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Ultrafast Pulse Shaping Applied to Multi-dimensional Spectroscopy and Novel Microscopy Methods

出版	University of Wisconsin--Madison, 2022
URL	http://books.google.com.hk/books?id=UwAV0AEACAAJ&hl=&source=gbs_api

註釋Semiconducting thin films are the building blocks of next generation photovoltaic devices. In many of these devices, energy transfer is necessary for creating a photocurrent from the initially excited electrons. Studying the energy transfer is a difficult task as it happens on the femtosecond to picosecond time scales and between grains that are 10 nanometers to 1 micrometer in diameter and layers that are hundreds of nanometers thick. The tools with both adequate spatial resolution and time resolution to resolve the energy transfer are limited. In this dissertation I will describe the use and development of methods to study the energy transfer within semiconducting thin films. Three projects are presented. In the first project I use a quartz acousto-optic modulator (AOM) pulse shaper to compensate for the temporal dispersion of a white-light laser pulse. The spectral phase of the pulse is measured with frequency resolved optical gating. In addition, the spatial dispersion of the pulse was measured for different applied temporal dispersions. When the AOM applies a Bragg mask to the pulse, all the light is deflected at the same angle, and there is zero spatial dispersion. The temporal dispersion of the optical path was manipulated so that the acoustic wave needed to correct for the temporal dispersion was nearly identical to the waveform of the Bragg mask. Next, I used the AOM pulse shaper to create the pump-pulse for two-dimensional white-light spectroscopy (2D WL). With 2D WL, I characterized the ultrafast free-carrier thermalization in various lead-halide perovskites. In the last study, I used the AOM pulse shaper to create a pulse-pair for a novel atomic force microscopy (AFM) detected time-domain microscopy experiment, Fourier transform photothermal spectroscopy (FTPT). In FTPT, an AFM tip measures the fast expansion of the sample due to the absorption of light. If the sample absorbs the light from the laser pulse, the energy is conserved mostly through heating of the sample. The increase in temperature causes the sample to expand. Using the AFM tip as the detection method yields sub-diffraction limit spatial resolution that is not possible for optically detected microscopy. Combining FTPT with an ultrafast pump pulse could allow for measurements with ultrafast time resolution and nanoscale spatial resolution to an extent that has not yet been achieved.