There exist a large number of composed documents in universities in the teaching process. Most of them are required to check the similarity for validation. A kind of similarity computation system is constructed for co...There exist a large number of composed documents in universities in the teaching process. Most of them are required to check the similarity for validation. A kind of similarity computation system is constructed for composed documents with images and text information. Firstly, each document is split and outputs two parts as images and text information. Then, these documents are compared by computing the similarities of images and text contents independently. Through Hadoop system, the text contents are easily and quickly separated. Experimental results show that the proposed system is efficient and practical.展开更多
Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber.Until now,spatiotemporal mode-locking has only been realized in normal-dispersion dissipative solit...Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber.Until now,spatiotemporal mode-locking has only been realized in normal-dispersion dissipative soliton and similariton fiber lasers.In this paper,we demonstrated the first experimental realization of a spatiotemporally mode-locked soliton laser in mid-infrared fluoride fiber with anomalous dispersion.The mode-locked fluoride fiber oscillator directly generated a record pulse energy of 16.1 nJ and peak power of 74.6 kW at 2.8µm wavelength.This work extends the spatiotemporal mode-locking to soliton fiber lasers and should have a wide interest for the laser community.展开更多
We demonstrated a femtosecond mode-locked Er:Zr F4-Ba F2-La F3-Al F3-Na F(Er:ZBLAN)fiber laser at 2.8μm based on the nonlinear polarization rotation technique.The laser generated an average output power of 317 m W wi...We demonstrated a femtosecond mode-locked Er:Zr F4-Ba F2-La F3-Al F3-Na F(Er:ZBLAN)fiber laser at 2.8μm based on the nonlinear polarization rotation technique.The laser generated an average output power of 317 m W with a repetition rate of 107 MHz and pulse duration as short as 131 fs.To the best of our knowledge,this is the shortest pulse generated directly from a mid-infrared mode-locked Er:ZBLAN fiber laser to date.Numerical simulation and experimental results confirm that reducing the gain fiber length is an effective way to shorten the mode-locked pulse duration in the Er:ZBLAN fiber laser.The work takes an important step towards sub-100-fs mid-infrared pulse generation from mode-locked Er:ZBLAN fiber lasers.展开更多
In past years, rare-earth-doped fluoride fiber lasers(FFLs) have developed rapidly in the mid-infrared(mid-IR)region. However, due to the lack of fiber optic devices and challenge of fluoride fiber splicing, most mid-...In past years, rare-earth-doped fluoride fiber lasers(FFLs) have developed rapidly in the mid-infrared(mid-IR)region. However, due to the lack of fiber optic devices and challenge of fluoride fiber splicing, most mid-IR FFLs have been demonstrated with free-space optic elements, limiting the advantages of all-fiber lasers for flexible delivery, stability, and compactness. Here, we report, to the best of our knowledge, the first pulsed all-fiber FFL in the mid-IR region. By taking advantage of the integration of black phosphorus flake, stable Q-switched and mode-locked pulses were obtained at 2.8 μm wavelength. We believe that this all-fiber design will promote the application of pulsed FFL in the mid-IR region.展开更多
The mode-locked fluoride fiber laser(MLFFL)is an exciting platform for directly generating ultrashort pulses in the mid-infrared(mid-IR).However,owing to difficulty in managing the dispersion in fluoride fiber lasers,...The mode-locked fluoride fiber laser(MLFFL)is an exciting platform for directly generating ultrashort pulses in the mid-infrared(mid-IR).However,owing to difficulty in managing the dispersion in fluoride fiber lasers,MLFFLs are restricted to the soliton regime,hindering pulse-energy scaling.We overcame the problem of dispersion management by utilizing the huge normal dispersion generated near the absorption edge of an infrared-bandgap semiconductor and promoted MLFFL from soliton to breathing-pulse mode-locking.In the breathing-pulse regime,the accumulated nonlinear phase shift can be significantly reduced in the cavity,and the pulse-energy-limitation effect is mitigated.The breathing-pulse MLFFL directly produced a pulse energy of 9.3 nJ and pulse duration of 215 fs,with a record peak power of 43.3 kW at 2.8μm.Our work paves the way for the pulse-energy and peak-power scaling of mid-IR fluoride fiber lasers,enabling a wide range of applications.展开更多
