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As a new member of two-dimensional (2D) phosphorene, 2D layered violet phosphorus (VP) has unique optoelectronic properties and good environmental stability, showing its huge advantages in optoelectronic applications. In this paper, the ultrafast nonlinear optical (NLO) properties of layered VP nanosheets at 1 µm band were explored, which exhibit an obvious saturable absorption response with a modulation depth of â¼1.97%. Meanwhile, the fast and slow carrier lifetimes of VP nanosheets at 1µm band were also determined as 295.9 fs and 2.36 ps, respectively, which are much shorter than that of most reported 2D materials. The excellent saturable absorption response combined with ultrashort carrier lifetimes indicate the prospect of layered VP nanosheets as a fast saturable absorber (SA) for ultrafast laser modulation. Then we demonstrated a Yb-doped fiber laser based on the VP-deposited taper-shaped fiber (TSF) SA, which delivers stable Q-switched mode-locked (QSML) pulses, dual-wavelength mode-locked pulses and 404-fs noise-like pulses. This work fully demonstrates the great potential of 2D VP materials for 1 µm ultrashort laser pulse generation.
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The laser diode (LD)-pumped Tm:YAP (a-cut, 3.5 at.%) laser generated a maximum â¼2.3â µm continuous wave (CW) laser output power of â¼3 W. The higher output power benefited from the positive effect of the cascade lasing (simultaneously operating on the 3H4 â 3H5 and 3F4 â 3H6 Tm3+ transition). It was the highest CW laser output power amongst the LD/Ti:Sapphire-CW-pumped â¼2.3 µm Tm3+-doped lasers reported so far. Under the cascade laser operation, the slope efficiency of the â¼2.3â µm laser emission versus the absorbed pump power increased from 13.0% to 21.4%.
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The polarized spectral properties and â¼2.3â µm high-power continuous-wave laser operation of Tm3+-doped yttrium orthovanadate crystal (Tm:YVO4) are reported. For the 3H4 â 3H5 transition, the stimulated-emission cross-section σSE is 1.01 × 10-20 cm2 at 2276â nm corresponding to a large emission bandwidth of 52â nm (for π-polarization). Pumped by a 794â nm laser diode, the 1.5 at.% Tm:YVO4 laser delivered 5.52 W at 2.29â µm with a slope efficiency of 19.9%, a laser threshold of 8.70 W, and a linear laser polarization (π). The Tm laser operated on the cascade scheme (on the 3H4 â 3H5 and 3F4 â 3H6 transitions) which was mainly responsible for the observed high laser slope efficiency. We also report on the first passively Q-switched Tm:YVO4 laser at 2.3â µm by employing porous nano-grained cuprous selenide (PNG-Cu2Se) as a saturable absorber. The shortest pulse duration and the highest single pulse energy amounted to 706â ns and 3.65 µJ, respectively, corresponding to a pulse repetition rate of 62.8 kHz.
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We report on the Czochralski crystal growth, polarized optical spectroscopy, and the first continuous-wave laser operation of 1.5 at.% Tm:LuVO4 crystal on the 3H4 â 3H5 transition. The polarized absorption and stimulated-emission properties of Tm3+ ions in LuVO4 were revised and the crystal-field splitting of the Tm3+ multiplets was determined by low-temperature (12â K) spectroscopy. The maximum stimulated-emission cross-section for the 3H4 â 3H5 transition is 2.48 × 10-20 cm2 at 2363â nm for π-polarization corresponding to an emission bandwidth of 28â nm. Evidence of phonon-assisted emissions of Tm3+ ions above 2â µm is presented. The broadband emission properties of the Tm:LuVO4 crystal make it promising for ultrashort pulse generation. Additionally, pumped by a 796â nm fiber-coupled laser diode, the Tm:LuVO4 laser generated a Watt-level output power at 2279-2295â nm with a slope efficiency of 9.2% and linearly polarized emission (π-polarization).
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We report on a Kerr-lens mode-locked Tm,Ho-codoped calcium aluminate laser with in-band pumping of the Tm ions by a spatially single-mode 1678 nm Raman fiber laser. The structurally disordered CaGdAlO4 host crystal is also codoped also with the passive Lu ion for additional inhomogeneous line broadening. The Tm,Ho,Lu:CaGdAlO4 laser generates soliton pulses as short as 79 fs at a central wavelength of 2073.6 nm via soft-aperture Kerr-lens mode-locking. The corresponding average output power amounts to 91 mW at a pulse repetition rate of â¼86 MHz. The average output power can be scaled to 842 mW at the expense of slightly longer pulses of 155 fs at 2045.9 nm, which corresponds to a peak power of â¼58 kW. To the best of our knowledge, this represents the first demonstration of an in-band pumped Kerr-lens mode-locked Tm,Ho solid-state laser at â¼2 µm.
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In this contribution, we measured the third-order nonlinear optical response of bismuth oxychloride (BiOCl) nanosheets with the open-aperture (OA) and the closed-aperture (CA) Z-scan techniques with a variable excitation intensity at 1.34â µm. The effective nonlinear absorption coefficient ßeff and the nonlinear refractive index n2 of the prepared BiOCl nanosheets with abundant oxygen vacancies were obtained under the excitation intensity. The third-order nonlinear optical susceptibility |χ(3)| was 1.64 × 10-9 esu. The nonlinear optical features of BiOCl enabled it as a superb saturable absorber for pulse laser generation. As a consequence, we demonstrated the first passively Q-switched Nd:GdVO4 laser with the BiOCl saturable absorber, producing a shortest pulse duration of 543â ns and a highest repetition rate of 227 kHz, leading to a maximum pulse energy of 74 nJ. Our findings show that BiOCl nanosheets with oxygen vacancies have large nonlinear optical sensitivities and can be exploited to generate optical pulses.
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The laser diode (LD)-pumped efficient high-power cascade Tm:GdVO4 laser simultaneously operating on the 3F4 â 3H6 (at â¼2â µm) and 3H4 â 3H5 (at â¼2.3â µm) Tm3+ transition was first reported in this paper. The cascade Tm:GdVO4 laser generated a maximum total continuous-wave (CW) laser output power of 8.42 W with a slope efficiency of 40%, out of which the maximum â¼2.3â µm CW laser output power was 2.88 W with a slope efficiency of 14%. To our knowledge, 2.88 W is the highest CW laser output power amongst the LD-CW-pumped â¼2.3â µm Tm3+-doped lasers reported so far.
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The exceptional mechanical, electronic, topological, and optical properties, make bismuthene an ideal candidate for various applications in ultrafast saturation absorption and spintronics. Despite the extensive research efforts devoted to synthesizing this material, the introduction of defects, which can significantly affect its properties, remains a substantial obstacle. In this study, we investigate the transition dipole moment and joint density of states of bismuthene with/without single vacancy defect via energy band theory and interband transition theory. It is demonstrated that the existence of the single defect enhances the dipole transition and joint density of states at lower photon energies, ultimately resulting in an additional absorption peak in the absorption spectrum. Our results suggest that the manipulation of defects in bismuthene has enormous potential for improving the optoelectronic properties of this material.
