Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Computer science. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Co/ZIF-8 Heterometallic Nanoparticles: Control of Nanocrystal Size and Properties by a Mixed-Metal Approach

Abstract: A mixed-metal approach has been used to control the size and physicochemical properties of heterometallic Co/ZIF-8 nanomaterials. Intentional substitution of zinc with cobalt in a broad concentration range (from 0 to 100 molar percent with a 10% step) provided a series of Co/ZIF-8 nanoparticles, whose sizes could be tuned in the range from 20 to over 500 nm in diameter. Zinc ions from the ZIF-8 matrix were found to be uniformly substituted with the cobalt ions. The increase of nanoparticles size resulted in a change of their nitrogen sorption–desorption characteristics due to decreasing participation of the external surface area in the total surface area. Insights from UV–vis-NIR and IR spectroscopies, as well as remarks on nonlinear optical properties are also provided.

Multilayer graphene-based saturable absorbers with scalable modulation depth for mode-locked Er- and Tm-doped fiber lasers

Abstract: We demonstrate an experimental study on the influence of the parameters of a graphene-based saturable absorber (SA) on the performance of mode-locked Er- and Tm-doped fiber lasers. We have fabricated a set of saturable absorbers with different number of graphene layers: 9, 12, 24, 37 and 48. Each SA was characterized in terms of nonlinear optical parameters (modulation depth, saturation intensity, saturation fluence) and tested in two state-of-the-art, low-power Er- and Tm-doped fiber lasers. Our results show, that in the Er-laser the broadest output spectrum (11 nm) and shortest pulses (345 fs) are generated using 37 layers of graphene in the SA. In case of a Tm-laser, the best performance (737 fs pulses with 5.82 nm bandwidth) was achieved with 24 layers. Additionally, we show that the modulation depth of a 9-layer SA is insufficient to initiate mode-locking in both lasers. This is the first reported comprehensive study on controlling of the parameters of a SA by scaling the number of graphene layers.

The role of acoustic phonons for Rabi oscillations in semiconductor quantum dots

Abstract: The damping of Rabi oscillations in quantum dots as well as the renormalization of the carrier-light coupling, due to the interaction with longitudinal acoustic phonons are studied as a function of temperature and laser pulse parameters. Numerical results are obtained by using a correlation expansion within the density matrix theory. The observed features like a non-monotonous dependence of the damping on the pulse duration are characteristic for the strongly non-Markovian nature of the phonon coupling in these systems. The results can be well interpreted on the level of a perturbation expansion in the carrier-phonon interaction.