Harald Schulz

Atomic spectroscopy with ultrashort laser pulses using frequency-resolved optical gating

Abstract The D 2 absorption line of rubidium vapour was detected using ultrashort laser pulses as light source. By the application of a frequency-resolved optical gating technique using second-harmonic generation it was possible to measure the absorption line in spite of the strong mismatch between absorption linewidth and pulse bandwidth. The experimental results are explained by a theoretical model.

Laser Treatment of Dental Substances with Spectroscopic Control

During the preparation of dental substances (e.g. enamel, dentine, cement, amalgam, titan) with femtosecond laser pulses, the ablation rate and the plasma radiation of the ablated substances were investigated. The ablation rate was as high as 16 mm3/min if demineralized enamel or dentine were treated. The obtained fluorescence spectra allowed the analysis of the removed substance. The data may be used to control the laser system so that only specific structures (e.g. carious tissue) are removed.

Polychromatische on-line Meßverfahren zur Charakterisierung dünner Schichten

Wir beschreiben zwei Mesverfahren zur Charakterisierung von Schichtsystemen, die auf dem Einsatz von polychromatischem Licht beruhen. Die im Vergleich zu monochromatischen Verfahren vergroserte Datenmenge wird zur Erhohung der Mesgenauigkeit sowie zur Beschleunigung des Mesprozesses verwendet.

Ultrafast Nonlinear Scattering and Deflection of Femtosecond Laser Pulses

Ultrafast processes in physics, chemistry, biology and material science are already investigated by time-resolved spectroscopy since picosecond (ps) and femtosecond (fs) laser sources became available [1]. Different interaction processes during the excitation and the relaxation of the illuminated matter were studied. The contribution due to the interaction of the photons with electrons, phonons, plasmons or other types of matter excitation can be separated with respect to the specific temporal and spectral characteristics [2].

Single-Shot Absorption Spectroscopy with Chirped Femtosecond Laser Pulses

The D2 line of rubidium (Rb) was recorded using femtosecond (fs) laser pulses and a spectrally resolving autocorrelator. The interaction between photons and atoms lead to a significant change of the pulse correlation signal near the half of the D2 wavelength.

Achromatic Phase Retarder Using Liquid Crystals

Liquid crystals (LC) are a low cost alternative to birefringent crystals commonly used in polarization optics, especially if large apertures are needed. One possible application are achromatic phase retarders (e.g. λ/2-plates) to modulate the polarization of a white light continuum. Such devices can be assembled from at least two layers of different birefringent materials [1]. In contrast to crystals LCs offer a large variety in range and dispersion of refractive indices and allow tuning of birefringence by low electrical fields. Since spectral data of refractive indices of commercial LC mixtures are normally not available we developed a technique to determine both birefringence and refractive indices of liquid crystalline compounds. The refractive indices of mixtures can then be found from that of their compounds.