropy and dynamics. The possibility of correlating the plasma acoustical response with the atomised fraction of the ablated mass was also considered. The found diversities of the acoustical response depending on the used sample have imposed suggestions for the potential applications. The threshold for the onset of the significant plasma screening effects was investigated depending on the laser irradiance and wavelength. It is well known that the screening process is a result of complex interplay of various processes, favoring conditions for the absorption of the trailing part of the laser pulse. The threshold value is obtained in the case of copper sample under reduced pressures of helium atmosphere, using precise estimation of mass before and after ablation. This threshold value was additionally verified using standard emission spectroscopy probing methods, based on the spectral line behavior. The results shown in this thesis present an authentic contribution and extension of existing results in the scientific fields related to both laser-material and laser-plasma interactions. Besides, there is a degree of novelty in terms of applying new approaches concerning atomic emission spectroscopy, spectral line shape investigations, atomic parameter determination and spatiotemporal evolution of the laser-induced plasma. These results should serve as a basis for the upcoming comprehensive modeling of the complex processes before, during and after plasma formation.

Površino zlitine Cu-Sn-Zn-Pb smo obsevali z laserskimi impulzi dušikovega laserja (valovna dolžina 337 nm). Pri tem sta se spremenila tako topografija površine kot tudi mikrostruktura pod njo. Ker je s klasičnimi metalografskimi metodami zelo težko primerno pripraviti obsevano površino za mikroskopsko opazovanje, smo kot temeljno orodje za metalografsko preiskavo uporabili fokusirani ionski curek (FIB), kajti FIB lahko odstranjuje material na specifičnih mestih v mikro- in nanoobmočju in odkrije mikrostrukturo brez prejšnje metalografske priprave. To nam je omogočilo, da smo raziskali vpliv obsevanja z laserjem na spremembo oblike površine, ugotovili profil kraterjev ter mikrostrukturne spremembe v območju toplotnega vpliva. Surface of a Cu-Sn-Zn-Pb alloy was irradiated by ultraviolet nitrogen laser pulses (wavelength 337 nm). As a result both surface topography and microstructure beneath the surface changed. Since it is very difficult to adequately prepare the damaged regions for microscopical observations using classical metallographic methods, we used a focussed ion beam (FIB) as the main tool for microstructural characterisation. Namely, FIB can remove material at specific sites in micro- and nanoregions and reveal microstructure without any previous metallographic preparation. This allowed us to investigate the influence of laser pulses on change of surface topography and subsurface microstructure.

Nanočestice su strukture koje su na neki način spona između atoma i molekula s jedne i čvrstog tijela s druge strane. Ono što ih čini drugačijima je omjer površine i volumena, koji je vrlo velik za razliku od čvrstih tijela. Iz tog razloga imaju vrlo zanimljiva svojstva te su predmet velikog broja istraživanja. Laserska ablacija ima vrlo velik potencijal za sintezu nanočestica zbog mnogih prednosti u odnosu na druge komplementarne metode. Laserska ablacija nije invazivna te ne proizvodi okolišu nepovoljne nusprodukte. Također, količina materijala potrebnog za proizvodnju nanočestica znatno je manja nego prilikom korištenja kemijskih metoda te nisu potrebne nikakve pripremne radnje koje prethode sintezi. Nadalje, laserska ablacija omogućuje sintezu nanočestica širokog spektra materijala ili kombinacije materijala budući da je moguće ablatirati velik broj različitih materijala u također velikom broju različitih tekućina. Problem ove tehnike je što još nije dovoljno istražena te nije u potpunosti poznata cijela teorijska slika samog procesa. Stoga su potrebna još mnoga istraživanja kako bi se mogli dokučiti uvjeti za pripremu standardiziranih nanočestica. U ovome smo se radu bavili sintezom nanočestica ZnO u destiliranoj vodi pomoću laserske ablacije. ZnO je poluvodič koji je zbog svojih svojstava vrlo zanimljiv u raznim primjenama, od prehrambene i kozmetičke industrije do primjena u energetici i medicini. U ovome smo radu analizirali vezu nekih uvjeta ablacije (valna duljina i energija lasera, te broj pulseva) s veličinom i strukturom dobivenih nanočestica. Za neke parametre smo dobili dobro definirane sferne strukture promjera oko 115 nm čija je distribucija po veličinama najbolje odgovarala Gauss prilagodbi, dok smo za druge parametre dobili drugačije strukture, poput nanomreža i krhotina. Nanoparticles are structures which are in between molecules and bulk materials, so they show very interesting and unique properties which can't be found in bulk. Property which differs them the most is surface to volume ratio, which is very high, contrary to bulk. For that reason they have some interesting properties and are an object of large number of studeis. Laser ablation has very high potential for nanoparticle synthesis due to it's advantages in comparison to other complementary methods. It's not invasive and doesn't produce materials which are hazardous for environment. Also, the amount of needed material is quite lower comparing to chemical methods and no preparation work is needed before synthesis. Laser ablation also enables production of very large spectrum of materials, as one can do it with a lot of different materials in a lot of different liquids. The problem of this technique is that it's not yet researched enough, so the whole theoretical background is yet somewhat unknown. That's why a lot of research is still needed to be done, so the conditions for preparation of standardized nanoparticles could be reached. In this work we were working on synthesis of ZnO nanoparticles in distilled water. ZnO is semiconductor which due to it's properties has a great potential in various fields, from food and cosmetic industry to applications in energetics and medicine. We analyzed relationship between some of the parameters of ablation (laser wavelength, energy and number of pulses) with size and structure of produced nanoparticles. For some parameters we got nicely defined spherical structures with diameter of approximately 115 nm with size distribution that fits best with Gaussian fit. For some other parameters we got different structures, like nanowires and debris.

