An active hyperspectral imaging(HSI) system was built with a supercontinuum(SC) laser illuminator and a visible/near-infrared hyperspectral camera, which was used for object spectrum detection in the dark. It was demo...An active hyperspectral imaging(HSI) system was built with a supercontinuum(SC) laser illuminator and a visible/near-infrared hyperspectral camera, which was used for object spectrum detection in the dark. It was demonstrated that the Gaussian-like distribution of the SC illuminator can still be used for accurate reflectance spectrum measurement once the illuminator was characterized in advance. The validity of active HSI results was demonstrated by comparison with passive results. Then, the active HSI system was used to acquire reflectance spectra of different objects in just one pushbroom measurement successfully. With algorithms of principal component analysis clustering and unsupervised K-means spectral classification, this active HSI system with high spectral and spatial resolutions was demonstrated to be efficient and applicable for specific spectrum detections.展开更多
Coherent anti-Stokes Raman scattering(CA RS)microscopy can resolve the chemical compo-nents and distribution of living biological systems in a label-firee manner and is favored in several disciplines.Current CA RS mic...Coherent anti-Stokes Raman scattering(CA RS)microscopy can resolve the chemical compo-nents and distribution of living biological systems in a label-firee manner and is favored in several disciplines.Current CA RS microscopes typically use bulky,high-performance solid-state lasers,which are expensive and sensitive to environmental changes.With their relatively low cost and environmental sensitivity,supercontinum fiber(SF)lasers with a small footprint have found increasing use in biomedical applications.Upon these features,in this paper,we homebuilt a low-cost CARS microscope based on a SF laser module(scCA RS microscope).This SF laser module is specially customized by adding a time synchronized seed source channel to the SF laser to form a dual-channel output laser.The performance of the scCARS microscope is evaluated with dimethyl sulfoxide,whose results confirm a spatial resolution of better than 500nm and a detection sensitivity of millimolar concentrations.The dual-color imaging capability is further demonstrated by imaging different species of mixed microspheres.We finally explore the potential of our scCARS microscope by mapping lipid droplets in different cancer cells and corneal stromal lenses.展开更多
A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum （SC） is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial s...A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum （SC） is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial signal of the seed laser is provided by the incident pump light and amplified in the cavity. Based on this, we obtain a 2-μm pulsed laser with pulse repetition rate of 50 kHz and pulse width of 2 ns from the Tm-doped fiber laser. This 2-μm pulsed laser is amplified by two stages of fiber amplifiers, then the amplified laser is used for mid-infrared （mid-IR） SC generation in a 10-m length of ZrF4-BaF2-LaF3-AIF3-NaF （ZBLAN） fiber. An all-fiber-integrated mid-IR SC with spectrum ranging from 1.8 ~tm to 4.3 μm is achieved. The maximal average output power of the mid-IR SC from the ZBLAN fiber is 1.24 W （average output power beyond 2.5 μm is 340 mW）, corresponding to an output efficiency of 6.6% with respect to the 790-nm pump power.展开更多
Experiments on fs laser-induced transient grating （LITG） in carbon bisulfide （CS2） are carried out to explore the chirp characteristics of a white-light supercontinuum （SC） generated by a 800-nm, 160-fs laser pu...Experiments on fs laser-induced transient grating （LITG） in carbon bisulfide （CS2） are carried out to explore the chirp characteristics of a white-light supercontinuum （SC） generated by a 800-nm, 160-fs laser pulse in a 4-mm thick Al2O3 crystal. Two orders of diffraction signals of SC by fs LITG in CS2 are observed, demonstrating that both the third-order process and the fifth-order process are present simultaneously. The experimental results also imply that the formation of an fs transient refractive-index grating in CS2 is mainly due to the electronic polarization process.展开更多
