Continuous wave and ReS2 passively Q-switched Er : SrF2 laser at ∼3 μm

28.02 W LD side-pumped CW laser operated at 2.8 µm in YSGG/Er:YSGG/YSGG crystal

We demonstrated a 978 nm laser diode (LD) side-pumped YSGG/Er:YSGG/YSGG composite crystal with a size of Ф 3 mm × 65 mm and continuous-wave (CW) mode. By optimizing resonator length and output mirror transmittance, a maximum output power of 28.02 W is generated, corresponding to slope efficiency of 17.55% and optical-optical efficiency of 12.29%, respectively. The thermal focal lengths are obtained by resonator stability condition. The laser wavelength is centered near 2.8 µm. Moreover, the beam quality factors M x2/M y2 are fitted to be 8.14 and 7.35, respectively. The above results indicate that a high-performance 2.8 µm CW laser can be achieved by LD side-pumped YSGG/Er:YSGG/YSGG composite crystal with excellent heat dissipation ability, which promotes effectively the development and applications of the mid-infrared solid-state lasers.

SnS2 as a Saturable Absorber for Mid-Infrared Q-Switched Er:SrF2 Laser

Two-dimensional (2D) materials own unique band structures and excellent optoelectronic properties and have attracted wide attention in photonics. Tin disulfide (SnS₂), a member of group IV-VI transition metal dichalcogenides (TMDs), possesses good environmental optimization, oxidation resistance, and thermal stability, making it more competitive in application. By using the intensity-dependent transmission experiment, the saturable absorption properties of the SnS₂ nanosheet nearly at 3 μm waveband were characterized by a high modulation depth of 32.26%. Therefore, a few-layer SnS₂ was used as a saturable absorber (SA) for a bulk Er:SrF₂ laser to research its optical properties. When the average output power was 140 mW, the passively Q-switched laser achieved the shortest pulse width at 480 ns, the optimal single pulse energy at 3.78 µJ, and the highest peak power at 7.88 W. The results of the passively Q-switched laser revealed that few-layer SnS₂ had an admirable non-linear optical response at near 3 μm mid-infrared solid-state laser.

Efficient continuous wave and passively Q switched Er:GdScO3 laser using Fe:ZnSe at 2.8 µm

We report on diode-pumped continuous wave and passively Q switched Er:GdScO₃ crystal lasers at around 2.8 µm. A continuous wave output power of 579 mW was obtained with a slope efficiency of 16.6%. Using Fe:ZnSe as a saturable absorber, a passively Q switched laser operation was realized. A maximum output power of 32 mW was generated with the shortest pulse duration of 286 ns at a repetition rate of 157.3 kHz, leading to a pulse energy of 204 nJ and a pulse peak power of 0.7 W.

Self-Q-switched Er:Lu2O3 laser at 2.74 µm

A diode-pumped self-Q-switched 2.74 µm Er:Lu₂O₃ crystal solid-state laser has been experimentally and theoretically studied. Without any additional modulation elements, stable self-Q-switched pulses with a pulse width of 145.3 ns, a repetition rate of 227.8 kHz, and an average output power of 877 mW were generated. Considering the excited-state absorption on the laser photons of the Er:Lu₂O₃ crystal, we have simulated the dynamic process of self-pulsed generation by solving the rate equations numerically. The simulation results are consistent with the typical characteristics of a Q-switched laser.

A Review on Rhenium Disulfide: Synthesis Approaches, Optical Properties, and Applications in Pulsed Lasers

Rhenium Disulfide (ReS₂) has evolved as a novel 2D transition-metal dichalcogenide (TMD) material which has promising applications in optoelectronics and photonics because of its distinctive anisotropic optical properties. Saturable absorption property of ReS₂ has been utilized to fabricate saturable absorber (SA) devices to generate short pulses in lasers systems. The results were outstanding, including high-repetition-rate pulses, large modulation depth, multi-wavelength pulses, broadband operation and low saturation intensity. In this review, we emphasize on formulating SAs based on ReS₂ to produce pulsed lasers in the visible, near-infrared and mid-infrared wavelength regions with pulse durations down to femtosecond using mode-locking or Q-switching technique. We outline ReS₂ synthesis techniques and integration platforms concerning solid-state and fiber-type lasers. We discuss the laser performance based on SAs attributes. Lastly, we draw conclusions and discuss challenges and future directions that will help to advance the domain of ultrafast photonic technology.

Mid-IR Optical Property of Dy:CaF2-SrF2 Crystal Fabricated by Multicrucible Temperature Gradient Technology

Dy3+-doped CaF2-SrF2 crystals with various Dy3+ dopant concentrations were synthesized by multicrucible temperature gradient technology (MC-TGT). Dy:CaF2-SrF2 crystals were fluorite structured and crystallized in cubic Fm3¯m space group, as characterized by X-ray diffraction. The crystallographic site concentration was calculated from the measured density by Archimedes’ hydrostatic weighing principle. The optical transmission reached over 90% with a sample thickness of 1.0 mm. The Sellmeier dispersion formula was obtained following the measured refractive index in a mid-IR range of 1.7–11 μm. Absorption coefficients of 6.06 cm−1 and 12.71 cm−1 were obtained at 804 nm and 1094 nm in 15% Dy:CaF2-SrF2 crystal. The fluorescence spectra of 15 at.% Dy:CaF2-SrF2 showed the strongest wavelength peak at 2919 nm with a full width at half maximum (FWHM) of 267 nm under an excitation wavelength of 808 nm. The fluorescence lifetimes were illustrated for different Dy3+ dopant levels of 5%, 10% and 15%. The results indicate that the Dy:CaF2-SrF2 crystal is a promising candidate for compact mid-IR lasers.

Spectroscopic and laser properties of Er:LuSGG crystal for high-power ∼2.8 µm mid-infrared laser

We demonstrate a novel Er:LuSGG active gain medium emitting laser wavelength at 2795 nm for the first time. The Er:LuSGG crystal is grown successfully by the Czochralski method with high crystalline and optical quality. The spectra properties, including absorption and fluorescence emission cross-section are presented in contrast with similar Er-doped garnet crystals. The fluorescence lifetimes of the upper (4I11/2) and lower (4I13/2) laser levels are 1.75 and 4.64 ms, respectively. Under 973 nm laser diode pumping, a maximum output power of 789 mW in continuous-wave mode, corresponding to optical-to-optical efficiency of 20.2% and slope efficiency of 24.4%, is achieved with high laser beam quality. The results show that the Er:LuSGG is a promising MIR laser material operated at 2.8 µm.

Heterostructure ReS2/GaAs Saturable Absorber Passively Q-Switched Nd:YVO4 Laser

Heterostructure ReS₂/GaAs was fabricated on a 110-μm (111) GaAs wafer by chemical vapor deposition method. Passively Q-switched Nd:YVO₄ laser was demonstrated by employing heterostructure ReS₂/GaAs as a saturable absorber (SA). The shortest pulse width of 51.3 ns with a repetition rate of 452 kHz was obtained, corresponding to the pulse energy of 465 nJ and the peak power of 9.1 W. In comparison with the ReS₂ Q-switched laser and the GaAs Q-switched laser, the heterostructer ReS₂/GaAs Q-switched laser can generate shorter pulse duration and higher pulse energy.