Double-layer graphene epitaxially grown on silicon carbide was used to Q-switch a Tm:YAG laser. Stable Q-switched laser pulses at the central wavelength of 2.01 μm were obtained. The maximum average output power, pulse repetition rate, and single pulse energy were 38 mW, 27.9 kHz, and 1.74 μJ, respectively. Our results illustrate that graphene can be used as a saturable absorber at the 2 μm region.

Solid-state single-frequency lasers around 1.6 µm are ideal sources for coherent Doppler wind lidars (CDWLs). A CDWL system with 1645 nm sing-frequency, injection-seeded Er:YAG ceramic laser is demonstrated. The Er:YAG laser based on an “M-shaped” ring resonator operates at pulse repetition frequencies (PRFs) of 300–1000 Hz at room temperature. The maximum single-frequency output energy is 10.1 mJ with a pulse width of 179 ns at 300 Hz. The 1645 nm Er:YAG laser is first used in a long-range CDWL system, and a line of sight (LOS) wind velocity up to 25 km is detected with 90 m range resolution in 0.5 s observation. To verify the reliability of the measurement results, the relationship between detection range, pulse energy, and accumulated numbers is also demonstrated.

Femtosecond vortex beams are of great scientific and practical interest because of their unique phase properties in both the longitudinal and transverse modes, enabling multi-dimensional quantum control of light fields. Until now, generating femtosecond vortex beams for applications that simultaneously require ultrashort pulse duration, high power, high vortex order, and a low cost and compact laser source has been very challenging due to the limitations of available generation methods. Here, we present a compact apparatus that generates powerful high-order femtosecond vortex pulses via astigmatic mode conversion from a mode-locked Hermite-Gaussian Yb:KGW laser oscillator in a hybrid scheme using both the translation-based off-axis pumping and the angle-based non-collinear pumping techniques. This hybrid scheme enables the generation of femtosecond vortices with a continuously tunable vortex order from the 1st up to the 30th order, which is the highest order obtained from any femtosecond vortex laser source based on a mode-locked oscillator. The average powers and pulse durations of all resulting vortex pulses are several hundred milliwatts and <650 fs, respectively. In particular, 424-fs 11th-order vortex pulses have been achieved with an average power of 1.6 W, several times more powerful than state-of-the-art oscillator-based femtosecond vortex sources.

A myriad of existing and emerging applications could benefit from coherent and broadband mid-infrared (MIR) light. Yet, existing tabletop sources are often complex or sensitive to interferometric optical misalignment. Here we demonstrate a significantly simplified scheme of broadband MIR generation by cascading the intra-pulse difference-frequency generation process in a specific nonlinear crystal. This allows pulses generated directly from mode-locked lasers to be used without further nonlinear temporal compression. The system, together with the driving beam, can provide an ultra-broadband coherent radiation coverage ranging from 2 to 17 μm with femtosecond pulse durations. To the best of our knowledge, this is the first demonstration of cascaded DFG in the MIR range, which brings emerging time-domain spectroscopic techniques closer to real-world applications.

We present a mid-infrared (MIR) source based on intra-pulse difference-frequency generation under the random quasi-phase-matching condition. The scheme enables the use of non-birefringent materials whose crystal orientations are not perfectly and periodically poled, widening the choice of media for nonlinear frequency conversion. With a 2 μm driving source based on a Ho:YAG thin-disk laser, together with a polycrystalline ZnSe element, an octave-spanning MIR continuum (2.7-20 μm) was generated. At over 20 mW, the average power is comparable to regular phase-matching in birefringent crystals. A 1 μm laser system based on a Yb:YAG thin-disk laser was also tested as a driving source in this scheme. The new approach provides a simplified way for generating coherent MIR radiation with an ultrabroad bandwidth at reasonable efficiency.

Femtosecond light sources in the 3–5 μm region are highly sought after for numerous applications. While they can be generated by using nonlinear effects in optical fibers, the efficiencies and effectiveness of frequency conversion can be significantly enhanced by using ultrashort driving pulses. Here, we report on a few-cycle Cr:ZnS oscillator driving low-order soliton dynamics in soft-glass fibers. By selecting appropriate parameters, sub-two-cycle pulses or broad supercontinua spanning over 1.7 octaves from 1.6 to 5.1 μm can be generated at average power levels exceeding 300 mW. In the same setting, Raman-induced soliton self-frequency shifting has been exploited to generate sub-100-fs pulses continuously tunable from 2.3 to 3.85 μm with a conversion efficiency of $\sim 50\%$. These results demonstrate the vast potential of using Cr:ZnS or Cr:ZnSe lasers for powerful mid-infrared generation.