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jc_168木虫 (正式写手)
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[求助]
关于强激光激发的电磁场问题
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The laser beams can produce electromagnetic fields whose intensity can reach very high values, beyond what is possible with other sources of electromagnetic radiation. In principle, it becomes possible to probe the fundamental properties of matter and verify the theories of physics under extreme conditions. In this exercise, you are asked to calculate the parameters of a laser beam as the maximum value of the energy density of the electromagnetic field corresponds to that associated with the energy density of matter at rest under relativistic (i.e. the formula mc^2). For your calculation, use the water density is 1 g/cm^3. Suppose that the laser beam is Gaussian transverse profile, the electric field of this beam is given by the following expression in the plane where it is a) Find the expression of the magnetic field associated with this beam. Neglect the longitudinal field components, i.e. along the axis z. b) Find the expression of the energy density of the electromagnetic field produced by this beam. Find the parameters of electric and magnetic fields that produce an energy density equal to that of matter at rest. Rate these extreme values of electric and magnetic fields, as well as the magnetic induction. c) Express the electromagnetic field in phasor notation. Find the expression of the average power per unit area (i.e. the intensity). What is the maximum intensity? d) What is the average power of this beam? Suppose a wavelength λ = 1 μm and a beam size w = 10 μm. e) In practice, we can not attain power with a continuous laser. It is necessary to use a pulsed laser. What is the energy of the laser pulse if its duration is 1 picosecond (1 ps = 10^-12 s)? f) What is the volume of medium required to produce the laser pulse is extracted if averaged 10^18 photons/cm^3 in this environment? [ Last edited by 华丽的飘过 on 2012-9-22 at 21:53 ] |
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