Development of Coherent Two-dimensional Spectroscopy at Optical Frequencies and Application to Model Chromophores
Author | : Hélène Seiler |
Publisher | : |
Total Pages | : |
Release | : 2018 |
ISBN-10 | : OCLC:1030147327 |
ISBN-13 | : |
Rating | : 4/5 (27 Downloads) |
Book excerpt: "Ultrafast coherent multi-dimensional spectroscopies are a powerful set of techniques used to unravel complex processes. These processes range from electronic coherences in molecular chromophores to many-body interactions in quantum-confined materials. Yet these spectroscopies remain challenging to implement at the high frequencies of vibrational and electronic transitions, thereby limiting their widespread use. The work herein demonstrates three significant methodological improvements of two-dimensional spectroscopy at optical frequencies, followed by applications of the method on two different systems. First, we introduce a hollow-fibre setup for the production of broadband visible pulses. This source is comparatively simple to operate, and yields stable, 45 [mu]J pulses over the 520-700 nm region. Second, we demonstrate the feasibility of two-dimensional electronic spectroscopy in a single beam. By appropriately modulating the phases of the pulses within the beam,we show that it is possible to directly read out the relevant optical signals. This work shows that one needs neither complex beam geometries nor complex detection schemes in order to measure 2D spectra at optical frequencies. Finally, we introducea setup for complete and independent polarization control of each pulse in the sequence. Together, these methodological improvements represent important enabling steps towards the longstanding goal of achieving an "Optical NMR", and extendsthe realm of all-optical multi-dimensional spectroscopies to spatially heterogeneous samples. The methods are applied on two classes of systems. The model system Nile Blue is used to validate the performance of the instrument. The spectrometeris then used to reveal new processes in colloidal semiconductor CdSe nanocrystals, a system of contemporary interest." --