·AIM: To compare the effect of suction on the macular thickness and retinal nerve fiber layer(RNFL) thickness during laser in situ keratomileusis(LASIK) used Ziemer FEMTO LDV femtosecond laser(Ziemer group) and M...·AIM: To compare the effect of suction on the macular thickness and retinal nerve fiber layer(RNFL) thickness during laser in situ keratomileusis(LASIK) used Ziemer FEMTO LDV femtosecond laser(Ziemer group) and Moria M2 automated microkeratome(Moria group) for flap creation.· METHODS: Fourier-domain optical coherence tomography(FD-OCT) was used to measure macular thickness, ganglion cell complex thickness and RNFL thickness of 204 eyes of 102 patients with the Ziemer femtosecond laser(102 eyes) and the Moria M2microkeratome(102 eyes) before surgery and 30min; 1,3d; 1wk; 1, 3mo; 1y after surgery.· RESULTS: The average foveal thickness and parafoveal retinal thickness 30 min after the surgery were statistically more than that before surgery(Ziemer P 【0.001,P =0.003 and Moria P=0.001, P=0.006) and the effect was less in the Ziemer group than that in the Moria group(P all 【0.05). The ganglion cell complex thickness was not significantly changed in both groups(P all 】0.05). The RNFL thickness was statistically less 30 min after surgery in both groups(P=0.014, P 【0.001), but the influence was less in Ziemer group than that in Moria group(P =0.038).However, the RNFL thickness had recovered to the preoperative level only 1d after surgery.·CONCLUSION: The suction of femtosecond laser and mechanical microkeratome led to the increase in macular central fovea thickness and the decrease in RNFL thickness values at the early stage after LASIK. The effect of suction on macular and the RNFL thicknesses in Ziemer group is smaller than that in Moria group.展开更多
We experimentally demonstrate a femtosecond mode-locked thulium-holmium(Tm-Ho) co-doped fiber laser incorporating a saturable absorber(SA) based on a bulk-structured bismuth selenide(Bi2Se3) topological insulato...We experimentally demonstrate a femtosecond mode-locked thulium-holmium(Tm-Ho) co-doped fiber laser incorporating a saturable absorber(SA) based on a bulk-structured bismuth selenide(Bi2Se3) topological insulator(TI). The SA was prepared by depositing a mechanically exfoliated Bi2Se3 TI layer onto a side-polished optical fiber platform. Unlike high-quality nano-structured Bi2Se3 TI-based SA, bulk-structured Bi2Se3 with non-negligible oxidation was used as a saturable absorption material for this experimental demonstration due to its easy fabrication process. The saturation power and modulation depth of the prepared SA were measured to be -28.6 W and -13.4%, respectively. By incorporating the prepared SA into a Tm-Ho co-doped fiber ring cavity, stable soliton pulses with a temporal width of - 853 fs could be generated at 1912.12 nm. The 3-dB bandwidth of the mode-locked pulse was measured to be -4.87 nm. This experimental demonstration reaffirms that Bi2Se3 is a superb base material for mid-infrared passive mode-locking even under oxidation.展开更多
We experimentally demonstrate that a tunable supercontinuum(SC) can be generated in a Yb3+-doped microstructure fiber by the concept of wavelength conversion with a Ti:sapphire femtosecond(fs) laser as the pump....We experimentally demonstrate that a tunable supercontinuum(SC) can be generated in a Yb3+-doped microstructure fiber by the concept of wavelength conversion with a Ti:sapphire femtosecond(fs) laser as the pump.Experimental results show that an emission light around 1040 nm in an anomalous dispersion region is first generated and amplified by fs pulses in the normal dispersion region. Then, SC spectra from 1100 to 1380 nm and 630 to 840 nm can be achieved by combined effects of higher-order soliton fission and Raman soliton self-frequency shift in the anomalous dispersion region and self-phase modulation, dispersive wave, and four-wave mixing in the normal dispersion region. It is also demonstrated that the 20 nm change of pump results in a 280 nm broadband shift of soliton and the further red-shift of soliton is limited by OH-absorption at 1380 nm.展开更多
