We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the lin...We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the linear polarizationmaintaining fiber laser to facilitate self-started mode-locking.Pulses with single pulse energy of 26.9 nJ and average output power of 73.9 mW are obtained at the pump power of 600 mW.The transmission characteristics of artificial saturable absorber used in this laser are analyzed theoretically,the influence of the half-wave plate state on mode-locking is discussed,and the mode-locking range is obtained,which is well consistent with the experimental results.展开更多
A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentall...A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentally.Given the optoelastic effect,which depends on fiber geometry,the modal and group birefringences of the PMF can be controlled by applying different twist angles.The spectral wavelength shifts,free spectral ranges,and transmission losses of the original,microtapered,and etched PMFs were compared.Notably,the interference dips for the etched PMF move in opposite directions.As a result,the proposed PMF-based sensor could have multiparameter sensing applications.展开更多
We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to sele...We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.展开更多
浙江大学医学院附属妇产科医院超声科鲁红主任、周一敏医生于2011年通过英国胎儿医学基金会（Fetal Medicine Foundation；FMF）孕早期暨NT超声筛查资格理论课程培训及图像分析记录考核，获得美国FMF早孕超声筛查认证资格。浙江省产前...浙江大学医学院附属妇产科医院超声科鲁红主任、周一敏医生于2011年通过英国胎儿医学基金会（Fetal Medicine Foundation；FMF）孕早期暨NT超声筛查资格理论课程培训及图像分析记录考核，获得美国FMF早孕超声筛查认证资格。浙江省产前诊断中心超声组也因此成为获得该基金会认证的11—13＋6孕周超声检查证书的中心，展开更多
<div style="text-align:justify;"> An in-fiber axial micro-strain sensor based on a Few Mode Fiber Bragg Grating (FM-FBG) is proposed and experimentally characterized. This FM-FBG is in inscribed in a m...<div style="text-align:justify;"> An in-fiber axial micro-strain sensor based on a Few Mode Fiber Bragg Grating (FM-FBG) is proposed and experimentally characterized. This FM-FBG is in inscribed in a multi-layer few-mode fiber (ML-FMF), and could acquire the change of the axial strain along fibers, which depends on the transmission dips. On account of the distinct dual-mode property, a good stability of this sensor is realized. The two transmission dips could have the different sensing behaviors. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. High sensitivity of the FM-FBG, ~4 pm/με and ~4.5 pm/με within the range of 0 με - 1456 με, is experimentally achieved. FM-FBGs could be easily scattered along one fiber. So this sensor may have a great potential of being used in sensor networks. </div>展开更多
A multiwavelength tunable ring-cavity erbium-doped fiber laser(EDFL)based on a Lyot filter was presented.For the proposed Lyot filter,a comb filter consisting of an EDF-polarization-maintaining fiber(EDF-PMF),a polari...A multiwavelength tunable ring-cavity erbium-doped fiber laser(EDFL)based on a Lyot filter was presented.For the proposed Lyot filter,a comb filter consisting of an EDF-polarization-maintaining fiber(EDF-PMF),a polarization controller(PC),and a circulator with four ports was used to suppress the mode competition.The light transmission direction was guaranteed by the circulator.For the proposed fiber laser,tunable single,dual,triple,quadruple,quintuple,sextuple,and septuple wavelengths were realized.A single-wavelength laser output with an optical signal-to-noise ratio(SNR)of up to30.56 dB was realized,and a tuning range of 1590.54 nm to 1599.54 nm was achieved by tuning the PC.The stability of the single,dual,triple,and quadruple-wavelength center power fluctuations was less than 0.05 dB,0.98 dB,5.07 dB,and7.71 dB respectively.When the laser was operated in the multiwavelength condition,the SNR was more than 20.97 dB.The proposed erbium-doped fiber laser is suitable for fiber-sensing system applications.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575011 and 61975003)the Beijing Natural Science Foundation,China(Grant No.4192015).
文摘We demonstrate a self-started,long-term stable polarization-maintaining mode-locked fiber laser based on the nonlinear polarization evolution technique.A polarized beam splitter is inserted into the cavity of the linear polarizationmaintaining fiber laser to facilitate self-started mode-locking.Pulses with single pulse energy of 26.9 nJ and average output power of 73.9 mW are obtained at the pump power of 600 mW.The transmission characteristics of artificial saturable absorber used in this laser are analyzed theoretically,the influence of the half-wave plate state on mode-locking is discussed,and the mode-locking range is obtained,which is well consistent with the experimental results.
