The conservation of artifacts and antiquities is central for the knowledge and preservation of our cultural heritage. The difficulties encountered in fullfiling this task successfully, are largely due to the fact that cultural heritage objects are diverse and dispersed, often suffering from different causes of natural or anthropogenic degradation, deterioration and conditioning. A complete knowledge of the materials involved and an optimal implementation of conservation methodologies relies on the existence of effective tools for non-invasive diagnosis and safe intervention. Optical sciences play a key role in this respect. For example, the development of powerful diagnostic methodologies, enabling the development of adaptable and complementary analytical and structural diagnostic techniques, as well as, the introduction of effective maintenance practices such as cleaning and restoration, rely greatly on the use of modern laser science and technology.
The discovery of lasers enabled us to produce coherent beams of light. These beams, like all electromagnetic waves, consist of coupled, time-varying electric and magnetic fields. Charged particles (for example, electrons) moving under the influence of these fields inside beams of light may be trapped in the region near the beam axis. Trapping mechanism and specific examples will be described in this talk.
Principles, operation and recent advances in four-wave optical parametric amplifiers based on bulk isotropic wide-bandgap media are overviewed. In particular, broadband optical parametric amplification is demonstrated in ultraviolet and infrared in fused silica, CaF2 and MgF2, suggesting a simple frequency up and down-conversion method for visible femtosecond pulses provided by commercial blue-pumped noncollinear optical parametric amplifiers (NOPA).
In my talk I will discuss the issue of coherence of Bose systems. Coherence is a basic property which distinguishes laser light from a thermal one. I will compare coherence properties of a laser light and of a Bose-Einstein condensate indicating some similarities and differences.
The high degree of control in cold atom experiments allows to simulate pending problems of condensed matter physics. Since many interesting phenomena involve the coupling of charged particles to a magnetic field, it is desirable to implement an artificial gauge field for cold neutral atoms. In my talk I will present a method taking advantage of Berry's phase, where the slow motion of dressed atoms in a laser field leads to the emergence of an effective magnetic field. I will discuss the prospects of this novel method.
The review of works focused on research, development and applications of solid state, mid infrared lasers carried out at the Institute of Optoelectronics in last quarter-century is given. Traditional lamp pumped Holmium and Erbium lasers as well as modern hybrid Ho:YAG and Er:YAG lasers resonantly pumped by fiber lasers were presented. Theoretical models explaining main physical and technical limitations of such laser sources were developed. Future works, potential applications and possibilities of cooperation were discussed.
Interaction of intense ultrashort light pulses with transparent materials reveals new properties and phenomena, which challenge common beliefs in optics. Demonstration of 3D nanograting formation and self-assembled form birefringence uncover new science and applications for image printing and 5D optical recording. These and more recent demonstrations of ultrafast laser calligraphy in glasses, anisotropic sensitivity of isotropic medium to femtosecond laser irradiation, referred as ultrafast light blade and nonreciprocal photosensitivity in crystals are reviewed.
Laser light is different from light emitted by ordinary thermal sources. This difference was crucial for Quantum Optics birth as an area of modern physics in 1963, three years after the creation of the first laser. In the following years it has been understood that coherent states of laser light are just a small island in a sea of other possible states of light. After a short historical introduction, the modern use of quantum optical achievements for a new area of quantum information will be presented.
Functional thin-films are of high importance in modern electronics for flat panel displays, photovoltaics, flexible & organic electronics. Versatile technologies are prompted for patterning thin-film materials on rigid and flexible substrates. Ultra-short laser processing is one of the ways to achieve the high quality and productivity material etching. Selectiveness of the laser processing depends on localization of laser energy coupling in multilayered thin-film structures, which can be controlled by wavelength and pulse duration of laser radiation. Results of structuring of simple mono-films of metals and transparent conducting oxides as well as multi-layer structures of thin-film solar cells using different fabrication routes: laser direct writing, laser beam interference and laser-induced self-organization are presented and review.
In the initial part of the talk we review the schemes enabling to produce the artificial magnetic field for cold atoms using several light beams. We discuss the possibilities to create both the usual Abelian artificial magnetic field and also the non-Abelian one. Subsequently we shall present some recent studies of the effects due to the non-Abelian gauge potentials for cold atoms including their quasi-relativistic behaviour and negative reflection. In the final part we shall present our latest work on generating the non-Abelian artificial magnetic field for cold atoms containing three degenerate dressed states, so their centre of mass motion is described by a three-component spinor.
