6. September at 15.15 in the Senat Hall of the University of Tartu (Ülikooli 18) will defend Peeter Piksarv his doctoral theses in physics "Spatiotemporal characterization of diffractive and non-diffractive light pulses"
Supervisor: Acad. Prof. Peeter Saari
Oponents: professor Kishan Dholakia (University of St Andrews, Scotland) and dr Cord Arnold (Lund University, Sweden).
"Spatiotemporal characterization of diffractive and non-diffractive light pulses"
Ultrashort laser pulses are invaluable optical tools and one of the shortest events ever created by humankind. In many areas of science and technology in which they are used—(micro-)machining, communications, laser surgery, lithography, optical micro-manipulation, spectroscopy, nonlinear optics, etc.—light pulses with a intensity maximum focused into a small as possible region in space and time are required. However, the shorter the pulses the more difficult it is to achieve high localization of the pulse maximum because of the diffraction and dispersion. In order to obtain ultrashort pulses as short as a few optical cycles, a spectrum spanning over an octave in the visible region is required. Such pulses are strongly affected by the dispersion. However, there exists a certain set of solutions to the wave equation that have a maximum which propagates seemingly unaffected by the diffraction and/or dispersion. In addition to the prolonged depth of focus, those light bullets exhibit other useful and somewhat intriguing properties. For example, the pulse apex may propagate at a velocity different from the speed of light in vacuum (both subluminally and superluminally) or may even accelerate in the free space without action of any force and self-reconstruct behind obstacles. In this thesis, the formation and spatiotemporal propagation of ultrabroadband non-diffractive waves are studied both theoretically and experimentally. A variant of spatial spectral interferometry called SEA TADPOLE is used for characterization of the pulsed wavefields. This method is further developed to allow measuring the impulse responses of the optical systems with very high temporal and spatial resolutions. In this thesis, the following wavefields are studied: superluminally propagating Bessel-X pulses, superluminal accelerating and decelerating Bessel pulses, subluminal pulsed Bessel beams, boundary diffraction wave pulses, and accelerating Airy pulses.