A dual-wavelength synchronously mode-locked homogeneously broadened bulk laser operating at 1985.6 and 1989 nm is presented for the first time, to the best of our knowledge, which delivers a maximum output power of 166 mW and a repetition rate of 85 MHz. The pulse duration was measured to be 16.8 ps by assuming a sech2 pulse shape. The recorded autocorrelation trace showed frequency beating signals with an interval of 3.8 ps and a full width at half-maximum duration of 2 ps, corresponding to an ultrahigh beating frequency of about 0.26 THz, which agrees well with the frequency difference of the emitted two spectral peaks. The results indicated that such a kind of dual-wavelength mode-locked Tm:YAlO₃ laser could be potentially used for generating terahertz radiations.

With tin diselenide (SnSe₂) film as a saturable absorber (SA), the passively Q-switched self-frequency doubling (SFD) lasers were realized in Nd³⁺:ReCa₄O(BO₃)₃ (Re = Y, Gd) crystals. For Nd:YCa₄O(BO₃)₃ crystal, the maximum average output power at 532 nm was 19.6 mW, and the corresponding pulse repetition frequency, pulse duration, single pulse energy, and peak power were 17.6 kHz, 91.9 ns, 1.1 μJ, and 12.1 W, respectively. For Nd:GdCa₄O(BO₃)₃ crystal, these values were 14.5 mW, 22.1 kHz, 48.7 ns, 0.66 μJ, and 13.5 W.

Space debris laser ranging was achieved with a 60 W, 200 Hz, 532 nm nanosecond slab, single-frequency green laser at the Shanghai Astronomical Observatory’s 60 cm satellite laser ranging system. There were 174 passes of space debris measured in 2017, with the minimum radar cross section (RCS) being 0.25 m² and the highest ranging precision up to 13.6 cm. The RCS of space debris measured with the farthest distances in 174 passes was analyzed. The results show that the farthest measurement distance (R) and RCS (S) were fitted to R = 1388.159S^0.24312, indicating that this laser can measure the distance of 1388.159 km at an RCS of 1 m², which is very helpful to surveillance and research on low-Earth-orbit space debris.

The excitation of high-order Laguerre–Gaussian (LG) modes in a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser resonator was presented by applying the diffraction of a second-order circular Dammann grating (CDG) for annular pumping. In the study, the 808 nm pump light was shaped into a double-ring structure by the CDG and matched spatially with that of an ideal LG₁₁ mode. As a result, the laser resonator generated an LG₁₁ vortex mode, and the laser power reached 204 mW with 14.5% slope efficiency. Also, when the cavity mirror was tilted, the laser output could switch to the LG₀₁ vortex mode. The results showed the convenience and versatility of CDG in an annular-pumped vortex laser.

A single output Q-switched Nd:GdVO₄ laser with a reflective graphene oxide (GO) saturable absorber was demonstrated. The shortest pulse duration in the Q-switched laser is 115 ns, and the output power ranges from 1.23 W at 1.71 MHz to 2.11 W at 2.50 MHz when the pump power rises from 7.40 to 10.90 W with the utilization of GO Langmuir–Blodgett (LB) films based on the convenient and low-cost LB technique. To the best of our knowledge, it is the highest output power in a Q-switched laser with a GO saturable absorber.

This study investigates the applicability of a few-layer structure ReSe₂ as a saturable absorber (SA) for demonstrating a passively Q-switched pulse laser. The ReSe₂ SA had a modulation depth of 6.86%. The Q-switched experiment was successful in delivering a maximum average output power of 180 mW at the wavelength of 1906.5 nm. The optimal pulse train had a pulse width of 1.61 μs and a repetition rate of 28.78 kHz. The experiment results verify that the few-layer structure ReSe₂ could behave as an excellent SA at all-solid-state lasers, increasing the selection of SAs at near 2 μm lasers.

We demonstrate a high-efficiency and high-power quasi-three-level laser based on a trapezoidal composite slab architecture with a 270 μm-thick Yb-doping surface. The design of a surface-doped slab architecture, temperature effects, laser oscillator model, and laser oscillator experiments with a surface-doped slab as a laser host medium have been presented. By theoretical calculation, the temperature rise in the surface-doped slab is only one seventh of that in the bulk-doped slab at the same maximum pump power of 30 kW. Finally, in the laser oscillator experiments, an output energy of 21.6 J is obtained when the pump energy is 48 J with a repetition rate of 5 Hz and a pulse width of 1 ms. The optical-optical efficiency is 45%.

We report on diode-pumped Er:Y2O3 ceramic lasers at about 2.7 μm in the tunable continuous-wave, self-Q-switching and tungsten disulfide (WS2)-based passively Q-switching regimes. For stable self-Q-switched operation, the maximum output power reaches 106.6 mW under an absorbed power of 2.71 W. The shortest pulse width is measured to be about 1.39 μs at a repetition rate of 26.7 kHz at maximum output. Using a spin-coated WS2 as a saturable absorber, a passively Q-switched Er:Y2O3 ceramic laser is also realized with a maximum average output power of 233.5 mW (for the first time, to the best of our knowledge). The shortest pulse width decreases to 0.72 μs at a corresponding repetition rate of 29.4 kHz, which leads to a pulse energy of 7.92 μJ and a peak power of 11.0 W. By inserting an undoped YAG thin plate as a Fabry–Perot etalon, for the passive Q switching, wavelength tunings are also demonstrated at around 2710, 2717, 2727, and 2740 nm.

Bismuth nanosheets (Bi-NSs) were successfully prepared and employed as saturable absorbers to generate a diode-pumped dual-wavelength Er3+:SrF2 laser in the mid-infrared region. Q-switched pulses with a maximum output power of 0.226 W were obtained at an absorbed pump power of 1.97 W. A repetition rate of 56.20 kHz and a minimum pulse duration of 980 ns were achieved. To the best of our knowledge, we present the first application of Bi-NSs in a mid-infrared all-solid-state laser. The results prove that Bi-NSs may be applied as an optical modulator in mid-infrared photonic devices or as a mode-locker and Q-switcher.

We report a double Q-switched 946 nm laser with a magnesium-oxide-doped LiNbO3 (MgO:LN) electro-optic (EO) crystal and a monolayer molybdenum diselenide (MoSe2) saturable absorber (SA). A pulsed laser diode side-pumped long neodymium-doped yttrium aluminum garnet rod (φ3×65 mm) is used as the gain medium. Large pulse energy up to 3.15 mJ and peak power up to 346 kW are generated at the repetition rate of 550 Hz, corresponding to the beam quality factors of Mx2=3.849, My2=3.868. Monolayer MoSe2 nanosheets applied in the experiment would be a promising SA for a passive Q-switching operation.