We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assis...We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assisted THz-wave communication system.By employing advanced Digital Signal Processing(DSP)and the PS technique,the 352-Gbit/s line rate(288-Gbit/s net rate)delivery with a net Spectral Efficiency(SE)of 9 bit/s/Hz is realized in the experiment,satisfying the 0.86-Normalized Generalized Mutual Information(NGMI)Low-Density Parity-Check(LDPC)threshold.展开更多
We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fab...We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling.It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm.The rise and fall time constants are 3.5 and 3.7μs,respectively,2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators.The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.展开更多
A method of fabricating pure germanium dioxide hollow-core fibers has been introduced for the first time. The inner diameter of the fiber is φ0.8mm, with the transmission loss of 1.23dB/m at 10.6μm. The mechanism of...A method of fabricating pure germanium dioxide hollow-core fibers has been introduced for the first time. The inner diameter of the fiber is φ0.8mm, with the transmission loss of 1.23dB/m at 10.6μm. The mechanism of transmitting CO<sub>2</sub> laser by the fiber is analyzed. The transmitting performances are discussed and its application fields are envisaged.展开更多
Hollow-core negative curvature fibers(HC-NCFs)have become one of the research hotspots in the field of optical fiber because of their potential applications in the data and energy transmissions.In this work,a new kind...Hollow-core negative curvature fibers(HC-NCFs)have become one of the research hotspots in the field of optical fiber because of their potential applications in the data and energy transmissions.In this work,a new kind of single-polarization single-mode HC-NCF with nested U-type cladding elements is proposed.To achieve the single-polarization single-mode transmission,we use two different silica tubes in thickness,which satisfy the resonance and anti-resonance conditions on the U-type cladding elements and the cladding tubes,respectively.Besides,the elliptical elements are introduced to achieve good single-mode performance.By studying the influences of the structure parameters on the propagation characteristics,the optimized structure parameters are obtained.The simulation results show that when the wavelength is fixed at 1550 nm,the single-polarization single-mode transmission is achieved,with the polarization extinction ratio of 25749 and minimum high-order mode extinction ratio of 174.Furthermore,the confinement loss is only 0.0015 dB/m.展开更多
We theoretically study the nonlinear compression of a 20-m J, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has ...We theoretically study the nonlinear compression of a 20-m J, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar(1 bar = 105Pa), 1.8-m hollow fiber,we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.展开更多
Two kinds of fabricated hollow-core photonic crystal fibres (HC-PCFs) are studied using finite element method (FEM) because the structures of the fibres are special. Normalized transmission spectra and transverse inte...Two kinds of fabricated hollow-core photonic crystal fibres (HC-PCFs) are studied using finite element method (FEM) because the structures of the fibres are special. Normalized transmission spectra and transverse intensity distribution of the modes are calculated and measured. And the dispersion characteristics of these two kinds of HCPCFs were analysed from 400nm to 800nm. Simulated and measured results show that the special structure could affect the properties of HC-PCFs. By comparing the simulated values with the measured results, it can be clarified that FEM is feasible and accurate for analysing photonic crystal fibres whose structures are irregular and complex.展开更多
We theoretically study the nonlinear compression of picosecond pulses with 10-m J of input energy at the 1053-nm center wavelength by using a one-meter-long gas-filled hollow-core fiber(HCF)compressor and considering ...We theoretically study the nonlinear compression of picosecond pulses with 10-m J of input energy at the 1053-nm center wavelength by using a one-meter-long gas-filled hollow-core fiber(HCF)compressor and considering the third-order dispersion(TOD)effect.It is found that when the input pulse is about 1 ps/10 m J,it can be compressed down to less than20 fs with a high transmission efficiency.The gas for optimal compression is krypton gas which is filled in a HCF with a 400-μm inner diameter.When the input pulse duration is increased to 5 ps,it can also be compressed down to less than 100 fs efficiently under proper conditions.The results show that the TOD effect has little impact on picosecond pulse compression and the HCF compressor can be applied on compressing picosecond pulses efficiently with a high compression ratio,which will benefit the research of high-field laser physics.展开更多
