Biomedical Engineering Reference
In-Depth Information
Figure 10.6
High-power vortex laser based on a side-pumped bounce
amplifier. HR is an end mirror, OC is an output coupler, CLs are an intra-
cavitycylindricallenspair,andCL
D
isafocusingopticsforpumplaserdiode.
The laser can produce a vortex outputat a pump power of
>
35 W.
modulator limits the power handling ability of the system. And
each of these methods can also suffer severe losses through the
conversion process.
Analternativemethodtoeffectivelygeneratehigh-qualityvortex
outputistodirectlyforcethelasertooscillateonanLGmodeinstead
of a Hermite-Gaussian mode. To date, several methods have been
demonstrated using an annular shaped beam pumping [31], intra-
cavity SPP [32], and a damaged resonator mirror [33]. However,
the fatal drawback to them is the requirement of additional phase
elements and extremely precise alignment. The achieved output
power has been limited to 1 W.
In recent years, we have proposed a thermal lens aperture
techniquefortransverselydiode-pumpedsolid-statelasers[34-36].
An ultrahigh-power (17.8 W) vortex output at a high e
ciency
of more than 30% has been achieved from a transversely diode-
pumped Nd:GdVO
4
laser, in which the thermal lens in the laser
material forms a limiting aperture for the desired LG mode in the
gain medium without any additional phase elements (seeFig. 10.6).
We have also produced high-power, pulsed OV outputs from a
diode-pumped solid-state master laser oscillator in combination
withastressed,ytterbium(Yb)-doped,large-mode-areafiberpower
amplifier [27, 37, 38]. A collimated master laser output with a
Gaussian profile is off-axially injected into a large-mode area fiber,
therebyyieldingin-phasecouplingoftwoorthogonalLP
11
modesat
a high e
ciency. These modes are 90
◦
or
90
◦
out of phase with
each other at the end of the fiber by providing appropriate stress to
−