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We report on the first laser operation of a disordered Tm:CaGdAlO4 crystal on the 3H4 â 3H5 transition. Under direct pumping at 0.79 µm, it generates 264â mW at 2.32â µm with a slope efficiency of 13.9% and 22.5% vs. incident and absorbed pump power, respectively, and a linear polarization (σ). Two strategies to overcome the bottleneck effect of the metastable 3F4 Tm3+ state leading to the ground-state bleaching are exploited: cascade lasing on the 3H4 â 3H5 and 3F4 â 3H6 transitions and dual-wavelength pumping at 0.79 and 1.05 µm combining the direct and upconversion pumping schemes. The cascade Tm-laser generates a maximum output power of 585â mW at 1.77â µm (3F4 â 3H6) and 2.32â µm (3H4 â 3H5) with a higher slope efficiency of 28.3% and a lower laser threshold of 1.43 W, out of which 332â mW are achieved at 2.32â µm. Under dual-wavelength pumping, further power scaling to 357â mW at at 2.32â µm is observed at the expense of increased laser threshold. To support the upconversion pumping experiment, excited-state absorption spectra of Tm3+ ions for the 3F4 â 3F2,3 and 3F4 â 3H4 transitions are measured for polarized light. Tm3+ ions in CaGdAlO4 exhibit broadband emission at 2.3 - 2.5 µm making this crystal promising for ultrashort pulse generation.
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We report on the first, to the best of our knowledge, laser operation on the 4I11/2 â 4I13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4â at.% Er:CLNGG continuous-wave laser generated 292â mW at 2.80â µm with 23.3% slope efficiency and a laser threshold of 209â mW. Er3+ ions in CLNGG feature inhomogeneously broadened spectral bands (σSE = 1.79 × 10-21â cm2 at 2.79â µm; emission bandwidth, 27.5â nm), a large luminescence branching ratio for the 4I11/2 â 4I13/2 transition of 17.9%, and a favorable ratio of the 4I11/2 and 4I13/2 lifetimes, exhibiting values of 0.34â ms and 1.17â ms (for 41.4â at.% Er3+), respectively.
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A compact Tm:GdVO4 laser pumped by a 794â nm laser diode generated 6.09â W at 2.29â µm (3H4 â 3H5 Tm3+ transition) with a high slope efficiency of 30.8% and linear laser polarization (π). The polarized spectroscopic properties of Tm3+ in GdVO4 were also revised. The peak stimulated-emission cross section of Tm3+ is 2.97 × 10-20 cm2 at 2280â nm, corresponding to an emission bandwidth of 42â nm for π-polarized light.
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We report on a soliton mode-locked Yb:Ca3Gd2(BO3)4 laser at â¼1.06 µm stabilized by a semiconductor saturable absorber mirror. Pumping with a single-transverse mode, fiber-coupled laser diode at 976 nm, the Yb:Ca3Gd2(BO3)4 laser delivers soliton pulses as short as 39 fs at a central wavelength of 1059.2 nm with an average output power of 70 mW and a pulse repetition rate of â¼67.3 MHz.
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A Tm,Ho:CALGO laser passively mode-locked by a GaSb-based SESAM generated pulses as short as 52 fs at a central wavelength of 2015 nm with a broad spectral bandwidth of 82â nm (full width at half maximum) owing to the combined gain profiles of both dopants for σ-polarized light. The average output power reached 376â mW at a repetition rate of 85.65â MHz. In the continuous-wave regime, the laser was power scaled up to 1.01 W at 2080.6 nm with a slope efficiency of 32.0%, a laser threshold of 155 mW and π-polarized emission. Polarized spectroscopic properties of Ho3+ ions in singly doped and codoped CALGO crystals were revisited to explain the observed laser performance.
RESUMO
In this Letter, the fabrication of large-scale (50.8 mm in diameter) few-layered MoS2 with physical vapor deposition on sapphire is described. Open-aperture Z-scan technology with a home-made excitation source at 2275â nm was applied to explore its nonlinear saturable absorption properties. The as-grown few-layered MoS2 membrane possessed a modulation depth of 17% and a saturable intensity of 1.185 MW cm-2. As a consequence, the deposited MoS2 membrane was exploited as a saturable absorber to realize a passively Q-switched Tm:YAP laser for the first time, to the best of our knowledge. Pulses as short as 316â ns were generated with a repetition rate of 228 kHz, corresponding to a peak power of 5.53 W. Results confirmed that the two-dimensional layered MoS2 could be beneficial for mid-infrared photonic applications.
