Laser Drilling of Small Holes in Different Kinds of Concrete

Recently, in Japan, safety measures such as earthquake-resistant reinforcement work and tile-reinforcement work are increasing. Current concrete drilling methods have issues such as noise, vibration, dust, and reaction force. These methods are causing stress for the residents. Consequently, solutions are being sought for work taking place on skyscrapers and at facilities that cannot shut down during construction, such as hotels, schools, hospitals and geriatric facilities for instance.   This study investigated how laser drilling change the conditions, depending on the type of concrete in order to determine the possibility of using laser drilling for tile-reinforcement work and repairing concrete on building exterior. The results confirmed that it’s possible to successfully drill holes for drilling diameters of 4 to 6 mm and depths of around 50 mm in concrete with a compressive strength within the range of 20 to 100 N/mm2 by adjusting laser conditions. In case of deep holes the CW-mode should be chosen. Furthermore, by controlling laser irradiation conditions, it is possible to change the shape of the holes. These different kinds of holes are suitable for different applications. It is expected that laser irradiation drilling will be applied to new construction methods

Mikro- und Nanostrukturierung von Polymeroberflächen mittels Mehrstrahl-Laserinterferenz-Technik

A two-beam laser interference technique is used for exposure of photoresist in combination with an etching technique. It is used in many different domains to generate micro- and nano-structures (interference-lithography). But this technique is time consuming and expensive. However if a photoresist is spun on a surface of a substrate and afterwards structured directly using a laser interference technique the whole process is quicker and much cheaper. In the presented doctoral thesis the direct structuring of different polymers and for the first time different photoresists are investigated. Different laser interference techniques for structuring are depicted. In addition to surface structuring via ablation by means of three-beam laser interference technique this thesis depicts at the first time a photo thermal induced structuring of the surface of a photoresist below the ablation threshold. The two-beam interference technique and the symmetrically three-beam laser interference technique in combination with the reactive ion etching are useful for structuring of glass surfaces. This thesis shows basic results and limitations regarding the direct structuring of polymers and especially of different photoresist by means of multi-beam interference technique. It shows a broad field of application resulting of the multifaceted application of the multi-beam interference technique especially applied to a directly structured photoresist