Valerijus Smilgevičius

Bio: Valerijus Smilgevičius is an academic researcher from Vilnius University. The author has contributed to research in topics: Optical parametric amplifier & Bessel beam. The author has an hindex of 19, co-authored 114 publications receiving 1246 citations.

Multimillijoule chirped parametric amplification of few-cycle pulses

Abstract: The concept of optical parametric chirped-pulse amplification is applied to attain pulses with energies up to 8 mJ and a bandwidth of more than 100 THz. Stretched broadband seed pulses from a Ti:sapphire oscillator are amplified in a multistage noncollinear type I phase-matched ?-barium borate parametric amplifier by use of an independent picosecond laser with lock-to-clock repetition rate synchronization. Partial compression of amplified pulses is demonstrated down to a 10-fs duration with a down-chirped pulse stretcher and a nearly lossless compressor comprising bulk material and positive-dispersion chirped mirrors.

Self-compression of millijoule 1.5 microm pulses.

Abstract: We demonstrate a four-stage optical parametric chirped-pulse amplification system that delivers carrier-envelope phase-stable approximately 1.5 microm pulses with energies up to 12.5 mJ before recompression. The system is based on a fusion of femtosecond diode-pumped solid-state Yb technology and a picosecond 100 mJ Nd:YAG pump laser. Pulses with 62 nm bandwidth are recompressed to a 74.4 fs duration close to the transform limit. To show the way toward a terawatt-peak-power single-cycle IR source, we demonstrate self-compression of 2.2 mJ pulses down to 19.8 fs duration in a single filament in argon with a 1.5 mJ output energy and 66% energy throughput.

Fabrication of micro-tube arrays in photopolymer SZ2080 by using three different methods of a direct laser polymerization technique

Abstract: In this paper we demonstrate femtosecond laser fabrication of micro-tubes with a height of several tens of micrometers in the photopolymer SZ2080 by three different methods: direct laser writing, using the optical vortex beam and holographic lithography. The flexibility of direct laser writing and dramatic increase of production efficiency by applying the vortex-shaped beam and four-beam interference approaches are presented. Sample arrays of micro-tubes were successfully manufactured applying all three methods and the fabrication quality as well as efficiency of the methods is compared. The processing time of a single micro-tube with 60 ?m height and 3 ?m inner radius is reduced 400 times for the holographic lithography technique and 500 times for the optical vortex method compared with the direct laser writing technique. The processing time of a micro-tube array containing 400?micro-tubes is the shortest for the holographic lithography method but not for the optical vortex method as in the case of a single micro-tube, because the holographic lithography method does not require time for sample translation. Additionally, the holographic lithography enables manufacturing of the whole micro-tube array by a single exposure. Although point-by-point photo-structuring ensures unmatched complexity of manufactured microstructures, employing nowadays high repetition rate amplified femtosecond lasers combined with beam shaping or several beam interference can envisage industrial applications for practical demands.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Ultrafast laser processing of materials: from science to industry

Abstract: Processing of materials by ultrashort laser pulses has evolved significantly over the last decade and is starting to reveal its scientific, technological and industrial potential. In ultrafast laser manufacturing, optical energy of tightly focused femtosecond or picosecond laser pulses can be delivered to precisely defined positions in the bulk of materials via two-/multi-photon excitation on a timescale much faster than thermal energy exchange between photoexcited electrons and lattice ions. Control of photo-ionization and thermal processes with the highest precision, inducing local photomodification in sub-100-nm-sized regions has been achieved. State-of-the-art ultrashort laser processing techniques exploit high 0.1–1 μm spatial resolution and almost unrestricted three-dimensional structuring capability. Adjustable pulse duration, spatiotemporal chirp, phase front tilt and polarization allow control of photomodification via uniquely wide parameter space. Mature opto-electrical/mechanical technologies have enabled laser processing speeds approaching meters-per-second, leading to a fast lab-to-fab transfer. The key aspects and latest achievements are reviewed with an emphasis on the fundamental relation between spatial resolution and total fabrication throughput. Emerging biomedical applications implementing micrometer feature precision over centimeter-scale scaffolds and photonic wire bonding in telecommunications are highlighted.

Chapter 4 - Singular optics

Abstract: Singular optics is a branch of modern physical optics that involves a wide class of effects associated with the phase singularities in wave fields and with the topology of wave fronts. Optical singularities (optical vortices) exhibit some fundamental features absent in the "usual" fields with smooth wave fronts. Namely, optical vortices possess orbital angular momentum, topological charge for helical wave front of beams with well-defined direction of propagation. As a result, an interesting spatial evolution can be generated such as optical vortices "nucleation" and "annihilation" by pairs with participation of phase saddles, often called "optical chemistry." To study the structure of the circular edge dislocation, an isolated dark (zero-amplitude) ring is created within a light beam, with an analytical description of the field. A screw wave-front dislocation has a feature that the spatial structure of the wave front has the form of a helicoid around the dislocation axis. The chapter also describes reflection, refraction, interference and diffraction of OVs. Both frequency up- and down-conversion processes possess essential peculiarities for light beams with OVs. The chapter discusses the topology of wave fronts and vortex trajectories. Gouy phase shift in singular optics is also described in the chapter.

Visible-Frequency Metasurface for Structuring and Spatially Multiplexing Optical Vortices.

Abstract: A multifocus optical vortex metalens, with enhanced signal-to-noise ratio, is presented, which focuses three longitudinal vortices with distinct topological charges at different focal planes. The design largely extends the flexibility of tuning the number of vortices and their focal positions for circularly polarized light in a compact device, which provides the convenience for the nanomanipulation of optical vortices.