Laboratory of Nonlinear Optical Interactions
headed by Prof. Aleksandr A Zemlyanov
- Atmospheric femtosecond optics.
- Propagation of intense laser beams along high-altitude extended paths.
- Photoacoustic atmospheric investigations.
- Optical properties in microresonators and frequency converters.
- Nonstationary nonlinear optics.
In historic aspect, the concept of studies in this field was proposed by V.E. Zuev in his book Propagation of Visible and IR Waves in the Atmosphere
(Sov. Radio, Moscow, 1970). By now, the Lab has performed a large cycle of fundamental studies in optics of high-power laser radiation in the atmosphere.
- Mechanisms of optical nonlinearity of aerodisperse media have been revealed and studied. Efficient calculation methods have been developed, and semiempirical models have been created, which provide the prediction of energy and direction losses of high-power laser beams at long atmospheric paths. Physical grounds for new methods of diagnostics of disperse media based on nonlinear optical interactions have been developed.
- Remaining urgent for several decades, this field goes through the new stage of development due to the advent of high-power femtosecond laser systems. Their application in the atmosphere opens new promises in the use of optical technologies for the study of natural phenomena.
- As a rule, nonlinear optical effects worsen the conditions of propagation of laser beam in the atmosphere and should be taken into account in the estimation of the efficiency of laser energy transfer to long distances. As the cw laser radiation propagates in air, the beam experiences thermal aberrations. However, in fogs, the transparency of the medium increases for IR radiation and long pulses due to the droplet evaporation.
- As high-power picosecond and femtosecond laser pulses propagate in air, the phenomenon of filamentation is observed. This phenomenon is connected with the self-focusing of a laser beam into filaments, formation of plasma, and generation of broadband luminescence, the so-called supercontinuum. The propagation of longer laser pulses in the aerosol medium is accompanied by the optical breakdown of air near aerosol particles, which leads to the additional extinction of the radiation.
- Many nonlinear optical effects have formed the basis for new methods of diagnostics of the atmosphere and water medium. The optical breakdown attracted the scientists’ attention as a source of the emission spectrum of the material components of suspended particles. Two-photon absorption in aerosols containing organic molecules induces their fluorescence, which serves as an indicator of these molecules. The use of the supercontinuum broadband radiation allows the diagnostics of gas and aerosol media by the method of multiwave sensing.
|Photo of explosive boiling of a water droplet 50 µm in radius in the field of a microsecond СО2 laser pulse
||Transverse structure of energy density of the Ti:Sapphire laser radiation with a wavelength of 800 nm, pulse duration of 60 fs, and energy of 10 mJ at the end of an 80-m long atmospheric path at filamentation in air
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