Highly efficient Cherenkov radiation(CR) is generated by the soliton self-frequency shift(SSFS) in the irregular point of a hollow-core photonic crystal fiber(HC-PCF) in our laboratory.The impacts of pump power and wa...Highly efficient Cherenkov radiation(CR) is generated by the soliton self-frequency shift(SSFS) in the irregular point of a hollow-core photonic crystal fiber(HC-PCF) in our laboratory.The impacts of pump power and wavelength on the CR are investigated,and the corresponding nonlinear processes are discussed.When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW,the Raman soliton shifts from 2210 nm to 2360 nm,the output power of the CR increases by 2.3 times,the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1,the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm,and the conversion efficiency η of the CR in the experiment can be above 32%.展开更多
We numerically study the propagation dynamics of intense optical pulses in gas-filled hollow-core fibers(HCFs). The spatiotemporal dynamics of the pulses show a transition from tightly confined to loosely confined cha...We numerically study the propagation dynamics of intense optical pulses in gas-filled hollow-core fibers(HCFs). The spatiotemporal dynamics of the pulses show a transition from tightly confined to loosely confined characteristics as the fiber core is increased, which manifests as a deterioration in the spatiotemporal uniformity of the beam. It is found that using the gas pressure gradient does not enhance the beam quality in large-core HCFs, while inducing a positive chirp in the pulse to lower the peak power can improve the beam quality. This indicates that the self-focusing effect in the HCFs is the main driving force for the propagation dynamics. It also suggests that pulses at longer wavelengths are more suitable for HCFs with large cores because of the lower critical power of self-focusing, which is justified by the numerical simulations. These results will benefit the generation of energetic few-cycle pulses in large-core HCFs.展开更多
We study theoretically the spectral intensity evolutions of the femtosecond Gaussian and parabolic pulses with different initial pulse energies and compare the nonlinear compressions of these pulses based on a meter-l...We study theoretically the spectral intensity evolutions of the femtosecond Gaussian and parabolic pulses with different initial pulse energies and compare the nonlinear compressions of these pulses based on a meter-long hollow-core fiber filled with neon for different initial pulse durations. The pulses are first coupled into gas-filled hollow-core fiber for spectrum broadening, then compressed by the optimal chirp compensation. The parabolic pulse possesses a shorter pulse duration, larger peak power, and cleaner wings than Gaussian pulse. The properties are useful for compressing the pulses and thus generating the high-energy, short-duration pulses.展开更多
We perform a numerical study for temporally compressing radially-polarized(RP) infrared pulses in a gas-filled hollow-core fiber(HCF). The dynamic transmission and nonlinear compression of RP pulses centered at wavele...We perform a numerical study for temporally compressing radially-polarized(RP) infrared pulses in a gas-filled hollow-core fiber(HCF). The dynamic transmission and nonlinear compression of RP pulses centered at wavelengths of0.8 m, 1.8 m, 3.1 m, and 5.0 m in HCFs are simulated. By comparing the propagation of pulses with the same optical cycles and intensity, we find that under proper conditions these pulses can be compressed down to 2–3 cycles. In the transverse direction, the spatiotemporal beam profile ameliorates from 0.8-m to 1.8-m and 3.1-m pulses before the appearance of high-order dispersion. These results show an alternative method of scaling generation for delivering RP infrared pulses in gas-filled HCFs, which can obtain energetic few-cycle pulses, and will be beneficial for relevant researches in the infrared scope.展开更多
We numerically study the self-compression of the optical pulses centered at 1.8-μm in a hollow-core fiber(HCF) filled with argon. It is found that the pulse can be self-compressed to 2 optical cycles when the input p...We numerically study the self-compression of the optical pulses centered at 1.8-μm in a hollow-core fiber(HCF) filled with argon. It is found that the pulse can be self-compressed to 2 optical cycles when the input pulse energy is 0.2-m J and the gas pressure is 500-mbar(1 bar = 10~5 Pa). Inducing a proper positive chirp into the input pulse can lead to a shorter temporal duration after self-compression. These results will benefit the generation of energetic few-cycle mid-infrared pulses.展开更多
We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber.From the perspective of self-phase modulation(SPM), we give the extensive study of the SPM influence on a...We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber.From the perspective of self-phase modulation(SPM), we give the extensive study of the SPM influence on a probe pulse with molecular phase modulation(MPM) effect. By comparing the two compression methods, we summarize their advantages and drawbacks to obtain the few-cycle pulses with micro- or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values.展开更多
We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber (HCPCF). The diameter of the light sou...We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber (HCPCF). The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.展开更多
Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0...Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45° , the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.展开更多
This paper investigates the zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres(PBGFs) by using a full-vector finite element method.By simulation we found that theoretically ...This paper investigates the zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres(PBGFs) by using a full-vector finite element method.By simulation we found that theoretically the zero dispersion wavelength can be tailored by respectively changing the rounded diameter of air holes,pitch,refractive index,normalized thickness of core rings,and hole diameter to pitch ratio.At the same time the tailoring of dispersion slope can also be realized by changing the rounded diameter of air holes or pitch or normalized thickness of core rings.To illustrate the reasonability of fibre designs,this paper also gives the variance of normalized interface field intensity which measures the scattering loss relatively versus wavelength for different designs.From the viewpoint of loss,varying the rounded diameter and the thickness of core ring could shift zero wavelength but it is difficult to get the required parameters within so tiny range in practical drawing of PBGFs,on the other hand,it is possible in practice to respectively alter the pitch and refractive index to shift zero wavelength.But varying hole diameter to pitch ratio is not worthwhile because they each induce large increase of loss and narrowness of transmission bandwidth.The zero dispersion wavelength can be engineered by respectively varying the rounded diameter of air holes,pitch,refractive index,and normalized thickness of core rings without incurring large loss penalties.展开更多
This paper investigates the guided-mode characteristics of hollow-core photonic band-gap fibre (HC-PBGF) with interstitial holes fabricated by an improved twice stack-and-draw technique at visible wavelengths. Based o...This paper investigates the guided-mode characteristics of hollow-core photonic band-gap fibre (HC-PBGF) with interstitial holes fabricated by an improved twice stack-and-draw technique at visible wavelengths. Based on the simulation model with interstitial holes, the influence of glass interstitial apexes on photonic band-gaps is discussed. The existing forms of guided-mode in part band gaps are shown by using the full-vector plane-wave method. In the experiment, the observed transmission spectrum corresponds to the part band gaps obtained by simulation. The fundamental and second-order guided-modes with mixture of yellow and green light are observed through choosing appropriate fibre length and adjusting coupling device. The loss mechanism of guided-modes in HC-PBGF is also discussed.展开更多
We report here on a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers(HCFs)towards an all-fiber structure by the tapering method. The pump laser is coupled into an acetylene-filled H...We report here on a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers(HCFs)towards an all-fiber structure by the tapering method. The pump laser is coupled into an acetylene-filled HCF through a tapered single-mode fiber. By precisely tuning the wavelength of the diode to match different absorption lines of acetylene near 1.5 μm, mid-infrared emission around 3.1–3.2 μm is generated. With 2 m HCFs and3 mbar acetylene gas, a maximum average power of 130 m W is obtained with a laser slope efficiency of ~24%.This work provides a potential scheme for all-fiber mid-infrared fiber gas lasers.展开更多
Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a n...Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss.We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum,and that this can be calculated from the structural parameters of a fiber using a simple analytical formula.This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength.It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure.展开更多
Fiber gas lasers based on gas-filled hollow-core fibers(HCFs)perfectly combine the advantages of fiber lasers and gas lasers and have obtained fast development in the past years.However,stable and efficient coupling o...Fiber gas lasers based on gas-filled hollow-core fibers(HCFs)perfectly combine the advantages of fiber lasers and gas lasers and have obtained fast development in the past years.However,stable and efficient coupling of high-power pump lasers into the HCFs is one of the key problems to be solved.In this paper,we study the coupling of high-power continuous wave fiber lasers into anti-resonant HCFs through an end-cap.By optimizing the splicing parameters,a maximum laser power of 1167 W was injected into the 1-m-long HCFs,and 1021W was obtained at the output end,giving a total transmission efficiency of〜87.5%.A more than 1 h test showed the stability of such a coupling method.Meanwhile,the laser beam quality was well maintained.This work opens new opportunities for stable and highly efficient coupling of high-power lasers into HCFs,which is significant for its applications in many other fields besides high-power fiber gas lasers,such as high-power laser delivering.展开更多
基金supported by National Key R&D Program of China(2018YFB1800900)National Natural Science Foundation of China(61935005,91938202,61720106015,61835002,61805043,62127802).
文摘We successfully demonstrate 32-Gbaud Probabilistically Shaped 4096-ary Quadrature Amplitude Modulation(PS-4096QAM)TeraHertz(THz)signal wired transmission at 325 GHz over the 1-m Hollow-Core Fiber(HCF)in a photon-assisted THz-wave communication system.By employing advanced Digital Signal Processing(DSP)and the PS technique,the 352-Gbit/s line rate(288-Gbit/s net rate)delivery with a net Spectral Efficiency(SE)of 9 bit/s/Hz is realized in the experiment,satisfying the 0.86-Normalized Generalized Mutual Information(NGMI)Low-Density Parity-Check(LDPC)threshold.
基金We are grateful for financial supports from the National Key Research and Development Program of China(2019YFB2203904)the National Natural Science Foundation of China(U21A20506,62105122,61827820,62005233)+1 种基金the Shenzhen STIC Funding(RCBS20200714114819032)the Local Innovative and Research Teams Project of Guangdong Pear River Talents Program(2019BT02X105).
文摘We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber.The phase modulation dynamics are studied by multi-physics simulation.A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling.It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm.The rise and fall time constants are 3.5 and 3.7μs,respectively,2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators.The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.
基金Supported by the High Technology Research and Development Programme of China
文摘A method of fabricating pure germanium dioxide hollow-core fibers has been introduced for the first time. The inner diameter of the fiber is φ0.8mm, with the transmission loss of 1.23dB/m at 10.6μm. The mechanism of transmitting CO<sub>2</sub> laser by the fiber is analyzed. The transmitting performances are discussed and its application fields are envisaged.
基金supported by the National Natural Science Foundation of China(Grant No.61935007)。
文摘Hollow-core negative curvature fibers(HC-NCFs)have become one of the research hotspots in the field of optical fiber because of their potential applications in the data and energy transmissions.In this work,a new kind of single-polarization single-mode HC-NCF with nested U-type cladding elements is proposed.To achieve the single-polarization single-mode transmission,we use two different silica tubes in thickness,which satisfy the resonance and anti-resonance conditions on the U-type cladding elements and the cladding tubes,respectively.Besides,the elliptical elements are introduced to achieve good single-mode performance.By studying the influences of the structure parameters on the propagation characteristics,the optimized structure parameters are obtained.The simulation results show that when the wavelength is fixed at 1550 nm,the single-polarization single-mode transmission is achieved,with the polarization extinction ratio of 25749 and minimum high-order mode extinction ratio of 174.Furthermore,the confinement loss is only 0.0015 dB/m.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB808101)the Funds from the Chinese Academy of Sciences,and the National Natural Science Foundation of China(Grant Nos.11127901,10734080,61221064,60908008,and 61078037)
文摘We theoretically study the nonlinear compression of a 20-m J, 1030-nm picosecond chirped pulse from the thin-disk amplifier in a krypton gas-filled hollow-core fiber. The chirp from the thin-disk amplifier system has little influence on the initial pulse, however, it shows an effect on the nonlinear compression in hollow-core fiber. We use a large diameter hollow waveguide to restrict undesirable nonlinear effects such as ionization; on the other hand, we employ suitable gas pressure and fiber length to promise enough spectral broadening; with 600-μm, 6-bar(1 bar = 105Pa), 1.8-m hollow fiber,we obtain 31.5-fs pulse. Moreover, we calculate and discuss the optimal fiber lengths and gas pressures with different initial durations induced by different grating compression angles for reaching a given bandwidth. These results are meaningful for a compression scheme from picoseconds to femtoseconds.
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2003CB314905)the National High Technology Development Program of China (Grant No 2003AA311010)
文摘Two kinds of fabricated hollow-core photonic crystal fibres (HC-PCFs) are studied using finite element method (FEM) because the structures of the fibres are special. Normalized transmission spectra and transverse intensity distribution of the modes are calculated and measured. And the dispersion characteristics of these two kinds of HCPCFs were analysed from 400nm to 800nm. Simulated and measured results show that the special structure could affect the properties of HC-PCFs. By comparing the simulated values with the measured results, it can be clarified that FEM is feasible and accurate for analysing photonic crystal fibres whose structures are irregular and complex.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11204328,61221064,61078037,11127901,and 11134010)the National Basic Research Program of China(Grant No.2011CB808101)+2 种基金the Commission of Science and Technology of Shanghai,China(Grant No.12dz1100700)the Natural Science Foundation of Shanghai,China(Grant No.13ZR1414800)the International Science and Technology Cooperation Program of China(Grant No.2011DFA11300)
文摘We theoretically study the nonlinear compression of picosecond pulses with 10-m J of input energy at the 1053-nm center wavelength by using a one-meter-long gas-filled hollow-core fiber(HCF)compressor and considering the third-order dispersion(TOD)effect.It is found that when the input pulse is about 1 ps/10 m J,it can be compressed down to less than20 fs with a high transmission efficiency.The gas for optimal compression is krypton gas which is filled in a HCF with a 400-μm inner diameter.When the input pulse duration is increased to 5 ps,it can also be compressed down to less than 100 fs efficiently under proper conditions.The results show that the TOD effect has little impact on picosecond pulse compression and the HCF compressor can be applied on compressing picosecond pulses efficiently with a high compression ratio,which will benefit the research of high-field laser physics.
基金Project supported by the National Basic Research Program of China (Grant Nos. 2010CB327605 and 2010CB328300)the Fundamental Research Funds for the Central Universities,China (Grant Nos. 2011RC0309 and 2011RC008)the Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications,China (Grant No. CX201023)
文摘Highly efficient Cherenkov radiation(CR) is generated by the soliton self-frequency shift(SSFS) in the irregular point of a hollow-core photonic crystal fiber(HC-PCF) in our laboratory.The impacts of pump power and wavelength on the CR are investigated,and the corresponding nonlinear processes are discussed.When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW,the Raman soliton shifts from 2210 nm to 2360 nm,the output power of the CR increases by 2.3 times,the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1,the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm,and the conversion efficiency η of the CR in the experiment can be above 32%.
文摘We numerically study the propagation dynamics of intense optical pulses in gas-filled hollow-core fibers(HCFs). The spatiotemporal dynamics of the pulses show a transition from tightly confined to loosely confined characteristics as the fiber core is increased, which manifests as a deterioration in the spatiotemporal uniformity of the beam. It is found that using the gas pressure gradient does not enhance the beam quality in large-core HCFs, while inducing a positive chirp in the pulse to lower the peak power can improve the beam quality. This indicates that the self-focusing effect in the HCFs is the main driving force for the propagation dynamics. It also suggests that pulses at longer wavelengths are more suitable for HCFs with large cores because of the lower critical power of self-focusing, which is justified by the numerical simulations. These results will benefit the generation of energetic few-cycle pulses in large-core HCFs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61221064,61078037,11127901,and 11134010)the National Basic Research Program of China(Grant No.2011CB808101)+2 种基金the Funds from the Commission of Science and Technology of Shanghai,China(Grant No.12dz1100700)the Natural Science Foundation of Shanghai,China(Grant No.13ZR1414800)the International S&T Cooperation Program of China(Grant No.2011DFA11300)
文摘We study theoretically the spectral intensity evolutions of the femtosecond Gaussian and parabolic pulses with different initial pulse energies and compare the nonlinear compressions of these pulses based on a meter-long hollow-core fiber filled with neon for different initial pulse durations. The pulses are first coupled into gas-filled hollow-core fiber for spectrum broadening, then compressed by the optimal chirp compensation. The parabolic pulse possesses a shorter pulse duration, larger peak power, and cleaner wings than Gaussian pulse. The properties are useful for compressing the pulses and thus generating the high-energy, short-duration pulses.
