Synthesizing and Shaping Ultrafast Pulses Effectively Using Coherently Generated Raman Sidebands
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Any chemical process can be, in principle, understood and manipulated through electron dynamics. Such dynamics occur on what is known as the “ultrashort" time scale, taking place in 10^-15 of a second (a femtosecond). Observing or controlling these processes is extremely challenging, as it requires electromagnetic forces that can be arbitrarily shaped in space and manipulated on the sub-femtosecond time scale, i.e. ultrashort laser pulses. Furthermore, the pulses used in such experiments are typically intense enough to modify the optical properties of the material system under study, thereby changing the way the laser pulses themselves propagate. There is thus a need to better understand this “nonlinear" regime before having the ability to demonstrate full control. This thesis describes the experiments and simulations we used to study the spatial and temporal physics in the ultrashort nonlinear processes of filamentation and stimulated coherent Raman scattering in solids. In particular, we develop several novel techniques for pulse synthesis by taking advantage of these two processes. By recombining Raman sidebands and characterizing the resultant pulse via cross-correlation interferometric FROG (ξFROG), we synthesize an ultrashort ≈ 5 fs pulse. Meanwhile, in filamentation, we contribute to an alternate pulse synthesis technique by means of nonlinear spatio-temporal waveform coupling. We use liquid crystal spatial light modulators to influence the spatial domain and find a substantial increase in the possible frequency bandwidth generated in this technique, potentially leading to shorter and more stable pulses. Deeper physical insight was achieved via comparison of experimental results with supercomputer simulations.
spatial light modulator
Zhdanova, Alexandra Antonovna (2018). Synthesizing and Shaping Ultrafast Pulses Effectively Using Coherently Generated Raman Sidebands. Doctoral dissertation, Texas A & M University. Available electronically from