Roman Kiyan

Leibniz Universität Hannover · Institut fur Quantenoptik

In this Letter, a completely ferrodielectric metasurface consisting of an array of cylinders on a substrate is studied. All structural elements are made of ferrodielectric material. The conditions for the excitation of Wood’s anomaly mode, obtained for different geometric parameters of the metasurface, are revealed. By continuously changing the str...

The endothelial glycocalyx and its regulated shedding are important to vascular health. Endo-β-D-glucuronidase heparanase-1 (HPSE1) is the only enzyme that can shed heparan sulfate. However, the mechanisms are not well understood. We show that HPSE1 activity aggravated Toll-like receptor 4 (TLR4)-mediated response of endothelial cells to LPS. On th...

High-resolution, high-speed 3D printing by two-photon polymerization (2PP) with a Nd:YVO4 Q-switched microchip laser at its fundamental wavelength of 1064 nm is demonstrated. Polymerization scan speeds of up to 20 mm/s and feature sizes of 250 nm are achieved using a high repetition rate Q-switched microchip laser with a semiconductor saturable abs...

Objective: The endothelial glycocalyx and the regulation of its shedding are important to vascular health. Endo-β-D-glucuronidase heparanase-1 (HPSE1) is the only enzyme that can shed heparan sulfate. However, the mechanisms are not well understood. Approach and results: To investigate HPSE1 and its endogenous inhibitor, heparanase-2 (HPSE2), we us...

A technique to increase nanosecond laser based production of ferric nanoparticles by elevating temperature of the iron target and controlling its surface exposure to oxygen is reported. High power near-infrared laser ablation of the iron target heated up to 600 °C enhances the particle generation efficiency by more than tenfold exceeding 6 μg/J. Te...

In this work, we have explored 3-D co-culture of vasculogenic cells within a synthetically modified fibrin hydrogel. Fibrinogen was covalently linked with PEG-NHS in order to improve its degradability resistance and physico-optical properties. We have studied influences of the degree of protein PEGylation and the concentration of enzyme thrombin us...

Almost all modern optical communication lines, both local and trunk ones, use the wavelength-division multiplexing principle (WDM or DWDM). We suggest that frequency encoded OCDMA algorithms be used as most suitable tools for local and metropolitan area networks. Coding is performed in this case in the frequency domain, i.e., code sequences can be...

We study theoretically the band-gap structures of several types of three-dimensional photonic crystals with the fcc lattice symmetry: synthetic opals, inverted yablonovite and woodpile. The samples of inverted yablonovite, inverted yablonovite with a glassy superstructure and woodpile are fabricated by two-photon polymerization through a direct las...

The modes of laser lithography fabrication of three-dimensional submicrometer structures have been studied. The method is based on the effect of threshold two-photon polymerization of a photosensitive material at the laser beam focus. To determine the lithograph workspace in the coordinates “laser power-speed of the sample displacement with respect...

A non-linear case of the transmitting of the TV-image by a pulsed laser light has been considered. An analytical solution for the diffracted light field for the practically important geometry of scattering corresponding to the wideband anisotropic light diffraction from a slow shear elastic wave propagating in the [110] direction in the TeO2 crysta...

As a demonstration of unique capabilities of three-dimensional laser lithography, an example complex-shape microobject and photonic crystals with “woodpile” structure for the infrared spectral range are fabricated by this technique. Photonic dispersion relations for the woodpile structure are calculated for different values of the permittivity cont...

A technique to fabricate electrically conductive all-polymer 3D microstructures is reported. Superior conductivity, high spatial resolution and three-dimensionality are achieved by successive application of two-photon polymerization and in situ oxidative polymerization to a bi-component formulation, containing a photosensitive host matrix and an in...

Current treatments for human coronary artery disease necessitate the development of the next generations of vascular bioimplants. Recent reports provide evidence that controlling cell orientation and morphology through topographical patterning might be beneficial for bioimplants and tissue engineering scaffolds. However, a concise understanding of...