In this talk I will briefly review the striking resemblances between cold atom physics and optics. Bose-Einstein condensates constitute a coherent ensemble of atoms, resembling to a large extent lasers. Interestingly, the interatomic interactions in condensates lead to Kerr-like nonlinearity, and hence the condensate physics resembles strikingly nonlinear optics. Finally, I will discuss how recent developments are moving the field of cold gases into the realm of quantum atom optics. In particular I will comment on the possibility of realizing non-classical states of matter, as squeezing.
Neutral atoms confined in magnetic traps are a versatile tool to study fundamental quantum and atomic as well as atom-surface interactions. In this talk I will describe how trapped atoms can be manipulated by laser light. I will discuss how the proximity of metallic surfaces influences the spectroscopic properties of atoms and discuss various experiments on the micrometer scale.
Spectroscopic investigations of atoms and molecules, including spontaneous emission from excited atoms, being a natural focus of early quantum mechanics, became an especially active area in 70s, after developing of narrow-band tunable lasers. Today, it is again at the forefront of quantum optics research, following the recent advances in the construction of atomic traps and direct observation of emission and absorption of individual quanta from isolated atoms. It is long known that multilevel atoms interacting with electromagnetic field can display a much broader range of effects than their two-level counterparts as a result of the coherences among the states induced by the radiation and quantum interference. Interference produced by the presence of coherences have been known since the development of quantum mechanics, and their creation has been largely exploited in spectroscopy and quantum optics. However, a macroscopic effect such as the total suppression of fluorescence emission by coherent population trapping is quite unusual. The talk will be focused on this phenomenon and its applications.
In the first part of my talk I will give a brief overview of material, electronic, optical and transport properties of graphene. Then I will discuss basic properties of graphene nanoribbons focusing on the formation of the transport gap dues to disorder.
Starting with the first laser launched in Lithuania in 1966, laser spectroscopy in semiconductors has become a rapidly evolving research area at Vilnius University. In particular, optical nonlinearities and high-density nonequilibrium carrier and exciton phenomena have been widely investigated and advanced characterization techniques, such as dynamic holography, have been developed. Recently, the expertise in the field of compound semiconductors acquired due to laser instrumentation allowed for the switching to the development of innovative solid-state sources of light and applications of solid-state lighting systems in phototherapy, horticulture, biofluorescence detection, and smart illumination with controlled colour quality.
Silicon with improved surface properties is urgently needed in many semiconductor and solar-energy devices. Porous silicon thin films are of great interest in many multidisciplinary fields of science and technology such as optoelectronics, chemical and biosensors, and photovoltaics. Due to unique surface properties, porous films have numerous advantages over bulk materials. A new thin film method of porous silicon formation is reported, which are based on thin silica layer electrochemical reduction in molten salts.
Nanoparticles (e.g. luminescent semiconductor nanocrystals) having unique chemical and/or physical properties are currently in the focus of interest. Many of these properties are dependent on size and shape. Concomitantly, methods have to be developed, which allow the precise and reliable measurement of particle size distributions. Capillary electrophoresis (CE) and isotachophoresis (ITP) will be discussed as possible means for characterization of the nanoparticles.
Many pharmaceuticals and natural products feature C-N and C-O bonds in 1,2 and 1,3 relative positions, with α- and β-amino acid and their derivatives being the most common parent moieties. In recent years, synthetic strategies towards these structural motifs that employ direct functionalisation of sp3-type C-H bond as a key bond-forming event are increasingly gaining momentum. The presentation will focus on two such methodologies to provide a convenient access to a wide range of 1,2 and 1,3-amino alcohols: (a) Pd-catalysed allylic C-H amination and (b) Fe-catalysed oxidative nitroso-ene reaction.
