Publications by authors named "Kejian Yang"

65 Publications

Simulation and experimental results of a high-gain two-stage and double-pass off-axis Nd:YVO picosecond laser amplifier.

Appl Opt 2021 Jan;60(1):186-193

A high-gain two-stage double-pass off-axis : picosecond laser amplifier has been developed. The comprehensive influence of crystal doping concentration and pump beam quality on the small-signal gain of the : amplifier is theoretically analyzed with a model developed by considering energy transfer upconversion and pump light absorption saturation effect. The thermal effect of : crystal with different doping concentrations, undoped end cap lengths, and pump beam quality is investigated as well. Based on the theoretical analysis, a high-gain two-stage and double-pass off-axis : amplifier based on picosecond fiber seed source is realized by choosing long-composite low-doping : crystal and with high brightness laser diode pumping, delivering a gain of 28 dB and an output pulse energy of 67.5 µJ at a repetition rate of 200 kHz.
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http://dx.doi.org/10.1364/AO.413502DOI Listing
January 2021

Generation of a square-shaped pulse in mode-locked fiber lasers with a microfiber-based few-layer NbC saturable absorber.

Appl Opt 2020 Dec;59(36):11240-11245

Niobium carbide (), a novel two-dimensional MXene material, has attracted much attention due to its outstanding electronic and optical properties. In this work, a microfiber-based few-layer saturable absorber (SA) is fabricated by the magnetron sputtering deposition technique. The reverse saturable absorption (RSA) response of few-layer nanosheets is observed with I-scan measurements. The square-wave pulses (SWPs) are generated by using the as-prepared microfiber-based few-layer SA in an erbium-doped fiber laser. The SWP width increases from 0.33 to 2.061 ns with the single pulse energy increases linearly up to 0.89 nJ while the amplitude remains as a constant. In addition, nonlinear polarization rotation mode-locking fiber lasers with different cavity lengths are constructed to explore the formation conditions of SWP. Our results indicate that the RSA effect of the few-layer nanosheets plays a decisive role in the formation of the SWP.
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http://dx.doi.org/10.1364/AO.412165DOI Listing
December 2020

Room temperature watt-level 3.87 µm MgO:PPLN optical parametric oscillator under pumping with a Tm:YAP laser.

Opt Express 2020 Oct;28(22):32916-32924

A room-temperature highly efficient Tm:YAP laser pumped MgO:PPLN optical parametric oscillator operating at 3.87 µm near degeneracy is demonstrated. The pump source is an acousto-optical (AO) Q-switched Tm:YAP laser, which delivers a maximum output power of 6.17 W with a pulse duration of 45 ns and a repetition rate of 6 kHz. The temperature dependent wavelength tuning characteristics of the PPLN-OPO is investigated, and a maximum OPO output power of 1.2 W at around 3.87 µm is achieved at 35°C, corresponding to an optical-optical conversion efficiency of 19.4%. To the best of our knowledge, this is the maximum output power ever reported from 2 µm waveband laser pumped 3-5 µm MgO:PPLN OPOs.
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http://dx.doi.org/10.1364/OE.409093DOI Listing
October 2020

Few-layer GaSe nanosheet-based broadband saturable absorber for passively Q-switched solid-state bulk lasers.

Appl Opt 2020 Oct;59(28):8834-8838

In this paper, few-layer two-dimensional (2D) GaSe nanosheets were fabricated and utilized as broadband saturable absorbers (SAs) for passively -switched (PQS) solid-state bulk lasers operating at 1.06 and 1.99 µm. For 1.06 µm laser operation, the maximum average output power, the shortest pulse width, and the largest single pulse energy were determined to be 438 mW, 285 ns, and 2.31 µJ, respectively, while for 1.99 µm PQS laser operation, they were 937 mW, 383 ns, and 9.56 µJ. Our results identified the great potential applications of few-layer 2D GaSe nanosheets for practical optical modulators such as SAs for pulsed laser generation.
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http://dx.doi.org/10.1364/AO.404017DOI Listing
October 2020

Passively Q-switched Er:LuO laser at 2.8  µm with TiC saturable absorber.