Broadband normal dispersion pumping supercontinuum （SC） generation in silica photonic crystal fiber （PCF） is investigated in this paper. A 1064-nm picosecond fiber laser is used to pump silica PCF for the SC gener...Broadband normal dispersion pumping supercontinuum （SC） generation in silica photonic crystal fiber （PCF） is investigated in this paper. A 1064-nm picosecond fiber laser is used to pump silica PCF for the SC generation. The length of PCF is optimized for the most efficient stimulated Raman scattering process in the picosecond pump pulse region. The first stimulated Raman Stokes peak is located in the anomalous dispersion regime of the PCF and near the zero dispersion wavelength; thus the SC generation process can benefit from both a normal dispersion pumping scheme and an anomalous dispersion pumping scheme. The 51.7-W SC spanning from about 700 nm to beyond 1700 nm is generated with an all-fiber configuration, and the pump-to-SC conversion efficiency is up to 90%. In order to avoid the output fiber end face damage and increase the stability of the system, an improved output solution for the high power SC is proposed in our experiment. This high-efficiency near-infrared SC source is very suitable for applications in which average output power and spectral power density are firstly desirable.展开更多
We present a systematic investigation of the depolarization properties of a supercontinuum accompanied with femtosecond laser filamentation in barium fluoride(BaF2)crystal.It is found that the depolarization of the su...We present a systematic investigation of the depolarization properties of a supercontinuum accompanied with femtosecond laser filamentation in barium fluoride(BaF2)crystal.It is found that the depolarization of the supercontinuum depends strongly on the crystal orientations with respect to the incident laser polarization.At most crystal orientations,the depolarization of the supercontinuum rises with the increase of the input laser energies and finally saturates.While at 45°,the depolarization of the supercontinuum is not changed and keeps nearly negligible with the increase of the input laser energies.These peculiar depolarization properties of the supercontinuum can be ascribed to the orientation dependence of the cross-polarized wave(XPW)generation and ionization-induced plasma scattering in the BaF2 crystal.展开更多
We demonstrate efficient supercontinuum generation extending into mid-infrared spectral range by pumping a twomode As2S3 fiber in the normal dispersion regime. The As2S3 fiber is fusion spliced to the pigtail of a nea...We demonstrate efficient supercontinuum generation extending into mid-infrared spectral range by pumping a twomode As2S3 fiber in the normal dispersion regime. The As2S3 fiber is fusion spliced to the pigtail of a near-infrared supercontinuum pump source with ultra-low splicing loss of 0.125 dB, which enables a monolithic all-fiber mid-infrared supercontinuum source. By two-mode excitation and mixed-mode cascaded stimulated Raman scattering, a supercontinuum spanning from 1.8 μm to 4.2 μm is obtained. Over 70% of the supercontinuum power is converted to wavelengths beyond2.4 μm. This is the first experimental report with respect to the multimode mid-infrared supercontinuum generation in a step-index two-mode chalcogenide fiber.展开更多
Fiber-based mid-infrared(MIR)supercontinuum(SC)sources benefit from their spectral brightness and spatial coherence that are needed for many applications,such as spectroscopy and metrology.In this paper,an SC spanning...Fiber-based mid-infrared(MIR)supercontinuum(SC)sources benefit from their spectral brightness and spatial coherence that are needed for many applications,such as spectroscopy and metrology.In this paper,an SC spanning from 2μm to 6μm is demonstrated in cascaded ZrF4-BaF2-LaF3-AlF3-NaF(ZBLAN)and As2Se3 step-index fibers.The pump source is a ZBLAN fiber-based MIR SC laser with abundant high-peak-power soliton pulses between 3000 nm and 4200 nm.By concatenating the ZBLAN fiber and the As2 Se3 fiber,efficient cascading red-shifts are obtained in the normal dispersion region of the As2 Se3 fiber.The spectral behavior of cascaded SC generation shows that the long-wavelength proportion of MIR SC generated in the ZBLAN fiber plays a critical role for further spectral extension in the As2 Se3 fiber.展开更多
