Spatially twisted light with femtosecond temporal structure is of particular interest in strong-field physics and light–matter interactions. However, present femtosecond vortex sources exhibit limited power handling capabilities, and their amplification remains an ongoing challenge particularly for high-order orbital angular momentum (OAM) states due to several inherent technical difficulties. Here, we exploit a straightforward approach to directly amplify a femtosecond optical vortex (FOV, OAM=-8ℏ) by using a two-stage single-crystal fiber (SCF) amplifier system without pulse stretching and compression in the time domain, delivering 23-W, 163-fs pulses at a repetition rate of 1 MHz. The spatial and temporal features are well-conserved during the amplification, as well as the high modal purity (>96%). The results indicate that the multi-stage SCF amplifier system is particularly suited for direct amplification of high-order FOVs. The generated high-power femtosecond OAM laser beams are expected to help reveal complex physical phenomena in light–matter interactions and pave the way for practical applications in attoscience, laser plasma acceleration, and high-dimension micromachining.

In this paper, we report on a wide wavelength tuning optical vortex carrying orbital angular momentum (OAM) of ±ħ, from a thulium-doped yttrium aluminum perovskite (YAP) laser employing a birefringent filter. The OAM is experimentally found to be well maintained during the whole wavelength tuning process. The Laguerre–Gaussian (LG0,+1) mode with a tuning range of 58 nm from 1934.8 to 1993.0 nm and LG0,-1 mode with a range of 76 nm from 1920.4 to 1996.6 nm, are, respectively, obtained. This is, to the best of our knowledge, the first experimental implementation of wavelength tuning for a scalar vortex laser in the 2 µm spectral range, as well as the broadest tuning range ever reported from the vortex laser cavity. Such a vortex laser with robust structure and straightforward wavelength tuning capability will be an ideal light source for potential applications in the field of optical communication with one additional degree of freedom.

We report on a power-scalable sub-100-fs laser in the 2-μm spectral range using a Tm³⁺-doped ‘mixed’ (Lu,Sc)₂O₃ sesquioxide ceramic as an active medium. Pulses as short as 58 fs at 2076 nm with an average output power of 114 mW at a pulse repetition rate of approximately 82.9 MHz are generated by employing single-walled carbon nanotubes as a saturable absorber. A higher average power of 350 mW at 2075 nm is obtained at the expense of the pulse duration (65 fs). A maximum average power of 486 mW is achieved for a pulse duration of 98 fs and an optical conversion efficiency of 22.3%, representing the highest value ever reported from sub-100-fs mode-locked Tm lasers.

Structured ultrashort-pulse laser beams, and in particular eigenmodes of the paraxial Helmholtz equation, are currently extensively studied for novel potential applications in various fields, e.g., laser plasma acceleration, attosecond science, and fine micromachining. To extend these prospects further, in the present work we push forward the advancement of such femtosecond structured laser sources into the 2-μm spectral region. Ultrashort-pulse Hermite– and Laguerre–Gaussian laser modes both with a pulse duration around 100 fs are successfully produced from a compact solid-state laser in combination with a simple single-cylindrical-lens converter. The negligible beam astigmatism, the broad optical spectra, and the almost chirp-free pulses emphasize the high reliability of this laser source. This work, as a proof of principle study, paves the way toward few-cycle pulse generation of optical vortices at 2 μm. The presented light source can enable new research in the fields of interaction with organic materials, next generation optical detection, and optical vortex infrared supercontinuum.

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$. A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range.