Appl Opt 2020 Sep;59(27):8066-8070

Titanium carbide (TiC) nanosheets of two-dimensional multilayer structure were prepared by the liquid-phase exfoliation method. By using the TiC as a saturable absorber, a stable passively -switched : laser at 2.85 µm was realized. Under an absorbed pump power of 7.32 W, the obtained maximum output power was 896 mW with a slope efficiency of 15.6%. The -switched pulse duration was measured to be 266.8 ns with repetition rates of 136.9 kHz, corresponding to a peak power of 24.6 W.
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http://dx.doi.org/10.1364/AO.402736DOI Listing
September 2020

Tellurium as the saturable absorber for the passively Q-switched laser at 1.34 µm.

Appl Opt 2020 Mar;59(9):2892-2896

The novel two-dimensional (2D) elementary tellurium is currently of great interest in optoelectronic and photonic applications. In this contribution, 2D tellurium nanosheets were successfully created by using the liquid-phase exfoliation method. With the as-prepared tellurium nanosheets as the saturable absorber (SA), we realized a passively $ Q $Q-switched ${\rm Nd} \text:{{\rm YVO}_4}$Nd:YVO laser operating at 1342 nm with a pulse width of 947 ns and single pulse energy of 2.25 µJ. Our work indicated the tellurium SA could be an efficient $ Q $Q-switcher for a near-infrared solid-state laser.
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http://dx.doi.org/10.1364/AO.386690DOI Listing
March 2020

High-peak-power Q-switched 1988  nm bulk laser based on an electro-optical LaGaSiO modulator.

Appl Opt 2020 Mar;59(8):2616-2620

An electro-optically (EO) $Q$Q-switched Tm:YAP laser with high peak power was demonstrated based on a ${{\rm La}_3}{{\rm Ga}_5}{{\rm SiO}_{14}}$LaGaSiO (LGS) crystal. The EO modulator was operated in a pulse-on mode driven by a 1/4 wave voltage of 2400 V, which was the lowest voltage designed for LGS-based EO modulators at 2 µm, to the best of our knowledge. At a repetition rate of 200 Hz, a maximum single-pulse energy of 3.15 mJ was obtained with a minimum pulse duration of 17 ns, corresponding to a peak power as high as 185.3 kW.
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http://dx.doi.org/10.1364/AO.388229DOI Listing
March 2020

When Do Employees Speak Up Under Job Stressors? Exploring the Potential U-Shaped Relationship Between Hindrance Stressors and Voice Behavior.

Front Psychol 2019 22;10:2336. Epub 2019 Oct 22.

Air Force Medical University, Xi'an, China.

Drawing upon the conservation of resources theory, we intend to examine the relationships between voice behaviors and job stressors. Specifically, we propose a non-linear relationship between hindrance stressors and prohibitive and promotive voice behaviors. Furthermore, we argue that challenge stressors moderate the non-linear relationship between hindrance stressors and voice behaviors. Based on a sample of 361 employees in China, our results indicate that the relationship between hindrance stressors and prohibitive and promotive voice is U-shaped. The relationships between challenge stressors and prohibitive and promotive voice are linearly positive. Moreover, challenge stressors moderate the relationships between hindrance stressors and voice behaviors; thus, when challenge stressors are high, hindrance stressors are negatively linear related to prohibitive and promotive voice behaviors, and when challenge stressors are low, hindrance stressors are curvilinearly related to prohibitive and promotive voice behaviors. The theoretical and practical implications of these results are discussed.
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http://dx.doi.org/10.3389/fpsyg.2019.02336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6817592PMC
October 2019

Humble leadership and innovative behaviour among Chinese nurses: The mediating role of work engagement.

J Nurs Manag 2019 Nov 18;27(8):1801-1808. Epub 2019 Oct 18.

Office of Science Research Management, Fourth Military Medical University, Xi'An, China.

Aim: This study aimed to investigate the effect of humble leadership on innovative behaviour among Chinese nurses and to examine the mediating role of work engagement in this relationship.

Background: Nurses' innovative behaviour and work engagement are critical to the quality of health care services. Although research has established that leadership is beneficial for individuals, teams and organisations, it's less clear whether humble leadership could promote innovative behaviour and work engagement among nurses.

Methods: The data were collected in China. A sample of 377 nurses completed measures of humble leadership, innovative behaviour and the Utrecht Work Engagement Scale. Structural equation model was adopted to verify the research hypotheses.

Results: Humble leadership was significantly and positively related to nurses' innovative behaviour and work engagement (p < .01). And work engagement partially mediated the association between humble leadership and innovative behaviour.

