Ponderomotive forces in the optics of nonlinear media

A theory of the electromagnetic field is developed for elastically deformable media. This theory can describe changes in the mechanical, electrical, and magnetic parameters of a medium under the action of ponderomotive forces. A simultaneous analysis of the field equations in a medium and of the equations of motion of the medium makes it possible to introduce thermodynamic functions relating these parameters to each other. Expressions are obtained for the law of conservation of energy, thermal and electron equilibrium, equilibrium density, and density of the ponderomotive forces. Two examples of media consisting of isotropically or anisotropically polarizable molecules in a strong electromagnetic field are discussed in detail.