Femtosecond laser structuring is applied to produce linear ion traps of AlN ceramics. Such ion trap can serve as an optical clock with exceptionally high long term stability. The selection of techniques, applicable to the high precision microstructuring of AlN ceramics, is limited due to high hardness and fragility of the material. Laser structurin...

The main goal in the production of nanocomposites for optical applications is the uniform and non-agglomerated incorporation of nanoparticles into polymer matrices. Therefore, in this work gold nanoparticles have been generated by short-pulsed liquid phase laser ablation in methyl methacrylate (MMA) with or without dissolved poly(methyl methacrylat...

Two photon polymerization technology has been used to fabricate sub-micron three-dimensional structures using a new polyfunctional perfluoropolyether-based resist, which is a polymer intrinsically hydrophobic and chemically resistant. The fluorinated resist was designed and synthesized in this work and successfully employed to fabricate woodpile st...

This paper reports on the synthesis of glassy nanostructures in which the framework is a face-centered cubic lattice of inverse yablonovite with a disordered glassy superstructure. The synthesis has been performed by the direct laser writing method based on two-photon polymerization of a photosensitive material. The fabricated structures have been...

Novel interaction regime of femtosecond laser pulses with steel surface at high peak irradiation fluences (0.82–10 J/cm2) has been observed and thoroughly investigated. This interaction regime allows the generation of well defined microrough surfaces. To investigate the mechanisms involved in the formation of sub-focus microscale cavities and protr...

Experimental results on synthesis of metal nanoparticles in ORMOCER by ion implantation are presented. Silver ions were implanted into organic/inorganic matrix at an accelerating energy of 30 keV and doses in the range of 0.25⋅1017 to 0.75⋅1017 ion/cm2. The silver ions form metal nanoparticles, which demonstrate surface plasmon absorption at the wa...

Three-dimensional photonic crystals with an inverted yablonovite structure have been fabricated by the direct laser writing method based on the two-photon polymerization of a photosensitive material. The correspondence of the structure of the samples to the inverted yablonovite lattice has been confirmed by scanning electron microscopy. The photoni...

We report on the fabrication of inverted Yablonovite-like three-dimensional photonic crystals by nonlinear optical nanolithography based on two-photon polymerization of a zirconium propoxide hybrid organic-inorganic material with Irgacure 369 as photo-initiator. Advantage of this material is ultra-low shrinkage that guaranty high fabrication fideli...

Ion implantation was used to locally modify the surface of silica glass to create periodic plasmonic microstructures with Cu nanoparticles. Nanoparticles were synthesized by Cu-ion irradiation of the silica glass at the ion energy of 40 keV, dose of 5×1016 ions/cm2 and current density of 5 μA/cm2. This procedure involves low-energy ion implantation...

Using modern laser fabrication techniques such as two-photon polymerisation (2PP), complex 3D and planar structures with the resolutions down to 100 nm can be achieved. Advantages of 2PP can be exploited by combining it with the nano-imprint lithography (NIL). We report on the fabrication of masters by 2PP and its replicas by the soft NIL technique...

The urokinase-type plasminogen activator (uPA) and its specific receptor (uPAR) are a potent multifunctional system involved in vascular remodeling. The goal of the study was to unravel the mechanisms of uPA/uPAR-directed vascular smooth muscle cell (VSMC) differentiation. Using cultured human primary VSMCs, we identified a new molecular mechanism...

Recent interest in photolithographic processes employing single and two-photon absorption processes have afforded advanced opportunities to fabricate both planar and three-dimensional microstructures. The fabrication of such structures is dependent on the local polymerization of the organic moieties using photoinitiating molecules, and a key parame...

Interference effects in systems with several coherently excited surface-plasmon-polariton beams are studied experimentally and theoretically. The influence of the excitation conditions and surface nanostructures on the interaction between the beams is discussed.

Laser-induced transfer approach for fabrication of functional 2D and 3D nanoparticle structures and arrays is developed. Applications of the nanostructures produced by this novel method for sensing and metamaterials are demonstrated.