The effect of pulse width on near-infrared supercontinuum generation in nonlinear fiber amplifier is investigated theoretically and experimentally. The complex Ginzburg–Landau equation and adaptive split-step Fourier...The effect of pulse width on near-infrared supercontinuum generation in nonlinear fiber amplifier is investigated theoretically and experimentally. The complex Ginzburg–Landau equation and adaptive split-step Fourier method are used to simulate the propagation of pulses with different pulse widths in the fiber amplifier, and the results show that a longer pulse is more profitable in near-infrared supercontinuum generation if the central wavelength of the input laser lies in the normal dispersion region of the gain fiber. A four-stage master oscillator power amplifier configuration is adopted and the output spectra under picosecond and nanosecond input pulses are compared with each other. The experimental results are in good accordance with the simulations which can provide some guidance for further optimization of the system.展开更多
Theoretical and experimental research on the effect of initial chirp on near-infrared supercontinuum generation by a nanosecond pulse in a nonlinear fiber amplifier is carded out. The complex Ginzburg-Landau equation ...Theoretical and experimental research on the effect of initial chirp on near-infrared supercontinuum generation by a nanosecond pulse in a nonlinear fiber amplifier is carded out. The complex Ginzburg-Landau equation is used to simulate the propagation of the pulse in the fiber amplifier and the results show that pulses with negative initial chirp produce the widest supercontinuum and pulses with positive initial chirp produce the narrowest supercontinuum when the central wavelength of the pump lies in the normal dispersion region of the gain fiber. A self-made line width narrowing system is utilized to control the initial chirp of the nanosecond pump pulse and a four-stage master oscillator power amplifier configuration is adopted to produce a high power near-infrared suppercontinuum. The experimental results are in good agreement with simulations which can provide some guidance on further optimization of the system in future work.展开更多
基金supported by the Opening Foundation of State Key Laboratory of High Performance Computing,China(Grant No.201601-02)the Open Research Fund of Hunan Provincial Key Laboratory of High Energy Technology,China(Grant No.GNJGJS03)+1 种基金the Opening Foundation of State Key Laboratory of Laser Interaction with Matter,China(Grant No.SKLLIM1702)the China Postdoctoral Innovation Science Foundation(Grant No.BX20180373)
文摘An active hyperspectral imaging(HSI) system was built with a supercontinuum(SC) laser illuminator and a visible/near-infrared hyperspectral camera, which was used for object spectrum detection in the dark. It was demonstrated that the Gaussian-like distribution of the SC illuminator can still be used for accurate reflectance spectrum measurement once the illuminator was characterized in advance. The validity of active HSI results was demonstrated by comparison with passive results. Then, the active HSI system was used to acquire reflectance spectra of different objects in just one pushbroom measurement successfully. With algorithms of principal component analysis clustering and unsupervised K-means spectral classification, this active HSI system with high spectral and spatial resolutions was demonstrated to be efficient and applicable for specific spectrum detections.
基金This work was supported in part by the National Key R&D Program of China(2018YFC0910600)the National Natural Science Foundation of China(81871397)+4 种基金the National Young Talent Program,the Shaanxi Science Fund for Distinguished Young Scholars(2020JC-27)the Key Research and Development Program of Shaanxi(2021ZDLSF04-05)the Shaanxi Young Top-notch Talent Program,the Best Funded Projects for the Scientific and Technological Activities for Excellent Overseas Researchers in Shaanxi Province(2017017)the Fundamental Research Funds for Central Universities(QTZX2105)Xueli Chen would like to thank Dr.Chi Zhang at Purdue University for his help in building the CARS microscope.
