The planar waveguide gain medium o ers a good approach to creating a high-
power lasers. Excellent thermal properties allow for lasers with good beam-quality
and high-e ciency. A Neodymium doped YAG planar waveguide laser was actively
Q-switched using a hybrid unstable resonator and acousto-optic modulator. A Yt-
terbium doped YAG planar waveguide laser was side-pumped using two laser diode
stacks with a total of 800 W incident pump power.
The Nd:YAG planar waveguide laser has a core 200 um thick and was face pumped
with ten laser diode bars. Q-switching was achieved through the use of a new hybrid
unstable resonator con guration providing high-speed modulation of the laser cavity.
The laser produced 100 W of average power with a pulse repetition rate of 100 kHz,
giving 1 mJ pulses with 50 ns duration. Shorter 15 ns pulses were achieved with
4.5 mJ pulse energy at lower pulse repetition rates.
The Yb:YAG planar waveguide laser has a 150 um core thickness, side pumped
by two 430 W, six-bar diode laser stacks. Each diode stack has a custom phase-
plate, correcting for collimation errors and lens aberrations. These gave a line focus
matching the dimensions of the waveguide core with an incident intensity on each
side of approximately 22 kWcm-2. Ray tracing of spontaneous emission within the
waveguide core shows side facet angles of 7 and 20 were required to minimise ASE
and parasitic oscillations within the waveguide core.
A technique to image the
uorescence from the Yb:YAG waveguide core has been
developed. This technique allows for easy alignment of the pump lasers to the waveg-
uide core and measurement of the pump intensity pro le throughout the planar waveg-
uide. This technique showed single-sided pumping to follow Beer's law, and with
double-sided pumping considerably improved the pump uniformity. A diode laser
probe was used to measure the gain present within the waveguide. The small signal
gain coe cient was shown to be 1 cm-1 with a uniform pro le across the width of
the waveguide when pumped to saturation. This highlights the potential of operating
the planar waveguide laser as an e cient ampli er.
High-power high-e ciency operation of the Yb:YAG planar waveguide laser was
achieved through the use of a hybrid stable waveguide resonator. Output power of
400 W was extracted in a multi-mode beam with a slope e ciency of 75%. This
result represents the highest output power from a diode-pumped solid-state planar
waveguide laser to date