A novel method for high-speed fabrication of large scale periodic arrays of nanoparticles (diameters 40-200 nm) is developed. This method is based on a combination of nanosphere lithography and laser-induced transfer. Fabricated spherical nanoparticles are partially embedded into a polymer substrate. They are arranged into a hexagonal array and can...

This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of mic...

Optical properties of spherical gold particles with diameters of 150–650nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond the quadrupole) in the scattering spectra of individual spherical...

A novel method for fabrication of 2D and 3D metal nanoparticle structures and arrays is proposed. This technique is based on laser-induced transfer of molten metal nanodroplets from thin metal films. Metal nanoparticles are produced by solidification of these nanodroplets. The size of the transferred nanoparticles can be controllably changed in the...

We demonstrate flexible and low-cost fabrication of dielectric-loaded surface plasmon–polariton waveguides. The waveguide structures are fabricated by two-photon polymerization of commercially available, spin-coatable epoxy-based UV-lithographic resist on a metal covered glass slide. The excitation and guiding properties of the plasmonic waveguides...

Growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of nanostructuring technologies. The application of two-photon polymerisation technique for the fabrication of dielectric and metallic SPP-structures, which can be used for localisation, guiding, and manipulation of SPP waves on a subwavelength scale are s...

We present an optimized isotropic metal deposition technique used for covering three-dimensional polymer structures with a 50nm smooth silver layer. The technology allows fast and isotropic coating of complex 3D dielectric structures with thin silver layers. Transmission measurements of 3D metallized woodpiles reveal a new phenomenon of enhanced op...

A novel approach, to our knowledge, for the fabrication of metallic micro- and nanostructures based on femtosecond laser-induced transfer of metallic nanodroplets is developed. The controllable fabrication of high-quality spherical gold micro- and nanoparticles with radius of 100 – 800 nm is realized. In combination with the two-photon polymerizati...

The paper presents the investigations into the fabrication of photonic structures by direct laser-writing and nanoimprint lithography using organic-inorganic hybrid materials that have: (i) nonlinear optical properties and (ii) can be selectively covered with metal. Direct laser-writing by two-photon polymerization (2PP) allows the fabrication of t...

We report on a method of making dielectric loaded surface-plasmon-polariton waveguides by nanoimprint lithography from master structures fabricated using two-photon polymerization. This method employing molds from polydimethylsiloxane allows rapid reproduction of waveguide structures using a large variety of resist and substrate materials. Both mas...

Renewed and growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of nanostructuring technologies. The application of two-photon polymerization technique for the fabrication of dielectric and metallic SPP-structures, which can be used for localization, guiding, and manipulation of SPPs waves on a subwavelengt...

Surface plasmon polaritons have become a research area of great importance. We present theoretical investigations on the realization of components and Y-splitters for surface plasmon polaritons guided by dielectric-loaded waveguides. The effect of the limited resolution of the fabrication process on the characteristics of fabricated Y-splitters is...

Scattering and splitting of surface plasmon polaritons (SPPs) by a chain of strongly interacting nanoparticles located near a metal surface are numerically studied. The applied numerical model is based on the Green’s function formalism and point–dipole approximation for scattering by nanoparticles. Dependencies of the splitting efficiency on the in...

3D photonic crystals based on Si inverted-opals are numerically explored as hosts for effective air-channel waveguides, which can serve as parts of photonic circuits. Two basic shapes of straight waveguides are considered: cylindrical and a chain of spheres. Modelling shows that transmission is heavily dependent on the lattice position of the waveg...

Deregulated apoptosis of MCs (mesangial cells) is associated with a number of kidney diseases including end-stage diabetic nephropathy. Cell death by apoptosis is a tightly orchestrated event, whose mechanisms are not completely defined. In the present study we show that the uPA (urokinase-type plasminogen activator)/uPAR (uPA receptor) system can...

We numerically investigate the efficiency of surface-plasmon-polariton (SPP) focusing by curved chains of gold (silver) nanoparticles located on a gold (silver) surface. The employed model is based on the Green’s function formalism and the dipole approximation for field scattering by nanoparticles. The SPP focusing is considered for two cases of se...