High-power femtosecond mid-infrared(MIR)lasers are of vast importance to both fundamental research and applications.We report a high-power femtosecond master oscillator power amplifier laser system consisting of a sin...High-power femtosecond mid-infrared(MIR)lasers are of vast importance to both fundamental research and applications.We report a high-power femtosecond master oscillator power amplifier laser system consisting of a singlemode Er:ZBLAN fiber mode-locked oscillator and pre-amplifier followed by a large-mode-area Er:ZBLAN fiber main amplifier.The main amplifier is actively cooled and bidirectionally pumped at 976 nm,generating a slope efficiency of 26.9%.Pulses of 8.12 W,148 fs at 2.8μm with a repetition rate of 69.65 MHz are achieved.To the best of our knowledge,this is the highest average power ever achieved from a femtosecond MIR laser source.Such a compact ultrafast laser system is promising for a wide range of applications,such as medical surgery and material processing.展开更多
In this work,we present a high-power,high-repetition-rate,all-fiber femtosecond laser system operating at 1.5μm.This all-fiber laser system can deliver femtosecond pulses at a fundamental repetition rate of 10.6 GHz ...In this work,we present a high-power,high-repetition-rate,all-fiber femtosecond laser system operating at 1.5μm.This all-fiber laser system can deliver femtosecond pulses at a fundamental repetition rate of 10.6 GHz with an average output power of 106.4 W–the highest average power reported so far from an all-fiber femtosecond laser at 1.5μm,to the best of our knowledge.By utilizing the soliton-effect-based pulse compression effect with optimized pre-chirping dispersion,the amplified pulses are compressed to 239 fs in an all-fiber configuration.Empowered by such a high-power ultrafast fiber laser system,we further explore the nonlinear interaction among transverse modes LP01,LP11 and LP21 that are expected to potentially exist in fiber laser systems using large-mode-area fibers.The intermodal modulational instability is theoretically investigated and subsequently identified in our experiments.Such a high-power all-fiber ultrafast laser without bulky free-space optics is anticipated to be a promising laser source for applications that specifically require compact and robust operation.展开更多
We report the direct generation of 75-femosecond pulses from a stretched-pulse fiber ring laser using the nonlinear polarization rotation mode-locking mechanism. As the gain media in the laser,the high-doped erbium-do...We report the direct generation of 75-femosecond pulses from a stretched-pulse fiber ring laser using the nonlinear polarization rotation mode-locking mechanism. As the gain media in the laser,the high-doped erbium-doped fiber working at positive dispersion was used to compensate the negative dispersion of standard single mode fiber. Under a 125 mW pump power,the average output power was higher than 15 mW,with a 25.9 MHz repetition rate and 53 nm spectrum width. Meanwhile,the pulse energy was greatly improved,which could reach 0.6 nJ. The laser easily achieved mode-locking and ran stably at room temperature. All-fiber construction makes it compactable and portable.展开更多
Seed laser pulses with average power of 146 pW and pulse duration of 480 fs were amplified to 14.5 mW. The pulse duration was compressed to 260 fs using 6 m high concentration Er3+ -doped fiber under forward pumping. ...Seed laser pulses with average power of 146 pW and pulse duration of 480 fs were amplified to 14.5 mW. The pulse duration was compressed to 260 fs using 6 m high concentration Er3+ -doped fiber under forward pumping. The amplified signal pulse energy was 0.691 nJ (corresponding to a peak power of 2 657.7 W) and the repetition rate was 20.84 MHz. Spectrum breakup was observed simultaneously. The spectrum of pulses amplified by 3 m Er3+ -doped fiber remains a single peak under different pump power. The amplified pulse duration was compressed abnormally with the increasing pump power using the backward pumping; that is, the amplified pulses were compressed with the increasing pump power under low pump power. When the pump power reached 38 mW, the shortest amplified pulse duration was 309 fs. With further increase in pump power, the amplified pulses began broadening, accompanied by a single peak spectrum under different pump power.展开更多
We propose a high temperature-sensitive long period fiber grating(LPFG) sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some pa...We propose a high temperature-sensitive long period fiber grating(LPFG) sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.展开更多
