Fundamental Gaussian beam
A plane wave has a unique propagation direction and is not physically realizable since infinite energy is required for its launching. Nearly plane waves or beams are formed by a group of plane waves having a narrow range of propagation directions about a specified direction. A general electromagnetic field is constructed from a single component of magnetic vector potential and a single component of electric vector potential, both in the same direction. The vector potential associated with an electromagnetic beam is separated into a rapidly varying phase and a slowly varying amplitude. The slowly varying amplitude satisfies the paraxial wave equation. For an input distribution having a simple Gaussian profile with circular cross section, the paraxial wave equation is solved to obtain the vector potential. For the fundamental electromagnetic Gaussian beam, the fields are evaluated and the characteristics of the radiation intensity distribution are described. The outward propagations in the +z direction in the space 0 < z < ∞ and in the -z direction in the space -∞ < z < 0 are considered. The secondary source is concentrated on the boundary plane z = 0. The source current density is obtained and the complex power is determined. The time average of the real power is equal to the time-averaged radiative power. The reactive power of the paraxial beam is found to vanish.
Fundamental Gaussian beam, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/books/ew/sbew518e/SBEW518E_ch1-1.gif /docserver/preview/fulltext/books/ew/sbew518e/SBEW518E_ch1-2.gif