The compatibility of continuous bed technique with the microseparations gained particular interest of the researchers and companies developing chromatographic materials for micro and nanochromatography and extraction. In current report we will focus on application of capillary format continuous bed inserts for coupling of capillary electrophoresis for in-line sample preparation and preconcentration for automated microanalysis of analytes present in different matrices including biological fluids. We will also demonstrate coupling of reaction detection to capillary electrophoresis for evaluation of radical scavenging activity of individual compounds in plant extract by means of the hyphenated microanalytical technique.
The main task of this study was to carry out a comparative evaluation of content of phenolic compounds and radical scavenging activity in different species traditionally used in a local cuisine Six spice plant samples, namely onion (Allium cepa), parsley (Petroselinum crispum), celery (Apium graveolens) and above-ground part of dill (Anethum graveolens) were analysed. Evaluation of plant extracts was carried out by means of various spectrophotometric and chromatographic analysis methods including high performance liquid chromatography with reaction detection and electrochemical detection.
Main limiting factor for solid state laser average output power is related to thermal effects in active medium. Optimizing heat dissipation should be a way to avoid this problem. For this reason thin active medium is used. Typically in thin disk laser systems single thin disk with a complex multi-pass pump arrangement is used. In this presentation we disclose a concept of multiple thin disk active elements configuration. In essence, we use several collinearly pumped thin disks in order to simplify pump system configuration, maintain similar absorption and gain and also reduce thermal load for individual disk.
We discuss a hybrid OPCPA-filamentation approach to pursue a single-cycle IR source that will find many applications in attosecond and high-field science. Starting point of the system is a four-stage IR OPCPA delivering CEP-stable 1.5-μm pulses with energies up to 12.5 mJ before recompression. Pulses with 62-nm bandwidth and 3.5-mJ energy have been recompressed to a 74.4-fs duration close to the transform limit. To reach few-cycle pulse durations, we demonstrate self-compression of 2.2-mJ 74.4-fs 1.57-μm pulses down to 19.8 fs duration in a single filament in argon (with 1.5-mJ output energy and a 66% energy throughput).
The solid-phase microextraction is very attractive, simple and unique sample preparation technique. In this study headspace solid-phase microextraction combined with gas chromatography-mass spectrometry applied to analyze the essential oils components in medicinal plant Calendula officinalis L. during vegetation periods.
Spatial and temporal coherence properties of the supercontinuum (SC), generated by sub-nanosecond pulses of Q-switched Nd:LSB laser (1062nm) in single mode photonic crystal fiber (PCF) have been experimentally investigated by interference techniques. The measured degree of spatial coherence was found to be high with the coherence length exceeding the diameter of the beam. It varies from 0,94 until 0,78 in the spectral range region of 800-1000 nm and depends slightly on the distance between selected point sources in Young’s double slit interference experiment. Temporal coherence has been studied by recording spectrally resolved interference patterns in Michelson’s interferometer with moveable mirror. The coherence time has been found to be dependent on wavelength. It grows up from 0.38ps until 1,7ps in the spectral region of 470-950nm.
We report on the generation of ~30-fs ultraviolet (UV) pulses with ~10 μJ energy by means of four-wave optical parametric chirped pulse amplification in fused silica. The idea of the experiment is essentially similar to that of the small-scale OPCPA: the visible pulses, delivered by a commercial noncollinear optical parametric amplifier (NOPA), are positively chirped and stretched, and then amplified in transparent isotropic medium by the four-wave mixing (FWM) process. The idler pulses are generated in the UV spectral range. The idler pulses acquire an opposite chirp as compared to that of the seed signal, and therefore are compressed down to 30 fs by simple propagation in a medium with normal group velocity dispersion. The major benefit of the proposed approach is that instead of conventional frequency upconversion of the NOPA output, FWM allows conversion of the visible NOPA pulses into the UV and amplification at the same time.
5-aminolevulinic acid interests researchers and medical community as a prodrug for skin cancer treatment. In this report we will discuss about cost-effective capillary electrophoresis method for determination of 5-aminolevulinic acid in human dermis. We will also demonstrate penetration enhancement across the stratum corneum barrier by lipid matrix disruption with acetone.
