Er^3+,Yb^3+:glass-Co^2+:MgAl2O4 diffusion bonded passively Q-switched laser

A Co^2＋：spinel passively Q-switched erbium-ytterbium-phosphate glass bonded laser pumped at 940 nm is reported.A pulse energy of 210 μJ, a peak power over 70 kW, and beam quality M-2 parameter of 1.2 are obtained under a pump power of 235 mW. An unbonded laser output experiment with the same dimension of the active material and the saturable absorber as the bonded laser output experiment is carried out. The reason why the output in the bonded laser is improved is determined.

Modelling of passively Q-switched lasers with intracavity Raman conversion

We present a model of passively Q-switched Raman lasers by utilizing the rate equations. The intracavity fun-damental photon density, Raman photon density and the initial population-inversion density of the gain medium are assumed to be of Gaussian spatial distributions. These rate equations are normalized by introducing some synthetic parameters and solved numerically, and a group of general curves are generated. Prom these curves we can understand the dependence of the Raman laser pulse characteristics on the parameters about the pumping, the gain medium, the Raman medium and the resonator. An illustrative calculation for a passively Q-switched Nd^3＋：GdVO4 self-Raman laser is presented to demonstrate the usage of the curves and related formulas.

High stability and low noise laser-diode end-pumped Nd:YAG ceramic passively Q-switched laser at 1123 nm based on a Ti_(3)C_(2)T_(x)-PVA saturable absorber

We report a high repetition frequency, high power stability and low laser noise laser-diode(LD) end-pumped Nd: YAG ceramic passively Q-switched laser at 1123 nm based on a Ti_(3)C_(2)T_(x)-polyvinyl alcohol(PVA) film as a saturable absorber(SA). A Brewster polarizer(BP) and a birefringent crystal(BC) are incorporated to enable frequency selection and filtering for the passively Q-switched 1123 nm pulsed laser to improve the power stability and reduce the noise. When the pump power is 5.1 W, an average output power of 457.9 m W is obtained, corresponding to a repetition frequency of 1.09 MHz,a pulse width of 56 ns, a spectral line width of 0.65 nm, a power instability of ±0.92%, and a laser noise of 0.89%.The successful implementation of the “Ti_(3)C_(2)T_(x)-PVA film passively Q-switching” combined with “frequency selection and filtering of BP + BC” technology path provides a valuable reference for developing pulsed laser with high repetition frequency, high stability and low noise.

High repetition rate passively Q-switched laser on Nd:SRA at 1049 nm with MXene Ti3C2Tx

A new disordered crystal Nd:SrAl12O19(Nd:SRA)with an Nd3+doping concentration of 5%was successfully grown using the Czochralski method.A diode-pumped Nd:SRA Q-switched laser operating at 1049 nm was demonstrated for the first time,to the best of our knowledge.Based on an MXene Ti3C2Tx sheet,a high repetition rate of 201 kHz and a Q-switched pulse width of 346 ns were obtained when the absorbed pump power was 2.8 W.The peak power and single pulse energy were 1.87 W and 0.65μJ,respectively.

Liquid metal as a broadband saturable absorber for passively Q-switched lasers

We demonstrated the efficient plasmon-induced nonlinear absorption of liquid metal GaInSn nanospheres prepared by a facile liquid-phase method. With GaInSn as saturable absorbers, a passively Q-switching operation was obtained at both 1.3 and 2 μm. The pulse width of 32 ns was achieved at 1.3 μm with repetition rate of44 kHz, single pulse energy of 51.9 μJ, and output power of 425 mW. Meanwhile, 510 ns and 92 kHz pulses with energy of 36.1 μJ and output power of 2.48 W were obtained at 2 μm. This work provides the potential of liquid metal for improving metal functions and flexible optical devices.

Passively Q-Switched Nd,Cr:YAG Laser Simultaneous Dual-Wavelength Operation at 946 nm and 1.3μm

A diode-end-pumped Q-switched high-efficiency Nd, Cr：YAG laser with simultaneous dual-wavelength emission at 946nm and 1.3μm is demonstrated. The maximum output power of 1.93 W with simultaneous dual-wavelength operation is achieved at an absorbed pump power of 13.32 W and an absorbed slope efficiency of 15.15%. The maximum optical-optical efficiency is 14.49% with pulse widths of 16.38ns at 946nm and 26.65ns at 1.3μm. A maximum total repetition rate of 43.25 kHz is obtained.

High-Power Passively Q-Switched Nd:YAG Laser at 1112 nm with a Cr^(4+):YAG Saturable Absorber

A high-power passively Q-switched Nd：YAG laser operating at lll2nm with Cr4＋：yAO as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at the pump power of 16.65 W, corresponding to an optical-to-optical conversion efficiency of 16.4%. At the same time, the pulse width, pulse repetition rate, single pulse energy and peak power are 27.2ns, 9 kHz, 303.3#3 and 11.2kW, respectively. As far as we know, the result gives the highest average output power at 1112nm generated by an 808 nm diode-end-pumped Nd：YAG laser.

1.5-MHz repetition rate passively Q-switched Nd:YVO4 laser based on WS2 saturable absorber

A transmission-type tungsten disulfide（WS_2）-based saturable absorber（SA） is fabricated and applied to passively Q-switched Nd：YVO_4 laser.The WS_2 nanosheets are deposited on a quartz substrate by the vertical evaporation method.By inserting the WS2 SA into the plano-concave laser cavity,we achieve 153-ns pulses with an average output power of1.19 W at 1064 nm.To the best of our knowledge,both of them are the best results among those obtained by the Q-switched solid-state lasers with WS_2-based absorbers.The repetition rate ranges from 1.176 MHz to 1.578 MHz.As far as we know,it is the first time that MHz level Q-switched pulses have been generated in all solid state lasers based on low-dimensional materials so far.

Passively Q-switched diode-pumped Tm,Ho:LuVO4 laser with a black phosphorus saturable absorber

We presented a passively Q-switched(PQS) diode-pumped c-cut Tm, Ho:LuVO_4 laser with a black phosphorus saturable absorber for the first time.Under PQS mode, an average output power of 0.86 W and a peak power of 2.32 W were acquired from the Tm, Ho:LuVO4 laser with the pump power of 14.55 W, corresponding to a pulse width of 2.89 μs,a pulse repetition rate of 71.84 kHz, and a pulse energy of about 6.70 μJ.

One-order-higher Cr4+ conversion efficiency in Cr4+:YAG transparent ceramics for a high-frequency passively Q-switched laser

The Cr4+-doped yttrium aluminum garnet(Cr4+:YAG) saturable absorber, a new generation of passively Q-switched solid-state laser material, faces a significant obstacle of low conversion rate of chromium from trivalent to tetravalent, degrading efficiency in a passively Q-switched laser. In this paper, highly transparent Cr4+:YAG ceramics were fabricated and committed to compare the laser performance with Cr4+:YAG crystals on a 1 μm passively Q-switched laser. Thanks to the grain boundary effect, the Cr4+conversion efficiency of 0.05 at.% Cr4+:YAG transparent ceramics coated with high transparency(HT) films(T = 86.46% at 1064 nm)was nine times higher than that of 0.1 at.% Cr4+:YAG single crystals coated with HT films(T = 84.00% at1064 nm). Differing from the counterpart Cr4+:YAG crystals, no absorption saturation tendency was observed for the 0.05 at.% Cr:YAG ceramics when the pump power exceeded ~1900 mW. Furthermore, the repetition frequency reached 217 kHz for 0.05 at.% Cr:YAG ceramics, which was a three-fold factor increase from that of the corresponding single crystal. The advantages of transparent ceramics over single crystals were proved through laser performance for the first time, to the best of our knowledge. This study also provided compelling evidence for replacing single crystals with ceramics for ultrafast dynamics.