Conclusion: Humble leaders are critical to enhancing nurses' innovative behaviour, and work engagement plays an intervening mechanism explaining how humble leaders promote innovative behaviour among nurses.

Implications For Nursing Management: Hospital managers should pay attention to improve head nurses' humble leadership, which could lead to a higher level of innovative behaviour and work engagement among nurse.
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http://dx.doi.org/10.1111/jonm.12879DOI Listing
November 2019

The Dark Side of Expressed Humility for Non-humble Leaders: A Conservation of Resources Perspective.

Front Psychol 2019 22;10:1858. Epub 2019 Aug 22.

Fourth Military Medical University, Xi'an, China.

Although existing studies to date predominately focus on the beneficial effects of leader expressed humility on followers, knowledge about how those behaviors impact the leaders themselves is scarce. Drawing on the conservation of resources theory, we develop and test a model that specifies for whom and how expressing humility has detrimental effects on leaders' emotional exhaustion and the downstream implications of this effect for leaders' turnover intentions and work-to-family conflict. Data from a multisource, time-lagged survey of 55 team leaders and 281 followers showed that expressed humility was positively associated with leaders' emotional exhaustion when Honesty-Humility was low, after controlling for Emotionality, sleep quality, overall job satisfaction, and hindrance stressors. In addition, we found that expressed humility was positively and indirectly related to leaders' turnover intentions and work-to-family conflict emotional exhaustion when Honesty-Humility was low. Overall, our research sheds light on why and under what conditions the dark side of humble leader behaviors is going to emerge and take its toll on the leaders themselves. Theoretical and practical implications are discussed.
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http://dx.doi.org/10.3389/fpsyg.2019.01858DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6713993PMC
August 2019

InAs-Nanowire-Based Broadband Ultrafast Optical Switch.

J Phys Chem Lett 2019 Aug 23;10(15):4429-4436. Epub 2019 Jul 23.

State Key Laboratory of Crystal Materials, Institute of Crystal Materials , Shandong University , Shandong , Jinan 250100 , China.

Due to their tunable optical properties with various shapes, sizes, and compositions, nanowires (NWs) have been regarded as a class of semiconductor nanostructures with great potential for photodetectors, light-emitting diodes, gas sensors, microcavity lasers, optical modulators, and converters. Indium arsenide (InAs), an attractive III-V semiconductor NW with the advantages of narrow bandgap and large electron mobility, has attracted considerable interest in infrared optoelectronic and photonic devices. Here, we studied the ultrafast carrier dynamics and nonlinear optical responses of InAs NWs ranging from 1.0 to 2.8 μm and demonstrated the InAs-NW-based ultrafast broadband optical switch for passively Q-switching in all-solid-state laser systems. Furthermore, we achieved ultrafast optical modulation for laser mode-locking at 1.0 μm, paving the way for their applications in the field of ultrafast optics. These exotic optical properties indicate that InAs NWs have significant potential for various optoelectronic and photonic devices, especially in the mid-infrared wavelength range.
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http://dx.doi.org/10.1021/acs.jpclett.9b01626DOI Listing
August 2019

Bismuth quantum dots as an optical saturable absorber for a 1.3  μm Q-switched solid-state laser.

Appl Opt 2019 Mar;58(7):1621-1625

Two-dimensional bismuth has attracted extensive attention for its unique properties, such as a moderate bandgap, high carrier mobility, and high stability. In this work, a uniform bismuth quantum dots saturable absorber (BiQDs-SA) was successfully fabricated by the liquid-phase exfoliation method. It was successfully employed in a passively Q-switched bulk laser operating at the telecommunication wavelength of 1.3 μm. The as-fabricated BiQDs-SA-based 1.3 μm Q-switched laser not only exhibits low timing jitter but also shows long-term stability for several days. The maximum average output power of 125 mW was obtained with the shortest pulse width of 510 ns and repetition rate of 135 kHz, corresponding to single-pulse energy and pulse peak power of 0.9 μJ and 1.8 W, respectively. The results indicate that BiQDs-SA is a potential optical modulator for passively Q-switched solid-state lasers.
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http://dx.doi.org/10.1364/AO.58.001621DOI Listing
March 2019

Alpha-phase indium selenide saturable absorber for a femtosecond all-solid-state laser.

