Double clad large mode area planar lasers or amplifiers comprising rare-earth
or transition metal doped planar core regions are used to generate near-diffraction-limited
optical beams of ultra-high power. The amplified light is guided in the core using
different guiding mechanisms in two orthogonal axes inside the core. Waveguiding
along a first long core axis is obtained substantially by gain-guiding or thermal
lensing. Waveguiding along a second short core axis is obtained by index guiding.
This is accomplished by surrounding the planar core region with regions of different
refractive index. The long sides of the planar core region are surrounded with
a depressed refractive index cladding region. The short sides of the planar core
region are surrounded with a cladding region substantially index-matched to the
core region. The whole structure is surrounded by an outer cladding region with
a low refractive index to enable cladding pumping of the planar waveguide with
high-power diode lasers. The rare-earth or transition metal doping level inside
the planar core can be constant and can also vary substantially without negatively
affecting the waveguiding properties. To avoid bend losses along the long axis
of the planar waveguide, the planar core region and the planar waveguide are aligned
parallel to each other and the planar waveguide is coiled with the long side of
the planar waveguide mounted to a drum. The drum can also be used as a heat sink.
A planar waveguide comprising a planar core region can be manufactured using conventional
fiber fabrication methods.