The spontaneous parametric down-conversion or parametric fluorescence in crystals with χ2 nonlinearity was observed experimentally in 1967. In this process, three optical fields with different frequencies, satisfying conservation of energy and momentum, are coupled through the second-order nonlinearity of the medium. Photon generation via parametric down-conversion, pumped by a laser source of high spatial and temporal coherence, is accessed in many different operating regimes, ranging from a single photon to broadband emission and in a variety of the nonlinear media using different interaction geometries. In this contribution we report how the parametric fluorescence with appreciable power is generated in bulk LiIO3, KDP and BBO crystals, using an incoherent high-brightness blue LED as a pump source. Present results suggest that high-brightness LEDs could be used as an attractive alternative to laser sources for excitation of well-detectable parametric fluorescence in bulk nonlinear crystals, so making LED a versatile source for many experiments in quantum optics.
In this report we present experimental results of the investigation of one-stage Yb-doped double-clad large-core fiber amplifier. A single mode seed was derived from Nd:LSB (duration 0.6 ns) and Nd:YAG (duration 1.2 ns) microchip lasers. Fiber amplifier was pumped by 8.8 W power diode-laser radiation (975 nm), the maximum energy of amplified signal was 220 μJ. Good amplified beam quality allows 60% efficiency of second harmonics, which was used to pump doubly resonant KTP OPO.
Structuring and patterning of thin layers via selective laser ablation are one of the key technologies in PV panel production. In this presentation, we discuss our results in laser structuring of multilayered films of the CIGS solar cells with the picosecond pulse duration at 1064 nm wavelength. Well-defined shapes of the isolating trenches down to metal back-contact were produced by laser ablation in thin film structures of the CIGS solar cells.
We report the first experimental evidences of light beams spatial filtering by three dimensional photonic crystals. Our photonic crystals were made in a glass bulk, where the refraction index has been periodically modified by tightly focused femtosecond laser pulses. We observe filtered areas in the angular distributions of the transmitted radiation, and we interpret the observations by theoretical and numerical analysis of the paraxial light propagation model.
Although neutral atoms do not naturally show electromagnetism, non-Abelian gauge potentials will appear in the presence of a general adiabatic motion of a quantum system with degenerate states. We study the wave packet dynamics of a cloud of ultracold atoms in the presence of non-Abelian gauge fields and discuss a non-Abelian Aharanov-Bohm effect in non-commutative interferometric arrangements. We show that the dispersion relation can lead to a quasi-relativistic motion of ultracold atoms similar to electrons in graphene and to Veselago-type lensing. Another consequence of the dispersion relation is the atom double reflection. Finally, by including interactions (BEC) we find solitonic solutions which are so far only known from high energy physics.
The essential oils of two medicinal plants (Bidens tripartita and Calendula officinalis) were obtained by supercritical CO2 extraction. Gas chromatographic-mass spectrometric (GC-MS) analysis showed, that B. tripartita essential oil can be characterized by high amounts of β-ocimene (40.6%), β-elemene (15.5%), and α-pinene (12.5%); while α-pinene, α-thujene, γ- and δ-cadinenes were predominant in the essential oil of C. officinalis (amount of these compounds in the oil varied from 10.5% to 14.8%).
We investigated the propagation of spin waves in a finite square array of cylindrical rods where the cylinders in the boundaries of this square have been modified. A set of Co rods was placed in Ni matrix. In the corrugated edges a change in the size of the rods or a shift in their positions was made. The information about eigen-frequency spectrum was extracted using plane wave method. We used in our model the Landau-Lifshitz equation with space dependent exchange length and saturation of magnetization. In order to apply the plane wave method we constructed a superlattice of supercells with an array of rods in each of them. The supercells start to be separated if the distance between them is wide enough ensuring weak interaction with other neighbour supercells. The states localized on the edge of array (surface states) were indentified by computation of squared dynamical magnetization.
Polymers containing carbazolyl and other amino groups as electro-active pendants have been widely studied and described in literature. They have been applied as charge transporting materials or triplet energy hosts. Here we present the synthesis and properties of new carbazole- and phenylindole-based polymers, which were studied as host materials for phosphorent light emitting diodes (PhOLEDs).
