Context

Despite a large volume of publications, experimental results and theoretical data, because of theirs complex and multitudinous of transient processes, covering different time scales and different research fields of physics, the laser-matter interaction mechanisms topic is far from being solved.

The basic laser surface interaction mechanisms, in variety of buffer gases types, chemically reactive or not, is a challenge to scientist both for fundamentals but also for applications of the deposited materials aiming to induce new optical properties of investigated materials. The dynamics of the laser ablation plasma plume structures formation is related to the equilibrium between particle production by elementary processes (direct and indirect ionization) and the loss of particles (recombination in the volume and at the walls). Knowledge of the processes that lead to the appearance of so called self-organization phenomenon and, on this basis, of the nano-structures, is very important since it permits the controlled action at a molecular and atomic level during the operation of PLD (pulse laser deposition) thin films preparation. PLD is one of the prospective techniques as well: being employed due its simplicity, easy of the process, often stoichiometric transfer of bulk material to the films and possibility to fabricate films of unusual composition

In relation with fundamental and applications of the novel materials type, discharge plasma and laser ablation plasma play significant importance and furthermore studies must be taking into account. Plasma is a significant issue for space systems satellite propulsion technology and significant challenges and advances in space propulsion have occurred over the last years. To maintain the satellites in geostationary orbit with North-South and East-West corrections, Hall Effect Thruster is recognized as one of the most interesting concepts because of its performances mainly in the economy in propellant mass (saving about 400 kg for a 4t-class satellite for a mission of 15 years – see formulae 3). In order to simulate the behavior of the HET thrusters, especially theirs stability, complex both experimental and theoretical research studies must take into account. The presence of numerous and complex processes in the like electron secondary emission, sputtering, normal or ab-normal erosion, sheath potential modifications or solid particle emission turns the efforts to completely control and parameterize the dielectric wall behavior into a difficult task. Moreover, the deposition of energy by the plasma discharge modifies the surface temperature and consequently may affect the evolution of the different wall processes.

One of the major global problems of human society is finding and developing new energy sources. In this context novel thermoelectric materials can play a role in both primary power generation and energy conservation. These materials are expected to play a more increasing role than it has in the past and will be one of several technologies working together to fiind best energy efficiency issues. Chalcogenide glasses are those compounds that have may atributes for future used thermoelectric materials. Through other important properties we underline theirs small variation in electronegativity between sulfur, selenium and tellurium that makes possible to obtain semiconductors with energy gap appropiate for thermoelectric applications even a large wide o temperature values.

Other sources clean energy with higly social and economicall impacts are the solar power that have already become a small part of daily life. The future of solar energy depends mostly of the materials type and efficiency solutions energy conversions. Recently spinel ferrites have been shown to be an alternatively solutions capable of splitting water to produce hydrogen using solar energy

HET ceramic materials - Hall Effect Thruster geostationary satellite

The anomal erosions, plasma-wall interactions, local thermal effect, some laser -plasma induced instabilities have been studied in France (Orleans and Lille) through various space- and time-resolved optical emission spectroscopy (OES), fast ICCD imaging and Langmuir probe diagnosis methodes upon various ceramics types (mostly BNSiO2, Al2O3, BN, SiO2, etc ). The thermal effects induced on the target have been thoroughly analyzed by means of IR thermography camera. In order to describe the dynamics of the particle cloud ejected after pulsed laser irradiation, qualitative and quantitative insight on the evolution of transient plasmas created by high-fluence ns pulsed laser and high power CW laser, both in vacuum and the free atmosphere have been studied. The modifications induced by the laser irradiation on the solid sample have been investigated by various techniques as examples, the profilometry, scanning electron microscopy, etc. A direct correlation has been established between the erosion rate (calculated through an actinometric method involving BI, XeI, and XeII spectral lines) and the quantity of ablated matter, opening the way towards a calibration of the erosion measurements in Hall Effect Thrusters. In order to reproduce the experimental observations, a theoretical model has been proposed and furthermore must be tested. By using the conservation laws of the particle number, momentum, and energy, the plasma expansion has been numerically simulated.