Opt Lett 2019 Feb;44(3):699-702

We successfully fabricated the high-quality few-layered α-InSe and investigated its carrier dynamics and nonlinear optical absorption properties by pump-probe and open-aperture Z-scan technologies. Intra- and inter-band relaxation times were determined to be 7.2 ps and 270 ps, respectively, and the effective nonlinear absorption coefficient was measured as β=-3.9×10  cm/GW (1064 nm). Based on α-InSe saturable absorber, a continuous-wave mode-locking operation was realized. Pulse duration, repetition rate, and maximum output power were measured to be 352 fs, 42.4 MHz, and 0.56 W, corresponding to pulse energy of 13.2 nJ and peak power of 37.5 kW. To the best of our knowledge, this is the first demonstration of non-transition metal chalcogenides applied in ultrafast all-solid-state bulk lasers. This work well verified that α-InSe should be a promising optical modulator candidate for all-solid-state lasers.
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http://dx.doi.org/10.1364/OL.44.000699DOI Listing
February 2019

High-repetition-rate kHz electro-optically Q-switched Ho, Pr: YLF 2.9 µm bulk laser.

Opt Express 2018 Dec;26(26):33671-33677

In this study, we operated a novel bulk laser: a dual-end-pumped electro-optically (EO) Q-switched Ho, Pr:YLF laser at 2945.9 nm with a repetition rate of kHz level. The shortest pulse duration of 25.2 ns was obtained at the repetition rate of 500 Hz, corresponding to a single pulse energy of 0.4 mJ and a peak power of 15.9 kW. A maximum output power of 268 mW was delivered at the repetition rate of 1.5 kHz. The beam quality factors of the EO Q-switched Ho, Pr:YLF laser at the maximum output power were M = 1.50 and M = 1.54 in x- and y- directions, respectively. The long-term output power instability was measured to be ± 1.5% (RMS) within five hours. The achieved results indicated the promising potential of Ho, Pr: YLF crystals for high repetition rate Q-switched mid-infrared laser pulse generation very well.
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http://dx.doi.org/10.1364/OE.26.033671DOI Listing
December 2018

Bilayer platinum diselenide saturable absorber for 2.0 μm passively Q-switched bulk lasers.

Opt Express 2018 Nov;26(24):31657-31663

A noble transition metal dichalcogenide, bilayers platinum diselenide (PtSe), has a narrow bandgap (0.21 eV) and high charge carrier mobility. This metal was manufactured for use as a saturable absorber via the chemical vapor deposition method. The saturable absorption properties of samples, at a wavelength of 2.0 μm, were characterized by the open aperture Z-scan method. An all-solid-state 2.0 μm passively Q-switched laser was achieved experimentally based on the as-prepared bilayers PtSe saturable absorber. The maximum average output power, shortest pulse width, highest single-pulse energy, and highest pulse peak power of this laser were 1.41 W, 244 ns, 24.3 μJ, and 99.6 W, respectively.
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http://dx.doi.org/10.1364/OE.26.031657DOI Listing
November 2018

Ternary chalcogenide TaNiS as a saturable absorber for a 1.9  μm passively Q-switched bulk laser.

Opt Lett 2019 Jan;44(2):451-454

In this Letter, a high-quality saturable absorber (SA) based on a multilayered two-dimensional ternary chalcogenide TaNiS with a narrow bandgap, has been successfully fabricated and used as a SA in a 1.9 μm spectral region. The nonlinear saturable absorption properties of the as-prepared SA have been investigated by using an open-aperture Z-scan method. A passively Q-switched all-solid-state laser operating at 1.9 μm has been realized with the TaNiS SA. The maximum average output power, shortest pulse width, pulse energy, and pulse peak power from the passively Q-switched (PQS) laser are 1.1 W, 313 ns, 22.0 μJ, and 71.0 W, respectively. This is the first demonstration of the saturable absorption property of TaNiS, to the best of our knowledge. The results indicate well the promising potential of TaNiS as a broadband SA in realizing pulsed mid-infrared lasers with high performance.
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http://dx.doi.org/10.1364/OL.44.000451DOI Listing
January 2019

High-efficiency watt-level continuous-wave 2.9  μm Ho,Pr:YLF laser.