Efficient Passively Q-Switched Nd:YAG/Cr4+:YAG/LBO Microchip Laser

Performance of an LD-end-pumped passively Q-switched Nd： YA G/Cr4＋ ： YA G microchip laser operating at 1123 nm is studied. A maximum average output power of 517row with an optical-to-optical conversion efficiency of 12.6% and a slope efficiency of 25.8% is obtained under a pump power of 4.1 W. A minimum pulse width of 1.1 ns with a pulse repetition rate of 20.2kHz is obtained, and the corresponding pulse energy and peak power are 25.6μJ and 23.3kW, respectively. To our knowledge, the 23.3kW peak power is the highest among 1123nm lasers. Additionally, based on the 1123 nm laser, with LBO as the frequency doubler, a 288-mW green-yellow laser at 561 nm is successfully achieved.

Passively Q-Switched Ho:SSO Laser by Use of a Cr2+:ZnSe Saturable Absorber

A cw operation and a passively Q-switched （PQS） Ho：SSO laser （Cr2＋ ：ZnSe as a saturable absorber） end-pumped by a TIn：YAP laser operating at near room temperature are reported. It is the first time to report a PQS Ho：SSO laser. For the ew mode, a maximum cw output power of 3.0 W is obtMned, corresponding to a slope efficiency of 31.4%. For the PQS mode, a Cr2＋ ：ZnSe is used as the saturable absorber, with transmission of 88.4% at 2112nm. A maximum pulse energy of 1.29mJ is obtained, corresponding to the pulse repetition frequency of 2.42kHz. In this study, we change the distance between Cr2＋ ：ZnSe and the output mirror to research the pulse characteristic of the PQ, S Ho：SSO laser. The minimum pulse width of 73.5ns is obtained, corresponding to the pulse energy of O. 9 mJ and the pulse repetition frequency of 2.65 kHz.

Passively Q-Switched Nd:YVO_4 Laser Using a Gold Nanotriangle Saturable Absorber

A passively Q-switched Nd：YVO4 laser at 1064 nm is demonstrated based on a gold nanotriangle saturable absorber（GNT SA）.Under a pump power of 3.82 W,the maximum average output power of 218mW is achieved,corresponding to a slope efficiency of 12.9%.The minimum pulse width is 165ns and the maximum pulse repetition rate is 300kHz at the pump power of 3.48 W.Our results prove that the GNT SA is a promising saturable absorber for near-infrared lasers.

A Single-Longitudinal-Mode Passively Q-Switched Nd:YVO4 Laser Using Black Phosphorus Saturable Absorber

A black phosphorus (BP) saturable absorber (SA) solution with different concentrations (1.0 and 0.5 mg/ml) is fabricated with the liquid-phase exfoliation method. By using the BP-SA, a compact diode-pumped passively Q-switched Nd:YVO4 laser is demonstrated. One reflecting Bragg gratings is used as the output coupler for mode selection. By inserting those BP-SA solutions in the laser cavity, the maximum single longitude mode, Q-switched output powers of 126mW at 692.5 kHz and 149mW at 630.3 kHz are achieved at the pump power of 8.0 W, corresponding to the pulse durations of 144 ns and 196 ns, respectively. Moreover, longitudinal-mode characteristics of Q-switched output laser in different optical cavity lengths based on two-kind BP-SA solution concentrations are investigated. Our results show that BP-SA could also be developed as an effective SA for the Q-switched, single longitudinal mode pulse laser.

Passively Q-Switched Yb-Doped Fiber Laser Operating at 1.06 μm with Two-Dimensional Silver Nanoplate as Saturable Absorber

A two-dimensional silver nanoplate is prepared with the seed-mediated growth method and is used for achieving pulse fiber laser operation. By controlling the dimension parameters of the silver nanoplate, the surface plasmon resonance absorption peak of the material is successfully adjusted to 1068 nm. Based on the silver nanoplate as a saturable absorber, a passively Q-switched Yb-doped fiber laser operating at 1062 nm is demonstrated. The maximum average output power of 3.49mW is obtained with a minimum pulse width of 1.84#s at a pulse repetition rate of 65.TkHz, and the corresponding pulse energy and peak power are 53.1 nJ and 28.8mW, respectively.