 Several papers published by Romanian and France parteners, as following:

C. Focsa, S. Gurlui, A. Lefort, M. Abbaoui, L. Guichaoua, F. Rossignol, M. Dudeck, "Étude expérimentale et numérique du transfert de chaleur dans du nitrure de bore et de la silice irradiés par laser", Congrès Français de Thermique, Perpignan, 24-27 mai 2011

C. Focsa, S. Gurlui, O. Pompilian, A. Lefort, M. Abbaoui, I. Balika, S. Pellerin, N. Pellerin, F. Gafari, M. Dudeck, "Laser energy deposition on BN and SiO2: experiment and model", 6th International Spacecraft Propulsion Conference, San Sebastian, Espagne, 3-6 mai 2010

C. Focsa, L. Balika, S. Gurlui, S. Pellerin, N. Pellerin, D. Pagnon, M. Dudeck, "Laser Experiments in a Running Hall Effect Thruster for Space Propulsion", 10th International Conference on Global Research and Education (Inter-Academia 2011), Sucevita, Roumanie, 26-29 septembre 2011

L. Balika, C. Focsa, S. Gurlui, S. Pellerin, N. Pellerin, D. Pagnon, M. Dudeck, "LIBS in a Running Hall Effect Thruster for Space Propulsion", 6th Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy, Cesme Izmir, Turquie, 11-15 septembre 2011

L. Balika, S. Pellerin, T. Gibert, C. Focsa, S. Gurlui, N. Pellerin, E. Veron, D. Pagnon, "Ageing of ceramics in Hall Eect Plasma thrusters", 32nd International Electric Propulsion Conference (IEPC), Wiesbaden, Allemagne, 11-15 septembre 2011

Lahib Balika, Cristian Focsa, Silviu Gurlui, Stéphane Pellerin, Nadia Pellerin, Daniel Pagnon and Michel Dudeck, "Laser Ablation in a Running Hall Effect Thruster for Space Propulsion", 11th Intl Conf on Laser Ablation (COLA), Playa del Carmen, Méxique, 13-18 novembre 2011

N. Pellerin, E. Véron, L. Balika, S. Pellerin, C. Focsa, D. Pagnon, M. Dudeck, "Ageing of ceramics in a Hall Effect Plasma thruster", 20th International Symposium on Plasma Chemistry, Philadelphia (USA) , 24-29 juillet 2011

C. Focsa, C. Ursu, S. Gurlui, l. Balika, S. Pellerin, N. Pellerin, M. Dudeck, "Laser Energy Deposition on the Chamber Surface of the PPS100-ML Hall Effect Thruster: Experiment and Simulation", 6th International Spacecraft Propulsion Conference, San Sebastian, Espagne, 3-6 mai 2010

C. Ursu, O. G. Pompilian, S. Gurlui, C. Focsa and M. Dudeck, "Optical characterization of Al2O3 laser produced plasma", 15th Intl. Conf. on Plasma Physics and Applications, Iasi, Roumanie, 1-4 juillet 2010

10.  L. Balika, C. Focsa, C. Ursu, S. Gurlui, S. Pellerin, N. Pellerin, V. Freyssengeas, M. Dudeck, "Laser-BNSiO2 ceramic interactions in working Hall Effect Thruster: experiment and simulation", 15th Intl. Conf. on Plasma Physics and Applications, Iasi, Roumanie, 1-4 juillet 2010

C. Ursu, O. G. Pompilian, S. Gurlui, P. Nica, M. Agop, M. Dudeck and C. Focsa, Al2O3 ceramics under high-fluence irradiation: plasma plume dynamics through space- and time-resolved optical emission spectroscopy, Applied physics A: materials science & processing, Volume 101, Number 1, 153-159, (2010), DOI: 10.1007/s00339-010-5775-0 

C. Focsa, C. Ursu, S. Gurlui, D. Pagnon, S. Pellerin, N. Pellerin, P. Echegut, M. Dudeck, Energy Deposition on the Surfaces of Hall Effect Thrusters for Satellites – Simulation by Laser Beam, 3rd EUCASS, the European Conference for AeroSpace Sciences, Versailles conference center – Paris, France, July 6-9th (2009);

