Open Access

Ultrashort pulse laser structuring enables direct modification of glass surfaces to generate superhydrophilic properties for anti-fogging applications. This approach makes coatings dispensable and the generated surfaces remain thermally, mechanically, and chemically resistant. However, the laser-generated structures usually cause scattering, which decreases transmission and may disturb the vision through the modified glass in the dry state. The aim of this study was to find a laser-processing strategy to achieve superhydrophilic, anti-fogging properties on glass surfaces with maximum transmission and minimal visual perception of the generated structure. For this purpose, we used an ultrashort-pulsed laser to generate periodic patterns of rippled circles or rough holes with varying pitch. The water contact angle and transmission of the structured glasses were measured as a function of the structured area. It was found that a periodic pattern of holes, which covers less than 1% of the surface, is already sufficient to reach the superhydrophilic state (contact angle < 5°) and provides nearly the same transmission as pristine glass. Pictures of objects imaged through dry, structured glasses, which were placed close to the lens or object, showed in both cases only a minimal decrease of contrast. If this minor drawback can be accepted, this direct laser structuring approach could be an interesting alternative to coating-based techniques and leaves even room to apply additional coatings for the fabrication of multi-functional special glasses.

Interstitial photodynamic therapy (iPDT) treats malignant brain cancer cells by irradiation with low power laser light. The light is guided into the human body by diffuse emitting fibers. This study targets the light distribution of optical diffusers within the brain tissue. It was shown, that by submerging an optical diffuser into human brain phantom, its radiation profile measured in air converges towards a Gaussian distribution with increasing phantom depth. A camera method using digital averaging filters as well as an integrating sphere setup, both, smoothing the diffuser radiation profile were applied onto the evaluated diffuser.