For applications of fiber guided pulsed UV-laser radiation in biomedical optics, laser spectroscopy or laser micro
processing which need good beam quality low mode or single mode optical fibers are required. We investigated the
transmission properties at 355 nm wavelength with laser peak powers up to 5 GW/cm2 or laser fluences up to 9.5 J/cm2.
In some cases fibers were damaged during prolonged irradiation at this intensity level. So these fluences or intensities
can be used as estimation for the damage threshold. It turns out, that degradation or microstructural damage in the fiber
core plays a minor role in long term transmission as long as the intensity stays below the damage threshold. Fiber lengths
of many meters are possible. Single mode UV laser beam guiding is possible. UV beam guiding with high pulse
repetition rate, moderate peak power will be compared with that of moderate repetition frequency, high peak power
lasers
Laser spectroscopy in the UV-region below 380 nm is a powerful tool for many biomedical or analytical applications.
For such purposes Polymer Optical Fibers (POFs) can be an interesting alternative to silica-based optical fibers if the
transmission in the UV-A region is sufficient. In addition to
high-power LED-light delivery shown in previous studies,
the short and long term performance of PMMA-based POFs under pulsed UV radiation was investigated using a nitrogen
laser at 337 nm and the 3rd harmonic of Nd:YAG laser at 355 nm. For thick POFs (core diameter: approx. 1000 μm), the
basic (initial) low intensity UV-attenuation is in the order of less than 2 dB/m. However, a typical initial attenuation
between 4 and 5 dB/m was determined using the pulsed UV-lasers. At 337 nm, the transmission for these POF is
independent of intensity up to 9 MW/cm2. No photodegradation was observed, up to 180k pulses if the intensity does not
exceed 6 MW/cm2. For both wavelengths, the surface damages have been observed, taking into account the differently
shaped intensity-profiles.
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