We demonstrate a femtosecond mode-locked erbium-doped fiber laser(EDFL) using a nickel oxide(Ni O) as a saturable absorber(SA). Ni O nanoparticles are hosted into polyethylene oxide film and attached to fiber fe...We demonstrate a femtosecond mode-locked erbium-doped fiber laser(EDFL) using a nickel oxide(Ni O) as a saturable absorber(SA). Ni O nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The Ni O-SA shows a 39% modulation depth with a 0.04 MW∕cm^2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum(FWHM) of around 2.85 nm centered at 1561.8 nm.The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.展开更多
Optical coherence tomography (OCT) with ultrahigh axial resolution was achieved by the super-contin-uum generated by coupling femtosecond pulses from a commercial Ti:sapphire laser into an air-silica microstructure fi...Optical coherence tomography (OCT) with ultrahigh axial resolution was achieved by the super-contin-uum generated by coupling femtosecond pulses from a commercial Ti:sapphire laser into an air-silica microstructure fiber. The visible spectrum of the super-continuum from 450 to 700 nm centered at 540 nm can be generated. A free-space axial OCT resolution of 0.64 μm was achieved. The sensitivity of OCT system was 108 dB with incident light power 3 mW at sample,only 7dB below the theoretical limit. Subcellular OCT imaging was also demonstrated,showing great potential for biomedical application.展开更多
文摘·AIM: To compare the effect of suction on the macular thickness and retinal nerve fiber layer(RNFL) thickness during laser in situ keratomileusis(LASIK) used Ziemer FEMTO LDV femtosecond laser(Ziemer group) and Moria M2 automated microkeratome(Moria group) for flap creation.· METHODS: Fourier-domain optical coherence tomography(FD-OCT) was used to measure macular thickness, ganglion cell complex thickness and RNFL thickness of 204 eyes of 102 patients with the Ziemer femtosecond laser(102 eyes) and the Moria M2microkeratome(102 eyes) before surgery and 30min; 1,3d; 1wk; 1, 3mo; 1y after surgery.· RESULTS: The average foveal thickness and parafoveal retinal thickness 30 min after the surgery were statistically more than that before surgery(Ziemer P 【0.001,P =0.003 and Moria P=0.001, P=0.006) and the effect was less in the Ziemer group than that in the Moria group(P all 【0.05). The ganglion cell complex thickness was not significantly changed in both groups(P all 】0.05). The RNFL thickness was statistically less 30 min after surgery in both groups(P=0.014, P 【0.001), but the influence was less in Ziemer group than that in Moria group(P =0.038).However, the RNFL thickness had recovered to the preoperative level only 1d after surgery.·CONCLUSION: The suction of femtosecond laser and mechanical microkeratome led to the increase in macular central fovea thickness and the decrease in RNFL thickness values at the early stage after LASIK. The effect of suction on macular and the RNFL thicknesses in Ziemer group is smaller than that in Moria group.
基金Project supported by the National Research Foundation of Korea(NRF)Grant Funded by the Korea Government(MSIT),Republic of Korea(Grant No.NRF-2018R1A2B6001641)Ministry of Science and ICT(MSIT)under the Information Technology Research Center(ITRC)Support Program(Grant No.IITP-2018-2015-0-00385)supervised by the Institute for Information and Communications Technology Promotion(IITP)
文摘We experimentally demonstrate a femtosecond mode-locked thulium-holmium(Tm-Ho) co-doped fiber laser incorporating a saturable absorber(SA) based on a bulk-structured bismuth selenide(Bi2Se3) topological insulator(TI). The SA was prepared by depositing a mechanically exfoliated Bi2Se3 TI layer onto a side-polished optical fiber platform. Unlike high-quality nano-structured Bi2Se3 TI-based SA, bulk-structured Bi2Se3 with non-negligible oxidation was used as a saturable absorption material for this experimental demonstration due to its easy fabrication process. The saturation power and modulation depth of the prepared SA were measured to be -28.6 W and -13.4%, respectively. By incorporating the prepared SA into a Tm-Ho co-doped fiber ring cavity, stable soliton pulses with a temporal width of - 853 fs could be generated at 1912.12 nm. The 3-dB bandwidth of the mode-locked pulse was measured to be -4.87 nm. This experimental demonstration reaffirms that Bi2Se3 is a superb base material for mid-infrared passive mode-locking even under oxidation.