Excitation, focusing, and directing of surface plasmon polaritons (SPPs) with curved chains of bumps located on a metal surface is investigated both experimentally and theoretically. We demonstrate that, by using a relatively narrow laser beam (at normal incidence) interacting only with a portion of a curved stripe or chain of nanoparticles, one ca...

Excitation, focusing, and directing of surface plasmon polaritons (SPPs) with curved chains of bumps located on a metal surface is investigated both experimentally and theoretically. We demonstrate that, by using a relatively narrow laser beam (at normal incidence) interacting only with a portion of a curved stripe or chain of nanoparticles, one ca...

Excitation, focusing and directing of surface plasmon polaritons (SPPs) with curved chains of nanoparticles located on a metal surface is investigated both experimentally and theoretically. We demonstrate that, by using a relatively narrow laser beam (at normal incidence) interacting only with a portion of a curved chain of nanoparticles, one can e...

The use of light as an information carrier is rapidly increasing. To fully exploit the advantages of this technology, the production of 3D photonic circuits is necessary. The inscription of defined defects by two-photon polymerization (2PP) of a photo polymer infiltrated in 3D photonic band gap templates has been identified as possible technique to...

The use of light as an information carrier is rapidly increasing. To fully exploit the advantages of this technology, the production of 3D photonic circuits is necessary. The inscription of defined defects by two-photon polymerization (2PP) of a photo polymer infiltrated in 3D photonic band gap templates has been identified as possible technique to...

Renewed and growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of nanostructuring technologies. In this paper, we will report on the application of two-photon polymerization (2PP) technique for the fabrication of dielectric SPP-structures, which can be used for localization, guiding, and manipulation of SP...

Rapid advance of nanostructuring technologies offers new possibilities for flexible and low-cost fabrication of plasmonic components and devices. In this contribution, we study applications of laser-based nonlinear lithography for the fabrication of dielectric surface-plasmon-polariton (SPP)-structures. These structures can be used for localization...

We report on advances in the fabrication of thick and homogeneous polymer opals films with bead sizes up to 600 nm; photo-ablation and point and line defect inscription with femtosecond laser pulses; analysis of the influence of imperfections on opal transmission-reflection properties and numerical and experimental characterization of fabricated sa...

Self-assembled polymer opal colloidal crystals can be useful either as templates for processing, followed by inversion with high-index material (leading to waveguide structures inside a full-band-gap photonic crystal) or as a stop-band material that has special mechanical properties, not achievable with the inorganic high-index-materials. Both opti...

One of the rapidly advancing femtosecond laser technologies is three-dimensional micro- and nanostructuring by two-photon polymerization (2PP) technique. This technique allows the fabrication of any computer-generated D structure by direct laser "recording" into the volume of a photosensitive material. Because of the threshold behavior and nonlinea...

This paper studies the applications of advanced femtosecond laser technologies for the fabrication of SPP structures. We demonstrate that resulting structures can be used for excitation, guiding, and manipulation of SPPs on a sub wavelength scale. Characterization of these structures is performed by detection of the plasmon leakage radiation. Two-p...

We present investigations on dielectric 2D surface-plasmon-polariton-(SPP)-structures on metal surfaces and their characterization. Line-, dot-, and waveguide-structures are fabricated by two-photon polymerization (2PP) of high refractive index inorganic-organic hybrid polymer.

Renewed and growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of nanostructuring technologies. The desired nanostructures are usually fabricated by electron- or ion-beam lithography. An alternative approach is the application of two-photon polymerization (2PP) or nonlinear lithography. Both these technolo...

Advanced femtosecond laser technology allows the fabrication of arbitrary 2D and 3D dielectric micro- and nanoscale structures by two-photon polymerization (2PP). In this paper, we present first investigations on excitation of surface plasmon polaritons (SPPs) on dielectric 2D structures fabricated on metal surfaces with this technology. Straight a...