基金the National Natural Science Foundation of China(Grant Nos.11804171,11674177,and 61775107)partly by the Natural Science Foundation of Tianjin,China(Grant No.16JCZDJC31000)partly by the Self-Made Experiment Teaching Instrument Project of Nankai University 2018(Grant No.2018NKZZYQ04).
文摘A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber(PMF)is proposed.The transmission properties of the sensor are investigated both theoretically and experimentally.Given the optoelastic effect,which depends on fiber geometry,the modal and group birefringences of the PMF can be controlled by applying different twist angles.The spectral wavelength shifts,free spectral ranges,and transmission losses of the original,microtapered,and etched PMFs were compared.Notably,the interference dips for the etched PMF move in opposite directions.As a result,the proposed PMF-based sensor could have multiparameter sensing applications.
基金supported by the National Natural Science Foundation of China under Grant No.62005040the Fundamental Research Funds for the Central Universities under Grant No.ZYGX2020KYQD003the Science and Technology Project of Sichuan Province under Grant No.2021YJ0368.
文摘We demonstrated the~2.8-μm and~3.5-μm linearly polarized continuous wave(CW)laser outputs from a polarization-maintaining(PM)Er^(3+)-doped fluoride fiber laser.By introducing a film polarizer into the cavity to select the laser polarization orientation,the~2.8-μm linearly polarized CW laser with a high polarization extinction ratio(PER)of~23 dB and maximum output power of 2.37 W was achieved under double-end pumping at 976 nm.By adding another 1981-nm pump source simultaneously,the~3.5-μm linearly polarized CW laser was also obtained,giving higher PER of~27 dB and maximum output power of 307 mW which is only limited by the available power of 1981-nm pump.To the best of our knowledge,this is the first report on a mid-infrared linearly polarized CW PM fiber laser in the>2.5-μm mid-infrared region.This work not only opens up opportunities for some new mid-infrared applications,but also provides a promising platform for developing high-stability and versatile mid-infrared laser sources.
文摘浙江大学医学院附属妇产科医院超声科鲁红主任、周一敏医生于2011年通过英国胎儿医学基金会（Fetal Medicine Foundation；FMF）孕早期暨NT超声筛查资格理论课程培训及图像分析记录考核，获得美国FMF早孕超声筛查认证资格。浙江省产前诊断中心超声组也因此成为获得该基金会认证的11—13＋6孕周超声检查证书的中心，
文摘<div style="text-align:justify;"> An in-fiber axial micro-strain sensor based on a Few Mode Fiber Bragg Grating (FM-FBG) is proposed and experimentally characterized. This FM-FBG is in inscribed in a multi-layer few-mode fiber (ML-FMF), and could acquire the change of the axial strain along fibers, which depends on the transmission dips. On account of the distinct dual-mode property, a good stability of this sensor is realized. The two transmission dips could have the different sensing behaviors. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. High sensitivity of the FM-FBG, ~4 pm/με and ~4.5 pm/με within the range of 0 με - 1456 με, is experimentally achieved. FM-FBGs could be easily scattered along one fiber. So this sensor may have a great potential of being used in sensor networks. </div>
基金Beijing Great Wall Scholars Program(Grant No.CIT&TCD20190323)Beijing Youth Talent Support Program(Grant No.Z2019042)the National Natural Science Foundation of China(Grant No.61875237).
文摘A multiwavelength tunable ring-cavity erbium-doped fiber laser(EDFL)based on a Lyot filter was presented.For the proposed Lyot filter,a comb filter consisting of an EDF-polarization-maintaining fiber(EDF-PMF),a polarization controller(PC),and a circulator with four ports was used to suppress the mode competition.The light transmission direction was guaranteed by the circulator.For the proposed fiber laser,tunable single,dual,triple,quadruple,quintuple,sextuple,and septuple wavelengths were realized.A single-wavelength laser output with an optical signal-to-noise ratio(SNR)of up to30.56 dB was realized,and a tuning range of 1590.54 nm to 1599.54 nm was achieved by tuning the PC.The stability of the single,dual,triple,and quadruple-wavelength center power fluctuations was less than 0.05 dB,0.98 dB,5.07 dB,and7.71 dB respectively.When the laser was operated in the multiwavelength condition,the SNR was more than 20.97 dB.The proposed erbium-doped fiber laser is suitable for fiber-sensing system applications.