Propagation of powerful femtosecond light pulses in transparent solids reveals surprising features on the nature of light and matter interactions. One of its ultimate manifestations is self-focusing and spontaneous break-up of intense elliptical laser beams into self-organized periodic arrays of narrow white-light beams, termed light filaments. We demonstrate that although white-light filaments emerge in apparently regular patterns, the individual filaments propagate in curved trajectories. The full three-dimensional picture of a filament bundle is captured with high spatial and temporal resolution and resembles optically turbulent propagation in fused silica slab. Our observation unveils an exciting physics of the nonlinear light and matter interactions, which facilitate the beam break-up process and force the light to propagate along the curved paths. These paths emerge as a result of the generation of new optical fields, whose coherence is neither spatial nor temporal, but rather is skewed in the unified space-time domain.
The construction of three dimensional (3D) artificial scaffolds for cell growth in vitro and in vivo is promising for the possibility to create specific tissue and transplant it to the patient. In this report we present production of complex shaped polymeric scaffolds with controlled porousity fabricated via Laser Multi-Photon Polymerization (LMPP) technique. This direct laser writing technique is based on ultra-localized polymerization reaction initiated by nonlinear absorption of short pulsed light in the tiny volume of the photosensitive material. While point by point scanning the trace of the computer aided CAD model the 3D microstructure can be manufactured. LMPP provides possibility to create artificial scaffolds of arbitrary form from various biocompatible materials. The direct writing is flexible and scalable when changing geometry of the required structure and provides tunable 0,1 µm to 20 µm spatial resolution. This enables to form millimeter in size submicrometer patterned structures for cell proliferation. Various biocompatable polymers can been used to fabricate 3D scaffolds. The cell growth, adhesion and viability in vitro investigations and in vivo tests show biocompatability of the produced structures.
It was demonstrated that spiraling zeroth-order Bessel like beam can be created by using a conventional axicon and a hologram. The analytical features of the beam propagation have been studied theoretically. By using the conventional axicon and the hologram combination, the spiraling zero-order Bessel like beam was experimentally generated and analyzed for the first time to our knowledge. It was obtained that the beam displacement is directly proportional to the depth of phase modulation. The period P that determines the distance over which spiraling zero order Bessel beam makes one revolution grows with growing period of phase spiral shape hologram. Obtained results are in a good agreement with the theoretical predictions.
We analyse manipulation of slow light with the orbital angular momentum (OAM) using control laser beams that might carry optical vortices. We consider situations where the atom-light interaction represents a single or double tripod scheme. In both cases the exchange of the optical vortex can take place between the control and probe fields. Using the single tripod scheme the optical vortex can be transferred from the control to the probe fields during either the storage or retrieval of the slow light. In the case of the double tripod setup, the transfer of OAM occurs during the slow light propagation without switching off the control beams. The manipulation of the slow light with the OAM has potential applications in the optical information processing in quantum atomic gases.
The material mixing in production of optical coatings is attractive due to the flexibility in obtaining thin film layers with tailored optical constants. In this study, we present our recent progress in research of mixed zirconia/silica and niobia/silica coatings prepared by Ion Beam Sputtering technique. Refractive index dispersions, band-gaps and volumetric fractions of materials in mixed coatings were analyzed from spectrophotometric data. Optical scattering, surface roughness, nano-structure and optical resistance were also studied. Zirconia-silica mixture coatings experience the transition from crystalline to amorphous phase by increasing the content of SiO2. This also results in reduced surface roughness. All niobia and silica coatings and their mixtures were amorphous. The obtained laser-induced damage thresholds in subpicosecond range also correlates with respect to the silica content in both zirconia- and niobia-silica mixtures.
Electromagnetically induced transparency (EIT) is an interference effect that results in a dramatic reduction of the group velocity of a propagating weak probe pulse accompanied by vanishing absorption. The group velocity of the probe depends on the intensity of a coupling field which has to be strong and thus it is usually a classical laser beam. In the present work we present a scheme where the coupling field is substituted by a quantized cavity field. The adiabatic transfer of probe photons to the cavity mode modifies the refractive index of medium in a similar manner as the coupling field does in the case of ordinary EIT. we show that this system can be used to generate and control quantum pulses of light with very high accuracy. In particular it can be used to spatially separate the single photon from higher photon-number components of a few photon probe pulse and thus to create an optical Fock-state filter or a deterministic single-photon source.