C. Focsa, M. Ziskind, C. Ursu, S. Gurlui, D. Pagnon, S. Pellerin, N. Pellerin, M. Dudeck,Laser - BnSiO2 Ceramics Interaction: simulation of the energy deposition on dielectric wall surfaces in Hall thrusters, J. Optoelecron. Adv. Mater. 10 2380 (2008); 

Laser Ablation (LA), Laser Induced Breakdown Spectroscopy (LIBS) and Laser Induced Fluorescences (LIF) 

The problem of the interaction of a pulsed laser to the matter is a complex one since it assumes a good understanding of the basic physics and chemistry associated with laser-target and particle-particle interaction within the laser and plasma plume The dynamics of plasma under reactive gas remains an interesting field of study, in order to understand the complex physico-chemical mechanism involved, including shockwaves, hydrodynamic instabilities and chemical reactions. These phenomena depend on gas pressure, laser parameters and focal spot size and shape but also of the target electrical charge type.

The dynamics and evolution of the space charge structures created by laser ablation of targets has been investigated (Lille) both by means of electrical (Langmuir) probes, optical (ICCD camera, 2 ns gate) and space- and time-resolved optical emission spectroscopy. These measurements emphasized a specific behaviour of each spectral line, with distinct spatial intensity profiles, leading to different velocities of the associated species.

The visible emitting regions of plasma exhibit two structures with different life-times and expansion velocities. Both the transient probe ionic current and target DC electrical potential present different oscillatory type profile associated mainly with de temporal evolution of the fast component. We report both of oscillatory structure of the transient ion current recorded by the Langmuir probe and target electric potential during the laser produced plasma expansion. Assuming the fractal structure of the space-time, these oscillations are explained through Scale Relativity Theory in the hydrodynamic version. These oscillations are found to be generated by the fractal part of a complex speed field by means of the fractal potential, which dictates the inside dynamics of the laser ablation plasma plume elementary processes. Spatially and temporally-resolved optical and spectral analysis of the plasma plume generated by laser ablation of sample micro-volumes was a powerful diagnosis tool for the study of Cucuteni historic artworks and artifacts. This approach has been applied to the investigation of ceramic fragments from Neolithic, medieval and ancient medieval ages by using the second harmonic (532 nm) of a Q-switched (10 ns) Nd:YAG laser focused on the samples placed in a vacuum chamber. Along with the laser ablation plasma composition and evolution, the modifications induced by laser irradiation on the targets surface have been investigated and different manufactured used technology of the historical artworks have been evidenced.

Several papers published by Romanian and France parteners, as following:

S. Gurlui, C. Focsa, Plasma Science, Laser Ablation Transient Plasma Structures Expansion in Vacuum, IEEE Transactions on Volume: PP, Issue: 99, Digital Object Identifier: 10.1109/TPS.2011.2151884, Publication Year: (2011), Page(s): 1 – 2.

M Agop, P Nica, S Gurlui, C Focsa, D Magop and Z Borsos, The chaotic atom model via a fractal approximation of motion, Phys. Scr. 84 045017 (2011) doi:10.1088/0031-8949/84/04/045017

A. Largeanu, G.O. Pompilian, D.G. Galusca, M. Agop, S. Gurlui, Pulsed laser deposition of NI thin films on metallic substrate, University Politehnica of Bucharest Scientific Bulletin-Series a-Applied Mathematics and Physics, 73(3):195-202, (2011)

C. Focsa, S. Gurlui, M. Ziskind, "Transient Plasmas Generated by High-Fluence Laser Ablation: Fundamentals and Applications", 11th International Balkan Workshop on Applied Physics, Constanta, Roumanie, 7 juillet 2010

M. Osiac, G. O. Pompilian, S. Gurlui, C. Focsa, "Langmuir probe investigations of transient plasma plumes generated by ultrafast laser ablation of various metallic targets", 4th Romanian National Conference of Applied Physics, Iasi, Roumanie, 19-20 novembre 2010

S. Gurlui, P. Nica, M. Agop, C. Focsa, "High-Fluence Laser Ablation Plasma Dynamics: Fundamentals and Applications", 4th Romanian National Conference of Applied Physics, Iasi, Roumanie, 19-20 novembre 2010

