A passive Q-switched flash-lamp-pumped Nd∶YAG laser with the ion-implanted semi-insulating GaAs wafer is reported.The wafer is implanted with 400keV As+ ions in the concentration of 10 16cm -2.Using GaAs wafer as a...A passive Q-switched flash-lamp-pumped Nd∶YAG laser with the ion-implanted semi-insulating GaAs wafer is reported.The wafer is implanted with 400keV As+ ions in the concentration of 10 16cm -2.Using GaAs wafer as an absorber and an output coupler,62ns pulse duration of single pulse is obtained.展开更多
We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generat...We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generated at a repetition rate of 285.7 kHz,approaching or very near the intrinsic upper limit imposed by the recovery time of the Cr^（4＋）：YAG saturable absorber,and the resulting pulse energy,duration and peak power are,respectively,8.2μJ,39.2ns and 0.209kW.展开更多
With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser...With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser emitted a maximum average output power of 62 mW and highest pulse energy of 0.72 μJ. Q-switched mode locking was also obtained in the experiment. The research results will open up applications of MoS2 at the mid-infrared wavelength.展开更多
Developing new saturable absorbers for use in the mid-infrared region has practical significance for short-pulsed lasers and related scientific and industrial applications.The performance of gold nanorods(GNRs)as satu...Developing new saturable absorbers for use in the mid-infrared region has practical significance for short-pulsed lasers and related scientific and industrial applications.The performance of gold nanorods(GNRs)as saturable absorbers at novel mid-infrared wavelengths needs to be evaluated even though these benefit from ultrafast nonlinear responses and broadband saturable absorption.Passive Q-switching of an LD-pumped 2.3μm Tm:YLF laser using GNRs was successfully realized in this study.Pulses with an 843 ns pulse width and a 6.67 kHz repetition rate were achieved using this Q-switched laser.Results showed that GNRs provide promising passive Q-switches for 2.3μm Tm-doped lasers.展开更多
A highly stable Q-switched laser incorporating a mechanically exfoliated tungsten sulphoselenide （WSSe） thin sheet saturable absorber （SA） is proposed and demonstrated. The SA assembly, formed by sandwiching a thi...A highly stable Q-switched laser incorporating a mechanically exfoliated tungsten sulphoselenide （WSSe） thin sheet saturable absorber （SA） is proposed and demonstrated. The SA assembly, formed by sandwiching a thin WSSe sheet between two fiber ferrules within the erbium-doped fiber laser, is used to effectively modulate the laser cavity losses. The WSSe-based SA has a saturation intensity of ~0.006 MW∕cm^2 and a modulation depth of 7.8%, giving an optimum Q-switched laser output with a maximum repetition rate of 61.81 kHz and a minimum pulse width of 2.6 μs. The laser＇s highest output power of 0.45 mW and highest pulse energy of 7.31 nJ are achieved at the maximum pump power of 280.5 mW. The tunability of the cavity＇s output at the maximum pump power is analyzed with a C-band tunable bandpass filter, giving a broad tunable range of ~40 nm, from 1530 nm to 1570 nm. The output performance of the tunable Q-switched laser correlates well with the gain spectrum of erbium-doped fibers, with the shift in the gain profile as a result of the saturated SA.展开更多
The pulsed single-longitudinal-mode(SLM)operation caused by the modal-gain difference in a repetitively passively Q-switched(PQS)laser is studied in detail.Firstly,the analytical expressions for the pulse buildup-time...The pulsed single-longitudinal-mode(SLM)operation caused by the modal-gain difference in a repetitively passively Q-switched(PQS)laser is studied in detail.Firstly,the analytical expressions for the pulse buildup-time difference of repetitively PQS four-level and quasi-three-level lasers have been developed respectively.Then,according to the temporal criterion,the required conditions for repetitively PQS four-level and quasi-three-level lasers to achieve SLM operation are analyzed.The analysis results show that in addition to the short cavity is conducive to obtaining the pulsed SLM laser,the use of a lower pump power(compared to the threshold power)will help to obtain a longer pulse buildup-time difference and thus enabling the SLM operation.Moreover,it is worth noting that for the quasi-three-level lasers,the pulse buildup-time difference also depends on the initial population inversion density.The results also reveal that setting resonator parameters that can obtain large initial population inversion density will be helpful to the SLM operation in both four-level and quasithree-level regimes.In addition,the use of saturable absorber with a low absorption cross-section ratio between the excited state and ground state also contributes to the realization of the SLM.Finally,the optimization model of passively Q-switched single-longitudinal-mode laser is established.In addition to predicting the output performance of the laser,this model can also be used to obtain the optimal resonator parameters and the upper limit of pump power for SLM operation.展开更多
