Title: Fiber Raman Amplifier Development for Laser Absorption Spectroscopy Measurements of Atmospheric Oxygen near 1.26 microns
Author: Jeremy Dobler
Organization: ITT Geospatial Systems
Co-Authors: Michael Braun, James Nagel, Valery Temyanko, Bryan Karpowicz, T. Scott Zaccheo

We will report on the latest development of a high power narrow linewidth fiber Raman amplifier for the measurement of atmospheric oxygen. This technology is focused on advancing engineered fibers to overcome the limitations imposed on this type of amplifier by the nonlinear effect of stimulated Brillouin scattering (SBS), and applying this to the laser absorption spectroscopy of atmospheric oxygen. Our work has focused on using P2O5 as the primary fiber dopant to take advantage of the large (~1330 cm^-1 ) Stokes shift which allows amplification in the 1.26 micron region using a commercially available Yb pump laser and a single amplification stage. Output powers of > 13 W continuous wave (CW) have been demonstrated with these fibers, but with reduced spectral purity. The latest implementation of the amplifier has demonstrated 3 W of CW output power and the ability to maintain the narrow spectral characteristics of the 1.26 micron distributed feedback (DFB) seed laser. In addition the current amplifier has been shown to produce clean modulation waveforms in the 50 KHz frequency range that are compatible with ITTøs unique laser absorption spectroscopy (LAS) technique. This presentation will focus on the amplifier development, integration with the ITT engineering development unit (which has demonstrated high precision CO2 measurements through multiple flight validation campaigns), evaluation of measurements of atmospheric oxygen and recent developments with the ongoing fiber work.