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Optical diffuser machined with 157nm laser radiation

The modification of the refractive index of fused silica by a 157nm excimer laser was used to inscribe an optical diffuser with discrete scattering areas into an optical fibre. Radiation which is launched into the fibre core emits radially from the fibre at the modified areas. Such diffusers are used in minimal-invasive therapies like laser induced thermo-therapy (LITT) and photodynamic therapy (PDT). The patient is punctured and a catheter system is inserted, which allows the placement of the diffusing fibre inside the tumour tissue.

In case of LITT, the tumour tissue is destroyed due to thermal damage caused by irradiation with laser light.

As for PDT, a medicament, a so-called photosensitizer is administered and cumulates in the target tissue where it is activated by laser radiation of appropriate wavelength (generally in the red spectral region). After excitation a photochemical reaction yields an irreversible damage of the target cells.

Diffusers with different emission profiles (decreasing and increasing alongside the fibre axis) were demonstrated. Thus, the developed technique is feasible to manufacture cylindrical diffusers with longitudinally homogeneous emission profile. Additionally, future application will include tailored diffusers whose emission characteristics is adapted to the specific topography of the tumour of each single patient.

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Reported by

CeramOptec GmbH
Siemensstrasse 44
53121 Bonn
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