The active/passive Q-switching operation of a 2 [tm a-cut Tm,Ho：YAP laser was experimentally demonstrated with an acousto-optical Q-switch/MoS2 saturable absorber mirror. The active Q-switch laser was operated for th...The active/passive Q-switching operation of a 2 [tm a-cut Tm,Ho：YAP laser was experimentally demonstrated with an acousto-optical Q-switch/MoS2 saturable absorber mirror. The active Q-switch laser was operated for the first time, to the best of our knowledge, with an average output power of 12.3 W and a maximum pulse energy of 10.3 mJ. The passive Q-switch laser was also the first acquired with an average output power of 3.3 W and per pulse energy of 23.31 μJ, and the beam quality factors of Mx^2 = 1.06 and My^2 = 1.06 were measured at the average output power of 2 W.展开更多
In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,th...In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.展开更多
We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We...We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We obtain a stabilized pulse laser and measure the pulse width of different orders. The first order of SBS has a central wavelength of 1549.75 nm, an average output power of 9 mW, and a pulse width of 400 ns. The pulse width of SBS is reduced by the higher-order signals with the larger fluctuations.展开更多
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 oper...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.展开更多
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...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.展开更多
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 o...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.展开更多
We demonstrate a Q-switched Raman fiber laser using molybdenum disulfide （MoS2） as a saturable absorber （SA）. The SA is assembled by depositing a mechanically exfoliated MoS2 onto a fiber ferrule facet before it i...We demonstrate a Q-switched Raman fiber laser using molybdenum disulfide （MoS2） as a saturable absorber （SA）. The SA is assembled by depositing a mechanically exfoliated MoS2 onto a fiber ferrule facet before it is matched with another clean ferrule via a connector. It is inserted in a Raman fiber laser cavity with a total cavity length of about 8kin to generate a Q-switching pulse train operating at 1560.2nm. A 7.7-kin-long dispersion compensating fiber with 584 ps.nm-i km-1 of dispersion is used as a nonlinear gain medium. As the pump power is increased from 395 m W to 422 m W, the repetition rate of the Q-switching pulses can be increased from 132.7 to 137.4 kHz while the pulse width is concurrently decreased from 3.35μs to 3.03μs. The maximum pulse energy of 54.3 nJ is obtained at the maximum pump power of 422 roW. These results show that the mechanically exfoliated MoS2 SA has a great potential to be used for pulse generation in Raman fiber laser systems.展开更多
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 ...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.展开更多
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 ...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.展开更多
Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these...Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.展开更多
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 e...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.展开更多
The performance of a passively Q-switched all-solid-state Nd:YVO_(4) laser using Cr^(4+):YAG as saturable absorber is reported.Optimum coupling operation at 1064nm resulted in 70ns pulses at 40kHz repetition rates wit...The performance of a passively Q-switched all-solid-state Nd:YVO_(4) laser using Cr^(4+):YAG as saturable absorber is reported.Optimum coupling operation at 1064nm resulted in 70ns pulses at 40kHz repetition rates with average output power of 2.1 W.A quantitative theoretical description agrees well with the experimental results.展开更多