基金Project supported by the National Natural Science Foundation of China(Grant No.61521093)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16)+1 种基金the International S&T Cooperation Program of China(Grant No.2016YFE0119300)the Program of Shanghai Academic/Technology Research Leader,China(Grant No.18XD1404200)
文摘We perform a numerical study for temporally compressing radially-polarized(RP) infrared pulses in a gas-filled hollow-core fiber(HCF). The dynamic transmission and nonlinear compression of RP pulses centered at wavelengths of0.8 m, 1.8 m, 3.1 m, and 5.0 m in HCFs are simulated. By comparing the propagation of pulses with the same optical cycles and intensity, we find that under proper conditions these pulses can be compressed down to 2–3 cycles. In the transverse direction, the spatiotemporal beam profile ameliorates from 0.8-m to 1.8-m and 3.1-m pulses before the appearance of high-order dispersion. These results show an alternative method of scaling generation for delivering RP infrared pulses in gas-filled HCFs, which can obtain energetic few-cycle pulses, and will be beneficial for relevant researches in the infrared scope.
基金supported by the National Natural Science Foundation of China(Grant Nos.61475169,61521093,and 11127901)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16)the International Science and Technology Cooperation Program of China(Grant No.2016YFE0119300)
文摘We numerically study the self-compression of the optical pulses centered at 1.8-μm in a hollow-core fiber(HCF) filled with argon. It is found that the pulse can be self-compressed to 2 optical cycles when the input pulse energy is 0.2-m J and the gas pressure is 500-mbar(1 bar = 10~5 Pa). Inducing a proper positive chirp into the input pulse can lead to a shorter temporal duration after self-compression. These results will benefit the generation of energetic few-cycle mid-infrared pulses.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11204328,61221064,61078037,11127901,11134010,and 61205208)the National Basic Research Program of China(Grant No.2011CB808101)the Natural Science Foundation of Shanghai,China(Grant No.13ZR1414800)
文摘We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber.From the perspective of self-phase modulation(SPM), we give the extensive study of the SPM influence on a probe pulse with molecular phase modulation(MPM) effect. By comparing the two compression methods, we summarize their advantages and drawbacks to obtain the few-cycle pulses with micro- or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674051 and 10811120010)the Program for Innovative Research Team of the Higher Education of Guangdong, China (Grant No 06CXTD005)
文摘We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber (HCPCF). The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.
基金Project supported by the National Basic Research Program of China (Grant Nos. 2010CB327605 and 2010CB328300)the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant Nos. 2011RC0309 and 2011RC008)the Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications, China (Grant No. CX201023)
文摘Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45° , the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.
