62 Works

Numerical reconstruction of 3D image in Fourier domain confocal optical coherence microscopy

Along with high longitudinal resolution of optical coherence tomography, confocal optical coherence microscopy (OCM) provides high transversal resolution due to relatively high numerical apertures. However, the presence of relatively high numerical apertures leads to limited depth of field, which reduces the speed of OCM and decreases the advantage of Fourier domain detection. In this paper we propose a numerical processing technique for three-dimensional image reconstruction in Fourier domain OCM. It takes into account not only...

Kerr-lens mode locking in a ring bidirectional YAG:Cr4+ laser

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This paper concerns a bidirectional ring YAG:Cr4+lаser. We investigated the features of bidirectional generation and explored the possibility of gyroscopic effect in the laser. We developed the model of bidirectional generation of such a laser taking into account spectral properties of the active medium.Experiments in our setup revealed that generation of the laser had a cluster character. Luminescence spectrum of the YAG:Cr4+ crystal and generation spectra of the laser showed that this medium has both...

Broadband Superfluorescent Source Based on Bismuth-Doped GeO2-SiO2 Fiber

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The first bismuth-doped superfluorescent fibersource operating at 1.44-μm was developed. Atpump power of 200 mW and pump wavelength of1310 nm, its output signal reaches 57 mW withspectrum width of 25 nm.

Fluorescent properties of the kindling fluorescent protein (KFP) at acidic pH values

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Kindling fluorescent protein (KFP) is the photoswitchable protein which can be used in high-resolution microscopy and as a quencher in FRET-sensors. Fluorescent properties of KFP depend on pH value. In this paper we investigate the influence of pH on the spectral properties and kindling/quenching ability of KFP in the acidic pH region.Shift to the acidic region leads to the increase of fluorescence intensity of KFP over time. The excitation spectrum has a new peak near...

Application of Photothermal and Photoacoustic Spectroscopy for the Monitoring of Aqueous Dispersions of Carbon Nanomaterials

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Photothermal and optoacoustic spectroscopy in their state-of-the-art techniques—multiwavelength, scanning and transient—are used for complex investigation and analysis (chemical analysis and the estimation of physicochemical properties and size) of novel carbon materials—fullerenes and nanodiamonds—and their aqueous dispersions as promising biomedical nanosystems. The estimation of the cluster size and the possibilities to determine subnanogram amounts of both nanodiamonds and fullerenes by these techniques are shown. The comparison of fullerene solutions in various solvents, toluene, N-methylpyrrolydone and water,...

Enhancement of the Raman Scattering and the Third-Harmonic Generation in Silicon Nanowires

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We studied features of Raman scattering and the third-harmonic generation in silicon nanowire (SiNW) ensembles formed by means of chemical etching of crystalline silicon (c-Si) wafers with preliminary deposited silver nanoparticles in hydrofluoric acid. The c-Si wafers of different crystallographic orientations and doping levels were used, which results in variations of the formed nanostructure size and degree of order. For the excitation at 1064 nm the ratio of Raman scattering signals for SiNWs and those...

CARS diagnostics of near-critical fluid in small mesopores

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Due to the high spacial resolution and theinterference nature, coherent anti-Stokes Ramanscattering (CARS) spectroscopy is well suited forthe diagnostics of composites based on transparentnanoporous hosts. In particular, the adsorption of afluid on the walls of nanopores and the formation ofa condensed phase in their volume leads to obvioustransformation of the CARS spectra. Recently wehave developed a model which describes thebehavior of molecular spectra at isothermalcompression in cylindrical nanopores. Calculationsbased on the model have shown a...

Development of the Methods of Control of Radiation Structure of

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Specific features of radiation structure of terahertz quantum cascade lasers are determined by wire geometry of their waveguides with small and sub-wavelength transverse dimensions and the length much larger than the wavelength. Here we present an overview of the results of beam profile investigations and of the methods proposed for the control of radiation structure of such lasers.

Zero-distance pulse fronts of stretcher and its optical system

A two-grating stretcher is a dispersion delay line that is widely used in chirped pulse amplification for ultrafast laser pulses. If the stretcher consists of two reflecting diffraction gratings with a perfectly reflective optical system between them, its dispersion can be calculated by using the concept of a „„zero-distance pulse front.” We introduce the concept of a „„zero-distance pulse front” of the real optical system, which characterizes its aberrations. The similarity of these zero-distance pulse...

