Quantum Electronics pdf

This in an excerpt from this book
Quantum Electronics is that discipline of Physics which deals with the impact of quantum mechanics on the specific behavior of electrons in elements or that of any matter. To get an in depth understanding of the quantum electronics as a whole, it is required that atomic physics, which studies and explains the inner workings of atoms in matter, has to be understood very well. Atomic Physics is widely acclaimed as the most active of the testing grounds of the quantum theory and is rightly the field of extensive research for both its contribution to quantum electronics and technology in general, as well as for its contribution to all physics fundamentally. Not only quantum electronics, but a plethora of other disciplines are heavily indebted to Atomic Physics in that regard, some of them are quantum chemistry, astrophysics, solid-state physics, laser physics etc. According to one of the greatest pioneers of quantum mechanics, Mr. Feynman, if for some reason, all the information regarding science that is known to man today has to go except only one sentence that could be passed on to the next generation of creatures, then the most important of all information to fit into that one sentence would be the idea of atoms or atomic hypothesis / fact, whichever you want to call it – that describes little particles that are under constant movement and attracting each other if apart and repelling each other when squeezed- With a little bit of thinking and imagination applied to that one sentence, one can easily observe the huge information as well as the great evaluation made about our world! The primary task of Atomic Physics is to determine the wave functions as well as the energies emitted out of the quantized electron, leaving everything else related to the nucleus is left to Nuclear Physics to determine. So, for concept building we need to put stress on the basics of atomic physics before moving on the applications of Quantum Electronics.

Generation and direct amplification of short laser pulses with high output energies requires the use of amplifiers and other large-aperture components, which greatly increases the difficulties encountered in construction of suitable systems and, in the final analysis, their cost. The progress made in the generation of maximum pulse intensities shows that the application of enhancement and compression has raised the intensity of chirped pulses.In the interaction of ultra-short pulses with solid targets, the contrast of such pulses should be sufficiently high to ensure that plasma does not form before the main pulse arrives on a target. The contrast may be improved by several factors, which manifest themselves in different ways at different time intervals. On the microsecond scale, the contrast may be reduced by super-luminescence of laser amplifiers, which can be eliminated effectively by a variety of methods such as spatial filters, optical switches.

The basic approach to improving the contrast of a pulse involves the use of some non-linear processes that depend strongly on the intensity and are characterized by not long enough time The use of super-intense laser radiation provides new opportunities for investigating the interaction of ultra-strong laser fields with matter and opens up new avenues in this branch of physics. This applies particularly to generate electric fields which have intensities considerably greater than the intra- atomic intensity. There is major interest in the creation of ions with a high ionic charge. At laser radiation intensities I > 10 17 Wcm -2 , when the acquired velocity of the electron oscillations, ? E , is higher than the thermal velocity, ? T , a new physical object can be created: this object is a high-temperature over dense laser plasma, subjected to high-contrast laser pulses, in which electrons do not manage to any significant energy to ions during the plasma lifetime. A further increase in the intensity above 10 19 Wcm ÿ2 makes it possible to reach the next physical threshold when the energy of electron oscillations in the field of an electromagnetic wave becomes equal to the electron rest energy. This situation corresponds to the physics of relativistic laser plasma when the electron energy acquired from the laser beam exceeds 1 MeV and the laser field can influence directly the state of the nuclei. At still higher laser intensities (I > 10 20 Wcm ÿ2 ) the processes of excitation of nuclei and of nuclear reactions by the direct action of a strong field become probable, so that a considerable number of excited nuclei can be created.