■ Solid-State Lasers
pretty dramatic cost reduction,” Kapteyn
He added that the same diodes will
also enable the scaling up of Ti:sapphire
power by a factor of 10 or more, in particular for the widely used high peak-power
Ti:sapphire amplifier systems. If higher
power can be achieved economically, it
opens up additional applications.
Researchers are also investigating how
to up the peak power of ultrashort-pulse-width fiber lasers, with an example being
work done by a team from Cornell University in Ithaca, N. Y. In a 2017 Optica
paper titled “Megawatt peak power from a
Mamyshev oscillator,” the group reported
on an environmentally stable design that
offered at least an order-of-magnitude
higher peak power than reported previously by lasers of similar fiber mode area.
Zhanwei Liu, an applied physics graduate student and lead author on the paper,
noted that possible applications include
metrology, micromachining, spectroscopy, nonlinear microscopy and more.
“These areas need short duration and/or
high peak power pulses. In addition, they
have a strong demand for a low-price,
compact and stable laser source. With further development, the Mamyshev oscillator may be a good solution,” he said.
He added that the group is working
to scale up the energy to a microjoule or
more. Liu also noted that research and
development must address how to make
the high-performance oscillator self-start-
ing. Another area that must be tackled
involves a better understanding of how
the Mamyshev oscillator works and the
nonlinear physics behind it.
Finally, for a look at where solid-state
lasers may be headed, consider the work
being done at the Lawrence Livermore
National Laboratory’s (LLNL) National
Ignition Facility & Photon Science (NIF)
in Livermore, Calif. Its 192-beam, 351-nm
light system replicates conditions found
in nuclear explosions and other extreme
states by concentrating all the beams on
a target. Thus, it enables research into
extreme conditions. The design also
offers a way to potentially scale up power
from the current 1.8 megajoules to that
needed to initiate hydrogen fusion, ac-
cording to the facility’s director, Mark
The system uses flash lamps to pump
the solid-state doped glass. Derivatives of
the technology are finding uses elsewhere.
At NIF, Constantin Haefner, program
director for Advanced Photon Technologies, and his group recently delivered a
pulsed solid-state laser to the European
Extreme Light Infrastructure facility in
the Czech Republic.
A key advance that made this laser
possible was a switch to using diodes for
energizing the gain medium. In contrast
to flash lamps, diodes pump close to the
emission spectrum and therefore lessen
the waste energy dumped into the system.
Residual heat is removed with high-velocity helium gas streaming over the
amplifier faces, a technology pioneered
at LLNL. Exploiting these and other innovations, the group delivered a reliable
petawatt, or 1015-watt, 10-pulse-per-
At those levels, the light that strikes
a target can produce x-rays, neutrons or
electrons that can be used for imaging,
with the only thing needed being a change
in the target. Today, such a capability
With increasing power, solid-state lasers enable
faster materials processing.
Direct diode pumping, shown here in a demonstration, promises to cut the cost of some ultrashort-pulse-width lasers significantly.