Infrared, femtosecond laser pulses are ideal for the fabrication of 3D structures in transparent media. Due to the low absorption cross-section, 2 or more photons are necessary for absorption. This multi-photon effect limits the affected volume to the focal area allowing for sharp features on the order of the wavelength of light. One possible multi...

We study the application of two-photon absorption of near infrared femtosecond laser pulses and nonlinear maskless femtosecond laser lithography for the fabrication of dielectric and metallic SPP-structures, being used for localization, guiding, and manipulation of SPPs on a subwavelength scale. Resolutions down to 100 nm are already achievable. Ch...

The science of surface plasmon polaritons (SPPs) has attracted a lot of attention in the last years. In this contribution, we study applications of two-photon absorption of femtosecond laser radiation for the fabrication of dielectric and metallic SPP-structures, which can be used for localization, guiding, and manipulation of SPPs. Dielectric SPP...

In this contribution, we demonstrate multi-photon femtosecond laser lithography for the fabrication and rapid prototyping of plasmonic components. Using this technology different dielectric and metallic SPP-structures can be fabricated in a low-cost and time-efficient way. Resolution limits of this technology will be discussed. Investigations of th...

Urokinase (uPA)-induced signaling in human vascular smooth muscle cells (VSMC) elicits important cellular functional responses, such as cell migration and proliferation. However, how intracellular signaling is linked to glycolipid-anchored uPA receptor (uPAR) is unknown. We provide evidence that uPAR activation by uPA induces its association with p...

The scheme of a bidirectional ring fiber laser with a 90 Faraday rotator in the cavity has been theoretically studied. The Faraday rotator is employed as a nonreciprocal phase element producing splitting of natural frequencies of the laser cavity modes propagating in opposite directions. The theory predicts two possible regimes of bidirectional ope...

The results of experimental investigation of an Er-doped fiber bidirectional ring laser with a 90° Faraday rotator in the cavity are presented. Two theoretically predicted regimes of the bidirectional generation of modes propagating in opposite directions with either complex-conjugate or orthoconjugate polarization states have been realized in prac...

The supermode noise of a harmonically mode-locked erbium-doped fiber laser with composite cavity is investigated both theoretically and experimentally. We propose a simple model based on the transfer function of the composite cavity. From this model, the frequencies of the cavity modes and their frequency-dependent losses are determined. A comprehe...

An experimental study of supermode noise of harmonically actively mode-locked erbium-doped fibre lasers in the composite-cavity configuration is reported. Our study shows that the number of supermodes is reduced, as expected. However, this reduction is by far less efficient than what was previously reported. In particular, we found in measured RF s...

We performed numerical simulations to obtain statistical and spectral characteristics of stimulated Brillouin scattering (SBS) initiated by Gaussian noise in single-mode optical fibers. Recently published experimental spectra of SBS power [e.g., Phys. Rev. Lett. 85, 1879 (2000)] are explained completely by a one-dimensional SBS model. We give a cle...

Bragg gratings were written in H2-loaded polarization- maintaining fiber (PM-FBGs) and inserted in an actively mode-locked Er-doped fiber laser. The use of PM-FBG in sigma laser cavity allows to effectively build all polarization- maintaining fiber laser. Long term stabilization of the laser was ensured by a feedback loop that controlled the cavity...

We propose a technique for measuring both pulse width and amplitude jitter noises of high-repetition-rate optical pulse trains and the cross correlation between these noises as well. The technique is based on time-domain amplitude demodulation of three harmonic components of the detected pulse train. We applied this technique to characterize noises...

We have fabricated bandpass filters based on π -shifted long-period gratings for application in actively mode-locked erbium fiber lasers. Introducing the π -phase shift in the middle of the grating opens a bandpass within the core–cladding mode resonance peaks. With a 22-nm bandwidth filter inserted in an actively mode-locked erbium fiber sigma las...

The effect of passive Q-switching was observed in an erbium fiber laser at a pumping power below 100 mW. The phenomenon is explained by a cascade process of the Rayleigh light scattering and the induced Mandelshtam-Brillouin scattering in a fiber resonator of the laser. In the Q-switched mode, the laser produced giant output pulses with a duration...