H. Cimpoesu, G. O. Pompilian, C. Baciu, N. Cimpoesu, C. Nejneru, M. Agop, S. Gurlui, C. Focsa, Pulsed laser deposition of poly (L-Lactide) acid on nitinol substrate, Optoelectronics and Advanced Materials-Rapid Communications, 4 ISS.12, p.2148-2153 (2010)

M. Agop, P. E. Nica, S. Gurlui, C. Focsa, V. P. Paun and M. Colotin, Implications of an extended fractal hydrodynamic model, The european physical journal d - atomic, molecular, optical and plasma physics, Volume 56, Number 3, 405-419, (2010) DOI: 10.1140/epjd/e2009-00304-5

P. Nica, M. Agop, S. Gurlui and C. Focsa, Oscillatory Langmuir probe ion current in laser produced plasma expansion, EPL-EUROPHYS LETT 89, 6 Art no: 65001 (2010) , doi: 10.1209/0295-5075/89/65001

M. Agop, P. Nica, S. Gurlui, C. Focsa – Fractal hydrodynamic model of high-fluence laser ablation plasma expansion, International High-Power Laser Ablation Conference, Santa Fe, USA, 2010;

C. Ursu, G. O. Pompilian, S. Gurlui, G. Popa, C. Focsa, Fundamental parameters of laser ablation plasma dynamics derived from space-and time-resolved optical diagnosis, E-MRS 2009, Spring Meeting, Congress Center, Strasbourg, June 8 - 12, (2009);

S. Gurlui, M. Agop, P. Nica, M. Ziskind, C. Focsa, Hydrodinamic model of high-fluence laser ablation plasma expansion, E-MRS 2009, Spring Meeting Congress Center, Strasbourg, June 8 - 12, (2009);

C. Ursu, G. O. Pompilian, S. Gurlui, C. Lungu, C. Focsa, Laser induced breakdown spectroscopy of ceramic materials, 10th International Balkan Workshop on Applied Physics, July 6-8, Constanta, Romania, (2009);

C. Ursu, S. Gurlui, P. Nica, M. Agop, C. Focsa, Some implications of a fractal hydrodynamic theory in modeling laser ablation transient plasmas, 10th International Balkan Workshop on Applied Physics, July 6-8, 2009, Constanta, Romania, (2009);

C. Focsa, S.Gurlui, C.Ursu, M.Agop, P. Nica, Laser ablation plasma dynamics: fractal hydrodynamic model and oscillatory behavior, 10th annual Conference on Laser Ablation (COLA), Singapore, 22-27 November (2009);

C. Ursu, S. Gurlui, O. Pompilian, C. Lungu M. Agop, P. Nica, C. Focsa, Ceramics under high fluence irradiation: plasma plume dynamics through space- and time-resolved optical emission spectroscopy, 10th annual Conference on Laser Ablation (COLA), Singapore, 22-27 November (2009);

L. Stratulat, S. Gurlui, C. Ursu, S. Rebegea, A. Constantin, C. Focsa, Laser ablation of archaeological artifacts: space- and time- resolved diagnosis, LACONA 8, Laser in the conservation of artworks, Sibiu - Romania, 21-25 September (2009);

P. Nica, P.Vizureanu, M. Agop, S. Gurlui, C. Focsa, N. Forna, P. D. Ioannou, Z. Borsos, Experimental and theoretical aspects of aluminum expanding laser plasma, Japanese Journal of Applied Physics, 48 (6), art. no. 066001 (2009);

C. Ursu, S. Gurlui, C. Focsa, G. Popa, Space- and time-resolved optical diagnosis for the study of laser ablation plasma dynamics, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 267 (2), pp. 446-450 (2009);

S. Gurlui, M. Agop, P. Nica, M. Ziskind, C. Focsa, Experimental and theoretical investigations of transitory phenomena in high-fluence laser ablation plasma, Phys. Rev. E 78, 026405 (2008);

C. Ursu, S. Gurlui, M. Ziskind, G. Popa and C. Focsa, on the dynamic of plasma plume in high-fluence laser ablation, 4th conference on elementary processes in atomic systems Cluj-Napoca, Romania, June 18-20, (2008);

