Thulium-doped fiber lasers (TFLs) emitting retina-safe 2-μm wavelengths offer substantial power-scaling advantages over ytterbium-doped fiber lasers for narrow linewidth, single-mode operation. This article reviews the design and performance of a pump-limited, 600 W, single-mode, single-frequency TFL amplifier chain that balances thermal limitations against those arising from stimulated Brillouin scattering (SBS). A simple analysis of thermal and SBS limits is anchored with measurements on kilowatt class Tm and Yb fiber lasers to highlight the scaling advantage of Tm for narrow linewidth operation. We also report recent results on active phase-locking of a TFL amplifier to an optical reference as a precursor to further parallel scaling via coherent beam combining.
A four-stage, Tm-doped fiber amplifier chain emitted 608 W of single-frequency (SF) output power with 53 dB gain,
54% slope efficiency, and M2 = 1.05 beam quality. The output power was limited by available pump power. The final
amplifier stage preserved the input <5-MHz linewidth and imposed negligible phase noise above 3 kHz. SBS limits at
the 2040-nm operating wavelength were measured by splicing different lengths of passive fiber to the amplifier exit.
Thermal limits of the fiber were explored analytically and are consistent with the measured power performance.
Comparison of the SBS and thermal limits suggests a maximum SF power of ~750 W from this fiber configuration, with
further potential to scale past 1 kW with different fiber parameters. To our knowledge, this is the highest power reported
to date from any single-frequency, single-mode fiber laser.
We present a method to determine system-bath correlation functions from third order optical coherence measurements. The importance of these correlation functions for understanding solvation dynamics is explained. A physical argument is made to explain why one coherence measurement, the photon echo peak shift, should strongly reflect system- bath dynamics. Finally, this method is applied to the system of bacteriochlorophyll in tetrahydrofuran solution.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.