Abstract
We report the high-energy flat-top supercontinuum covering the
midinfrared wavelength range of 1.9–2.5 μm as well as electronically
tunable femtosecond pulses between 1.98 and 2.22 μm directly from the
thulium-doped fiber laser amplifier. Comparison of experimental results
with numerical simulations confirms that both sources employ the same
nonlinear optical mechanism—Raman soliton frequency shift occurring inside
the Tm-fiber amplifier. To illustrate that we investigate two versions of
the compact diode-pumped SESAM mode-locked femtosecond thulium-doped
all-silica-fiber-based laser system providing either broadband
supercontinuum or tunable Raman soliton output, depending on the
parameters of the system. The first system operates in the Raman soliton
regime providing femtosecond pulses tunable between 1.98 and 2.22 μm. Wide
and continuous spectral tunability over 240 nm was realized by changing
only the amplifier pump diode current. The second system generates
high-energy supercontinuum with the superior spectral flatness of better
than 1 dB covering the wavelength range of 1.9–2.5 μm, with the total
output energy as high as 0.284 μJ, and the average power of 2.1 W at
7.5-MHz repetition rate. We simulate the amplifier operation in the Raman
soliton self-frequency shift regime and discuss the role of induced Raman
scattering in supercontinuum formation inside the fiber amplifier. We
compare this system with a more traditional 1.85–2.53-μm supercontinuum
source in the external highly-nonlinear commercial chalcogenide fiber
using the Raman soliton MOPA as an excitation source. The reported
systems11Patent pending, ATLA Lasers AS, Trondheim, Norway. can be readily
applied to a number of industrial applications in the mid-IR, including
sensing, standoff detection, medical surgery, and fine material
processing.
© 2016 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription