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A diode-pumped acousto-optically (AO) Q-switched 1066 laser with a novel Nd:Gd0.69Y0.3NbO4 crystal under 879 nm pumping was demonstrated for the first time. In CW operation, the maximum output power of 7.5 W was obtained with a slope efficiency of 37.6%. The different modulation repetition rates from 5 kHz to 30 kHz in the pulsed Nd:GdYNbO4 laser were investigated. At an absorbed pump power of 7.44 W and a repetition rate of 10 kHz, the pulse width and peak power were 17.8 ns and 6.75 kW, respectively. We also got the highest repetition rate 61.214 kHz of this new mixed crystal.

In this paper, we present the acousto-optical (AO) Q-switched performance of a holmium (Ho):gadolinium tantalate (GdTaO4) (Ho:GTO) laser pumped by a thulium (Tm)-fiber laser emitting at 1.94 µm. In the efficient continuous wave (CW) regime, a maximum output power of 30.5 W at 2068.8 nm was achieved, corresponding to a slope efficiency of 74.9% with respect to the absorbed pump power. In the Q-switching regime, pulse energies of 2.4 mJ, 1.2 mJ, and 0.9 mJ were obtained with pulse repetition frequencies of 10 kHz, 20 kHz, and 30 kHz, respectively. The minimum pulse widths were 18 ns, 23 ns, and 26 ns, corresponding to peak powers of approximately 133.3 kW, 52.2 kW, and 34.6 kW, respectively.

We demonstrate for the first time a Cr4+:YAG passively Q-switched 1066 nm pulse-burst laser under 879 nm direct pump with a novel Nd:Gd0.69Y0.3NbO4 crystal. The output laser characteristics with different pump repetition rates and different Cr4+:YAG initial transmission are studied. Without the Cr4+:YAG, we obtain a maximum output energy of 2.55 mJ at an absorbed pump energy of 5.79 mJ with the highest 48% slope efficiency. The pulse-burst laser contains a maximum of 7 pulses for a Cr4+:YAG initial transmission of 55% and a pump repetition rate of 1 kHz. The single-pulse energy and narrowest pulse width reach 160 μJ and 5.5 ns at 38.2 kHz, with a peak power of 32 kW.

A diode-pumped 1347 nm laser with a novel Nd:GdNbO4 crystal is demonstrated for the first time to our best knowledge. Laser performance around 1.3 μm under 879 nm laser diode pumping is investigated with different output mirrors, pump radii and repetition rates. A maximum average power of ∼ 373 mW at 1347 nm is achieved at 50 Hz, corresponding to an optical-to-optical efficiency of 5.5% and a slope efficiency of 6.8%.

Saturable absorber (SA) based on antimony telluride (Sb2Te3)-graphene oxide (GO) had been fabricated. We demonstrated a compact passively Q-switched Nd:GGG laser with the mixed Sb2Te3-GO SA. Stable Q-switching operation at a central wavelength of 1066 nm was performed. The shortest single pulse width of 237 ns with repetition rate of 72 kHz and the maximum output power for Q-switched operation of 408 mW was achieved under the pump power of 4.5 W, corresponding to the optical-to-optical conversion of 9.1%.

Nd:GdNbO4 crystal was grown successfully by the Czochralski (CZ) method. The continuous wave (CW) laser operation of Nd:GdNbO4 crystal at 1066 nm was reported for the first time. A maximum output power of 1.076 W with the incident power of 3.28 W was successfully obtained, corresponding to an optical-to-optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The absorption and fluorescence spectra of the crystal were measured at room temperature. By using the Judd-Ofelt approach, the intensity parameters were calculated to be 6.13 × 10−20, 1.56 × 10−20, and 2.81 × 10−20 cm2, respectively. The large absorption cross section (9.5 × 10−20 cm2) and broad absorption band (5 nm) at around 808 nm indicates that Nd:GdNbO4 crystal can be pumped efficiently by laser diodes (LD). The small emission cross section (9.3 × 10−20 cm2) and relatively long fluorescence lifetime (178 μs) of Nd3+ demonstrate good energy capacity of Nd:GdNbO4. All the results show that Nd:GdNbO4 crystal is a promising novel laser crystal suitable for LD pumping.

In this work, harmonic mode locking in a laser diode pumped passively Q-switched mode-locked Nd:GdTaO4 1066 nm laser is presented by using Cr4+:YAG as saturable absorber. The average output power of the passively Q-switched mode-locked 1066 nm laser reaches 4.7 W with a repetition rate of 200.0 MHz and a pulse width of ~1.3 ns within a Q-switched envelope of 150.0 ns. By changing the Z-type cavity length, high-order harmonic mode locking operation of the passively Q-switched 1066 nm laser is conducted. The 3rd-order harmonically mode-locked 1066 nm laser yields a maximum average output power of 3.2 W and a pulse width of ~570 ps at 164.5 MHz repetition rate inside a Q-switched envelope of 419.7 ns long. The pulse repetition rate reaches 655.3 MHz in the 9th-order harmonically mode-locked 1066 nm laser.

This study investigated the laser performance of a Nd:GdYTaO4 crystal in continuous-wave and acousto-optically Q-switched operation. Laser performance comparison was conducted under 808 nm and 879 nm laser diode (LD) pumping. In continuous-wave operation, the maximum power at 1066 nm reached 4.4 W with an optical-to-optical efficiency of ~33.6% and the slope efficiency was ~35.9% under 808 nm laser diode pumping. In comparison, an output power of 7.7 W with an optical-to-optical efficiency of ~47.8% and a slope efficiency of ~48.3% were achieved in 879 nm LD pumped 1066 nm laser. Under 808 nm LD pumping, the Nd:GdYTaO4 crystal yielded an average output power of 1.1 W and a pulse width of 59.5 ns at the repetition rate of 30 kHz. By using direct pumping directly into the 4F3/2 emitting level, the average power was increased to 1.9 W and the pulse width was shortened to 33.0 ns at the repetition rate of 30 kHz.

This study investigated the laser performance of a Nd:GdTaO4 crystal for the 4F3/2→4I9/2 and 4F3/2→4I13/2 transitions at 928 nm and 1328 nm, respectively. A 5-mm-thick, 1.4 at.% Nd:GdTaO4 crystal was used in the experiments, under a pump at 879 nm, directly into the 4F3/2 emitting level. At a 10 Hz pump repetition rate, the maximum pulse energy at 928 nm reached 35.7 mJ, with an optical-to-optical efficiency of ~19.3%. When the pump repetition rate increased to 100 Hz, the laser pulse energy decreased to 13.5 mJ; the laser beam was characterised by M2 factors of Mx2 = 1.4 and My2 = 1.8 for the Ox and Oy axis, respectively. The Nd:GdTaO4 crystal yielded laser pulses at 1328 nm with a maximum energy of 9.7 mJ for operation at 10 Hz repetition rate; the overall optical-to-optical efficiency amounted to ~5.2%. Increasing the pump repetition rate to 100 Hz reduced the laser pulse energy to 5.8 mJ; the laser beam M2 factors were Mx2 = 1.2 and My2 = 1.4.

927.8nm laser operating on the 4F3/2 to 4I9/2 transition is investigated with a Nd:Gd0.3Ta0.69O4 crystal. The average power reaches 1.35 W under 879 nm pumping with beam quality factors of M x2 = 1.4 and My2=1.8.

In this paper, self-Q-switched (SQS) and passively Q-switched mode-locked (QML) dual-wavelength Nd:YSAG lasers are reported, that works at 1058.97 and 1061.49 nm, simultaneously. Till now, the performance on SQS, and passively QML operation by using black phosphorus (BP) in Nd:YSAG crystal lasers have not been reported as per the author’s knowledge. The Nd:YSAG laser SQS operation was realized by designing a simple plano-plano resonator cavity. The maximum output power of 0.471 W at absorbed pump power 2.64 W and the pulse duration was 885 ns. The Nd:YSAG laser QML operation was realized by designing a Z-type resonator cavity. The duration of mode-locked pulse inside the Q-switched envelop was estimated to be 235 ps with 96.5 MHz repetition rate at the absorbed pump power of 4.08 W in QML with black phosphorus saturable absorber (BP-SA).

A new laser medium Nd3+:GdTaO4 single crystal with high optical quality was grown successfully by the Czochralski method, and its high-efficiency laser operation at 1,066 nm was demonstrated for the first time. The absorption cross section of the crystal at 808 nm is 5.098 × 10−20 cm2, and the full width at half maximum of this absorption band is about 6 nm. Spectral properties are investigated by Judd–Ofelt theory. The stimulated emission cross section at 1,066 nm is 3.9 × 10−19 cm2, and the fluorescence lifetime of 4F3/2 level is 178.4 μs. A diode end-pumped Nd:GdTaO4 laser at 1,066 nm with the maximum output power of 2.5 W is achieved in the continuous-wave mode. The optical-to-optical conversion efficiency and slope efficiency are 34.6 and 36 %, respectively. In addition, the fluorescence branching ratio of 4F3/2 → 4I9/2 transition reaches 44.4 %, indicating that Nd:GdTaO4 may be an efficient laser medium at 920 nm. All the results demonstrate that Nd:GdTaO4 crystal is a good candidate for laser diode-pumped laser material.

Rare-earth tantalates, with high density and monoclinic structure, and niobates with monoclinic structure have been paid great attention as potential optical materials. In the last decade, we focused on the crystal growth technology of rare-earth tantalates and niobates and studied their luminescence and physical properties. A series of rare-earth tantalates and niobates crystals have been grown by the Czochralski method successfully. In this work, we summarize the research results on the crystal growth, scintillation, and laser properties of them, including the absorption and emission spectra, spectral parameters, energy levels structure, and so on. Most of the tantalates and niobates exhibit excellent luminescent properties, rich physical properties, and good chemical stability, indicating that they are potential outstanding scintillators and laser materials.

Based on Faraday effect we demonstrate a thulium fiber pumped continuous-wave single-longitudinal-mode laser with a new Ho:GdTaO4 crystal. By inserting a faraday rotator and a half-wave plate into the laser cavity, the single-longitudinal-mode output power of 392 mW at wavelength of 2068.33 nm was obtained in unidirectional Ho:GdTaO4 ring laser, corresponding to a slope efficiency of 60.2% respect to the absorbed pump power. Furthermore, utilizing the Ho:GdTaO4 power amplifier, the maximum single-longitudinal- mode output power of 1.02 W was achieved.

We report an 879 nm laser diode directly pumped passively Q-switched Nd:GdTaO4 laser at 1066 nm. The continuous-wave output power at 1066 nm reaches 5.6 W under an incident pump power of 12.8 W, corresponding to an optical-to-optical efficiency of 43.8% and a slope efficiency of 48.0%. By using Cr4+:YAG as the saturable absorber, passively Q-switched laser operation is conducted, yielding a highest pulse repetition frequency of 185 kHz and a maximum average power of 3.6 W. The shortest pulse width of 15.2 ns is achieved with a peak power of 2.34 kW at 33.7 kHz. The beam quality factors at the maximum average output power is measured to be Mx2 = 2.2, My2 = 1.5 by using knife-edge method. The thermal focal length and internal loss for Nd:GdTaO4 crystal is also investigated.

We demonstrate a continuous-wave 2.1-µm laser with a new Ho:GdTaO4 crystal pumped by a 1940.3-nm Tm fiber laser at room temperature. The maximum output power of 11.2 W at 2068.39 nm was achieved, corresponding to a slope efficiency of 72.9%. Moreover, the beam quality factor was measured to be about 1.4 at the maximum output level.

