A Caltech Library Service

Nonlinear Effects in Traveling Wave Laser AmpIfiers


Close, Donald Henry (1965) Nonlinear Effects in Traveling Wave Laser AmpIfiers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Y5FC-GV56.


Using semiclassical radiation theory, a formalism similar to that used by Lamb in his "Theory of an Optical Maser" is developed for studying the amplification of vector traveling waves in a laser-type medium. The effect of the medium on the waves is given in terms of space (or time) dependent field amplitudes and phases and a nonlinear index of refraction. With particular emphasis on typical gaseous media, the effects of Doppler broadening are treated in detail for arbitrary ratios of natural to Doppler linewidths. Polarization and propagation vectors in various directions are considered, and the nonlinear effects are found to make an isotropic medium effectively anisotropic. Lowest order nonlinear effects (due to a polarization cubic in the field amplitudes) are studied extensively, and the frequency dependence of several of these processes is presented in graphical form. In particular, the introduction of fields at new frequencies and polarization effects are considered. The characteristics of these nonlinear processes peculiar to Doppler broadened lines are discussed, and the processes are interpreted in terms of saturation and coherent modulation of the population inversion density. Strong nonlinear effects are considered in a more approximate way and are found to consist of saturation of the various linear and nonlinear processes previously considered. These strong nonlinear effects should occur at low enough intensities to be easily observed in practice on a CW basis. With the present formalism, the analytical results of Gordon, White and Rigden regarding gain saturation in laser amplifiers are obtained, and the extension is made to include frequencies away from line center and the effects of multiple spectral components. Again, the introduction of fields at new frequencies is considered in detail. These results are also discussed in terms of saturation and coherent modulation of the populations and "hole burning".

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Electrical Engineering and Physics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Minor Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • George, Nicholas A.
Thesis Committee:
  • Unknown, Unknown
Defense Date:12 May 1965
Record Number:CaltechETD:etd-09122002-090900
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3480
Deposited By: Imported from ETD-db
Deposited On:16 Sep 2002
Last Modified:08 Feb 2024 00:10

Thesis Files

PDF (Close_d_1965.pdf) - Final Version
See Usage Policy.


Repository Staff Only: item control page