Sofia University (Sofia, Bulgaria)
Department of Quantum Electronics, Sofia University, Bulgaria
The laboratory is the first femtosecond photonics facility in Bulgaria and on the east Balkans. It is presently part of the National Consortium ELI-ERIC-BG, which also includes two institutes of the Bulgarian Academy of Sciences. The consortium is an object of the Bulgarian National Roadmap of the Research Infrastructures (2020-2027).
Sub-30-fs Ti:Sapphire femtosecond oscillator, sub-7-fs laser with CEP stabilization, supercontinuum white light fiber laser, pulse/beam diagnostic equipment and spatial light modulators (both LCOS phase modulators and digital micromirror devises) are available and are used for ultrashort pulse characterization, for generating singular femtosecond beam/pulses and for studying their nonlinear evolution, as well as for laser-matter interaction and high harmonics generation.
Research highlights
In some of the analyses we study modifications of inverted field interferometers/autocorrelators for measuring the magnitudes and signs of the topological charges of optical vortices, for measuring/eliminating pulse front tilt of femtosecond pulses, for generating long-range quasi-non-diffracting femtosecond Gauss-Bessel beams, and for sculpting laser beams in the focal planes of lenses.
Realignment-free switching between interferometric and intensity autocorrelation is demonstrated by using a vortex phase plate. Optical schemes for controllable beam splitting of laser beams in ordered arrays of focal peaks by large lattices of optical vortices are developed. Coherent recombination of such arrays of sub-beams is demonstrated.
Expertise
We are working on alternative femtosecond pulse characterization techniques to determine/elliminate specific spatio-temporal distortions like pulse front tilt and spatial phase dislocations [Optics Communications 371, 51-58 (2016); Optics Communicatons 456, 124530 (2020)]. In this context, we are theoretically modeling and testing experimentally autocorrelation schemes combining classical and singular optics [Optics Communications 504, 127493 (2022)].
We are also interested in the dynamics of highly-charged optical vortices in mono- and polychromatic laser fields for e.g. Gauss-Bessel beam generation [Scientific Reports 10, 21981 (2020); Optics Express 29, 10997-11008 (2021); Photonics 12(2), 119 (2025)] and for a controllable focal beam structuring [Scientific Reports 9, 9:2128 (2019); Optical and Quantum Electronics 54, 34 (2022)]/recombination/pulse compression [Optics Express 32, 48758-48771 (2024)] of femtosecond beams/pulses.
The research team has some experience in high harmonics generation in a gas-filled hollow fiber achieving up to the 29-th harmonic of the 800nm radiation of a Ti:Sapphire laser system [Bulg. J. of Physics 44, 99-108 (2017)].
Equipment offered to external users
- Sub-30-fs Ti:Sapphire oscillator
- Sub-7-fs Ti:Sapphire laser with CEP stabilization
- Supercontinuum white light fiber laser
- Pulse/beam diagnostic equipment and spatial light modulators