Laser Beam Propagation

1 gaussian irradiance profiles are symmetric around the center of the beam and decrease as the distance from the center of the beam perpendicular to the direction of propagation increases figure 1.

Laser beam propagation.

The focusing characteristics of a laser beam which may be of interest to anyone using a laser for work or experimentation. For laser beams for which the second order moments of intensity beam width and divergence can be determined the beam propagation ratio m 2 is often used to characterize beam quality. The m 2 factor also known as the beam quality factor compares the performance of a real laser beam with that of a diffraction limited gaussian beam. Important developments in the theory of beam wave propagation through a random medium which have been incorporated into this second edition.

R is the radial distance from the. The iso 11142 protocol calls for measurements to be made along the z axis of a beam both around the waist formed by the lens and additionally at positions at least two rayleigh ranges away from the beam waist. Assuming polarization in the x direction and propagation in the z direction the electric field in phasor complex notation is given by. Laser beam propagation we ll begin our discussion of beam propagation with a practical topic.

The gaussian beam is a transverse electromagnetic tem mode. In general laser beam propagation can be approximated by assuming that the laser beam has an ideal gaussian intensity profile which corresponds to the theoretical tem 00 mode. Home ebooks laser beam propagation through random media second edition. 2 2 gaussian beam optics in most laser applications it is necessary to focus modify or shape the laser beam by using lenses and other optical elements.

The mathematical expression for the electric field amplitude is a solution to the paraxial helmholtz equation. The m 2 factor compares the actual shape of the beam to that of an ideal gaussian beam. Focusing characteristics of a real laser beam focus spot size due to diffraction. The propagation of high energy laser hel beams in the atmosphere is rich in fundamental physics and of paramount importance to the navy s directed ener gy research program.

D m f d f π 2λ 0 4. The m beam propagation measurement is made by observing how a laser beam behaves when focused with a lens. Where. Laser beam propagation through random media second edition.