Electromagnetic waves energy density

Let us assume an active medium that responds to the energy-level diagram of Figure 2.6(a). It consists into four energy levels E, with respective population densities M (i = 0,..., 3). Let us also assume that laser action can take place due to the stimulated emission process E2 Ei. When a monochromatic electromagnetic wave with frequency v, such as (E2 — E )lh = v, travels in the z direction through the medium, the intensity of the beam at a depth z into the crystal is given by... 

Note that both of the above energy quantities depends qmdmtically on the fields E and B. In a propagating electromagnetic wave, the electric and magnetic contributions to the energy density (2.3) are equal. It is useful to define the amplitude of an electromagnetic wave at each point in space and time r. t by the function... 

The energy flux density in the plane electromagnetic wave is equal to the... 

A freely propagating electromagnetic wave transports the same amount of energy per second. When the wave enters a solid the increase in oscillations of the electrons causes the energy density to increase, so that the wave travels more slowly. An electric field is set up by the oscillating electrons, and this causes a part... 

The prediction [19] that a low power optical field can induce appreciable director reorientation just above the dc field induced Freedericksz transition has been verified experimentally [20,21] concurrently with experimental and theoretical work on optical reorientation [22-24]. Since then, it has become one of the most intensively studied nonlinear optical effects in liquid crystals [3]. The phenomenon originates from the tendency of the director to align parallel to the electric field of light due to the anisotropic molecular polarizability. The free energy density arising from the interaction of a plane electromagnetic wave and the liquid... 

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