Researchers at ETH propose a novel multi-pass resonator architecture for energy scaling of mode-locked thin-disk lasers in the mJ regime at MHz repetition rates and picosecond pulse length. The new laser design can be used in precision laser machining as well as academic tabletop experiments.
Precision laser machining of materials requires intense (high-energy, ultrashort) laser pulses. The laser systems delivering this pulses usually consist of a mode-locked la- ser followed by amplifier stages, whose operation is usually restricted to a low repetition rate (kHz).
Alternatively, multi-pass resonators can deliver high pulse energies at significantly higher repetition rates (MHz) providing higher average powers. However, their power scaling is limited due to thermal lens effects in the active medium.
This particular laser design bypasses this limitation opening the way for the increase of industrial production throughput (e.g. machining of large surfaces), and for novel applications.
The chart below visualizes the extraction of ultrashort pulses of mJ energy with MHz repetition rate directly from an oscillator that can be operated in air.
The multi-pass architecture shows a stability region which is independent of the number of passes on the thin-disk. This is realised by concatenating quasi- identical segments, each of which being optically equivalent to a stable resonator, see schematic drawing below. An array of mirrors as shown in the two figures provides a simple alignment procedure and a compact layout.
Features & Benefits
• Resonator design stable against thermal lens variations granting energy and power scalability
• Mode-locked resonator based on Yb:YAG for mJ pulse energy, MHz repetition rate, ≈ 10 ps pulse length and 1030 nm wavelength
• Other wavelengths and pulses in the fs regime can be realized by using other active materials
• Reduced complexity
Fields of Application
• Accurate and fast micro patterning, micro drilling and micro cutting of large workpieces of high throughput
• Nano structuring of surfaces
• Precision cutting of composite and transparent materials
• Scientific applications as tabletop high power X-ray lasers, nonlinear chemistry and high power terahertz radiation
http://arxiv.org/pdf/1603.00404.pdf (main idea)
http://arxiv.org/pdf/1607.08873.pdf (further advantage)
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