We study the fine structure of transverse modes of an optical micro cavity. We measure the transmission of a 633 nm He-Ne laser as a function of the cavity length, from which we can extract the...Show moreWe study the fine structure of transverse modes of an optical micro cavity. We measure the transmission of a 633 nm He-Ne laser as a function of the cavity length, from which we can extract the mirror radius of curvature, the well known paraxial shifts, and higher-order corrections. The goal is to distinguish between fine structure caused by non-paraxial effects and mirror related effects. We find that the resonant cavity lengths predicted by the non-paraxial model is only correct for certain resonant modes. We also measure the mirrors with an AFM and find that mirror related effects are small compared to the non-paraxial effects. Further investigation with a polarization-resolving CCD camera reveals that the polarization profiles of transverse modes are similar to what the non-paraxial theory predicts, but it also shows that the occurrence of almost all modes is shifted. The experiment suggests that the models are good, but insufficient to fully describe the fine structure of a Fabry-Pérot interferometer.Show less
This thesis investigates the fluorescence properties of 605 nm and 655 nm colloidal quantum dots. Samples with different densities of both types of quantum dots were created and examined with a...Show moreThis thesis investigates the fluorescence properties of 605 nm and 655 nm colloidal quantum dots. Samples with different densities of both types of quantum dots were created and examined with a confocal fluorescence microscope. In particular, the thesis focuses on the spatial distribution of the quantum dots on the sample, the characteristics of their luminescence decay and the effects of blinking and bleaching. Three different methods were used to study the former phenomena. Spatial scans of the samples helped to locate the quantum dots and revealed that they have a high tendency to cluster. Time-resolved measurements under pulsed excitation provided information on the luminescence decay and show varying, multi-exponential decay times. Finally, extended (minutes long) observation under c.w. excitation provided information on the effects of blinking and bleaching. Based on the experimental results, the thesis finally gives an advice on the use of the investigated quantum dots for follow-up research.Show less
In this thesis we explored various characterisation techniques that can be used to analyse lenses, including the characterisation of a focus and the characterisation of spherical aberration. We...Show moreIn this thesis we explored various characterisation techniques that can be used to analyse lenses, including the characterisation of a focus and the characterisation of spherical aberration. We used these techniques to analyse two near perfect lenses. We also designed and analysed seven lenses that were printed using the Nanoscribe Photonic Professional GT 3d printer. From this analysis we found that 3d-printed lenses performed as decent lenses. The waist of the focus, produced by the lenses, was smaller than 1 $\mu$m for all lenses. This was within 3 times the diffraction limited waist and the intensity in the focus was up to 360 ($\pm$ 30) times higher than if the lens had not been there. The Strehl ratio of each of the 3d printed lenses has been estimated, which all lie between 0.007 and 0.023. We found that the printed lenses behaved in a predictable manner and even though the micro-lenses show defects under optical inspection, their behaviour is predictable. We attempted to find the limits in quality, quantity and size that can be achieved using the Nanoscribe PPGT and made a beginning in answering this question. We found that micro-lenses created with the Nanoscribe PPGT can be used by the Quantum Optics department to enhance the intensity by acting as solid immersion lenses.Show less