Cr2+:ZnS Saturable Absorber Passively Q-Switched Ho:LuVO4 Laser

We report a cw Tm：YAP laser resonantly pumped Ho：LuV04 laser in passively Q-switched （PQS） mode with Cr2＋ ：ZnS as a saturable absorber （SA）. The influence of different transmittances of the output coupler on laser output performance is analyzed. With T = 50%, the max/mum PQS average output power of 2.3 W is ob- tained, corresponding to the slope efficiency and the optical-optical conversion efficiency are 35.1% and 19.8%, respectively. Also, the minimum pulse width of 100ns is achieved at the maximum pulse repetition frequency of 34.2kHz. When the maximum cw output power is 2.7W, the beam quality factor of the horizontal direc- tion Mx2 = 1.04 and the vertical direction M2 = 1.10 are obtained. In addition, the central wavelength of the laser output remains to be 2057.5nm with the output coupler transmittances of 50% and 60% in both cw and PQS operations. The results show that the Cr2＋：ZnS can be used as an SA in a Ho：LuVO4 laser around 2-μm wavelength.

Experimental Study on a Passively Q-Switched Ho:YLF Laser with Polycrystalline Cr2+:ZnS as a Saturable Absorber

Output performance of a continuous-wave TIn：YAP laser pumped passively Q-switched Ho：YLF laser is demon- strated with a polycrystalline Cr2＋ ：ZnS as the saturable absorber. We compare the experimental results at the three different distances L of the polycrystalline Cr2＋ ：ZnS saturable absorber to the output coupler. The pulse width almost remains constant for different L, when the incident pump power is changed in the range of 7.9 27.1 W. The shortest pulse duration of 33.3 ns for L = 105 mm and the highest average output power of 6.8 W for L = 5 mm are obtMned at the incident pump power of 27.1 W. The output wavelength of the passively Q-switched laser shifts to 2045.2nm from 2064.7nm in the cw operation. The beam quality factor of M2 is 1.2.

Dual-Wavelength Passively Q-Switched Ytterbium-Doped Fiber Laser Based on Aluminum Oxide Nanoparticle Saturable Absorbers

We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle （Al2O3-NP） thin film. A thin film of Al2O3 was prepared by embedding Al2O3-NPs into a polyvinyl alcohol （PVA） as a host polymer, and then inserted between two fiber ferrules to act as a saturable absorber （SA）. By incorporating the Al2O3-PVA SA into the laser cavity, a stable dual-wavelength pulse output centered at 1050 and 1060.7nm is observed at threshold pump power of 80mW. As the pump power is gradually increased from 80 to 300mW, the repetition rate of the generated pulse increases from 16.23 to 59 kHz, while the pulse width decreases from 19 to 6μs. To the best of our knowledge, this is the first demonstration for this type of SA operating in the 1 μm region.

High single-pulse energy passively Q-switched laser based on Y b,Gd:SrF2 crystal

We report on laser diode(LD) pumped passively Q-switched Yb,Gd:SrF2 lasers with high single-pulse energy for the first time, to the best of our knowledge. In addition, a stable Q-switched laser based on a Cr4+:Y3Al5O12 saturable absorber was demonstrated. The maximum output power of the Q-switched laser obtained was 495 m W, with a pulse width and a pulse repetition rate of 233 ns and 1.238 kHz, respectively. The corresponding single-pulse energy and the peak power were as high as 400 μJ and 1.714 k W. The laser was operated under a transverse electromagnetic mode, and the beam quality was near-diffraction-limited.

Passively Q-Switched Erbium-Doped Fiber Laser Based on GeSe Saturable Absorber

GeSe nanosheets were prepared by ultrasonic-assisted liquid phase exfoliation (LPE), and the nonlinear saturated absorption performance was experimentally studied. The modulation depth and saturation intensity of the prepared GeSe saturable absorber (SA) were 15% and 1.44 MW/cm2, respectively. Using the saturated absorption characteristics of GeSe SA, a passively Q-switched erbium-doped fiber laser was systematically demonstrated. As the pump power increases, the pulse repetition frequency increases from 22.8 kHz to 77.59 kHz. The shortest pulse duration is 1.51 μs, and the corresponding pulse energy is 46.14 nJ. Experimental results show that GeSe nanosheets can be used as high-efficiency SA in fiber lasers. Our results will provide a useful reference for demonstrating pulsed fiber lasers based on GeSe equipment.