Andreas Valdmann will defend his PhD thesis "Generation and characterization of accelerating light pulses" on 17 January 2019.
Prof. Peeter Saari, Institute of Physics, University of Tartu
Dr. Peeter Piksarv, Institute of Physics, University of Tartu
Prof. Daniele Faccio, University of Glasgow (Great Britain)
Photonics is the science of light that covers the advanced applications of light in the same manner as electronics is related to electricity. Many photonics-based inventions have already found their way into our homes or are widely used in the industry—optical fibres transferring high-speed Internet, smartphone screens with vibrant colours, laser surgery, and laser welding are only a few examples in a long list.
Similar to the advances in electronics throughout the last century, where bulky vacuum tubes were replaced with smaller transistors and those with microchips containing millions of transistors, the trends in photonics are also leading towards smaller and faster devices. One example is laser micromachining where small pieces of material are removed with ultrashort laser pulses just like a sculptor chisels the rock. Following this analogy, it is clear that a sharp and narrow chisel is better for carving fine details than a big and blunt one.
However, when we try to confine the laser light into a narrow beam, it appears that the beam starts to spread and widen seemingly all by itself even when propagating in empty space. This is caused by the diffraction of light—the bending of light waves around the edges of a small aperture (in this case the output aperture of the laser). This phenomenon makes it difficult to manipulate small objects with a laser beam.
As a solution, scientists have proposed and experimentally realized the so-called non-diffractive light beams that seem to resist diffraction. They have a small bright spot in the middle (the main intensity lobe) that stays much narrower on propagation than the laws of diffraction would predict. Surely, there is no escape from the laws of physics—the overall width of such a beam is actually wider as the intense main lobe is accompanied by fainter side lobes.
In this thesis the so-called Airy beams are studied that are non-diffractive, and moreover, bend even in free space, where there is no matter that could have an effect on the light. It is determined which optical elements are most suitable for creating ultrashort Airy light pulses.
In addition to several scientific applications and potential improvements to optical micromachining, the results of this work could be used to improve resolution in microscopy.