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R7 Final Version
New Oscillator
r7fosc.jpg
(Actual photo)
r7fosc.gif
(Schematic) Dual flashlamps were wire wrapped from cathode up to
beginning of anode arc (about 1 inch from anode terminal to provide better
ground plane for easlier triggering)
frao1.jpg Pulse
recorded with CCD camcorder on black board. Single longitudinal mode. Below
some indication of transverse mode quality..
fr7o2.gif 3d view of
recorded pulse. fr7o5.gif 3d view of 2nd
recorded pulse Refer to r7beam.htm
regarding recording setup and image processing procedures used to process
the above recorded CCD camcorder on black board image.
fr7o3.gif Ideal
beam
fr7o4.gif Contour map of pulse.
fr7o6.gif Contour map of 2nd pulse.
New modification for version 7:
Dual flashlamp oscillator. Beam quality M2 value was approximately
2.1 at 13.2mj with 1.2mm aperture (1.01 Fresnel number) as calculated
by measuring the beam waist from a 150mm plano-convex lens**. Reference: :http://www.uslasercorp.com/Envoy/m2.htm This beam quality measurement
indirectly suggests possible mulitmode output (TEM00 mode + smaller percentage
of some higher modes combined due to larger spot size). But there is another
factor effecting M squared for solid state lasers as they generally have
thermal lensing effects. For Q-switched ruby lasers, the laser has a negative
lens effect at the time of q-switch output and will increase
spherical aberration effects with increasing pump input. These effects
contribute to a change in beam divergence. Since this is a holographic
laser, this M2 value doesn't reveal wavefront errors and
phasefronts critical to holograms that might be revealed with a Shack-Hartmann
sensor. The beam quality rests on clean and good quality oscillator and
amps and the rest of the optics system to provide good quality holograms. The
amplifiers for example will reduce the beam quality M2 value due to
this thermal lensing aberrations by increasing divergence yet won't change the
TEM content. Overall the beam quality as viewed from a ccd camcorder (see
contour maps above) and after being focused showed tight focus with nice beam
symmetry at focus suggesting the beam quality approached toward
diffraction limited gaussian quality but only at a reduction in output (around
11mj or less).
Finally R7-MOPA will be upgraded
by installing a larger diameter flashlamp SG-2800 modified for the
amplifiers to remove hot flashlamp further away from rod reducing potential
thermal surface damage to laser rods.
** Careful beam centering on Plano-convex lens
with shape factor +1 (curved surface toward laser). Repeated pulse firings to
find minimal spot size. More precise spot measuring. Measured beam spot value
was .005 inch and calculated gaussian spot size 59 inches away from OC
was 0.0034 inch based on Thorlabs lens 150mm FL but at 694.3nm was found
to be around 162mm from the beam measurements.