Gisbert Staupendahl

Optical constants n and κ of various technical and optical glasses at λ = 10.59 μm

The optical constants n (refractive index) and κ (absorption index) of several technical and optical glasses were determined with high accuracy for the CO2 laser wavelength λ = 10.59 μm by angular- and polarization-dependent measurements of reflection at the surface of these glasses. The exact knowledge of n and κ is important for modeling the interaction between CO2 laser radiation and glasses. The investigations were made with low-intense CO2 laser radiation polarized perpendicular as well as parallel to the plane of incidence. The angle of incidence was varied in the range between 0° and 90°. The values of n and κ were determined by means of a fitting procedure between the measured values of the reflectivity and the theoretical curves from Fresnels formulas. In the case of high absorbing index glasses, the accuracy of this method exceeds ±2% (n) and ±4% (κ), respectively. The measured values show significant differences between typical optical and technical glasses resulting in a linear absorption coe...

Sensitive ablation of brittle materials with pulsed CO2 laser radiation

The interaction process between pulsed CO2 laser radiation and glass was studied systematically. The concept of the structuring process is related to an absorption-controlled ablation of small elementary material volumes with reduced melt formation, the so-called elementary volume ablation (EVA). For this purpose, suitable pulse parameters were predicted on the basis of the optical and thermal materials properties. These pulses with durations as low as 10 μs and a peak power of up to 600 W were generated using a specific arrangement consisting of a commercially available continuous CO2 laser of high beam quality and a cascade of two interference laser beam modulators. Optical microscopy, scanning electron microscopy, white light interferometry, and tactile profilometry were used to investigate the influence of the CO2 laser pulse parameters on the processing quality. The results obtained from the ablation of borosilicate glass (Borofloat33) and 100 μm thick sheets of cerium doped borosilicate glass demons...

CO2 laser welding with dynamic polarization

This paper reports on a new arrangement for CO2 laser welding, allowing the fast variation of the polarization of radiation (DP). The experiments with steel St37 and Ck45 show a significant influence of a DP on the melt pool dynamic, especially a remarkable smoothing of the top bead at certain frequencies of DP.

Precision processing of composites : Laser beam and water jet abrasion techniques

Advanced composites with their diffcrent material characteristics combined in one prefabricated component put great demands on the processing technologies, Optimized paranieters for laser beam and water let abrasion techniques lead to a significautly improved surjace quality of the products.