Opt Lett 2018 Dec;43(24):6109-6112

The bottleneck in Ho:I5→I52.9  μm laser emission, where the upper-level lifetime (I5) is significantly shorter than that of the lower-level (I5) lifetime, is overcome by co-doping Ho and Pr ions. A novel kind of Ho,Pr:YLIF (Ho,Pr:YLF) crystal is fabricated by optimizing the doping concentration ratios. By using as-grown Ho,Pr: YLF crystals with doping concentrations of 0.498 at. % Ho, 0.115 at. % Pr and 0.489 at. % Ho, 0.097 at. % Pr as gain media, both high-efficiency and continuous-wave 2.9 μm laser operations are realized under 1150 nm fiber laser pumping, respectively. With the 0.498 at. % Ho, 0.115 at. % Pr: YLF crystal, a maximum output power of 1.27 W with a corresponding slope efficiency of 28.3% is yielded under a 4.48 W absorbed pump power, which is the highest output power among the Ho-doped 2.9 μm lasers ever reported, to the best of our knowledge. The results well reveal the great potential of Ho,Pr:YLF crystals in developing high-power, high-efficiency 2.9 μm mid-infrared lasers.
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http://dx.doi.org/10.1364/OL.43.006109DOI Listing
December 2018

Silicon-nanoparticle-based broadband optical modulators for solid-state lasers.

Opt Lett 2018 Dec;43(24):5957-5960

Motivated by the tremendous success of carbon nanomaterials in acting as optical nonlinear modulators, in this Letter, the optical nonlinearity of their counterpart, silicon nanoparticles (SiNPs), is investigated. For the first time, to the best of our knowledge, the nonlinear optical property of SiNPs in 1 μm and 2 μm wavelength bands is observed. Its practical modulation performance is investigated by employing SiNPs as a saturable absorber (SA) in pulsed lasers, and the fabrication process, surface morphology, and linear and nonlinear optical response properties of the prepared SiNPs-SA are presented. Based on the SiNPs-SA, the formed Q-switched Nd:LuAG laser can generate laser pulses with the shortest duration of 490 ns at ∼1  μm and ∼2  μm laser pulses with the shortest duration of 453 ns are delivered from a Q-switched Tm:YAP laser, which shows that the SiNPs can be employed as a promising broadband SA for near- and mid-infrared spectral regions.
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http://dx.doi.org/10.1364/OL.43.005957DOI Listing
December 2018

Few-layer TiCT (T = O, OH, or F) saturable absorber for a femtosecond bulk laser.

Opt Lett 2018 Aug;43(16):3862-3865

Few-layered titanium carbide (TiCT), a novel two-dimensional (2D) Van der Waals material in the MXene family, was fabricated with a liquid-phase method and applied as a saturable absorber for a continuous-wave mode-locked femtosecond bulk laser. Pulses as short as 316 fs with a repetition rate of 64.06 MHz and maximum output power of 0.77 W were achieved at the central wavelength of 1053.2 nm, demonstrating the first known, to the best of our knowledge, application of MXene in an all-solid-state laser. Considering the flexible band gap for different surface functional groups of TiCT, these results may promote the development of ultrafast photonics and further applications of 2D optoelectronic layered materials in the infrared and mid-infrared regions.
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http://dx.doi.org/10.1364/OL.43.003862DOI Listing
August 2018

Nonlinear optical property of a Bi-doped GaAs semiconductor saturable absorber.

Opt Express 2018 Apr;26(7):8542-8549

By using an Open-Aperture Z-scan technique with both femtosecond and nanosecond laser pulses at 1064nm, the nonlinear optical properties of GaAs and Bi-doped GaAs, including the saturable absorption property and reverse saturable absorption property are systematically measured and analyzed directly in detail. Compared to pure GaAs, Bi-doped GaAs has a lower saturation intensity, wider saturable absorption energy region, lower two-photon absorption coefficient, better saturable absorption response and stronger optical limiting response. The results suggest that the incorporation of Bismuth in GaAs is an effective way of improving the nonlinear optical properties of GaAs, which provide crucial experimental evidence for that the characteristics of the passively Q-switched laser with Bi-doped GaAs saturable absorber is better than pure GaAs.
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http://dx.doi.org/10.1364/OE.26.008542DOI Listing
April 2018

Continuous wave and ReS passively Q-switched Er : SrF laser at ∼3  μm.