基金Supported by the National Natural Science Foundation of China under Grant No 61735011the Natural Science Foundation of Hebei Province under Grant Nos F2016203389 and F2018105036+2 种基金the Science and Technology Research Project of College and University in Hebei Province under Grant No BJ2017108the Open Subject of Jiangsu Key Laboratory of Meteorological Observation and Information Processing under Grant No KDXS1107the Science and Technology Project of Tangshan City under Grant No 17130257a
文摘We experimentally demonstrate that a tunable supercontinuum(SC) can be generated in a Yb3+-doped microstructure fiber by the concept of wavelength conversion with a Ti:sapphire femtosecond(fs) laser as the pump.Experimental results show that an emission light around 1040 nm in an anomalous dispersion region is first generated and amplified by fs pulses in the normal dispersion region. Then, SC spectra from 1100 to 1380 nm and 630 to 840 nm can be achieved by combined effects of higher-order soliton fission and Raman soliton self-frequency shift in the anomalous dispersion region and self-phase modulation, dispersive wave, and four-wave mixing in the normal dispersion region. It is also demonstrated that the 20 nm change of pump results in a 280 nm broadband shift of soliton and the further red-shift of soliton is limited by OH-absorption at 1380 nm.
基金the National Natural Science Foundation of China(61975136,61935014,62105222,61775146,61905151)the Basic and Applied Basic Research Foundation of Guangdong Province(2019A1515010699)+1 种基金the Shenzhen Science and Technology Innovation Program(CJGJZD20200617103003009,JCYJ20210324094400001,GJHZ20210705141801006)the Beijing Natural Science Foundation(JQ21019).
文摘High-power femtosecond mid-infrared(MIR)lasers are of vast importance to both fundamental research and applications.We report a high-power femtosecond master oscillator power amplifier laser system consisting of a singlemode Er:ZBLAN fiber mode-locked oscillator and pre-amplifier followed by a large-mode-area Er:ZBLAN fiber main amplifier.The main amplifier is actively cooled and bidirectionally pumped at 976 nm,generating a slope efficiency of 26.9%.Pulses of 8.12 W,148 fs at 2.8μm with a repetition rate of 69.65 MHz are achieved.To the best of our knowledge,this is the highest average power ever achieved from a femtosecond MIR laser source.Such a compact ultrafast laser system is promising for a wide range of applications,such as medical surgery and material processing.
基金NSFC Development of National Major Scientific Research Instrument(61927816)the Introduced Innovative Team Project of Guangdong Pearl River Talents Program(2021ZT09Z109)+6 种基金the Natural Science Foundation of Guangdong Province(2021B1515020074)the Mobility Programme of the Sino-German(M-0296)the Double First Class Initiative(D6211170)the Guangdong Key Research and Development Program(2018B090904003)the National Natural Science Foundation of China(NSFC)(U1609219)the Science and Technology Project of Guangdong(2020B1212060002)the Key R&D Program of Guangzhou(202007020003).