We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating me...We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 gs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets.展开更多
The first experimental comparison between the actively and passively Q-switched intracavity optical parametric oscillators (IOPOs) at 1.57μm driven by a small-scale diode-pumped Nd:YVO4 laser are thoroughly presented...The first experimental comparison between the actively and passively Q-switched intracavity optical parametric oscillators (IOPOs) at 1.57μm driven by a small-scale diode-pumped Nd:YVO4 laser are thoroughly presented.It is found that the performances of the two types of IOPOs are complementary.The actively Q-switched IOPO features a shorter pulse duration,a higher peak power,and a superior power and pulse stability.However,in terms of compactness,operation threshold and conversion efficiency,passively Q-switched IOPOs are more attractive.It is further indicated that the passively Q-switched IOPO at 1.57 μm is a promising and cost-effective eye-safe laser source,especially at the low and moderate output levels.In addition,instructional improvement measures for the two types of IOPOs are also summarized.展开更多
文摘A passive Q-switched flash-lamp-pumped Nd∶YAG laser with the ion-implanted semi-insulating GaAs wafer is reported.The wafer is implanted with 400keV As+ ions in the concentration of 10 16cm -2.Using GaAs wafer as an absorber and an output coupler,62ns pulse duration of single pulse is obtained.
基金Supported by the National Natural Science Foundation of China under Grant No 11574170
文摘We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generated at a repetition rate of 285.7 kHz,approaching or very near the intrinsic upper limit imposed by the recovery time of the Cr^（4＋）：YAG saturable absorber,and the resulting pulse energy,duration and peak power are,respectively,8.2μJ,39.2ns and 0.209kW.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61008018 and 11421064)the National Basic Research Program of China (Grant No. 2013CBA01505)
文摘With MoS2 as saturable absorber, passive Q-switching and Q-switched mode-locking operations of a Tm-doped calcium lithium niobium gallium garnet（Tm:CLNGG） laser were experimentally demonstrated. The Q-switched laser emitted a maximum average output power of 62 mW and highest pulse energy of 0.72 μJ. Q-switched mode locking was also obtained in the experiment. The research results will open up applications of MoS2 at the mid-infrared wavelength.
基金Project supported by the National Natural Science Foundation of China(Nos.61875077 and 61911530131)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.18KJA510001)。
文摘Developing new saturable absorbers for use in the mid-infrared region has practical significance for short-pulsed lasers and related scientific and industrial applications.The performance of gold nanorods(GNRs)as saturable absorbers at novel mid-infrared wavelengths needs to be evaluated even though these benefit from ultrafast nonlinear responses and broadband saturable absorption.Passive Q-switching of an LD-pumped 2.3μm Tm:YLF laser using GNRs was successfully realized in this study.Pulses with an 843 ns pulse width and a 6.67 kHz repetition rate were achieved using this Q-switched laser.Results showed that GNRs provide promising passive Q-switches for 2.3μm Tm-doped lasers.
基金supported by the Ministry of Higher Education,Malaysia(Grant No.LRGS(2015)NGOD/UM/KPT)the University of Malaya(Grant Nos.RU001-2017 and RP 029A–15 AFR)
文摘A highly stable Q-switched laser incorporating a mechanically exfoliated tungsten sulphoselenide （WSSe） thin sheet saturable absorber （SA） is proposed and demonstrated. The SA assembly, formed by sandwiching a thin WSSe sheet between two fiber ferrules within the erbium-doped fiber laser, is used to effectively modulate the laser cavity losses. The WSSe-based SA has a saturation intensity of ~0.006 MW∕cm^2 and a modulation depth of 7.8%, giving an optimum Q-switched laser output with a maximum repetition rate of 61.81 kHz and a minimum pulse width of 2.6 μs. The laser＇s highest output power of 0.45 mW and highest pulse energy of 7.31 nJ are achieved at the maximum pump power of 280.5 mW. The tunability of the cavity＇s output at the maximum pump power is analyzed with a C-band tunable bandpass filter, giving a broad tunable range of ~40 nm, from 1530 nm to 1570 nm. The output performance of the tunable Q-switched laser correlates well with the gain spectrum of erbium-doped fibers, with the shift in the gain profile as a result of the saturated SA.
