As a crucial parameter in the design and analysis of laser performances, stimulated emission(SE) cross-section is currently considered to be dependent on several factors, such as temperatures and eigen-polarizations f...As a crucial parameter in the design and analysis of laser performances, stimulated emission(SE) cross-section is currently considered to be dependent on several factors, such as temperatures and eigen-polarizations for anisotropic crystals. In contrast with these factors, impact of propagating directions upon SE cross-section has garnered less attention.In this paper, to investigate the SE cross-section in arbitrary propagating directions, fluorescence spectra for the transition ~4F_(3/2)→~4I_(11/2) in Nd:YVO_4 are measured in different propagating directions. Based on Fuchtbauer–Ladenburg equation model, the propagating direction-dependent SE cross-section spectra in Nd:YVO_4 are obtained for the first time, to our best knowledge. A novel concept of anisotropic SE cross-section is proposed to interpret the propagating direction-dependent effect. The experiment results reveal that for an arbitrary propagating direction the SE cross-section of e light around 1064 nm can be expressed as a superposition from two principle axial propagating directions with a weight of plane projection.展开更多
Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrod...Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrodynamics sharing similar mathematics.Akin to a fluid vortex with a central flow singularity,an optical vortex beam has a phase singularity with a certain topological charge,giving rise to a hollow intensity distribution.Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics.These amazing properties provide a new understanding of a wide range of optical and physical phenomena,including twisting photons,spin–orbital interactions,Bose-Einstein condensates,etc.,while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible.Hitherto,owing to these salient properties and optical manipulation technologies,tunable vortex beams have engendered tremendous advanced applications such as optical tweezers,high-order quantum entanglement,and nonlinear optics.This article reviews the recent progress in tunable vortex technologies along with their advanced applications.展开更多
We introduce a high-density three-dimensional optical data storage approach by using a pyrryl-sub-stituted fulgide photochromic material with a method of single-beam two-photon recording and fluorescence confocal read...We introduce a high-density three-dimensional optical data storage approach by using a pyrryl-sub-stituted fulgide photochromic material with a method of single-beam two-photon recording and fluorescence confocal readout. The detailed information about the photochromic material and the experimental setup are presented. The experiments about multi-layered recording and readout are carried out with a 100-μm-thick transparent photochromic material film. The results show that the lateral resolution is better than 1 μm, and the longitudinal resolution is about 3 μm. Besides, the readout times for the recorded data aredesirable when using a readout laser power smaller than 5 mW.展开更多
Metasurfaces have found broad applicability in free-space optics,while its potential to tailor guided waves remains barely explored.By synergizing the Jones matrix model with generalized Snell’s law under the phase-m...Metasurfaces have found broad applicability in free-space optics,while its potential to tailor guided waves remains barely explored.By synergizing the Jones matrix model with generalized Snell’s law under the phase-matching condition,we propose a universal design strategy for versatile on-chip mode-selective coupling with polarization sensitivity,multiple working wavelengths,and high efficiency concurrently.The coupling direction,operation frequency,and excited mode type can be designed at will for arbitrary incident polarizations,outperforming previous technology that only works for specific polarizations and lacks versatile mode controllability.Here,using silicon-nanoantenna-patterned silicon-nitride photonic waveguides,we numerically demonstrate a set of chip-scale optical couplers around 1.55μm,including mode-selective directional couplers with high coupling efficiency over 57%and directivity about 23 d B.Polarization and wavelength demultiplexer scenarios are also proposed with 67%maximum efficiency and an extinction ratio of 20 d B.Moreover,a chip-integrated twisted light generator,coupling free-space linear polarization into an optical vortex carrying 1 h orbital angular momentum(OAM),is also reported to validate the mode-control flexibility.This comprehensive method may motivate compact wavelength/polarization(de)multiplexers,multifunctional mode converters,on-chip OAM generators for photonic integrated circuits,and high-speed optical telecommunications.展开更多
The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical bui...The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.展开更多
In this paper, we reported both the experimental demonstration and theoretical analysis of a Raman fiber laser based on a master oscillator–power amplifier configuration. The Raman fiber laser adopted the dual-wavele...In this paper, we reported both the experimental demonstration and theoretical analysis of a Raman fiber laser based on a master oscillator–power amplifier configuration. The Raman fiber laser adopted the dual-wavelength bidirectional pumping configuration, utilizing 976 nm laser diodes and 1018 nm fiber lasers as the pump sources. A 60-m-long25/400 μm ytterbium-doped fiber was used to convert the power from 1070 to 1124 nm, realizing a maximum power output of 3.7 kW with a 3 dB spectral width of 6.8 nm. Moreover, we developed a multi-frequency model taking into consideration the Raman gain spectrum and amplified spontaneous emission. The calculated spectral broadening of both the forward and backward laser was in good agreement with the experimental results. Finally, a 1.5 kW, 1183 nm second-order Raman fiber laser was further experimentally demonstrated by the addition of a 70-m-long germaniumdoped passive fiber.展开更多
Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bul...Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals.展开更多
Vector beams,non-separable in spatial mode and polarisation,have emerged as enabling tools in many diverse applications,from communication to imaging.This applicability has been achieved by sophisticated laser designs...Vector beams,non-separable in spatial mode and polarisation,have emerged as enabling tools in many diverse applications,from communication to imaging.This applicability has been achieved by sophisticated laser designs controlling the spin and orbital angular momentum,but so far is restricted to only two-dimensional states.Here we demonstrate the first vectorially structured light created and fully controlled in eight dimensions,a new state-of-the-art.We externally modulate our beam to control,for the frst time,the complete set of classical Greenberger-Horne-Zeilinger(GHZ)states in paraxial structured light beams,in analogy with high-dimensional multi-partite quantum entangled states,and introduce a new tomography method to verify their fidelity.Our complete theoretical framework reveals a rich parameter space for further extending the dimensionality and degrees of freedom,opening new pathways for vetorilly structured light in the classical and quantum regimes.展开更多
A frequency-degenerate cavity(FDC) is the resonator that the ratio of transverse and longitudinal mode frequency spacings is a simple rational number. When an optical resonator is close to the FDC, transverse-mode-loc...A frequency-degenerate cavity(FDC) is the resonator that the ratio of transverse and longitudinal mode frequency spacings is a simple rational number. When an optical resonator is close to the FDC, transverse-mode-locking(TML) takes place with drastic changes of laser mode. We report for the first time, to the best of our knowledge,the multi-frequency emission and spectral modulation effects coupled with TML in FDC. The Yb:CaGdAlO_4(Yb:CALGO) crystal with large gain bandwidth was used as a gain medium in an off-axis-pumped hemispherical FDC for realizing broadband emission. Interestingly, the spectrum can transform from a single smooth packet shape to a multi-peak structure; meanwhile, the transverse pattern accordingly transforms into some exotic wave-packet profiles through controlling off-axis displacement in a special degenerate state.展开更多
We present a spatiotemporal model of pulse amplification in the double-pass active mirror(AM)geometry.Three types of overlap condition are studied,and the spatiotemporal scaling under the four-pulse overlapping(4 PO)c...We present a spatiotemporal model of pulse amplification in the double-pass active mirror(AM)geometry.Three types of overlap condition are studied,and the spatiotemporal scaling under the four-pulse overlapping(4 PO)condition is fully characterized for the first time,by mapping the temporal and spatial segments of beam to the instantaneous gain windows.Furthermore,the influence of spatiotemporal overlaps on the amplified energy,pulse distortion and intensity profile is unraveled for both AM and zigzag configurations.The model,verified by excellent agreement between the predicted and measured results,can be a powerful tool for designing and optimizing high energy multi-pass solid-state laser amplifiers with AM,zigzag and other geometries.展开更多
High coherence of the laser is indispensable light sources in modern long or short-distance imaging systems, because the high coherence leads to coherent artifacts such as speckle that corrupt image formation. To deli...High coherence of the laser is indispensable light sources in modern long or short-distance imaging systems, because the high coherence leads to coherent artifacts such as speckle that corrupt image formation. To deliver low coherence pulses in fiber amplifiers, we utilize the superluminescent pulsed light with broad bandwidth, nonlongitudinal mode structure and chaotic mode phase as the seed source of the cascaded fiber amplifiers. The influence of fiber superluminescent pulse amplification(SPA) on the limitations of the performance is analyzed. A review of our research results for SPA in the fibers are present, including the nonlinear theories of this low coherent light sources, i.e., self-focusing(SF), stimulated Raman scattering(SRS) and self-phase modulation(SPM) effects, and the experiment results of the nanosecond pulses with peak power as high as 4.8 MW and pulse energy as much as 55 mJ. To improve the brightness of SPA light in the future work, we introduce our novel evaluation term and a more reasonable criterion, which is denoted by a new parameter of brightness factor for active large mode area fiber designs. A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of 180 μm is designed by this method. The designed fiber allows near diffracted limited beam quality operation, and it can achieve 100 mJ pulse energy and 540 W average power by analyzing the mode coupling effects induced by heat.展开更多
