Electrostrictive fluid pressure from a laser beam

Recent times have seen surge of research activity on systems combining fluid mechanics and electromagnetic fields. In radiation optics, whenever information about the distribution of pressure in a dielectric fluid is required, the contribution from electrostriction becomes important. In the present paper we calculate how the local pressure varies with position and time when a laser beam is imposed in a uniform fluid. A Gaussian intensity profile of arbitrary time dependence is assumed for the beam, and general results are derived in this case. For demonstration we analyze two different cases: first, that the beam is imposed suddenly (mathematically in the form of a step function); secondly, that the beam is switched on in a soft way. In both cases, simple analytical expressions for the pressure distribution are found.