基金Project supported by National Natural Science Foundation of China(Grant No.62205102)。
文摘The pulsed single-longitudinal-mode(SLM)operation caused by the modal-gain difference in a repetitively passively Q-switched(PQS)laser is studied in detail.Firstly,the analytical expressions for the pulse buildup-time difference of repetitively PQS four-level and quasi-three-level lasers have been developed respectively.Then,according to the temporal criterion,the required conditions for repetitively PQS four-level and quasi-three-level lasers to achieve SLM operation are analyzed.The analysis results show that in addition to the short cavity is conducive to obtaining the pulsed SLM laser,the use of a lower pump power(compared to the threshold power)will help to obtain a longer pulse buildup-time difference and thus enabling the SLM operation.Moreover,it is worth noting that for the quasi-three-level lasers,the pulse buildup-time difference also depends on the initial population inversion density.The results also reveal that setting resonator parameters that can obtain large initial population inversion density will be helpful to the SLM operation in both four-level and quasithree-level regimes.In addition,the use of saturable absorber with a low absorption cross-section ratio between the excited state and ground state also contributes to the realization of the SLM.Finally,the optimization model of passively Q-switched single-longitudinal-mode laser is established.In addition to predicting the output performance of the laser,this model can also be used to obtain the optimal resonator parameters and the upper limit of pump power for SLM operation.
基金National Natural Science Foundation of China(NSFC)(61378029,61775053,51572053,51777046)Science Foundation for Outstanding Youths of Heilongjiang Province(JC2016016)Science Foundation for Youths of Heilongjiang Province(QC2017078)
文摘The active/passive Q-switching operation of a 2 [tm a-cut Tm,Ho：YAP laser was experimentally demonstrated with an acousto-optical Q-switch/MoS2 saturable absorber mirror. The active Q-switch laser was operated for the first time, to the best of our knowledge, with an average output power of 12.3 W and a maximum pulse energy of 10.3 mJ. The passive Q-switch laser was also the first acquired with an average output power of 3.3 W and per pulse energy of 23.31 μJ, and the beam quality factors of Mx^2 = 1.06 and My^2 = 1.06 were measured at the average output power of 2 W.
基金supported by the Nanjing University of Posts and Telecommunications Foundation,China(Grant Nos.JUH219002 and JUH219007)the Key R&D Program of Shandong Province,China(Grant No.2021CXGC010202)。
文摘In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.
基金Supported by the National Natural Science Foundation of China under Grant No 61675188the Open Fund of Key Laboratory Pulse Power Laser Technology of China under Grant No SKL2016KF03
文摘We propose a new method to separate different orders of an all-fiber passive Q-switching stimulated Brillouin scattering（SBS） laser. We use two fiber Bragg gratings connected by two circulators for the filtering. We obtain a stabilized pulse laser and measure the pulse width of different orders. The first order of SBS has a central wavelength of 1549.75 nm, an average output power of 9 mW, and a pulse width of 400 ns. The pulse width of SBS is reduced by the higher-order signals with the larger fluctuations.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632704
文摘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.
基金Supported by the Natural Science Foundation of Shandong Province under Grant Nos ZR2015FM018 and ZR2014FM028the National Natural Science Foundation of China under Grant No 61475086
文摘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.
基金Supported by the Foundation of Shandong Province under Grant No J13LN28the National Natural Science Foundation of China under Grant No 11304184
文摘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.
