Theses 2023

Knöfel, Martin

Experimental Characterisation of Spatially and Temporally Focused Femtosecond Laser Pulses

Conclusions and recommendations:  SSTF offers a wide variety of potential applications where light with a high energy density is required and needs to be controlled in all three dimension. Differently to SF of ultrashort pulses, this technique enables its users to manipulate the duration, shape and propagation of light pulses in unique ways and it is not surprising that variations of the concept are ariseing, specially for medical, industrial and reserch applications. The current setup can certainly be improved by embracing one or more of the approaches mentioned in the discussion. It could also be helpful to characterise the beam prior to the focusing with a FROG, TERMITES or STRIPED FISH technique, to better understand and model experiments using SSTF. One final thought is that even if an unexpected result, the steady exclusion of a part of the optical axis with two strongly focused ultrafast beams on either side could find their own application in scenarion wher something has to be illuminiated which confines another part which should remain unaffected, or the concept could be expanded similarly to what is being research for so-called optical bottle which could be employed for inducing flat-top temperature distributions.

Zamani, Amin

Towards Two-Dimensional Sources of Quantum Light

Conclusions:  This thesis is dedicated to the generation of correlated photon pairs via SPDC in a 2D flake of GaSe. In the following, I will describe the conclusions of this work.

  • I demonstrated for the rst time the generation of entangled photons from a flake of GaSe with 130 nm thickness. To my knowledge, so far, this is the first time that photon pairs have been generated via SPDC in a subwavelength GaSe flake. I built a setup for generation and detection of photon pairs and using 10 mW of CW pumping, I achieved a pair generation rate of 3.6 Hz from the sample.
  • I measured the dependence of the rate of photon pair generation on the power of the pump and veried its linear dependence. I also used a long dispersive fiber to measure the spectrum of photon pairs using single-photon spectroscopy technique and veried that the spectrum is broad and extends over the entire range allowed by the transmission window of the single-mode bers used in the setup.

The results of this work will pave the way for future investigations.