M. Agop, P. Nica, S. Gurlui, Georgeta Strat, M. Strat, Fractal space-time and ball lightening as a self-organizing process in laser produced plasma, Journal of Optoelectronics and advanced materials, 10, 1526 (2008);

S. Gurlui, C. Focsa, P. Nica, M. Agop, Solvay Workshop - A Tribute to Professor Radu Balescu (The Physics of Charged Particles: Radu Balescu's Life Passion), Bruxelles, Belgium, 2008

C. Mihesan, M. Ziskind, B. Chazallon, E. Therssen, P. Desgroux, S. Gurlui, and C. Focsa, IR wavelength-selective laser desorption via O-H and C-H stretching modes, Applied Surface Science 253 (3), 1090 (2006);

S. Gurlui, M. Sanduloviciu, M. Strat, G. Strat, C. Mihesan, M. Ziskind, and C. Focsa, Dynamic space charge structures in high fluence laser ablation plumes, Journal of Optoelectronics and Advanced Materials, 8, 148 (2006);

S. Gurlui, M. Ziskind, and C. Focsa, Fast ICCD Imaging of Dynamic space charge structures in high fluence laser ablation plasma plume, 7th International Balkan Workshop on Applied Physics July 5-7th, 2006, Constanta, Romania

Chalcogenide glasses

Within the many fields where integrated optics may apply, the development of amplifiers and laser sources, optical sensors and all-optical processing based on non linear properties are the most promising leading to low cost and highly compact optical systems. The used chalcogenide glasses based on the elements such of S, Se or Te, in combination with elements of Groups IV and V of the periodic system (typically Ge, As, etc.), in different fields of integrated optics (amplifiers and sources laser, optical sensors and optical processing components based on the nonlinear properties) offers promising advantages, particularly in terms of cost and size. These materials exhibit remarkable optical properties: wide transmission window (~ 1-20 µm, depending on the composition), refractive indices, and large photoinduced effects. Because of these properties, chalcogenides are of great importance for applications in wavelength conversion, switching and all-optical modulation, Raman and parametric amplification etc. Slab waveguides based on chalcogenide amorphous films with good adherence and controlled composition have been obtained using pulsed laser deposition allowing to design and to manufacture complex optical functions on waveguides within a small and compact chip. We characterized the ejection plume obtained by laser ablation of AsxSe1-x samples in order to better understand the ablation phenomena for optimizing the pulsed laser deposition process. A systematic study has been performed at different laser pulse energies and wavelengths. Moreover, the dynamics of the plume has been investigated by ICCD camera fast imaging and space- and time-resolved optical emission spectroscopy.   

Several papers published by Romanian and France parteners, as following: 

Gloria Pompilian, Petr Nemec, Silviu Gurlui, Virginie Nazabal, Bertrand Chazallon and Cristian Focsa, "Pulsed Laser Deposition of Chalcogenide Glasses Amorphous Thin Films", 11th Intl Conf on Laser Ablation (COLA), Playa del Carmen, Méxique, 13-18 novembre 2011 

O. G. Pompilian, S. Gurlui, P. Nemec, V. Nazabal, C. Focsa, "Space- and Time-Resolved Optical Emission Spectroscopy of Chalcogenide Glasses Laser Ablation for Thin Films Growth", 6th Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy, Cesme Izmir, Turquie, 11-15 septembre 2011 

O. G. Pompilian, P. Nemec, V. Nazabal, S. Gurlui, B. Chazallon, C. Focsa, "Chalcogenide Thin Films Growth by Pulsed Laser Deposition", 10th International Conference on Global Research and Education (Inter-Academia 2011), Sucevita, Roumanie, 26-29 septembre 2011 

C. Focsa, P.Nemec, M. Ziskind, C. Ursu, S. Gurlui, V. Nazabal, Laser ablation of AsxSe100-x chalcogenide glasses: Plume investigations, Applied Surface Science, 255 (10), pp. 5307-5311 (2009);  

C. Ursu, S. Gurlui, M. Ziskind, C. Focsa, P. Nemec, V. Nazabal, Plasma plume dynamics in pulsed laser deposition of AsxSe1-x chalcogenide glasses, 9th international, Balkan Workshop on Applied Physics, (2008); 

