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Chapter VI UV-Vis Spectroscopic….
Figure: 6.3 Experimental set-up of Kurtz powder method.
This experimental setup used a mirror and a 50/50 beam splitter (BS)
to generate a beam with pulse energies about 4.0 mJ. The input laser beam
was passed through an IR reflector, beam splitter (50/50) and then
directed on the micro-crystalline powdered sample. The sample was
prepared by sandwiching the graded crystalline powder with average particle
size of about 90 µm between two glass slides, using copper spacers of 0.4
mm thickness. Since typical values of the coherence length are in the range
of 1-10 µm, this value of average particle size yields maximum second
harmonic signal independent of particle size in phase matchable crystalline
powder.
The energy meter D1 served as a reference to monitor the fluctuation in
the input pulse, Filter F1, which transmits the fundamental laser emission, is
used to filter out any visible radiation present in the fundamental laser
emission by flash lamps. Filter F2 is used to cut off the fundamental laser
radiation and to pass the generated second harmonic. The second harmonic
signal emitted in the sample is collected by the lens (L) and detected by
photo diode detector then measured by oscilloscope assembly. The out
put power and frequency of the pulse is thus determined and compared
with the standard KDP crystal.
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