文摘Coherent anti-Stokes Raman scattering(CA RS)microscopy can resolve the chemical compo-nents and distribution of living biological systems in a label-firee manner and is favored in several disciplines.Current CA RS microscopes typically use bulky,high-performance solid-state lasers,which are expensive and sensitive to environmental changes.With their relatively low cost and environmental sensitivity,supercontinum fiber(SF)lasers with a small footprint have found increasing use in biomedical applications.Upon these features,in this paper,we homebuilt a low-cost CARS microscope based on a SF laser module(scCA RS microscope).This SF laser module is specially customized by adding a time synchronized seed source channel to the SF laser to form a dual-channel output laser.The performance of the scCARS microscope is evaluated with dimethyl sulfoxide,whose results confirm a spatial resolution of better than 500nm and a detection sensitivity of millimolar concentrations.The dual-color imaging capability is further demonstrated by imaging different species of mixed microspheres.We finally explore the potential of our scCARS microscope by mapping lipid droplets in different cancer cells and corneal stromal lenses.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61235008 and 61077076)
文摘A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum （SC） is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial signal of the seed laser is provided by the incident pump light and amplified in the cavity. Based on this, we obtain a 2-μm pulsed laser with pulse repetition rate of 50 kHz and pulse width of 2 ns from the Tm-doped fiber laser. This 2-μm pulsed laser is amplified by two stages of fiber amplifiers, then the amplified laser is used for mid-infrared （mid-IR） SC generation in a 10-m length of ZrF4-BaF2-LaF3-AIF3-NaF （ZBLAN） fiber. An all-fiber-integrated mid-IR SC with spectrum ranging from 1.8 ~tm to 4.3 μm is achieved. The maximal average output power of the mid-IR SC from the ZBLAN fiber is 1.24 W （average output power beyond 2.5 μm is 340 mW）, corresponding to an output efficiency of 6.6% with respect to the 790-nm pump power.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 20973050 and 10904023)
文摘Experiments on fs laser-induced transient grating （LITG） in carbon bisulfide （CS2） are carried out to explore the chirp characteristics of a white-light supercontinuum （SC） generated by a 800-nm, 160-fs laser pulse in a 4-mm thick Al2O3 crystal. Two orders of diffraction signals of SC by fs LITG in CS2 are observed, demonstrating that both the third-order process and the fifth-order process are present simultaneously. The experimental results also imply that the formation of an fs transient refractive-index grating in CS2 is mainly due to the electronic polarization process.
基金supported by the International Science and Technology Cooperation Program of the Ministry of Science and Technology of China (Grant No. 2012DFG11470)the State Key Program of the National Natural Science Foundation of China (Grant No. 61235008)+3 种基金the National Natural Science Foundation of China (Grant Nos. 10904173,11004247,11274385,61077076,and 61007037)the Science Foundation for Distinguished Young Scholars of Hunan Province,China (Grant No. 12JJ1010)the Postgraduate Innovation Foundation of Hunan Province,China (Grant No. CX2011B034)the Postgraduate Innovation Foundation of National University of Defense Technology,China (Grant No. B110704)
文摘Broadband normal dispersion pumping supercontinuum （SC） generation in silica photonic crystal fiber （PCF） is investigated in this paper. A 1064-nm picosecond fiber laser is used to pump silica PCF for the SC generation. The length of PCF is optimized for the most efficient stimulated Raman scattering process in the picosecond pump pulse region. The first stimulated Raman Stokes peak is located in the anomalous dispersion regime of the PCF and near the zero dispersion wavelength; thus the SC generation process can benefit from both a normal dispersion pumping scheme and an anomalous dispersion pumping scheme. The 51.7-W SC spanning from about 700 nm to beyond 1700 nm is generated with an all-fiber configuration, and the pump-to-SC conversion efficiency is up to 90%. In order to avoid the output fiber end face damage and increase the stability of the system, an improved output solution for the high power SC is proposed in our experiment. This high-efficiency near-infrared SC source is very suitable for applications in which average output power and spectral power density are firstly desirable.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11527807,11674356,11834015,and 91850121)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21010400)the Open Fund of the State Key Laboratory of High Field Laser Physics,China
