Multipass Faraday rotators and isolators.

Faraday isolators are usually limited to Faraday materials with strong Verdet constants. We present a method to reach the 45° polarization rotation angle needed for optical isolators with materials exhibiting a weak Faraday effect. The Faraday effect is enhanced by passing the incident radiation multiple times through the Faraday medium while the rotation angle accumulates after each pass.

Quasi-waveguide amplifiers based on bulk laser gain media in Herriott-type multipass cells.

We present here what we believe to be a new geometry for laser amplifiers based on bulk gain media. The overlapped seed and pump beams are repetitively refocused into the gain medium with a Herriott-type multipass cell. Similar to a waveguide, this configuration allows for a confined propagation inside the gain medium over much longer lengths than in ordinary single pass bulk amplifiers.

Amplification-free GW-level, 150 W, 14 MHz, and 8 fs thin-disk laser based on compression in multipass cells.

We report an amplification-free thin-disk laser system delivering 0.9 GW peak power. The 120 fs pulses, at 14 MHz, centered around 1 µm, containing 12.

Free-space quasi-phase matching.

We report a new, to the best of our knowledge, approach to phase matching of nonlinear materials based on the free-space multipass cells. This technique is applicable to noncentrosymmetric nonlinear crystals, including crystals that cannot be birefringent phase-matched or quasi-phase matched by periodic poling. Notably, by using this approach, the crystalline quartz is quasi-phase matched with the demonstrated increase of the second harmonic generation efficiency by a factor of 40.

110 MW thin-disk oscillator.

A compact Kerr-lens mode-locked thin-disk oscillator reproducibly delivering 110 MW output peak power, the highest among all oscillators, is reported. This simple and stable femtosecond oscillator delivering a unique combination of high average power (202 W) and peak power, is an ideal driver and an important milestone for the development of extreme ultraviolet transportable frequency comb sources.