Pulse shaping technique

Control of the lattice vibrations in crystals has so far been achieved only through classical interference. Optical control in solids is far more complicated than in atoms and molecules, especially because of the strong interaction between the phononic and electronic subsystems. Nevertheless, we expect that the rapidly developing pulse-shaping techniques will further stimulate pioneering studies on optical control of coherent phonons. 

The development of a mixed time-frequency representation in which both characteristics of the field and the response function are highlighted is currently receiving considerable attention. This activity is triggered by the rapid progress in pulse-shaping techniques, which made it possible to control the temporal profiles as well as the phases of optical fields with a remarkable accuracy [1-4]. These developments have further opened up the possibility of coherent control of dynamics in condensed phases [5-7]. 

More elaborate gating profiles may be obtained using pulse-shaping techniques [2, 3]. 

The investigation of simple systems offers a possibility to learn how to use control as a tool for analyzing the underlying processes. Therefore, metallic dimers [66-71, 84, 121, 292, 293] and diatomic molecules [292, 294] have been extensively studied. This is due to the fact that they are suitable model systems for establishing scopes of different control schemes and because they became easily accessible to experimental pulse-shaping techniques [72-83]. In fact. 

In order to guarantee a quasi-static state in the dynamic Brazilian test, pulse shaping technique is employed for all our dynamic tests. The dynamic force balance on the two loading ends of the sample is critically assessed. Figure 3 shows the forces on both ends of the specimen in a typical test. From Eq. 1 and 2, the dynamic force on one side of the specimen PI is proportional to the sum of the incident (In) and reflected (Re) stress waves, and the dynamic force on the other side P2 is proportional to the transmitted (Tr). It can be seen from Figure 3 that the dynamic forces on both sides of the specimens are almost identical during the whole dynamic loading period. The... 

Frew, D. J., Forrestal, M. J., Chen, W. (2002). Pulse shaping techniques for testing brittle materials with a split Hopkinson pressure bar. Experimental Mechanics, 42,93-106. doi 10.1007/ BF02411056... 

In the first scheme it is not necessary to use two different lasers if a femtosecond pulse with a broad spectral range is used for excitation. The different spectral components in the pulse give rise to many different excitation paths. In order to achieve optimum population in the excited state, the relative phases of these different spectral components have to be optimized. This can be realized by the pulse-shaping techniques discussed in Sect. 6.1.11 (Fig. 10.11). Here a plate of many liquid crystal pixels are placed in the laser beam, which changes the phases of the lightwave by orientation of the molecules where a feedback loop with a learning algorithm is used to maximize or minimize the wanted decay channel of the excited state [1402,1403]. 

Sudani G, Baudrin E, Dunn B, Tarascon JM (2004) Synthesis and electrochemical properties of vanadium oxide aerogels prepared by a freeze-drying process. J Electrochem Soc 151 A666-A671 Frew DJ, Forrestal MJ, Chen W (2002) Pulse-shaping techniques for testing brittle materials with a spht Hopkinson pressure bar. Exp Mech 42 93-106... 

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