Generating high-field infrared and terahertz radiation during interaction of a super-intense laser pulse with a complex nanodimensional target consisting of nanowires or nanofoils is studied. During interaction, dense bunches of electrons are extracted out of the target and accelerated in the laser field, generating intense electromagnetic radiation. Depending on the duration and shape of the laser pulse, three interaction modes can be realized. In the first mode, the laser pulse is smooth, and the electrons are only partially displaced from the target. In this case, a unipolar radiation pulse is generated with duration of about that of the laser pulse. In the second mode, the laser pulse is nonadiabatic with the amplitude of the first half-cycle about the maximum pulse amplitude. Here, most of the electrons are extracted from the target at the beginning of interaction, and unipolar and bipolar pulses with duration of dozens of laser periods can be generated. Changing the target geometry allows one to control the period and number of oscillations in the generated radiation. Finally, in the intermediate mode of short laser pulses with an insufficiently steep front, oscillations of the formed electron bunches may occur in the Coulomb field of ions, leading to radiation with a frequency several times lower than that of the laser. Using numerical simulation, the characteristics of infrared and terahertz radiation in three interaction modes are found. It is shown that the amplitude of generated radiation can reach subrelativistic values, and the intensity conversion efficiency can be about one percent. The advantages of using complex nanowire targets are elucidated. Such targets allow to generate a train of terahertz and infrared pulses with controlled delay between them.
A Fabry-Perot-Michelson gravitational free mass interferometer is considered for a registration of the low frequency Earth gravity gradients. A variation of the Earth gravity force vector cause the corresponding misalignment of the interferometer mirrors thus providing information about the Earth gravity field. Gravitational interferometer with suspended mirrors provides a unique possibility to measure a relative angle variation between two plumb lines (gravity force vectors) separated by the large distance 3divided by4 km. So at very low frequencies the setup presents a long based angular gravity gradiometer for registering global geodynamics through the surface gravity gradient. A possibility of measuring the geophysical phenomena resulted in gravity field variations (core movements, Earth free oscillations, tidal harmonics, Earth rotation variations, etc.) Is discussed and technical requirements for the setup optical elements are formulated. Comparison with conventional geophysical devices is carried out. Estimates of the basic instrumental and seismic noises limiting sensitivity at low frequency (in the quasi-static regime) are discussed briefly. These estimates show that there is a hope for measurement of the gravitational angular perturbation of the mirrors at the level of 10-12divided by10-13 rad for the observation time about several hours. The possibility of arm signals reconstruction in the presence of recycling mirror is demonstrated. The auxiliary optical system for precise justification between up-down movements and tilts of the end spherical mirrors is considered. The requirements on the stability of laser system are discussed.
An interaction of a super strong linear-polarized electromagnetic wave with a dense plasma layer is investigated with the help of a self-consistent method of the analysis. It is shown that at falling a powerful harmonic wave at thin plasma layer the reflected field can be in the form of ultrashort pulses of radiation with amplitude considerably larger than an amplitude of an incident wave. A process of interaction of a plasma layer with a standing electromagnetic wave is considered also and a generalization of classical results about character of an electron motion in an electromagnetic field is obtained for a case of a strong field and large radiation friction. In a strong field a minimum of an effective potential splits into two new that results in violation of mirror symmetry of plasma layer radiation.
KEYWORDS: Transducers, Mirrors, Signal processing, Oscillators, Stochastic processes, Interferometers, Signal detection, Signal to noise ratio, Data processing, Interference (communication)
A process of squeezed light generation by electron beam in a field of two strong external electromagnetic waves propagating in the counter directions is considered. In such a field the electron bunches are formed. Each bunch can be considered as a simple electron mirror placed in a minimum of an effective potential. The input fluctuations change the position of the minimum, providing a parametric interaction inside the system. The squeezing of the output waves is considered. To obtain a large squeezing coefficient one has to mix with proper phases the electromagnetic waves leaving the system from two opposite directions.
A process of non-classical (squeezed) light generation by electron beam in a field of a strong external electromagnetic wave is considered. Each electron move in such field along the figure of eight therefore in the direction of the wave vector there is an oscillations of electrons position with a double frequency of the wave. For input noises a degenerate parametric regime is realized therefore a state of an output field can be squeezed. A squeezing coefficient is estimated and for a large amplitude of the input field it can be considerable.
The goal of the project is the construction of a wideband gravitational gradiometer based on a laser 100-m Fabry- Perot-Michelson interferometer on free masses in deep rock surroundings. The device is aimed at registering bursts of gravitational radiation with an amplitude of the dimensionless metric variations as small as 10-21 in the frequency range 102 - 103 Hz. The auxiliary purpose is to measure low-frequency variations of the Earth gravity gradients bearing information on the internal dynamics of our planet. The deep under-rock position of the installation inside tunnels of Baksan Neutrino Observatory provides a two-order of magnitude decrease in the geophysical noise level which allows the combination of parallel astrophysical and geophysical studies. For geophysics, the long-based interferometer with hanging mirrors presents a new type of geophysical instrument--an angular gravity gradiometer at low frequencies 10-4 - 10-5 Hz with a resolution of 10-8 - 10-10 rad, which is enough to register weak geodynamical perturbations due to oscillations of the Earth interiors.
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