Dissipative solitons have been realized in mode-locked fiber lasers in the theoretical framework of the Ginzburg±Landau equation and have significantly improved the pulse energy and peak power levels of such lase...Dissipative solitons have been realized in mode-locked fiber lasers in the theoretical framework of the Ginzburg±Landau equation and have significantly improved the pulse energy and peak power levels of such lasers.It is interesting to explore whether dissipative solitons exist in optical parametric oscillators in the framework of three-wave coupling equations in order to substantially increase the performance of optical parametric oscillators.Here,we demonstrate a temporalfiltering dissipative soliton in a synchronously pumped optical parametric oscillator.The temporal-gain filtering of the pump pulse combined with strong cascading nonlinearity and dispersion in the optical parametric oscillator enables the generation of a broad spectrum with a nearly linear chirp;consequently,a significantly compressed pulse and high peak power can be realized after dechirping outside the cavity.Furthermore,we realized,for the first time,dissipative solitons in an optical system with a negative nonlinear phase shift and anomalous dispersion,extending the parameter region of dissipative solitons.The findings may open a new research block for dissipative solitons and provide new opportunities for mid-infrared ultrafast science.展开更多
We report on a grating-free fiber chirped pulse amplifier(CPA)at 2.8μm for the first time.The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium(Ge)rods as the compressor...We report on a grating-free fiber chirped pulse amplifier(CPA)at 2.8μm for the first time.The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium(Ge)rods as the compressor with a compact structure.High-energy picosecond pulses of 2.07μJ were generated at the repetition rate of 100 kHz.Using highly dispersive Ge rods,the amplified pulses were compressed to 408 fs with a pulse energy of 0.57μJ,resulting in a peak power of approximately 1.4 MW.A spectral broadening phenomenon in the main amplifier was observed,which was caused by the special gain shape of the Er:ZBLAN fiber amplifier in operation and confirmed by our numerical simulation.This compact fiber CPA system at 2.8μm will be practical and meaningful for application fields.展开更多
High-power ultrafast fiber lasers operating at the 2μm wavelength are extremely desirable for material processing,laser surgery,and nonlinear optics.Here we fabricated large-core(LC)double-cladding Tm-doped silica fi...High-power ultrafast fiber lasers operating at the 2μm wavelength are extremely desirable for material processing,laser surgery,and nonlinear optics.Here we fabricated large-core(LC)double-cladding Tm-doped silica fiber via the sol-gel method.The sol-gel-fabricated Tm-doped silica(SGTS)fiber had a large core diameter of 30μm with a high refractive index homogeneity(Δn=2×10^(-4)).With the newly developed LC SGTS fiber as the gain fiber,high-power mode-locking was realized.By using a semiconductor saturable absorber mirror(SESAM)as a mode locker,the LC SGTS fiber oscillator generated mode-locked pulses with an average output power as high as 1.0 W and a pulse duration of 23.9 ps at the wavelength of 1955.0 nm.Our research results show that the self-developed LC Tm-doped silica fiber via the sol-gel method is a promising gain fiber for generating high-power ultrafast lasers in the 2μm spectral region.展开更多
文摘There exist a large number of composed documents in universities in the teaching process. Most of them are required to check the similarity for validation. A kind of similarity computation system is constructed for composed documents with images and text information. Firstly, each document is split and outputs two parts as images and text information. Then, these documents are compared by computing the similarities of images and text contents independently. Through Hadoop system, the text contents are easily and quickly separated. Experimental results show that the proposed system is efficient and practical.
基金This work was partially supported by the National Natural Science Foundation of China(Nos.62075126 and 62005161)the Fundamental Research Funds for the Central Universities.
文摘Spatiotemporal mode-locking creates great opportunity for pulse energy scaling and nonlinear optics research in fiber.Until now,spatiotemporal mode-locking has only been realized in normal-dispersion dissipative soliton and similariton fiber lasers.In this paper,we demonstrated the first experimental realization of a spatiotemporally mode-locked soliton laser in mid-infrared fluoride fiber with anomalous dispersion.The mode-locked fluoride fiber oscillator directly generated a record pulse energy of 16.1 nJ and peak power of 74.6 kW at 2.8µm wavelength.This work extends the spatiotemporal mode-locking to soliton fiber lasers and should have a wide interest for the laser community.
基金supported by the National Natural Science Foundation of China(Nos.61675130,91850203,and 11721091)the National Postdoctoral Program for Innovative Talents(No.BX20170149)。
文摘We demonstrated a femtosecond mode-locked Er:Zr F4-Ba F2-La F3-Al F3-Na F(Er:ZBLAN)fiber laser at 2.8μm based on the nonlinear polarization rotation technique.The laser generated an average output power of 317 m W with a repetition rate of 107 MHz and pulse duration as short as 131 fs.To the best of our knowledge,this is the shortest pulse generated directly from a mid-infrared mode-locked Er:ZBLAN fiber laser to date.Numerical simulation and experimental results confirm that reducing the gain fiber length is an effective way to shorten the mode-locked pulse duration in the Er:ZBLAN fiber laser.The work takes an important step towards sub-100-fs mid-infrared pulse generation from mode-locked Er:ZBLAN fiber lasers.