A precise characterization of tightly focused laser beams is not just a challenge but is essential for their applications. Though quite different in their nature, many popular beam characterization methods share the common theoretical background ‑ the scalar diffraction theory, so the precise characterization of highly focused vector beams by the classical evaluation schemes is not a trivial and often a hard task. The aim of our work is a detailed study on the implementation of the scattering of highly focused various polarizations optical beams on a small metal sphere for the reconstruction of the individual electric field components. We develop an algorithm, which enables us to reconstruct the longitudinal and transverse components of the incident electric field, As a result, a good reconstruction of the electric field is possible.
In this work we report our studies on the modifications induced inside lithium niobate and KDP crystals with ultrafast, Yb:KGW based, laser pulses, having 300 fs pulse duration and operating at 100 kHz repetition rate. By focusing laser beam with 0.42 numerical aperture objective we have recorded homogeneous volume Bragg gratings in the bulk of the niobate crystal that showed excellent diffraction efficiencies reaching up to 87% and remained permanent after thermal annealing at 150 ºC temperature. Optimal parameters and the influence of the focusing depth on the structural quality of modifications are also discussed in this work. The results show that lithium niobate is very promising crystal candidate for microphotonics applications. In the KDP crystal no smoothly modified refractive index zones were created mainly due to the low material tolerance to femtosecond-pulse induced stress which creates microcracks at the laser affected zones.
We investigate band-gap solitons, i.e. the solitons in defocusing Kerr-nonlinear media with periodic space modulation of potential, and show that they are unstable for their eigen-frequencies around the middle of the bandgap due to the radiation into mode continuum of the upper and lower bands. We identify the mechanism of four-wave mixing that causes this radiation of solitons. We also show, that the solitons self-stabilize by losing their mass due to the radiation and thus by moving into the area of the band-gapwith negligibly small radiation.
We present an analytical theory for the gate electrostatics and the classical and quantum capacitance of the graphene nanoribbons (GNRs) and compare it with the exact self-consistent numerical calculations based on the tight-binding p-orbital Hamiltonian within the Hartree approximation. We demonstrate that the analytical theory is in a good qualitative and quantitative agreement with the exact calculations. There are however some discrepancies. In order to understand the origin of these discrepancies we investigate the self-consistent electronic structure and charge density distribution in the nanoribbons. We show that the effect of electron-electron interaction leads to the significant modification of the self-consistent charge distribution in comparison to the noninteracting electron description, which is used in the analytical model. In turn, the nonuniform distribution of charge and potential produces an effective transverse electric field resulting in the modification of the electronic structure of the GNRs.
Multi-photon polymerization by interference is a promising technique for mass fabrication of 3D periodic microstructures over large areas, which can be used in various fields such as microbiology (cell growing), photonics and so on. As direct laser writing approach is a relative slow process, fabrication of periodic structures by interference field of a few laser beams can be a significantly faster alternative route of parallel processing. The periodic structures are produced by the single laser exposure over whole irradiated area. In this poster we present examples how periodic microstructures can be fabricated by multi-photon polymerization using four-beam interference of a femtosecond laser in photopolymer SZ2080 (ORMOSIL).
Just after the discovery of the laser (over the past 40 years) the Vilnius University Physics faculty Semiconductor Department's researchers group of photoelectrical phenomena (head J. V. Vaitkus) has applied pulsed laser for time resolved photo-Hall effect measurements in semiconductors. In short time first diploma works and scientific publications were presented. This method improved to be very useful in investigating semiconductors electrical characterization. During past 40 years results from this method's data was published in over 150 scientific publications and described in 7 dissertations. Time resolved photo-Hall measurements and photoconductivity gave much information about scattering and recombination centers in up-to-date semiconductors (GaAs, irradiated Si by high energy particles, CdSe, GaN et al.), especially in compensated ones. Other advantages of this method are: electron-hole scattering at high excitation level; the minimized influence of GaAs technological defects by doping with indium in purpose to eliminate clusters. To evaluate point defects and clusters parameters the perfect technique is time resolved photo-Hall method. Further measurements would be made investigating radiation defects in purpose to recognize hard materials for ionizing radiation detectors.