文摘In this work,we present a high-power,high-repetition-rate,all-fiber femtosecond laser system operating at 1.5μm.This all-fiber laser system can deliver femtosecond pulses at a fundamental repetition rate of 10.6 GHz with an average output power of 106.4 W–the highest average power reported so far from an all-fiber femtosecond laser at 1.5μm,to the best of our knowledge.By utilizing the soliton-effect-based pulse compression effect with optimized pre-chirping dispersion,the amplified pulses are compressed to 239 fs in an all-fiber configuration.Empowered by such a high-power ultrafast fiber laser system,we further explore the nonlinear interaction among transverse modes LP01,LP11 and LP21 that are expected to potentially exist in fiber laser systems using large-mode-area fibers.The intermodal modulational instability is theoretically investigated and subsequently identified in our experiments.Such a high-power all-fiber ultrafast laser without bulky free-space optics is anticipated to be a promising laser source for applications that specifically require compact and robust operation.
基金the National Natural Science Foundation of China (Grant No. 60577048)the Science and Technology Committee of Shanghai Municipal (Grant No. 04DZ14001)
文摘We report the direct generation of 75-femosecond pulses from a stretched-pulse fiber ring laser using the nonlinear polarization rotation mode-locking mechanism. As the gain media in the laser,the high-doped erbium-doped fiber working at positive dispersion was used to compensate the negative dispersion of standard single mode fiber. Under a 125 mW pump power,the average output power was higher than 15 mW,with a 25.9 MHz repetition rate and 53 nm spectrum width. Meanwhile,the pulse energy was greatly improved,which could reach 0.6 nJ. The laser easily achieved mode-locking and ran stably at room temperature. All-fiber construction makes it compactable and portable.
文摘Seed laser pulses with average power of 146 pW and pulse duration of 480 fs were amplified to 14.5 mW. The pulse duration was compressed to 260 fs using 6 m high concentration Er3+ -doped fiber under forward pumping. The amplified signal pulse energy was 0.691 nJ (corresponding to a peak power of 2 657.7 W) and the repetition rate was 20.84 MHz. Spectrum breakup was observed simultaneously. The spectrum of pulses amplified by 3 m Er3+ -doped fiber remains a single peak under different pump power. The amplified pulse duration was compressed abnormally with the increasing pump power using the backward pumping; that is, the amplified pulses were compressed with the increasing pump power under low pump power. When the pump power reached 38 mW, the shortest amplified pulse duration was 309 fs. With further increase in pump power, the amplified pulses began broadening, accompanied by a single peak spectrum under different pump power.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.91323301,51505505,51475482,and 51475481)the Natural Science Foundation of Hunan Province(No.2016JJ3147)+2 种基金the China Postdoctoral Science Foundation(Nos.2015M572264 and 2016T90757)the Self-selected Topic Fund of State Key Laboratory of High Performance and Complex Manufacturing(No.ZZYJKT2015-08)the Fundamental Research Funds for the Central Universities of Central South University
文摘We propose a high temperature-sensitive long period fiber grating(LPFG) sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.
文摘We demonstrate a femtosecond mode-locked erbium-doped fiber laser(EDFL) using a nickel oxide(Ni O) as a saturable absorber(SA). Ni O nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The Ni O-SA shows a 39% modulation depth with a 0.04 MW∕cm^2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum(FWHM) of around 2.85 nm centered at 1561.8 nm.The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.
基金the National Basic Research Program of China (Grant No.001CB510307)Hi-tech Research and Development Program of China (Grant No.2006AA02Z472)+1 种基金National Natural Science Foundation of China (Grant Nos.90508001,10574081)the Ministry of Education of China (Grant No.306020)
文摘Optical coherence tomography (OCT) with ultrahigh axial resolution was achieved by the super-contin-uum generated by coupling femtosecond pulses from a commercial Ti:sapphire laser into an air-silica microstructure fiber. The visible spectrum of the super-continuum from 450 to 700 nm centered at 540 nm can be generated. A free-space axial OCT resolution of 0.64 μm was achieved. The sensitivity of OCT system was 108 dB with incident light power 3 mW at sample,only 7dB below the theoretical limit. Subcellular OCT imaging was also demonstrated,showing great potential for biomedical application.