Samenvatting

In this thesis the workings of a time-resolved setup are treated as well as the underlying physics. The setup is based on optical gating, which gives control over very short moments in time to let light pass through a gate. As this process is stable, light can be studied in very short and low intensities. When building this setup, first the “gate-open” time was measured (via cross convolution), the time the gate is open is 320 femtoseconds. When this is compared to a cross convolution measurement of the setup in 2012 it is now 90 fs longer open, which implies a degradation of the temporal resolution. The significance of this is low, as the measured samples have much longer decay times (20 ps).
After this an experiment was conducted of a light pulse ( λ = 810 nm) travelling through a sheet of paper. The findings from this experiment are that there is some light going ballistically through the paper when the intensity peak in time is compared with and without the paper (the rising of the peak is both the same). Also from the decay of the intensity the transport mean free path is calculated, which describes the average length a photon is “walking” through the medium before it is scattering completely randomly. The transport mean free path is: 20±5 μm. Compared to earlier measurements, it is longer but still in the same degree of length. The cause of a longer transport mean free path can be that the paper used in earlier measurements was denser than the paper used in this thesis, resulting in more scattering events closer together. Also time-resolved images were made that shows the propagation of light through the paper in detail.
Finally, an experiment was conducted to see if a waveguide assembly with a whispering gallery mode resonator attached to it could be measured. In order to do so the setup needed to change, interchanging the probe and gate beam as the couplers of the waveguide are more susceptible to the wavelength of the gate beam. The Time-resolved change in intensity is measured from the output coupler as well as images from the pulse coming out of the coupler. This is a world’s first in a wide field setup (as opposed to scanning pixel by pixel with a fiber). As the possibility for further research of the waveguide assembly was prohibited, the designation of the measured peaks is incomplete. Verification as well as more intricate waveguide assemblies belong to the future of this Time-resolved setup.
In appendix A, a brief note is given to the changing of the sum frequency generation crystal that is used in the setup. This crystal is the core of the optical gating technique, and changing the crystal from BBO to BiBO enhanced the spatial resolution almost tenfold. Because the setup was broken by a power outage, further research on this improvement was not an option, but a tentative insight is given into this positive outcome.