文摘We demonstrate a Q-switched Raman fiber laser using molybdenum disulfide （MoS2） as a saturable absorber （SA）. The SA is assembled by depositing a mechanically exfoliated MoS2 onto a fiber ferrule facet before it is matched with another clean ferrule via a connector. It is inserted in a Raman fiber laser cavity with a total cavity length of about 8kin to generate a Q-switching pulse train operating at 1560.2nm. A 7.7-kin-long dispersion compensating fiber with 584 ps.nm-i km-1 of dispersion is used as a nonlinear gain medium. As the pump power is increased from 395 m W to 422 m W, the repetition rate of the Q-switching pulses can be increased from 132.7 to 137.4 kHz while the pulse width is concurrently decreased from 3.35μs to 3.03μs. The maximum pulse energy of 54.3 nJ is obtained at the maximum pump power of 422 roW. These results show that the mechanically exfoliated MoS2 SA has a great potential to be used for pulse generation in Raman fiber laser systems.
基金Project supported by the Serving Local Special Project of Shaanxi Provincial Department of Education of China (Grant No. 19JC040)the National Natural Science Foundation of China (Grant No. 61905193)。
文摘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.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775053,51572053,51777046,and 61705140)
文摘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.
基金supported by the Fundamental Research Funds for Central Public Welfare Research Institute,No.2020CZ-5(to WS and GS)the National Natural Science Foundation of China,No.31970970(to JSR)Fundamental Research Funds for the Central Universities,No.YWF-23-YG-QB-010(to JSR)。
文摘Patients with complete spinal cord injury retain the potential for volitional muscle activity in muscles located below the spinal injury level.However,because of prolonged inactivity,initial attempts to activate these muscles may not effectively engage any of the remaining neurons in the descending pathway.A previous study unexpectedly found that a brief clinical round of passive activity significantly increased volitional muscle activation,as measured by surface electromyography.In this study,we further explored the effect of passive activity on surface electromyographic signals during volitional control tasks among individuals with complete spinal cord injury.Eleven patients with chronic complete thoracic spinal cord injury were recruited.Surface electromyography data from eight major leg muscles were acquired and compared before and after the passive activity protocol.The results indicated that the passive activity led to an increased number of activated volitional muscles and an increased frequency of activation.Although the cumulative root mean square of surface electromyography amplitude for volitional control of movement showed a slight increase after passive activity,the difference was not statistically significant.These findings suggest that brief passive activity may enhance the ability to initiate volitional muscle activity during surface electromyography tasks and underscore the potential of passive activity for improving residual motor control among patients with motor complete spinal cord injury.
基金Project supported by the National Natural Science Foundation of China(Grant No.61378024)
文摘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.
基金Supported by the 863 Program of National Advanced Materials Committee
文摘The performance of a passively Q-switched all-solid-state Nd:YVO_(4) laser using Cr^(4+):YAG as saturable absorber is reported.Optimum coupling operation at 1064nm resulted in 70ns pulses at 40kHz repetition rates with average output power of 2.1 W.A quantitative theoretical description agrees well with the experimental results.
基金Project supported by the National Scientific Research Project of China(Grant No.61177047)Beijing Municipal Natural Science Foundation+1 种基金China(Grant No.1102005)the Basic Research Foundation of Beijing University of Technology,China(Grant No.X3006111201501)
文摘We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 gs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets.
基金Supported by the National Natural Science Foundation of China under Grant No 61108008the Shandong-Provincial Natural Science Foundation under Grant No ZR2010FQ022the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology under Grant No HIT.NSRIF.201007.
文摘The first experimental comparison between the actively and passively Q-switched intracavity optical parametric oscillators (IOPOs) at 1.57μm driven by a small-scale diode-pumped Nd:YVO4 laser are thoroughly presented.It is found that the performances of the two types of IOPOs are complementary.The actively Q-switched IOPO features a shorter pulse duration,a higher peak power,and a superior power and pulse stability.However,in terms of compactness,operation threshold and conversion efficiency,passively Q-switched IOPOs are more attractive.It is further indicated that the passively Q-switched IOPO at 1.57 μm is a promising and cost-effective eye-safe laser source,especially at the low and moderate output levels.In addition,instructional improvement measures for the two types of IOPOs are also summarized.