A promising 2.911 μm Yb,Ho:GdYTaO4 laser crystal was grown successfully by the Czochralski method for the first time. The crystal belongs to the monoclinic space group of I2/a (no. 15) and high crystalline quality is demonstrated by X-ray rocking curves. The effective segregation coefficient keff of Yb, Ho, and Y are 1.08, 0.96, and 0.9, respectively, all close to 1. Crystal density is measured to be 8.59 g cm−3 by the buoyancy method. Thermal property indicates that the Yb,Ho,Y:GdTaO4 crystal should be pumped along the c-axis in order to reduce the thermal lensing effect. Strong absorption in the range of 900–1000 nm and emission at 2911 nm are obtained in the as-grown crystal. In comparison with corresponding level lifetimes of Yb,Ho:YSGG, Tm,Ho:LuAG, Tm,Ho:YAG, and Ho:YAG, the Yb,Ho,Y:GdTaO4 crystal exhibits a relatively shorter lifetime of 7.298 ms for lower laser level 5I7 and longer lifetime of 419 μs for upper laser level 5I6, which are beneficial to realize population inversion and laser output.

We demonstrate a 968 nm diode end-pumped Er:GYSGG (Gd1.17Y1.83Sc2Ga3O12) laser at 2.796 μm operated in the pulse and continuous-wave (CW) modes. A maximum laser energy of 2.43 mJ is obtained at a pulse width of 2 ms, corresponding to a peak power of 1.25 W and a slope efficiency of 7.2%. In the CW mode, the maximum output power is 348 mW, corresponding to an optical–optical conversion efficiency of 9.2% and a slope efficiency of 10.1%. The M2 factor is 1.94, and the beam divergence is 6.4 mrad. Gamma irradiation at 100 Mrad only slightly affects laser output performance. This result suggests that Er:GYSGG crystal is a potentially new mid-infrared radiation-resistant laser material that can be applied in space and ionizing radiation environment.

The continuous-wave (CW) and passively Q-switched 1066 nm laser performances with a novel Nd:Gd 0.69 Y 0.3 TaO 4 mixed crystal was demonstrated. The attained maximum peak power was 1.34 kW with the pulse repetition frequency of 74 kHz.

A mixed laser crystal of Nd-doped GYNO crystal was grown successfully by Czochralski method. The crystal belongs to monoclinic system with space group I2/a, the structural parameters are obtained by the X-ray Rietveld refinement method. The defects and dislocations along three crystallographic orientations were studied by using the chemical etching method with the phosphoric acid etchant. The mechanical properties (including hardness, yield strength, fracture toughness, and brittle index) of the crystal were estimated by Vickers hardness test. The transmission spectrum was measured at room temperature, and the absorption peaks were assigned. Spectral properties of the as-grown crystal were investigated by Judd–Ofelt theory, and the Judd–Ofelt intense parameters Ω2,4,6 were obtained to be 9.674 × 10−20, 2.092 × 10−20, and 4.061 × 10−20 cm2, respectively.

A dual-wavelength passively Q-switched Nd:GYSGG laser using vacuum evaporating tungsten disulfide (WS2) as a saturable absorber was demonstrated for the first time to the best of our knowledge. The WS2 saturable absorber was prepared simply by evaporating nanometer WS2 powders onto a quartz substrate in a vacuum. By inserting the WS2 saturable absorber into the laser cavity, stable Q-switched laser operation was achieved with a maximum average output power of 367 mW, a pulse repetition rate of 70.7 kHz, the shortest pulse width of 591 ns, and pulse energy of about 1.05 μJ. By vacuum evaporation method, a high-quality WS2 saturable absorber can be produced, and it seems to be a suitable method for fabrication of 2D transition metal dichalcogenides.

We report an 879 nm laser diode (LD) end-pumped quasi-three-level 927 nm laser with a Nd:GdYNbO4 mixed crystal for the first time to the best of our knowledge. Comparing the 927 nm laser's performance under 808 nm and 879 nm LD pumping, we find performance enhancement is achieved by using direct 879 nm LD pumping. A maximum output energy of 42 mJ at 10 Hz is obtained in the 879 nm LD pumped 927 nm laser with an optical-to-optical efficiency of 24% and a beam quality factor of M 2 = 1.7. The dependence of output characteristics on the pumping repetition rate is discussed. The average output power at 927 nm reaches 1.13 W at 100 Hz with an optical-to-optical efficiency of 6.5%.

