Fig. 1. Schematic diagram of the generation of a high-energy Hermite–Gaussian laser. LD, laser diode; CL, collimating lens; FL, focusing lens; IC, input coupler; OC, output coupler. Inset: defect stripes at the OC and crystal structure of HfTe₂.

Fig. 2. (a) Light transmittance of HfTe₂ in the wavelength range of 350–1100 nm. Inset: energy band structure and density of states of HfTe₂. (b) Saturation absorption and reverse saturation absorption results of HfTe₂ based on an open aperture Z-scan. Inset: the principle of saturation absorption and reverse saturation absorption process. (c) Surface microstructure of HfTe₂ by SEM. (d) Thickness of single-layer HfTe₂ nanosheets by AFM. Inset: the AFM height image in the area of 30 μm × 30 μm. (e) Raman spectrum of HfTe₂. Inset: EDS element analysis. (f) XRD pattern of HfTe₂.

Fig. 3. (a) The far-field intensity distribution of Hermite–Gaussian lasers of different orders and the vortex laser. (b) The corresponding defect areas on the output coupling mirror.

Fig. 4. (a) Output characteristics of high-energy HG₁₀, HG₂₀ laser and vortex laser. Transition state pulse of the HG₁₀ laser at (b) 10 μs; (c) 5 ms; (d) 200 μs scales.

Fig. 5. (a) Spectrum. (b) Repetition rate. (c) Pulse width. (d) Pulse energy. (e) Peak power of the HG₁₀ mode versus absorbed pump power at the low-repetition-rate state. (f) Typical Q-switched pulse train and (g) temporal pulse shape of the HG₁₀ mode at maximum average output power.

Fig. 6. (a) Repetition rate. (b) Pulse energy. (c) Pulse width. (d) Peak power of HG₂₀ and vortex mode laser versus absorbed pump power.

Fig. 7. (a) Schematic diagram of wavelength-tunable Q-switched vortex laser based on an etalon. (b) Fluorescence spectrum of alexandrite excited by a 638 nm pump laser. (c) Laser spectra and relative intensities at different wavelengths within the alexandrite wavelength tuning range. (d) Repetition rate and pulse width. (e) Pulse energy and peak power of passively Q-switched vortex laser versus wavelength.

Fig. 8. (a) Typical intensity profile of the high-energy vortex pulse laser. (b) Mach–Zehnder interferometer for characterizing the topological charge of the optical vortex. (c) Beam profile interference patterns for the vortex laser. (d) Experimentally measured transverse intensity profile and its theoretical fit.