文摘We present a systematic investigation of the depolarization properties of a supercontinuum accompanied with femtosecond laser filamentation in barium fluoride(BaF2)crystal.It is found that the depolarization of the supercontinuum depends strongly on the crystal orientations with respect to the incident laser polarization.At most crystal orientations,the depolarization of the supercontinuum rises with the increase of the input laser energies and finally saturates.While at 45°,the depolarization of the supercontinuum is not changed and keeps nearly negligible with the increase of the input laser energies.These peculiar depolarization properties of the supercontinuum can be ascribed to the orientation dependence of the cross-polarized wave(XPW)generation and ionization-induced plasma scattering in the BaF2 crystal.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61435009,61235008,and 61405254)
文摘We demonstrate efficient supercontinuum generation extending into mid-infrared spectral range by pumping a twomode As2S3 fiber in the normal dispersion regime. The As2S3 fiber is fusion spliced to the pigtail of a near-infrared supercontinuum pump source with ultra-low splicing loss of 0.125 dB, which enables a monolithic all-fiber mid-infrared supercontinuum source. By two-mode excitation and mixed-mode cascaded stimulated Raman scattering, a supercontinuum spanning from 1.8 μm to 4.2 μm is obtained. Over 70% of the supercontinuum power is converted to wavelengths beyond2.4 μm. This is the first experimental report with respect to the multimode mid-infrared supercontinuum generation in a step-index two-mode chalcogenide fiber.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61435009,61235008,and 61405254)the Fund from China Scholarship Council(Grant No.201803170210)Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX2018B008)
文摘Fiber-based mid-infrared(MIR)supercontinuum(SC)sources benefit from their spectral brightness and spatial coherence that are needed for many applications,such as spectroscopy and metrology.In this paper,an SC spanning from 2μm to 6μm is demonstrated in cascaded ZrF4-BaF2-LaF3-AlF3-NaF(ZBLAN)and As2Se3 step-index fibers.The pump source is a ZBLAN fiber-based MIR SC laser with abundant high-peak-power soliton pulses between 3000 nm and 4200 nm.By concatenating the ZBLAN fiber and the As2 Se3 fiber,efficient cascading red-shifts are obtained in the normal dispersion region of the As2 Se3 fiber.The spectral behavior of cascaded SC generation shows that the long-wavelength proportion of MIR SC generated in the ZBLAN fiber plays a critical role for further spectral extension in the As2 Se3 fiber.
基金supported by the National Natural Science Foundation of China(Grant Nos.11404404 and 11274385)the Outstanding Youth Fund Project of Hunan Provincethe Fund of Innovation of National University of Defense Technology,China(Grant No.B120701)
文摘The effect of pulse width on near-infrared supercontinuum generation in nonlinear fiber amplifier is investigated theoretically and experimentally. The complex Ginzburg–Landau equation and adaptive split-step Fourier method are used to simulate the propagation of pulses with different pulse widths in the fiber amplifier, and the results show that a longer pulse is more profitable in near-infrared supercontinuum generation if the central wavelength of the input laser lies in the normal dispersion region of the gain fiber. A four-stage master oscillator power amplifier configuration is adopted and the output spectra under picosecond and nanosecond input pulses are compared with each other. The experimental results are in good accordance with the simulations which can provide some guidance for further optimization of the system.
基金supported by the State Key Program of the National Natural Science Foundation of China(Grant No.61235008)the National Natural Science Foundation of China(Grant Nos.61077076,11004247,and 11274385)+3 种基金the International Science&Technology Cooperation of China(Grant No.2012DFG11470)the Natural Science Foundation for Distinguished Young Scholars of Hunan Province of China(Grant No.12JJ1010)the Outstanding Youth Fund Project of Hunan Province of Chinathe Fund of Innovation of National University of Defense Technology of China(Grant No.B120701)
文摘Theoretical and experimental research on the effect of initial chirp on near-infrared supercontinuum generation by a nanosecond pulse in a nonlinear fiber amplifier is carded out. The complex Ginzburg-Landau equation is used to simulate the propagation of the pulse in the fiber amplifier and the results show that pulses with negative initial chirp produce the widest supercontinuum and pulses with positive initial chirp produce the narrowest supercontinuum when the central wavelength of the pump lies in the normal dispersion region of the gain fiber. A self-made line width narrowing system is utilized to control the initial chirp of the nanosecond pump pulse and a four-stage master oscillator power amplifier configuration is adopted to produce a high power near-infrared suppercontinuum. The experimental results are in good agreement with simulations which can provide some guidance on further optimization of the system in future work.