Fiber fuse effect can occur spontaneously and propagate along optical fibers to cause widespread damage;it threatens all applications involving optical fibers. This paper presents two results. First, it establishes th...Fiber fuse effect can occur spontaneously and propagate along optical fibers to cause widespread damage;it threatens all applications involving optical fibers. This paper presents two results. First, it establishes that the initiation of fiber fuse(IFF) in silica fibers is caused by virtual-defect-induced absorption. Critical temperatures and critical optical powers for IFF are simulated for the first time using a 3D solid-state heat transfer model with heat source generated by the virtual-defect-induced absorption. In this method, formation energies of the virtual defects can be uniquely determined, which offers critical information on the chemical reasons for fiber fuse. Second, this paper offers a method to evaluate operating temperatures of fiber lasers. General analytical solutions of the operating temperatures along gain fibers are deduced. Results of 976-nm laser-diode-pumped and 1018-nm tandem-pumped ytterbium-doped fiber(YDF) amplifiers using 10/130-μm YDFs are calculated.Potential limits caused by fiber fuse are discussed.展开更多
文摘As a crucial parameter in the design and analysis of laser performances, stimulated emission(SE) cross-section is currently considered to be dependent on several factors, such as temperatures and eigen-polarizations for anisotropic crystals. In contrast with these factors, impact of propagating directions upon SE cross-section has garnered less attention.In this paper, to investigate the SE cross-section in arbitrary propagating directions, fluorescence spectra for the transition ~4F_(3/2)→~4I_(11/2) in Nd:YVO_4 are measured in different propagating directions. Based on Fuchtbauer–Ladenburg equation model, the propagating direction-dependent SE cross-section spectra in Nd:YVO_4 are obtained for the first time, to our best knowledge. A novel concept of anisotropic SE cross-section is proposed to interpret the propagating direction-dependent effect. The experiment results reveal that for an arbitrary propagating direction the SE cross-section of e light around 1064 nm can be expressed as a superposition from two principle axial propagating directions with a weight of plane projection.
基金funded by The National Key Research and Development Program of China(Grant No.2017YFB1104500)Natural Science Foundation of Beijing Municipality(4172030)+3 种基金Beijing Young Talents Support Project(2017000020124G044)Leading talents of Guangdong province program(00201505)National Natural Science Foundation of China(U1701661,91750205,61975133,11604218,61975087)Natural Science Foundation of Guangdong Province(2016A030312010,2017A030313351).
文摘Thirty years ago,Coullet et al.proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex.Since then,optical vortices have been widely studied,inspired by the hydrodynamics sharing similar mathematics.Akin to a fluid vortex with a central flow singularity,an optical vortex beam has a phase singularity with a certain topological charge,giving rise to a hollow intensity distribution.Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics.These amazing properties provide a new understanding of a wide range of optical and physical phenomena,including twisting photons,spin–orbital interactions,Bose-Einstein condensates,etc.,while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible.Hitherto,owing to these salient properties and optical manipulation technologies,tunable vortex beams have engendered tremendous advanced applications such as optical tweezers,high-order quantum entanglement,and nonlinear optics.This article reviews the recent progress in tunable vortex technologies along with their advanced applications.
基金This work was supported by the National Key Basic Research Project (Grant No. G19990330).
文摘We introduce a high-density three-dimensional optical data storage approach by using a pyrryl-sub-stituted fulgide photochromic material with a method of single-beam two-photon recording and fluorescence confocal readout. The detailed information about the photochromic material and the experimental setup are presented. The experiments about multi-layered recording and readout are carried out with a 100-μm-thick transparent photochromic material film. The results show that the lateral resolution is better than 1 μm, and the longitudinal resolution is about 3 μm. Besides, the readout times for the recorded data aredesirable when using a readout laser power smaller than 5 mW.
基金National Natural Science Foundation of China(61675114,61875103,61935013,61975133,U1701661)Natural Science Foundation of Beijing Municipality(501100004826)+1 种基金Tsinghua University Initiative Scientific Research Program(20151080709)Beijing Young Talents Support Project(2017000020124G044)。
文摘Metasurfaces have found broad applicability in free-space optics,while its potential to tailor guided waves remains barely explored.By synergizing the Jones matrix model with generalized Snell’s law under the phase-matching condition,we propose a universal design strategy for versatile on-chip mode-selective coupling with polarization sensitivity,multiple working wavelengths,and high efficiency concurrently.The coupling direction,operation frequency,and excited mode type can be designed at will for arbitrary incident polarizations,outperforming previous technology that only works for specific polarizations and lacks versatile mode controllability.Here,using silicon-nanoantenna-patterned silicon-nitride photonic waveguides,we numerically demonstrate a set of chip-scale optical couplers around 1.55μm,including mode-selective directional couplers with high coupling efficiency over 57%and directivity about 23 d B.Polarization and wavelength demultiplexer scenarios are also proposed with 67%maximum efficiency and an extinction ratio of 20 d B.Moreover,a chip-integrated twisted light generator,coupling free-space linear polarization into an optical vortex carrying 1 h orbital angular momentum(OAM),is also reported to validate the mode-control flexibility.This comprehensive method may motivate compact wavelength/polarization(de)multiplexers,multifunctional mode converters,on-chip OAM generators for photonic integrated circuits,and high-speed optical telecommunications.