Mechanism of femtosecond laser nano-ablation for metals

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Metals have three ablation threshold fluences (high,middle and low-threshold fluence, here called) forfemtosecond laser pulses. In order to investigatethe physics of metal ablation under an intenseoptical field, the ions emitted from a laserirradiatedcopper surface were studied by time-offlightenergy spectroscopy. The low laser fluenceat which ions are emitted, Fth,L is 0.028 J/cm2, andtwo higher emission thresholds were identified atfluences of Fth,M =0.195 J/cm2 and Fth,H =0.470J/cm2. The relation between the number of emittedions per pulse Ni...

Infrared broadband source from 1000nm to 1700nm, based on an Erbium, Neodymium and Bismuth doped double-clad fiber

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A Nd3+, Er3+ and Bi3+ doped double-clad fiber (core diameter of 25.5μm, cladding diameter of 125μm) with a broad infrared emission has been fabricated based on technique of dry granulated oxides and investigated. Upon the excitation with a 800nm cw pump source all of the three dopant materials showed fluorescence in the infrared region of interest (1000-1700nm). The observed emitted fluorescence power was measured to be 659μW. Changing the pump wavelength to 976nm led to...

Progress in the fabrication of rare earth doped optical fiber by standard and Sol-Gel derived granulated oxides

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We produced active optical fibers by the doped granulate silica-method. The granulates were derived from the sol-gel technology. We determined volume percentage and distribution of chemical elements in the fabricated glasses fiber by the analytical technique of Energy-Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA) and the degree of crystallization by X-Ray Diffraction analysis (XRD). Furthermore we measured fluctuations of the Refractive Index Profile (RIP) and scattering losses of the fiber core....

20th International Conference on Advanced Laser Technologies ALT’12: Conference Program

Beat Neuenschwander &
The ALT Conference series are focused on the recent achievements and advances in laser technology and laser applications in various areas. These series of conferences, held annually since 1993, were established by Nobel Prize laureate Alexander Prokhorov, director of the General Physics Institute of the Russian Academy of Sciences. Previous conferences were organized in Russia, Czech Republic, Germany, Greece, France, Italy, Romania, Switzerland, United Kingdom, China, Hungary, Finland, Turkey, The Netherlands and Bulgaria. The key...

Photon-Correlation Spectroscopy in Albumin Water Solutions Containing Gadolinium Ions

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Gadoteric acid and gadodiamide molecules havegadolinium-containing chelate structures that areused in magnetic resonance tomography (MRT). [1].Over the past two decades, they were considered safeand effective for medical imaging. However, recentresults indicate the presence of gadolinium in the skinand soft tissues in patients with renal insufficiency,even with the current hemodialysis [2]. Nephrogenicsystemic fibrosis (NSF), which was described in1997, is a recently discovered rare disease ofunknown etiology that affects patients with renalinsufficiency. The development of NSF was...

Self-Q-switched Cr,Nd:ReVO4 (Re=Gd, Y) crystal lasers

Self-Q-switched Cr,Nd:ReVO4 (Re=Gd, Y) crystallasers are demonstrated. The spectroscopic and self-Q-switched laser properties of Cr,Nd:ReVO4 arestudied. Polarized absorption spectra weremeasured at room temperature, which showed thatthe absorption bands display polarization characterand an absorption band of Cr5+ ions at 1110 nmenables the crystals to be self-Q-switched lasermaterials. The maximum pulse energy are achievedto be 1.12 μJ with Re=Gd , and the shortest pulsewidth is 85.8 ns with Re=Y. The results show thatCr,Nd:ReVO4 crystals are new potential...

THz and Raman Spectroscopy in Steroid Chemistry

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The terahertz time-domain and Raman spectra of steroids in the region of 0.1-3.5 THz have been measured. Steroids have several intense and specific absorption features in the THz frequency region. The features are uniquely determined by a hormone structure. This allows us to analyze steroids in complex samples such as pharmaceuticals, foodstuffs and biological fluids, and in process of the pharmacological and chemical synthesis.

Measuring Optical Properties On Rough And Liquid Metal Surfaces

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For understanding and optimizing laser processing of metals and alloys the optical properties, especially the absorption of the work piece in function of the temperature up to the liquid phase have to be known [1]. There are several approaches to extend the Drude-Model [2] for optical properties of metal to temperature dependence [3, 4, 5]. However, a verification of these models is difficult due to the lack of sufficient experimental data. Even though measuring optical...

