This thesis presents work on the high average power operation of pulsed diode-pumped
solid-state lasers by using a laser configuration known as the bounce geometry.
The bounce geometry has previously produced efficient, high power and
high spatial quality laser outputs in continuous-wave, Q-switched and modelocked
regimes. This thesis explores the capabilities of the bounce geometry for power
scaling, shown using Nd:YVO4 and Nd:GdVO4 in both a passively Q-switched laser
system and a variety of nonlinear mirror modelocked systems.
The high gain experienced by Nd-doped gain media pumped at 808 nm has traditionally
posed difficulties in producing stable passive Q-switching with Cr4+:YAG.
By using a novel stigmatic design of the bounce geometry that experiences lower
gain, but highly circular output, passive Q-switching with > 11 W of average power
is produced, at a pulse repetition rate of 190 kHz. This is the highest output power
ever achieved from a passively Q-switched Nd-doped vanadate laser to date.
Nonlinear mirror modelocking is a passive modelocking technique that employs a
χ(2) nonlinear medium in combination with a dichroic output coupler. The first
nonlinear mirror modelocking of a bounce geometry laser is presented, obtaining
11.3 W of average power and 57 ps pulse duration using a type-II phase-matched
KTP nonlinear crystal. Using type-I phase-matched BiBO, shorter pulses of 5.7 ps
in duration are obtained at an average power of 6.1 W. The nonlinear mirror modelocking
technique is then applied to the stigmatic bounce geometry laser, obtaining
a highly stable train of modelocked pulses with pulse duration 14 ps and an average
power of 12 W, with high spatial quality output.
Mixed vanadate lasers offer customisation of the laser fluorescence spectrum, but
tend to experience lower gain than single vanadates. Using the mixed vanadate
combination Nd:Gd0.6Y0.4YVO4 in the bounce geometry, 27.5 W of average power
in continuous-wave operation is shown. This is the highest power of any mixed
vanadate laser ever reported. By then applying the nonlinear mirror modelocking
technique to the mixed vanadate system, 16.8 W of average modelocked output
power and a pulse duration of 12.7 ps is obtained. This is simultaneously the first
time that the nonlinear mirror technique has been applied to mixed vanadate gain
media and the highest power of any modelocked mixed vanadate laser to date.
Finally, power scaling of a nonlinear mirror modelocked Nd:GdVO4 laser in the
bounce geometry is achieved through use of the double bounce geometry design
and through use of a high power pump diode. The system employing the high
power pumping produced > 30 W of average power — world record power using the
nonlinear mirror technique.