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Molybdenum thin films on glass substrates play an important role as contact layer for thin film solar cells. They can be ablated by picosecond laser pulses irradiated from the substrate side at low laser fluences of less than 1 J cm−2, while structured trenches remain free from thermal damage and residues. The fluence for that so-called direct induced ablation from the substrate side is in contrast to metal side ablation reduced by approximately one order of magnitude and is far below the thermodynamic limit for heating, melting and evaporating the complete layer. For an extended investigation of the direct induced laser ablation and the underlying mechanism, further thin film materials, chromium, titanium and platinum, with thicknesses between 200 nm and 1 µm were examined. Finally, a simple thermo-dynamical model is able to connect the observed ablation energetics with the mechanical ductility and stress limit of the metal thin films.

A grating spectrograph in InGaAsP/InP suitable for use in the wavelength region from 1.2 to 1.6 μm is presented. Experiments for devices with a channel spacing of 3.7 nm and more than 30 channels between 1.48 and 1.59 μm are described. The measured cross talk level is below −25 dB. The devices have only very low polarization sensitivity. This spectrograph is suited for monolithic integration with photodiodes, laser diodes, or optical amplifiers on a single chip.

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