基金Q.X.acknowledges support from National Natural Science Foundation of China(Grants Nos.62075113,61675114)S.S.is supported by National Key Research and Development Program of China(Nos.2020YFA0710101,2017YFA0303504)+8 种基金National Natural Science Foundation of China(11874118)Natural Science Foundation of Shanghai(18ZR1403400,20JC1414601)Fudan University-CIOMP Joint Fund(No.FC2018-008)M.Z.is supported by National Natural Science Foundation of China(61775069,61635004)J.A.F.is supported by Office of Naval Research(under Award No.N00014-20-1-2105)ARPA-E(under Award No.DE-AR0001212)Z.X.and X.Y.acknowledge support from National Natural Science Foundation of China(61935013,U1701661,61975133)the Natural Science Foundation of Guangdong Province(2020A1515011185)the Science and Technology Innovation Commission of Shenzhen(JCYJ20180507182035270,JCYJ20200109114018750).
文摘The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip.The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits,giving rise to numerous metawaveguides with unprecedented strength in controlling guided electromagnetic waves.Here,we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms,such as dielectric or plasmonic waveguides and optical fibers.Foundational results and representative applications are comprehensively summarized.Brief physical models with explicit design tutorials,either physical intuition-based design methods or computer algorithms-based inverse designs,are cataloged as well.We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems,by enhancing light-matter interaction strength to drastically boost device performance,or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities.We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits,biomedical sensing,artificial intelligence and beyond.
基金supported in part by the National Natural Science Foundation of China (Nos. 61675114 and 61875103)the Tsinghua University Initiative Scientific Research Program (No. 20151080709)
文摘In this paper, we reported both the experimental demonstration and theoretical analysis of a Raman fiber laser based on a master oscillator–power amplifier configuration. The Raman fiber laser adopted the dual-wavelength bidirectional pumping configuration, utilizing 976 nm laser diodes and 1018 nm fiber lasers as the pump sources. A 60-m-long25/400 μm ytterbium-doped fiber was used to convert the power from 1070 to 1124 nm, realizing a maximum power output of 3.7 kW with a 3 dB spectral width of 6.8 nm. Moreover, we developed a multi-frequency model taking into consideration the Raman gain spectrum and amplified spontaneous emission. The calculated spectral broadening of both the forward and backward laser was in good agreement with the experimental results. Finally, a 1.5 kW, 1183 nm second-order Raman fiber laser was further experimentally demonstrated by the addition of a 70-m-long germaniumdoped passive fiber.
基金This work was supported by the National Key Research and Development Program of China(Grant number 2017YFA0701004)the National Natural Science Foundation of China(Grant numbers 61975251,61875150,61735012,and 11774288).
文摘Broadband light sources emitting in the terahertz spectral range are highly desired for applications such as noninvasive imaging and spectroscopy.Conventionally,THz pulses are generated by optical rectification in bulk nonlinear crystals with millimetre thickness,with the bandwidth limited by the phase-matching condition.Here we demonstrate broadband THz emission via surface optical rectification from a simple,commercially available 19nmthick indium tin oxide(ITO)thin film.We show an enhancement of the generated THz signal when the pump laser is tuned around the epsilon-near-zero(ENZ)region of ITO due to the pump laser field enhancement associated with the ENZ effect.The bandwidth of the THz signal generated from the ITO film can be over 3 THz,unrestricted by the phasematching condition.This work offers a new possibility for broadband THz generation in a subwavelength thin film made of an ENZ material,with emerging physics not found in existing nonlinear crystals.
基金Marie S.-Curie MULTIPLY Fellowship (GA713694)National Key Research and Development Program of China (2017YFB1104500)+2 种基金National Natural Science Foundation of China (61975087)Natural Science Foundation of Beijing Municipality (4172030)Beijing Young Talents Support Project (2017000020124G044).