基金supported by the National Natural Science Foundation of China (Grant No 60578043)the Beijing Education Committee Common Build Foundation (Grant No XK100130637)
文摘This paper investigates the zero dispersion wavelength and dispersion slope control of hollow-core photonic bandgap fibres(PBGFs) by using a full-vector finite element method.By simulation we found that theoretically the zero dispersion wavelength can be tailored by respectively changing the rounded diameter of air holes,pitch,refractive index,normalized thickness of core rings,and hole diameter to pitch ratio.At the same time the tailoring of dispersion slope can also be realized by changing the rounded diameter of air holes or pitch or normalized thickness of core rings.To illustrate the reasonability of fibre designs,this paper also gives the variance of normalized interface field intensity which measures the scattering loss relatively versus wavelength for different designs.From the viewpoint of loss,varying the rounded diameter and the thickness of core ring could shift zero wavelength but it is difficult to get the required parameters within so tiny range in practical drawing of PBGFs,on the other hand,it is possible in practice to respectively alter the pitch and refractive index to shift zero wavelength.But varying hole diameter to pitch ratio is not worthwhile because they each induce large increase of loss and narrowness of transmission bandwidth.The zero dispersion wavelength can be engineered by respectively varying the rounded diameter of air holes,pitch,refractive index,and normalized thickness of core rings without incurring large loss penalties.
基金Project supported by the National Key Basic Research Special Foundation (Grant No. 2010CB327605)National High-Technology Research and Development Program of China (Grant No. 2009AA01Z220)+2 种基金the Key Grant of the Chinese Ministry of Education (Grant No.109015)the Discipline Co-construction Project of Beijing Municipal Commission of Education (Grant No. YB20081001301)the Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications (Grant No. CX201023)
文摘This paper investigates the guided-mode characteristics of hollow-core photonic band-gap fibre (HC-PBGF) with interstitial holes fabricated by an improved twice stack-and-draw technique at visible wavelengths. Based on the simulation model with interstitial holes, the influence of glass interstitial apexes on photonic band-gaps is discussed. The existing forms of guided-mode in part band gaps are shown by using the full-vector plane-wave method. In the experiment, the observed transmission spectrum corresponds to the part band gaps obtained by simulation. The fundamental and second-order guided-modes with mixture of yellow and green light are observed through choosing appropriate fibre length and adjusting coupling device. The loss mechanism of guided-modes in HC-PBGF is also discussed.
基金supported by the Outstanding Youth Science Fund Project of Hunan Provincial Natural Science Foundation(No.2019JJ20023)the National Natural Science Foundation of China(NSFC)(No.61705266)
文摘We report here on a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers(HCFs)towards an all-fiber structure by the tapering method. The pump laser is coupled into an acetylene-filled HCF through a tapered single-mode fiber. By precisely tuning the wavelength of the diode to match different absorption lines of acetylene near 1.5 μm, mid-infrared emission around 3.1–3.2 μm is generated. With 2 m HCFs and3 mbar acetylene gas, a maximum average power of 130 m W is obtained with a laser slope efficiency of ~24%.This work provides a potential scheme for all-fiber mid-infrared fiber gas lasers.
文摘Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss.We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum,and that this can be calculated from the structural parameters of a fiber using a simple analytical formula.This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength.It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure.
基金This work was supported by the Outstanding Youth Science Fund of Hunan Provincial Natural Science Foundation(No.2019JJ20023)National Natural Science Foundation of China(NSFC)(Nos.11974427 and 12004431)+2 种基金State Key Laboratory of Pulsed Power Laser(Nos.SKL2020ZR05 and SKL2021ZR01)Science and Technology Innovation Program of Hunan Province(No.2021RC4027)Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20200017).
文摘Fiber gas lasers based on gas-filled hollow-core fibers(HCFs)perfectly combine the advantages of fiber lasers and gas lasers and have obtained fast development in the past years.However,stable and efficient coupling of high-power pump lasers into the HCFs is one of the key problems to be solved.In this paper,we study the coupling of high-power continuous wave fiber lasers into anti-resonant HCFs through an end-cap.By optimizing the splicing parameters,a maximum laser power of 1167 W was injected into the 1-m-long HCFs,and 1021W was obtained at the output end,giving a total transmission efficiency of〜87.5%.A more than 1 h test showed the stability of such a coupling method.Meanwhile,the laser beam quality was well maintained.This work opens new opportunities for stable and highly efficient coupling of high-power lasers into HCFs,which is significant for its applications in many other fields besides high-power fiber gas lasers,such as high-power laser delivering.