In this work two methods of material processing with the picosecond laser are discussed. Holes were drilled in steel using 532 nm radiation with the sample placed on rotating stage. Laser optical power and processing time were varied during experiments. We succeeded to drill 100 μm diameter hole in 1 mm thickness steel with a small taper. Using 1064 nm wavelength and the galvanoscanner experiments of cutting ceramics were conducted. We succeeded to cut 1 mm thickness Al2O3 ceramics without applying a focus shift.
A multiwavelength lighting source composed of at least four different coloured light-emitting diodes (LEDs) can generate white light of a particular chromaticity within different spectral power distributions (SPDs) that provide with different colour quality of illumination. We report on a prototype red-amber-green-blue (RAGB) tetrachromatic lighting source that can be operated within a dynamical trade-off between several colour rendition characteristics, such as the ability to render colours with high fidelity and the ability to render colours with increased or decreased chromatic saturation. The SPD of the source is varied as a weighted sum of two trichromatic end-point SPDs with the maximized ability to render object colours with increased chromatic saturation (RGB source), and decreased chromatic saturation (AGB source), respectively. Such RAGB sources with tailored colour quality can be used in "smart" lighting with individual needs and preferences of colour vision met.
Terahertz emission from air excited by the focused fundamental and second harmonic pulses of femtosecond Ti:Sapphire laser have been investigated both experimentally and theoretically. The broadband terahertz pulses generated during this nonlinear optical process have been applied for the creation of the automated spectroscopic system capable to measure the absorption spectra of many materials in 0.1-4 THz spectral range.
Artificial structures borrowed from the nature are applied in automotive industry as well as in photonics and bio-medical research. A new growing application area is frequency-selective surfaces, which are working as a filter for electro-magnetic waves in THz, infrared or visible range depending on the period and the feature size of the fabricated surface. In this work, we report on the resonant THz filters, made of cross-shape holes in thin metal foils and films, fabricated employing the ultrashort-pulse UV laser milling process, when focused laser beam was used to ablate the material. The spectral performance of the filters was investigated experimentally and numerically. More periodic structures were fabricated on thin metal films (chromium, aluminum, gold and copper) deposited on glass substrate using the multibeam laser interference patterning. 1D and 2D grating with period of 2 μm and 5 μm respectively were fabricated using this technique, which can be used as beamsplitters, partially reflected surfaces, polarisers and low or high pass filters.
Quantitative distribution of flavonoids in a raw material of the medicinal plant willow herb during different vegetation phases (intensive growing, bud, massive blooming, ripening of fruits (seeds), end of vegetation) was evaluated by HPLC method. Identification of the biologically active phenolic compounds was carried out. It was determined, that quantity of flavonoids and values of radical scavenging activity correlate in all phases of vegetation.
The present poster discusses two work in progress research projects: (a) the dynamics of an ultra-cold quantum gas or BEC after a ramp of the two particle interaction energy. Here we were especially interested in the excess energy deposited in the considered system after the ramp period. (b) the formation of Faraday patterns in Spinor condensates under the influence of spin-orbit coupling. To date Faraday pattern have only been discussed and experimentally verified for scalar condensates. Here we discuss the possibility to produce Faraday pattern in Spinor condensate with an spin-orbit coupling.
Permanent demand of micro- and nanostructures in photonics, plasmonics, metamaterials, bioengineering and microoptics science requires high quality 3D fabrication methods. One of them is Direct Laser Writing (DLW) lithography – Femtosecond Laser Multi-Photon Polymerization (FLMPP) technology. Ultralocalized photochemical reaction initiated by Multi-Photon Absorption (MPA) in the bulk of the photopolymer leads to the formation of subdiffraction elements – voxels (volumetric pixels). Direct writing and point-by-point fabrication allows photostructuring of microoptical components of complex geometry directly from Computer Aided Design (CAD) models. Versatility of the FLMPP technology enables fabrication of microstructures on various substrates such as glass, plastic or metal. In this report, we present possibility to fabricate micro-optical components on the top of the optical fiber out of commercially available hybrid zirconium-silicon containing photopolymer SZ2080 (FORTH, Crete, Greece). We compare optical focusing characteristics of the single optical fiber with microlenses fabricated on the glass and on the top of the fiber. The structural quality of the lenses was investigated by Scanning Electron Microscopy (SEM). The obtained results show possibility to integrate micro-optical components on the top of the fiber and use it for creation of 3D optical circuitries.