Opt Lett 2018 Apr;43(8):1726-1729

We report on an efficient Er:SrF laser at 2.79 μm. A continuous wave output power of 1.06 W was obtained with a slope efficiency of 41%, significantly exceeding the Stokes efficiency of 35%. Stable Q-switched laser operation was realized by using an ReS saturable absorber, generating an average output power of 0.58 W with a pulse duration of 508 ns at a repetition rate of 49 kHz, corresponding to a pulse energy of 12.1 μJ.
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http://dx.doi.org/10.1364/OL.43.001726DOI Listing
April 2018

High-peak-power mode-locking pulse generation in a dual-loss-modulated laser with BP-SA and EOM.

Opt Lett 2017 Dec;42(23):4820-4823

In this Letter, a high-quality black phosphorus saturable absorber (BP-SA) with a multilayer structure was prepared, and its corresponding characteristics were investigated. Based on the BP-SA and an electro-optic modulator (EOM), a dual-loss-modulated mode-locked laser with a controllable repetition rate and high peak power was realized, which has the repetition rate of EOM and the mode-locking pulse width in the Q-switching and mode-locking laser. The output performances versus the pump power were measured. The maximum pulse peak power of 3.89 MW was obtained with the minimum pulse duration of 119 ps. To the best of our knowledge, this is the highest pulse peak power with BP-SA reported.
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http://dx.doi.org/10.1364/OL.42.004820DOI Listing
December 2017

Passively mode-locked 1.34 μm bulk laser based on few-layer black phosphorus saturable absorber.

Opt Express 2017 Aug;25(17):20025-20032

By using few-layer black phosphorus (BP) as saturable absorber, an efficient mode-locked Nd:GdVO bulk laser operating at 1.34 μm was realized. An average output power of 350 mW was achieved with a slope efficiency of 15%. The corresponding mode-locking pulse repetition rate, pulse duration and pulse energy were 58.14 MHz, 9.24 ps and 3.0 nJ, respectively. To the best of our knowledge, the pulse width is the shortest among the mode-locked 1.34 μm neodymium lasers ever obtained with other two-dimensional materials saturable absorber. The results clearly indicate the few-layered BP is a kind of promising saturable absorber for ultrafast 1.34 μm lasers.
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http://dx.doi.org/10.1364/OE.25.020025DOI Listing
August 2017

Few-layered ReS as saturable absorber for 2.8  μm solid state laser.

Opt Lett 2017 Sep;42(17):3502-3505

A novel two-dimensional (2D) material member in the transition metal dichalcogenides family, few-layered rhenium disulfide (ReS) was prepared by liquid phase method successfully. By using the open-aperture Z-scan method, the saturable absorption properties at 2.8 μm were characterized with a saturable fluence of 22.6  μJ/cm and a modulation depth of 9.7%. A passively Q-switched solid-state laser at 2.8 μm was demonstrated by using the as-prepared ReS saturable absorber successfully. Under an absorbed pump power of 920 mW, a maximum output power of 104 mW was obtained with a pulse width of 324 ns and a repetition rate of 126 kHz. To the best of our knowledge, this is the first demonstration of applying ReS in an all-solid-state laser. Moreover, this represents the shortest pulses in Q-switched MIR lasers based on a 2D material as the saturable absorber, which demonstrated the superiority of ReS acting as an optical modulator for generating short-pulsed lasers. The results well prove that 2D ReS is a reliable optical modulator for MIR solid-state lasers.
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http://dx.doi.org/10.1364/OL.42.003502DOI Listing
September 2017

Passively Q-switched Ho,Pr:LiLuF laser with graphitic carbon nitride nanosheet film.

Opt Express 2017 May;25(11):12796-12803

A few-layer graphitic carbon nitride (g-CN) nanosheet film on an yttrium aluminum garnet substrate was fabricated and employed as saturable absorber for a passively Q-switched Ho,Pr:LiLuF laser at 2.95 μm. Under an absorbed pump power of 3.89 W at a pump wavelength of 1.15 μm, a maximum average output power of 101 mW was realized with a pulse duration of 420 ns and a repetition rate of 93 kHz. Even shorter pulse durations of 385 ns were obtained at a reduced output coupler transmission.
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http://dx.doi.org/10.1364/OE.25.012796DOI Listing
May 2017

Few-layered MoS2 as a saturable absorber for a passively Q-switched Er:YAG laser at 1.6  μm.