Influence of the pre-treatment of glass substrates on Laser-Induced Backside Wet Etching using NIR Nanosecond-Pulses and Cu-based solutions

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Laser induced backside wet etching (LIBWE) has shown to be a promising tool for the micro-structuring of transparent materials. Our group has investigated LIBWE using NIR ns-laser pulses and Cu-based absorber liquids. Focus of this paper is to investigate the influence of the pre-treatment of the transparent substrate on ablation. For this purpose experiments were done on untreated and silanized soda lime glass surfaces. Our results show that depending on the absorber liquid the silanization...

Modeling of non-equilibrium effects in silicon irradiated by pulsed laser

In this paper, we use the methods of mathematical modeling to investigate the action of laser pulse (picosecond) with a wave length of λL=0.53μm and the photon energy exceeding the band gap of silicon ħω>Eg on silicon target. The main feature of these regimes of laser irradiation is strong non-equilibrium of heating and melting processes, which is manifested in a large temperature difference between the carriers and the lattice.

Multi-stage ytterbium fiber-amplifier seeded by a gain-switched laser diode

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We demonstrated all-fiber amplification of 11 ps pulses from a gain-switched laser diode at 1064 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 µW of fiber-coupled average output power. For the low output pulse energy of 325 fJ we have designed a multi-stage core pumped pre-amplifier in order to keep the contribution of undesired amplified spontaneous emission as low as possible. By using a novel time-domain approach for...

Microsurgery of Cell Membrane with Femtosecond Laser Pulses for Cell Fusion and Optical Injection

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We report on results of using femtosecond laserscalpel for microsurgery of plasma membrane ofliving cells. Femtosecond laser pulses were appliedto initiate cell fusion as well as to performreversible permeabilization of cell membranerequired for efficient injection of extrinsicsubstances into the target cells. Laser-based cellfusion of mammalian embryo blastomeres as wellas fusion of cell bodies of neurons of molluskLymnaea stagnalis were successfully carried out byapplying single femtosecond laser pulses (secondharmonic of a Cr:Forsterite laser system) 620 nm,100...

A method of treatment microbe nature disease using multiwave laser radiation

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Multiwave laser medical device "Livadia" has been developed either for bactericidal or for therapeutic impact on the affected organism parts. This device is on the diode pumped solid state laser and main wavelength radiation conversion 1064 nm into the second harmonic 532 nm and forth harmonic 266 nm. It has been shown that UV radiation on t he wavelength 266 nm on bronchia mucosa with various inflammation types improves regenerative processes in bronchia tissues that...

Efficient femtosecond optical parametric amplification and wavelength conversion in silicon waveguides

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Efficient femtosecond optical parametric amplification and wavelength conversion via four-wave mixing (FWM) in silicon waveguides are demonstrated. In the femtosecond FWM process, the spectra are greatly broadened, and it is difficult to achieve efficient wavelength conversion and parametric amplification when the pump and signal pulse widths are close to or less than 100 fs because of the spectral overlap. The spectral overlap can be suppressed by tailoring the dispersion profiles of the silicon waveguides, and...

Selective Ablation in Cu(In,Ga)Se2 thin-film solar cells – analysis of different process regimes at sub-picosecond to nanosecond pulse duration.

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Recent achievements in Cu(In,Ga)Se2 (CIGS) thin film technology allow the industrial production ofhighly efficient solar modules. A large growth of the CIGS-based solar cell production volume can beexpected for the coming years thanks to some favorable properties inherent to this absorber type. A majordrawback of CIGS is the inefficient patterning process. Since CIGS is a particularly difficult material forlaser ablation there is still no industrial all-laser scribing solution available. Manufacturers fall back onmechanical needle scribing...

Laser Structuring of Glass-Carbon for Improvement of Its Emitting Properties

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Laser structuring as a stage of laser micromachining operations for a glass-carbon plate processing is described. The operations of laser scribing, milling, cleaning and marking were used for production of the field-emission multi-beam cathode preform. The operation of structuring was applied for production of micropeaks on the surface of the cathode beams. Two different approaches were tested for laser structuring of the cathode beams - linear scan and overlapping blind holes. The nanopeaks are self-organized...

Registration Year

  • 2013