U ovome radu proučavan je efekt laserske ablacije dobivene s dva, vremenski korelirana, laserska pulsa. Kao glavni parametar javlja se vrijeme kašnjenja između laserskih pulseva τ, koje je varirano između 0 i 50 μs. Eksperiment se bazira na mjerenju vremenski ovisne apsorpcije, odnosno emisije ablacijskog oblaka titana u vakuumu u ovisnosti o τ. Mjereni su apsorpcijski i emisijski spektri atoma Ti, te emisijski spektri atoma Ti i iona Ti+, te je praćeno njihovo vremensko odvijanje. Za mjerenje apsorpcije korištena je laserska apsorpcijska spektroskopija pomoću optičkog rezonatora (laspor), a za mjerenje emisije klasična emisijska spektroskopija pomoću monokromatora. Rezultati apsorpcije i emisije pokazuju višestruko pojačanje signala prilikom dvostruke ablacije za dani τ u odnosu na jednostruku. U apsorpcijskim se mjerenjima, za određene prostorno-vremenske paremetre, javlja dopplerovo cijepane apsorpcijskih linija što je indikacija povećane paralelne brzine (u odnosu na površinu mete) ablatiranih čestica, odnosno posljedica eksplozije faze. Također je razvijen i model koji simulira apsorpcijska mjerenja, a pomoću kojega je moguće odrediti i neke dodatne parametre (npr. Raspodjela brzina, te oblik funkcije gustoće ablatiranih čestica). Mjereni su i volumeni kratera nastali na površini mete nakon ablacije, te njihova dubina i radijus, za razna vremena τ. Za najmanja vremena τ dominira efekt zasjenjenja za drugi puls pa volumen nije najveći iako je meta za drugi puls najzagrijanija (najmanji prag za ablaciju). Također se za veća vremena kašnjenja (2 μs) dobivaju napareni filmovi titana na Si substrat s najmanjom hrapavošću i najvećom debljinom. In this work the effect of laser ablation which is induced with two, time separated, laser pulses was studied. As a main parameter in dual-pulse laser ablation delay time between the laser pulses τ appeared and it was scanned within interval 0 – 50 μs. Experiment is based on measurement of time-dependent absorption and emission from plasma plume of titanium ablated in vacuum in respect to τ. Absorption and emission spectra of Ti, and emission spectra of Ti+ were also measured as well as its temporal dependence. Absorption measurements were performed by means of cavity ring-down spectroscopy while emission measuremenst were performed by means of classical monocromator. Results shows many-fold increase of measured signal in dual-pulse in comparison to single-pulse laser ablation. For given temporal and spatial parameters absorption line profiles appeared doppler-splitted. It is indication of increased velocity component parellel to the target surface, i.e. increased phase explosion. The model was developed for simulation of absorption measurements. From the model parameters such are velocity distributuin of ablated species, or anisotropy function can be assessed. Otherway those parameters cannot be obtained directly from the experiment. Volumes, radii and depths of the craters induced by laser ablation were also measured in respect to τ. It was found that largest volumes were given for shorters τ when ablation threshold is lowest, except that for the shortest τ where screening effect dominates for the second pulse hence energy delievered to the target was decreased. Ti films deposited on si depend on τ and on regime of ablation (single or dual). The thickest and smoothed layer was made with τ = 2 μs.