# Accession Number:

## ADP006705

# Title:

## Beam Fanning in Coupled-Wave Theory of 2-Beam Coupling,

# Descriptive Note:

# Corporate Author:

## ROCKWELL INTERNATIONAL THOUSAND OAKS CA

# Personal Author(s):

# Report Date:

## 1992-05-22

# Pagination or Media Count:

## 4.0

# Abstract:

Simple coupled-wave theory accounts for depletion of the pump beam due to energy transfer i.e., amplification to the probe beam. Ignoring absorption, the probe gain g can be expressed as g I sub 1z divided by I sub 1O 1r sub pp divided by 1r sub pp e to the -Gamma z where I sub 1O is the incident probe intensity, Gamma is the two-beam-coupling coefficient and r sub pp is the incident pump-to-probe beam ratio given by r sub pp I sub 2O divided by I sub 1O with I sub 2O being the incident pump intensity. Equation 1 remains valid even when the pump-to-probe ratio r sub pp is not sufficiently large only the approximation for the probe gain g approximates e to the gamma L becomes invalid when r sub pp is not much greater than e to the gamma l. Similarly, the pump depletion d can be expressed as d I sub 2z divided by I sub 2sO 1r sub pp divided by r sub pp e to the gamma z. These expressions for the probe gain and pump depletion have proven inadequate in describing the two-beam-coupling process, particularly when the coupling coefficient IF is very large recently, rs exceeding 60cm have been reported.

# Descriptors:

# Subject Categories:

- Optics