With the demonstration of a sub-picosecond thin-disk laser oscillator delivering a record-excessive 350-W common output energy, the group of Ursula Keller units a brand new benchmark and paves the trail in the direction of much more highly effective lasers.
Ultrafast laser sources are on the coronary heart of an ever-increasing vary of elementary scientific research and industrial purposes, from high-field-physics experiments with attosecond temporal decision to micrometre-precision machining of supplies. So as to push the envelope even additional, repetition charges of a number of megahertz and common output powers of lots of of Watt are required. A very compelling route to realizing such high-energy laser pulses is to generate them straight by scaling up the facility output from laser oscillators, somewhat than counting on multi-stage amplifier techniques. The latter strategy provides a excessive diploma of complexity, whereas the previous leads to sturdy and doubtlessly cost-efficient units. Reporting recently in Optics Specific, the group of Ursula Keller on the Institute of Quantum Electronics has now taken the ‘power-scaling’ strategy to a brand new degree. They current a supply that mixes the simplicity and excessive repetition charges of oscillators with record-excessive common output energy from this kind of laser.
The ETH staff labored with a so-known as thin-disk laser oscillator, the place the acquire medium — the fabric in which the quantum processes main to lasing happen — is formed as a disk, usually some 100 μm skinny. This geometry affords a comparatively massive floor space, which in flip helps cooling. Nonetheless, thermal results remained a significant bottleneck, and since 2012 the file output energy stood at 275 W.
Till now. Combining a number of advances in thin-disk laser know-how developed in the Keller group, PhD pupil Francesco Saltarelli, senior analysis scientist Christopher Phillips and colleagues took a decisive step and achieved a median output energy of 350 W, with pulses which can be solely 940 femtoseconds lengthy, carry an vitality of 39 microjoule and repeat at a 8.88-megahertz charge — values which can be of fast curiosity for purposes each in science and trade.
A key side of the work is that the researchers discovered a method to allow a number of passes of the pump beam by way of the acquire medium with out inflicting detrimental thermal results, and so to scale back the stress on the related parts. The power to management results due to heating opened the gate to go firmly past the 275-W degree and to set the brand new benchmark. The strategy now developed will be taken even additional although, and output powers past 500 W appear life like. With additional enhancements, the ETH researchers estimate, the kilowatt degree may come into view.
Reference: “Power scaling of ultrafast oscillators: 350-W average-power sub-picosecond thin-disk laser” F. Saltarelli, I. J. Graumann, L. Lang, D. Bauer, C. R. Phillips and U. Keller, Optics Specific, Vol. 27, Concern 22, pp. 31465-31474 (2019).