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Compact diode-pumped continuous wave (CW) and passively Q switched Tm:YAG lasers operating on the 3H4 â 3H5 transition are demonstrated. Using a 3.5-at.% Tm:YAG crystal, a maximum CW output power of 1.49â W is achieved at 2330â nm with a slope efficiency of 10.1%. The first Q switched operation of the mid-infrared Tm:YAG laser around 2.3 µm is realized with a few-atomic-layer MoS2 saturable absorber. Pulses as short as 150â ns are generated at a repetition rate of 190 kHz, corresponding to a pulse energy of 1.07â µJ. Tm:YAG is an attractive material for diode-pumped CW and pulsed mid-infrared lasers emitting around 2.3 µm.
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In this Letter, a watt-level laser diode (LD)-pumped â¼2.3-µm (on the 3H4â3H5 quasi-four-level transition) laser is reported based on a 1.5 at.% a-cut Tm:YVO4 crystal. The maximum continuous wave (CW) output power obtained is 1.89 W and 1.11 W with the maximum slope efficiency of 13.6% and 7.3% (versus the absorbed pump power) for the 1% and 0.5% transmittance of the output coupler, respectively. To the best of our knowledge, the CW output power of 1.89 W we obtained is the highest CW output power amongst the LD-pumped â¼2.3-µm Tm3+-doped lasers.
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We report on the first sub-100 fs mode-locked laser operation of a Tm3+-doped disordered calcium lithium tantalum gallium garnet (Tm:CLTGG) crystal. Soliton mode-locking was initiated and stabilized by a transmission-type single-walled carbon nanotube saturable absorber. Pulses as short as 69 fs were achieved at a central wavelength of 2010.4 nm with an average power of 28 mW at a pulse repetition rate of â¼87.7 MHz. In the sub-100 fs regime, the maximum average output power amounted to 103 mW.
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Sub-100 fs pulse generation from a passively mode-locked Tm,Ho-codoped cubic multicomponent disordered garnet laser at â¼2 µm is demonstrated. A single-walled carbon nanotube saturable absorber is implemented to initiate and stabilize the soliton mode-locking. The Tm,Ho:LCLNGG (lanthanum calcium lithium niobium gallium garnet) laser generated pulses as short as 63 fs at a central wavelength of 2072.7 nm with an average output power of 63 mW at a pulse repetition rate of â¼102.5 MHz. Higher average output power of 121 mW was obtained at the expense of longer pulse duration (96 fs) at 2067.6 nm using higher output coupling. To the best of our knowledge, this is the first report on mode-locked operation of the Tm,Ho:LCLNGG crystal.
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We report on sub-50 fs pulse generation from a passively mode-locked (ML) Tm,Ho-codoped crystalline laser operating in a 2 µm spectral region. A ${\rm Tm},{\rm Ho}{:}{\rm Ca}({\rm Gd},{\rm Lu}){{\rm AlO}_4}$ laser delivers pulses as short as 46 fs at 2033 nm with an average power of 121 mW at a pulse repetition rate of ${\sim}{78}\;{\rm MHz}$ employing a semiconductor saturable absorber mirror as a saturable absorber. To the best of our knowledge, this result represents the shortest pulses ever generated from a Tm- and/or Ho-based solid-state laser. Polarization switching in the anisotropic gain material is observed in the ML regime without any polarization selection elements which is essential for the shortest pulses.
RESUMO
Kerr-lens mode-locked solid-state laser operation at â¼2µm is investigated. Using a Tm3+-doped (Lu,Sc)2O3 "mixed" sesquioxide ceramic as a gain medium, pulses as short as 58 fs are generated at â¼2081nm via soft-aperture Kerr-lens mode locking. The average output power amounts to 220 mW at a pulse repetition rate of 84.8 MHz. The emitted spectrum at the long-wavelength wing extends to >2.2µm which is attributed to vibronic transitions of the Tm3+ ions. The latter is found to be essential for generating pulses with durations in the 50 fs range.