We demonstrate an Yb:YAG thin-disk laser oscillator operating in the self-phase modulation broadened regime. The laser delivers 100 W of average power in 50-fs pulses at 17-MHz repetition rate with an optical-to-optical efficiency of 25%.

High power ultrafast laser systems directly emitting in the short-wavelength infrared region (1.4-3 µm) has seen strong interest, due to applications in science and technology. Among different laser technologies, the development of 2-µm thin-disk lasers is very promising for power and energy scaling. Recently, we have demonstrated record results with Ho:YAG thin-disk oscillator, delivering 112-W CW power, and 40.5-W modelocked operation with 1.66-ps pulse duration at 52.2-MHz. Here we would like to briefly review the recent achievements of 2-µm thin-disk lasers and discuss the potential development and applications.

We present a novel pumping scheme relying on cross-polarization that overcomes previous bandwidth and efficiency limitations. Implementing this pumping scheme in a soft-aperture Kerr-lens mode-locked laser oscillator based on Yb:CALGO, we demonstrate more than one order of magnitude higher optical-to-optical efficiency compared to previous few-cycle laser oscillators based on Yb-doped gain materials operating in the sub-30-fs pulse duration regime.

We report an approach to generation of femtosecond pulses and optical frequency combs in the 2 – 20 µm spectral range. The laser architecture is based on a combination of laser and nonlinear interactions in polycrystalline Cr:ZnS media that enables simultaneous amplification of ultrashort pulses, nonlinear pulse compression to 2-optical-cycle, and nonlinear broadening of pulses’ spectrum to an optical octave. This has allowed us to implement robust and reliable shoe-box sized middle-IR frequency combs with ultra-low timing jitter of the pulse trains, broad instantaneous spectra, and Watt-level average power.

We present InGaSb/GaSb quantum well based high-quality SESAM at infrared wavelength of 2.4 µm. Using the SESAM we demonstrate self-starting soliton modelocking of Cr:ZnS oscillators delivering 155-fs pulses at record-high 2 GHz repetition rate and short pulses of only 79-fs at 250 MHz repetition rate, both at a high average output power of 0.8 W.

We present a high-precision (<0.03%) nonlinear reflectivity and pump-probe characterization of InGaSb/GaSb quantum-well-based SESAMs for high-power 2.1 μm Ho-doped lasers. The SESAMs have ~1% modulation depth, high saturation fluences and fast recovery times.