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Direct writing of single-mode waveguides into crystalline silicon using ps laser pulses is presented. The embedded structures were fabricated by moving the focal position along the beam axis with the help of a long distance microscope objective. In situ monitoring during inscription was performed to analyze the processing dynamics. The waveguide generation is based on pronounced multi-pulse interaction at moderate pulse energies around 100 nJ. All samples were characterized in terms of mode field distribution and damping losses. Calculations indicate an induced refractive index change in the range of 10 to 10. Moreover, a Y-splitter was realized to demonstrate the potential of this process.

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We present THz ultrashort pulse detection by a photoconductive antenna array consisting of 16 photoconductive antennas. The efficient excitation of the photoconductive antennas has been realized by a microlens array which generates 16 single spots from the exciting fs-laser beam. This combination of optoelectronics and microoptics improves the detection efficiency by an order of magnitude in comparison to an excitation by a line focus.

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Within the field of laser-assisted additive manufacturing, the application of ultrashort pulse lasers for selective laser melting came into focus recently. In contrast to conventional lasers, these systems provide extremely high peak power at ultrashort interaction times and offer the potential to control the thermal impact at the vicinity of the processed region by tailoring the pulse repetition rate. Consequently, materials with extremely high melting points such as tungsten or special composites such as AlSi40 can be processed. In this paper, we present the selective laser melting of copper using 500 fs laser pulses at MHz repetition rates emitted at a center wavelength of about 1030 nm. To identify an appropriate processing window, a detailed parameter study was performed. We demonstrate the fabrication of bulk copper parts as well as the realization of thin-wall structures featuring thicknesses below 100 μm. With respect to the extraordinary high thermal conductivity of copper which in general prevents the additive manufacturing of elements with micrometer resolution, this work demonstrates the potential for sophisticated copper products that can be applied in a wide field of applications extending from microelectronics functionality to complex cooling structures

A large-area terahertz emitter based on an interdigital finger electrode photoconductive switch on low-temperature grown GaAs attached to a hexagonal microlens array is demonstrated. The hexagonal arranged microlenses direct the incident IR excitation pulses into specified electrode gaps, resulting in constructive interference in the terahertz far field. Using a Ti:sapphire oscillator running at 80 MHz with 150 fs pulses, 6.5 mu m THz average power at 540 mW optical excitation is obtained. The maximum IR-to-terahertz conversion efficiency achieved is >= 1.35x10(-5)