C. Focsa, P. Nemec, M. Ziskind, C. Ursu, S. Gurlui, V. Nazabal, Laser ablation of AsxSe1-x chalcogenide glasses: plume investigations, EMRS, (2008); 

C. Mihesan, S. Gurlui, M. Ziskind, B. Chazallon, G. Martinelli, H. Zeghlache, M. Guignard, V. Nazabal, F. Smektala, C. Focsa, Photo-excited desorption of multi-component systems: Application to chalcogenide glasses, Appl. Surf. Sci., 248, 224 (2005) 

Laser-polymer ablation

Laser-induced surface polymer deformation, laser-surface polymer relief grating formation (SRG), laser- ablation both of photochemical polymer but also of doped polymer processing, pulse laser deposition (PLD) have been the object of growing interest due to potential in nonlinear optics (NLO), laser direct patterning (LDP), fuel in the micro laser plasma ablation satellite propulsion thruster (μALPT), biocompatible metal-doped polymers, etc Polymer ablation still yields a big potential, even though it has a research field over 20 years. Although, generally commercially known available polymers such as polyamide (KAPTON, APICAL, UPILEX), polymetilmetacrylate (MAKROFOL), polyester (MYLAR), etc that are applied in extensive papers, both for fundamental and applicative research area, make them unsuitable for high quality structuring, e.g. low sensitivity, carbonization upon radiation, redeposition of ablated melting material on the polymer structure surface, etc

Therefore, in order to improve the sensitivity of the resulting materials under the action of coherent and incoherent optical radiation, to arise at high mechanical, thermal, electrical and optical properties, novel photopolymers with diazobenzene, stilbene and pyrene pendants covalently attached to polymers have been introduced and studied by our research team

The laser polymer ablation mechanism is a complex interrelated system where the photochemical and phototermal reactions are very important.Photochemical decomposition is intrinsically capable of higher spatial resolution because thermal damage to the surrounding material is minimal and explains many futures of laser ablation, especially in the low fluence range.

A study concerning the surface structuring capacity of the polymers showed that the irradiation conditions significantly influence the surface geometry of the polymers.For example, the photo-sensitivity of the polymers that contain diazo-benzene groups is of basic importance not only as a model of structure for studies concerning the energy absorption or as investigation source in self-organized systems, but also as photo-sensitive materials for the realization of devices with various applications in nanotechnologies.Surface irradiation was carried out under the action of an optical radiation field with a controlled distribution represented by an interference pattern of electromagnetic radiation beams. The explanation of the surface patterning in azo-polymer materials as on optical -mechanical effect is quite true it take into account the well known concept of the self- structuring and self-organizing phenomena. Self- organization and spontaneous ordering into the periodic structure can be found in different fields of science. As an example, plasma is a strong nonlinear medium, very suitable for the development of self-organized structures inside it. The self-organized structures appear in plasma discharge or laser ablation plasma devices as beautiful intense luminous almost spherical bodies, attached to the surface of the exciting electrode, or not. The double layer is, in fact, the active part of the self-organized structure, ensuring the exchange of the matter and energy between the structure and the surrounding medium.The dynamics of these structures is related to the equilibrium between particle production by elementary processes (direct and indirect ionization) and the loss of particles (recombination in the volume and at the walls).Knowledge of the processes that lead to the appearance of the self-organization phenomenon and, on this basis, of the nano-structures, is very important since it permits the controlled action at a molecular and atomic level during the operation of nanomaterial preparation. This control at atomic and molecular level is necessary for the development of new technologies able to work at a nano-scale in a controlled and reproducible manner, representing the basis for the future production processes. Many of these technologies, such as SPM (Scanning Probe Microscopy), were first developed in research laboratories, but we need to specify that they have not yet reached their entire potential

The nano-technologies will influence the increase of the efficiency of the production processes, thus permitting, for instance, a considerable diminution of the consumption of strategic materials and energy. Many of these processes will be optimized by means of nanoparticles and nano-porous systems. Knowledge of the processes which lead to the appearance of the self-organization phenomenon in polymers with complex molecular structures is also important for the nano-electronics field. Moreover, nano-electronics plays a strategic part in technologies related to the computer science and telecommunications.