We demonstrated an 879-nm-diode-pumped Nd:Gd0.69Y0.3TaO4 laser in continuous-wave-(CW), pulse-pumped, pulse-reflection-mode Q-switched, and cavity-dumped burst-mode Q-switched operations for the first time. A maximum output power of 9.3 W at 1,066 nm was obtained in the CW operation with a slope efficiency of ~48%. The slope efficiency reached the value of ~68% in the pulse-pumped operation. A peak power of 150 kW and pulse width of 3.4 ns were obtained in the cavity-dumped burst-mode Q-switched operation at a Q-switching repetition rate of 20 kHz.

Laser performances around 1.3 μm are investigated in 879 nm laser diode (LD) end pumped Nd3+ doped mixed crystals with Nd:Gd0.69Y0.3TaO4 and Nd:Gd0.68Y0.3NbO4 crystals for the first time to our best knowledge. The maximum average power in LD end pumped Nd:Gd0.69Y0.3TaO4 1328 nm laser reaches 435 mW at 50 Hz with an optical-to-optical efficiency of 5.0% and a slope efficiency of 6.9%. In comparison, the highest average power of LD end pumped Nd:Gd0.68Y0.3NbO4 laser at 1337 nm is 190 mW at 50 Hz, corresponding to an optical-to-optical efficiency of 3.5% and a slope efficiency of 4.2%.

Dual-wavelength continuous-wave and Q-switched lasers are demonstrated in a Tm,Ho:GdYTaO4 crystal under 790 nm laser diode end pumping for the first time to the best of our knowledge. The laser operates with a dual wavelength at 1949.677 nm and 2070 nm for continuous-wave with a spacing of about 120 nm. The maximum output power is 0.332 W with a pump power of 3 W. By using graphene as the saturable absorber, a passively Q-switched operation is performed with a dual-wavelength at 1950.323 nm and 2068.064 nm with a wavelength interval of about 118 nm. The maximum average output power of the Q-switched laser goes up to 200 mW with a minimum pulse duration of 1.2 µs and a maximum repetition rate of 34.72 kHz.

A new laser crystal Nd:Gd0.69Y0.3TaO4 (Nd:GYTO) with high quality was grown by Czochralski method. The physical properties, including temperature dependent density, specific heat, thermal expansion coefficient, and thermal conductivity, were systematically characterized. The maximum absorption cross section at 809 nm and the stimulated emission cross section at 1066.6 nm are 6.886 × 10−20 cm2 and 22 × 10−20 cm2, respectively. The fluorescence lifetime is measured to be 182.4 μs. Up to 2.37 W of continuous wave (CW) laser operating at 1066.5 nm has been successfully realized, corresponding to an optical conversion efficiency of 36.5% and a slope efficiency of 38%. Compared with Nd:GdTaO4, Nd:GYTO shows an enhancement of the laser performance. These results demonstrate that Nd:Gd0.69Y0.3TaO4 is a novel laser crystal with low symmetry and has great potential as low to moderate power lasers.

We demonstrate a 968 nm diode end-pumped Er,Pr:GYSGG (Gd₁.₁₇Y₁.₈₃Sc₂Ga₃O₁₂) laser at 2.79 μm operated in the pulse and continuous-wave (CW) modes. The lifetimes for the upper laser level ⁴I₁₁/ ₂ and lower level ⁴I₁₃/₂ are 0.52 and 0.60 ms, respectively. The laser produces 284 mW of power in the CW mode, corresponding to the optical-to-optical efficiency of 14.8% and slope efficiency of 17.4%. The maximum laser energy achieved is 2.4 mJ at a repetition rate of 50 Hz and pulse duration of 0.5 ms, corresponding to a peak power of 4.8 W and slope efficiency of 18.3%. These results suggest that doping deactivator Pr3+ ions can effectively decrease the lower-level lifetime and improve the laser efficiency.