基金National Basic Research Program of China(2013CBA01505)National Natural Science Foundation of China(NSFC)(11721091,61675130)+1 种基金National Postdoctoral Program for Innovative Talents(BX20170149)China Postdoctoral Science Foundation(2017M620150)
文摘In past years, rare-earth-doped fluoride fiber lasers(FFLs) have developed rapidly in the mid-infrared(mid-IR)region. However, due to the lack of fiber optic devices and challenge of fluoride fiber splicing, most mid-IR FFLs have been demonstrated with free-space optic elements, limiting the advantages of all-fiber lasers for flexible delivery, stability, and compactness. Here, we report, to the best of our knowledge, the first pulsed all-fiber FFL in the mid-IR region. By taking advantage of the integration of black phosphorus flake, stable Q-switched and mode-locked pulses were obtained at 2.8 μm wavelength. We believe that this all-fiber design will promote the application of pulsed FFL in the mid-IR region.
基金the National Natural Science Foundation of China(Grant Nos.61675130,91850203,and 11721091)the National Postdoctoral Program for Innovative Talents(Grant No.BX20170149).
文摘The mode-locked fluoride fiber laser(MLFFL)is an exciting platform for directly generating ultrashort pulses in the mid-infrared(mid-IR).However,owing to difficulty in managing the dispersion in fluoride fiber lasers,MLFFLs are restricted to the soliton regime,hindering pulse-energy scaling.We overcame the problem of dispersion management by utilizing the huge normal dispersion generated near the absorption edge of an infrared-bandgap semiconductor and promoted MLFFL from soliton to breathing-pulse mode-locking.In the breathing-pulse regime,the accumulated nonlinear phase shift can be significantly reduced in the cavity,and the pulse-energy-limitation effect is mitigated.The breathing-pulse MLFFL directly produced a pulse energy of 9.3 nJ and pulse duration of 215 fs,with a record peak power of 43.3 kW at 2.8μm.Our work paves the way for the pulse-energy and peak-power scaling of mid-IR fluoride fiber lasers,enabling a wide range of applications.
基金the National Natural Science Foundation of China(Nos.61675130,62075126 and 91850203)。
文摘Dissipative solitons have been realized in mode-locked fiber lasers in the theoretical framework of the Ginzburg±Landau equation and have significantly improved the pulse energy and peak power levels of such lasers.It is interesting to explore whether dissipative solitons exist in optical parametric oscillators in the framework of three-wave coupling equations in order to substantially increase the performance of optical parametric oscillators.Here,we demonstrate a temporalfiltering dissipative soliton in a synchronously pumped optical parametric oscillator.The temporal-gain filtering of the pump pulse combined with strong cascading nonlinearity and dispersion in the optical parametric oscillator enables the generation of a broad spectrum with a nearly linear chirp;consequently,a significantly compressed pulse and high peak power can be realized after dechirping outside the cavity.Furthermore,we realized,for the first time,dissipative solitons in an optical system with a negative nonlinear phase shift and anomalous dispersion,extending the parameter region of dissipative solitons.The findings may open a new research block for dissipative solitons and provide new opportunities for mid-infrared ultrafast science.
基金partially supported by the National Natural Science Foundation of China(Nos.62075126 and 62005161)the Chenguang Program。
文摘We report on a grating-free fiber chirped pulse amplifier(CPA)at 2.8μm for the first time.The CPA system adopted Er:ZBLAN fiber with large anomalous dispersion as the stretcher and germanium(Ge)rods as the compressor with a compact structure.High-energy picosecond pulses of 2.07μJ were generated at the repetition rate of 100 kHz.Using highly dispersive Ge rods,the amplified pulses were compressed to 408 fs with a pulse energy of 0.57μJ,resulting in a peak power of approximately 1.4 MW.A spectral broadening phenomenon in the main amplifier was observed,which was caused by the special gain shape of the Er:ZBLAN fiber amplifier in operation and confirmed by our numerical simulation.This compact fiber CPA system at 2.8μm will be practical and meaningful for application fields.
基金partially supported by the National Basic Research Program of China(No.2013CBA01505)the Shanghai Excellent Academic Leader Project(No.15XD1502100)the National Natural Science Foundation of China(Nos.61675130 and 11421064)
文摘High-power ultrafast fiber lasers operating at the 2μm wavelength are extremely desirable for material processing,laser surgery,and nonlinear optics.Here we fabricated large-core(LC)double-cladding Tm-doped silica fiber via the sol-gel method.The sol-gel-fabricated Tm-doped silica(SGTS)fiber had a large core diameter of 30μm with a high refractive index homogeneity(Δn=2×10^(-4)).With the newly developed LC SGTS fiber as the gain fiber,high-power mode-locking was realized.By using a semiconductor saturable absorber mirror(SESAM)as a mode locker,the LC SGTS fiber oscillator generated mode-locked pulses with an average output power as high as 1.0 W and a pulse duration of 23.9 ps at the wavelength of 1955.0 nm.Our research results show that the self-developed LC Tm-doped silica fiber via the sol-gel method is a promising gain fiber for generating high-power ultrafast lasers in the 2μm spectral region.