文摘Vector beams,non-separable in spatial mode and polarisation,have emerged as enabling tools in many diverse applications,from communication to imaging.This applicability has been achieved by sophisticated laser designs controlling the spin and orbital angular momentum,but so far is restricted to only two-dimensional states.Here we demonstrate the first vectorially structured light created and fully controlled in eight dimensions,a new state-of-the-art.We externally modulate our beam to control,for the frst time,the complete set of classical Greenberger-Horne-Zeilinger(GHZ)states in paraxial structured light beams,in analogy with high-dimensional multi-partite quantum entangled states,and introduce a new tomography method to verify their fidelity.Our complete theoretical framework reveals a rich parameter space for further extending the dimensionality and degrees of freedom,opening new pathways for vetorilly structured light in the classical and quantum regimes.
基金funded by the National Key Research and Development Program of China(No.2017YFB1104500)the Natural Science Foundation of Beijing Municipality(No.4172030)and the Beijing Young Talents Support Project(No.2017000020124G044)
文摘A frequency-degenerate cavity(FDC) is the resonator that the ratio of transverse and longitudinal mode frequency spacings is a simple rational number. When an optical resonator is close to the FDC, transverse-mode-locking(TML) takes place with drastic changes of laser mode. We report for the first time, to the best of our knowledge,the multi-frequency emission and spectral modulation effects coupled with TML in FDC. The Yb:CaGdAlO_4(Yb:CALGO) crystal with large gain bandwidth was used as a gain medium in an off-axis-pumped hemispherical FDC for realizing broadband emission. Interestingly, the spectrum can transform from a single smooth packet shape to a multi-peak structure; meanwhile, the transverse pattern accordingly transforms into some exotic wave-packet profiles through controlling off-axis displacement in a special degenerate state.
基金National Key Research and Development Program of China(No.2017YFB0405100)National Natural Science Foundation of China(No.61975087)Beijing Young Talents Support Project(No.2017000020124G044)。
文摘We present a spatiotemporal model of pulse amplification in the double-pass active mirror(AM)geometry.Three types of overlap condition are studied,and the spatiotemporal scaling under the four-pulse overlapping(4 PO)condition is fully characterized for the first time,by mapping the temporal and spatial segments of beam to the instantaneous gain windows.Furthermore,the influence of spatiotemporal overlaps on the amplified energy,pulse distortion and intensity profile is unraveled for both AM and zigzag configurations.The model,verified by excellent agreement between the predicted and measured results,can be a powerful tool for designing and optimizing high energy multi-pass solid-state laser amplifiers with AM,zigzag and other geometries.
基金supported by the National High Technology Research and Development Program of Chinathe National Natural Science Foundation of China (No.61475081)the State Key Laboratory of Tribology, Tsinghua University (No.SKLT2014B09)
文摘High coherence of the laser is indispensable light sources in modern long or short-distance imaging systems, because the high coherence leads to coherent artifacts such as speckle that corrupt image formation. To deliver low coherence pulses in fiber amplifiers, we utilize the superluminescent pulsed light with broad bandwidth, nonlongitudinal mode structure and chaotic mode phase as the seed source of the cascaded fiber amplifiers. The influence of fiber superluminescent pulse amplification(SPA) on the limitations of the performance is analyzed. A review of our research results for SPA in the fibers are present, including the nonlinear theories of this low coherent light sources, i.e., self-focusing(SF), stimulated Raman scattering(SRS) and self-phase modulation(SPM) effects, and the experiment results of the nanosecond pulses with peak power as high as 4.8 MW and pulse energy as much as 55 mJ. To improve the brightness of SPA light in the future work, we introduce our novel evaluation term and a more reasonable criterion, which is denoted by a new parameter of brightness factor for active large mode area fiber designs. A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of 180 μm is designed by this method. The designed fiber allows near diffracted limited beam quality operation, and it can achieve 100 mJ pulse energy and 540 W average power by analyzing the mode coupling effects induced by heat.
文摘Fiber fuse effect can occur spontaneously and propagate along optical fibers to cause widespread damage;it threatens all applications involving optical fibers. This paper presents two results. First, it establishes that the initiation of fiber fuse(IFF) in silica fibers is caused by virtual-defect-induced absorption. Critical temperatures and critical optical powers for IFF are simulated for the first time using a 3D solid-state heat transfer model with heat source generated by the virtual-defect-induced absorption. In this method, formation energies of the virtual defects can be uniquely determined, which offers critical information on the chemical reasons for fiber fuse. Second, this paper offers a method to evaluate operating temperatures of fiber lasers. General analytical solutions of the operating temperatures along gain fibers are deduced. Results of 976-nm laser-diode-pumped and 1018-nm tandem-pumped ytterbium-doped fiber(YDF) amplifiers using 10/130-μm YDFs are calculated.Potential limits caused by fiber fuse are discussed.