Nanopatterning of the dielectric surface by a pair of femtosecond laser pulses of different colors through a monolayer of microspheres.

This paper considers the nanostructuring of the surface of dielectrics under the effect of two successive femtosecond laser pulses, one of the fundamental frequency (FF) and the other of the second harmonic (SH) of a Ti:sapphire laser, through a layer of polystyrene microspheres 1 µm in diameter, which act as microlenses. Polymers with strong (PMMA) and weak (TOPAS) absorption at the frequency of the third harmonic of a Ti:sapphire laser (sum frequency FF + SH) were used as targets. Laser irradiation led to the removal of microspheres and the formation of ablation craters with characteristic dimensions of about 100 nm.

Experimental observation of optically generated unipolar electromagnetic precursors.

It was recently predicted [Phys. Rev. A95(6), 063817 (2017) 10.

Efficient optical-to-terahertz conversion in large-area InGaAs photo-Dember emitters with increased indium content.

In this Letter, optical-to-terahertz (THz) conversion of 800 nm femtosecond laser pulses in large-area bias-free InGaAs emitters based on photo-Dember (PD) and lateral photo-Dember (LPD) effects is experimentally investigated. We use metamorphic buffers to grow sub-micrometer thick layers with indium mole fractions =0.37, 0.

Highly efficient Cherenkov-type terahertz generation by 2-μm wavelength ultrashort laser pulses in a prism-coupled LiNbO layer.

Terahertz generation by optical rectification of femtosecond laser pulses propagating in a 40-m thick LiNbO layer attached to an output Si prism has been experimentally investigated for different laser wavelengths from 800 to 2100 nm. For longer wavelengths, the saturation of the optical-to-terahertz conversion efficiency has been observed at higher laser pulse energies, thus enabling higher efficiencies. In particular, record high conversion efficiency of 1.

Electro-optic sampling of terahertz waves by laser pulses with an edge-cut spectrum in birefringent crystal.

We demonstrate a terahertz detection technique based on variations of the energy of femtosecond laser pulses with an edge-cut spectrum in birefringent electro-optic crystal-periodically poled lithium niobate (PPLN). The method is compared with the standard electro-optic detection scheme utilizing GaP crystal. The experimental results show that the studied technique is suited for use with birefringent crystals and allows one to achieve a much better response to the terahertz wave radiation at quasi-phase-matching frequencies of PPLN.

Terahertz radiation from bismuth surface induced by femtosecond laser pulses.

We report on the first experimental observation of terahertz (THz) wave generation from bismuth mono- and polycrystalline samples irradiated by femtosecond laser pulses. Dependencies of the THz signal on the crystal orientation, optical pulse energy, incidence angle, and polarization are presented and discussed together with features of the sample surfaces. The optical-to-THz conversion efficiency was up to two orders of magnitude higher than for metal at a moderate fluence of ∼1  mJ/cm.

Terahertz time-domain electro-optic measurements by femtosecond laser pulses with an edge-cut spectrum.

Balanced electro-optic detection techniques of terahertz wave radiation are proposed based on variations of the energy and ellipticity of laser pulses with an edge-cut spectrum. The techniques are compared with the standard electro-optic detection scheme utilizing laser pulses with Gaussian spectrum shape. Our calculations and measurements show that the studied schemes have a much better response to the terahertz wave radiation at high frequencies compared with the standard one.

Colloidal particle lens arrays-assisted nano-patterning by harmonics of a femtosecond laser.

We consider nanopatterning of dielectric substrates by harmonics of single powerful femtosecond pulses from a Ti:Sapphire laser. The nanopatterning is mediated by closely packed monolayers of polystyrene microspheres that act as microlenses at the surface. Observed modification of the material proceeds via ionization.

Terahertz emission from a metallic surface induced by a femtosecond optic pulse.

Results of experimental and theoretical investigations on generation of terahertz radiation at the interaction of femtosecond laser pulses with a metal surface are presented. Investigations are performed with the laser pulse intensities higher compared with that used in papers [Opt. Lett.

Highly efficient optical-to-terahertz conversion in a sandwich structure with LiNbO3 core.

We demonstrate experimentally the efficiency of a recently proposed scheme of terahertz generation based on Cherenkov emission from ultrashort laser pulses in a sandwich structure. The structure has a thin nonlinear core covered with a prism of low terahertz absorption. Using an 8 mm long Si-LiNbO(3)-BK7 structure with a 50 microm thick LiNbO(3) core, we converted 40 microJ, 50 fs Ti:sapphire laser pulses into terahertz pulses of approximately 3 THz bandwidth with a record efficiency of over 0.

[Expert system of choosing lower limb (thigh) prosthesis and diagnosis of the quality of prosthetics (II)].

The authors review an expert system (ES) of diagnosing the prosthetics quality, elucidate problems of the ES functioning within the framework of the general ES. Special attention is paid to the description of the knowledge and datum surface, to the algorithms of direct and reverse illegible logical data output in taking decisions as to defects of the patient's prosthesis in accordance with the signs observable. The work of the ES is demonstrated with special reference to concrete cases.

[An expert system for choosing prostheses for the lower extremities (hip) and assessing the quality of the prosthesis. I].

The authors describe the structure, characteristic features and experience gained with the employment of an expert system for the choice of hip prostheses (in cases of unilateral amputation) and assessment of the prosthetics quality. Word the requirements for hardware and software, present functional subsystems corresponding to certain interrelated stages of prosthetics. A variant has been devised of an appropriate training expert system with a profound representation of intelligence in an object area.