Appl Opt 2017 Apr;56(10):2766-2770

The passively Q-switched Er:YAG laser at 1.6 μm was achieved with a YAG-based MoS2 saturable absorber (SA) for the first time. The saturable absorption properties of the MoS2 SA near 1.6 μm were investigated. Under an absorbed pump power of 8.09 W, an average output power of 1.08 W with a pulse duration of 1.138 μs and a repetition rate of 46.6 kHz was obtained, corresponding to an optical conversion efficiency of 40.67%. The pulse energy and peak power were calculated to be 23.08 μJ and 20.28 W, respectively.
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http://dx.doi.org/10.1364/AO.56.002766DOI Listing
April 2017

83.4  W, 17.69  kHz spectral bandwidth, continuous-wave, beam densely folded Innoslab amplifier.

Opt Lett 2017 Mar;42(6):1109-1112

Combined with the advantages of the narrow bandwidth of a non-planar ring oscillator seed laser and the structure of a direct pumped Innoslab amplifier, a high-efficiency and high-power continuous-wave (CW) single-frequency laser was obtained by densely folding the seed laser beam in an Innoslab amplifier with a wedged multi-folded configuration. A maximum output power of 83.4 W of a single-frequency amplifier with a bandwidth of 17.69 kHz was obtained under a pump power of 234 W, corresponding to an optical-to-optical conversion efficiency of 33.2%. The beam quality factor M2 at the maximum output power in horizontal and vertical directions was measured to be 1.15 and 1.24, respectively. The long-term power instability in 2 h was less than 1.63%.
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http://dx.doi.org/10.1364/OL.42.001109DOI Listing
March 2017

Hybrid Q-switched laser with MoS2 saturable absorber and AOM driven sub-nanosecond KTP-OPO.

Opt Express 2017 Feb;25(4):4227-4238

Two-dimensional (2D) materials, especially transition-metal dichalcogenides, such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), have attracted great interests due to their exceptional optical properties as saturable absorbers in laser systems. In this work, at first, we presented a diode-pumped passively Q-switched laser with MoS2 saturable absorber (MoS2-SA). At an incident pump power of 6.54 W, a maximum output power of 1.15 W with a minimum pulse duration of 70.6 ns was obtained, which is the shortest pulse duration of diode pumped passively Q-switched laser with MoS2-SA to the best of our knowledge. Then, by using a hybrid Q-switched laser with a MoS2-SA and an acousto-optic modulator (AOM) as pumping fundamental laser, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillation (IOPO) was realized. With an incident pump power of 10.2 W and AOM repetition rate of 10 kHz, the maximum output power of 183 mW with minimum pulse duration of 850 ps was obtained. The experimental results indicate that the IOPO pumped by the hybrid Q-switched laser with AOM and MoS2-SA can generate signal wave with shorter pulse duration than those IOPOs pumped by hybrid Q-switched laser with AOM and Cr4+:YAG or single-walled carbon nanotube saturable absober (SWCNT-SA) or monolayer graphene SA.
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http://dx.doi.org/10.1364/OE.25.004227DOI Listing
February 2017

Diode-end-pumped Ho, Pr:LiLuF4 bulk laser at 2.95  μm.

Opt Lett 2017 Feb;42(4):699-702

A diode-end-pumped continuous-wave (CW) and passively Q-switched Ho, Pr:LiLuF4 (Ho, Pr:LLF) laser operation at 2.95 μm was demonstrated for the first time, to the best of our knowledge. The maximum CW output power was 172 mW. By using a monolayer graphene as the saturable absorber, the passively Q-switched operation was realized, in which regimes with the highest output power, the shortest pulse duration, and the maximum repetition rate were determined to be 88 mW, 937.5 ns, and 55.7 kHz, respectively. The laser beam quality factor M2 at the maximum CW output power were measured to be Mx2=1.48 and My2=1.47.
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http://dx.doi.org/10.1364/OL.42.000699DOI Listing
February 2017

Graphitic C3N4 as a new saturable absorber for the mid-infrared spectral range.

Opt Lett 2017 Jan;42(2):286-289

The saturable absorption properties of few-layer graphitic carbon nitride (g-C3N4) nanosheets near 3 μm were investigated. A stable Q-switched Er:Lu2O3 laser at 2.84 μm was realized by using a home-made g-C3N4 saturable absorber (SA), generating a pulse duration of 351 ns and an average output power of 1.09 W at a repetition rate of 99 kHz, corresponding to a pulse energy of 11.1 μJ. Our result indicates a great potential of g-C3N4 as a new SA in the 3 μm wavelength range.
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http://dx.doi.org/10.1364/OL.42.000286DOI Listing
January 2017