TiSa TD

Ultrafast High-Average Power Ti:Sapphire Thin-Disk Oscillators and Amplifiers

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 Obiettivo del progetto (Objective)

Although hardly visible in daily life, today precision laser micro-machining is employed in a broad and rapidly growing range of medical and industrial applications significantly affecting everybody's life. Short and ultrashort pulsed lasers enable producing structures with sub-micron accuracy, for example diesel injection nozzles which help reducing air pollution significantly when compared to nozzles made by conventional fabrication techniques. So far, most of the powerful industrial ultrafast laser sources are operating in the picosecond range, which is sufficient for precision micro-machining of metals. On the other hand, to achieve optimum precision in micro-machining of transparent materials like glass and ceramics, pulse durations in the order of 100 femtoseconds are required. Therefore, the main objective of the project is to demonstrate the feasibility of industrial high-average power ultrafast Ti:sapphire (Ti:Sa) lasers and their excellent qualification for demanding high-productivity precision laser mate-rial processing applications. To achieve the targeted high output powers, the thin-disk (TD) geometry shall be employed, which already enabled the efficient generation of up to 740 W of cw fundamental mode power from one Yb:YAG crystal. Symmetrical double-sided cooling with two transparent diamond heat spreaders shall be used to optimize the cooling of the thin Ti:Sa crystal. Within the project, two ultrafast Ti:Sa TD laser systems, one with chirped pulse amplification (CPA) to obtain high-energy pulses and the other without CPA for high repetition rates, both with a maximum average output power of at least 200 W at a pulse duration of well below 100 fs shall be demonstrated. The CPA system, comprising a multipass TD amplifier, shall achieve a pulse energy of 10 mJ at 20 kHz repetition rate. The multipass amplifier will be pumped by two nanosecond pulsed frequency-doubled solid-state lasers developed within the project which are operating at 532 nm with an average output power of 300 W each. The high-repetition rate system shall be a high-power TD oscillator with a pulse energy of 20 µJ at about 10 MHz. A commercial cw Yb:YAG TD laser with intracavity frequency doubling emitting about 500 W at 515 nm shall be used as pump source. To demonstrate the excellent qualification of the ultrafast oscillator for fast, ultra-precise micromachining of transparent materials, high-speed cutting of glass, e.g. Gorilla® glass, which is widely used for mobile phones and tablets, will be investigated as high-volume reference application. With the CPA system, which is especially well suited for ultra-precise drilling, the ultra-high aspect ratio percussion and single-shot drilling of transparent substrates shall be investigated. Other potential applications, including – but not limited to – large area precision volume structuring for microfluidics or integrated optics, enabled by the new powerful femtosecond sources will also be studied in the project.