• S Konar

      Articles written in Pramana – Journal of Physics

    • Underwater optical generation of sound: Oblique incidence

      M S Sodha V Rai M P Verma S Konar K P Maheshwari

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      This paper addresses itself to the problem of thermoacoustic generation by an obliquely incident laser beam in a body of water. Far-field directivity pattern of thermoacoustic source (TS) has been studied analytically and numerically. Our study suggests the possibility of getting highly directional sound beams in a simple configuration.

    • Generation of ultrasonic waves in water by an elliptical Gaussian laser beam

      M S Sodha S Konar M P Verma V Rai

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      The paper presents an analysis of ultrasonic wave generation in water by intensity modulated elliptical Gaussian laser beams. It is found that generated acoustic radiation is highly directional both in polar and azimuthal directions. An increase in the assymmetry of the transverse intensity distribution from the Gaussian dependence enhances the source directivity considerably. An obvious conclusion is that elliptical Gaussian beams are better choice in applications where it is desired to communicate in an approximately prescribed small solid angle.

    • Self focusing of elliptic Gaussian laser beams: Saturable nonlinearity

      S Konar A Sengupta

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      An analysis of self focusing of an elliptic Gaussian laser beam, propagating through a medium with saturable nonlinearity has been presented. It has been established that stationary self trap propagation of the beam is not possible. Though stationary self trap propagation does not occur, one can define a virtual threshold power for self focusing. Above this threshold power value, but not far from it, the beam focuses; below this threshold value it defocuses. As a whole three different defocusing zones and two focusing zones have been identified. It is also shown that effective beam radius never reaches zero.

    • Self tapering and uptapering of a self guided laser beam in an absorbing/gain medium with nonlinearity

      Sarang Medhekar S Konar Rajkamal

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      The absorption/gain induced self tapering and uptapering of a self guided Gaussian laser beam when the beam propagates in a saturable nonlinear medium has been discussed. Using the WKBJ and abberationless paraxial ray approximation a beam width equation has been derived. Conditions for tapering/uptapering for both cases i.e., for absorption and gain have been discussed. The beam width of tapered/uptapered beam depends on the rate of absorption/gain, and the length of absorption/gain region along the beam propagation direction. The importance of the present study is pointed out.

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