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A novel laser beam shaping system was designed to demonstrate the potential of using high
power UV laser sources for large scale disinfection of liquids used in the production of food
products, such as juices, beer, milk and other beverage types. The design incorporates a patented
assembly of optical components including a diffractive beam splitting/shaping element and a
faceted pyramidal or conically shaped Lambertian diffuser made from a compression molded
PTFE compounds. When properly sintered to an appropriate density, as an example between
1.10 and 1.40 grams per cubic centimeter, the compressed PTFE compounds show a ~99%
reflectance at wavelengths ranging from 300 nm to 1500 nm, and a ~98.5% refection of
wavelengths from 250 nm to 2000 nm [1]. The unique diffuser configuration also benefits from
the fact that the PTFE compounds do not degrade when exposed to ultraviolet radiation as do
barium sulfate materials and silver or aluminized mirror coatings [2]. These components are
contained within a hermetically sealed quartz tube. Once assembled a laser beam is directed
through one end of the tube. This window takes the form of a computer generated diffractive
splitter or other diffractive shaper element to split the laser beam into a series of spot beamlets,
circular rings or other geometric shapes. As each of the split beamlets or rings cascade
downward, they illuminate various points along the tapered PTFE cone or faceted pyramidal
form. As they strike the surface they each diffuse in a Lambertian reflectance pattern creating a
pseudo-uniform circumferential illuminator along the length of the quartz tube enclosing the
assembly. The compact tubular structure termed Longitudinal Illuminated Diffuser (LID)
provides a unique UV disinfection source that can be placed within a centrifugal reactor or a pipe
based reactor chamber. This paper will review the overall design principle, key component
design parameters, preliminary analytic and bench operational testing results.
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