The laser-induced damage behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running laser mode. The absorption measurement of such coatings ha...The laser-induced damage behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running laser mode. The absorption measurement of such coatings has been performed by surface thermal lensing (STL) technique. The relationship between damage morphology and absorption under the two different laser modes was studied in detail. The explanation was given by the standing-wave distribution theory.展开更多
We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. Fo...We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. For a 2-mm-long and 10-μm-wide laser coated with high-reflectivity on the rear facet, more than 170mW of output power is obtained at 20℃ with a threshold power consumption of 2.4 W, corresponding to 30mW with a threshold power consumption of 3.9 W at 90℃. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.展开更多
When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of...When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of supersonic airflow on the development of a laser ablation pit. Results show that the aerodynamic convection cooling effect not only reduces the ablation velocity but also changes the symmetry morphology of the ablation pit due to the non-uniform convective heat transfer. Flow mode transition is also observed when the pit becomes deeper, and significant change in flow pattern and heat transfer behavior are found when the open mode is transformed into the closed mode.展开更多
Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different wave...Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry-Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165mW is obtained for a 1-mm-long uncoated laser.展开更多
The fundamental transverse mode(TEM00)is preferable for experimental and theoretical study on the laser-induced retinal injury effect,for it can produce the minimal retinal image andestablish the most strict laser saf...The fundamental transverse mode(TEM00)is preferable for experimental and theoretical study on the laser-induced retinal injury effect,for it can produce the minimal retinal image andestablish the most strict laser safety standards.But actually lasers with higher order mode werefrequently used in both earlier and recent studies.Generally higher order mode leads to largerretinal spot size and so higher damage threshold,but there are few quantitative analyses on thisproblem.In this paper,a four-surface schematic eye model is established for human and macaque.The propagation of 532-nm laser in schematic eye is analyzed by the ABCD law of Gaussianoptics.It is shown that retinal spot size increases with laser transverse mode order.For relativelower mode order,the retinal spot diameter will not exceed the minimum laser-induced retinallesion(25~30μm in diameter),and so has little effect on retinal damage threshold.While forhigher order mode,the larger'retinal spot requires more energy to induce injury and so the damage threshold increases.When beam divergence is lowered,the retinal spot size decreasescorrespondingly,so the efect of mode order can be compensated.The retinal spot size of macaqueis slightly smaller than that of human and the ratio bet ween them is independent of mode order.We conclude that the laser mode order has significant influence on retinal spot size but limitedinfluence on the retinal injury ffect.展开更多
In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistabili...In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistability characteristics of the dominant and injected modes are strongly dependent on the injected input optical power and wavelength detuning in an SMFP-LD. We observe three types of hysteresis loops： counterclockwise, clockwise, and butterfly hysteresis with various loop widths. In the case of a bistability loop caused by injection power, the transition from counterclockwise to clockwise in the hysteresis direction with the wavelength detuning from 0.028 nm to 0.112 nm is observed in a way of butterfly hys- teresis for the dominant mode by increasing the wavelength detuning. The width of hysteresis loop, induced by wavelength detuning is also changed while the injection power is enhanced from -7 dBm to -5 dBm.展开更多
Mode-locked fiber lasers are excellent platforms for soliton generation.Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity.Here we propose an exper...Mode-locked fiber lasers are excellent platforms for soliton generation.Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity.Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser.The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity,thereby enabling indepth observation and manipulation of soliton evolution along the dispersion map.The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution.Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics,fostering advancements in nonlinear and ultrafast optics.展开更多
Owing to the dynamic tunability and strong confinement,graphene plasmons(GPs)have emerged as an excellent candidate for the manipulation of light-matter interaction.Surface plasmons(SPs)have been admitted as another e...Owing to the dynamic tunability and strong confinement,graphene plasmons(GPs)have emerged as an excellent candidate for the manipulation of light-matter interaction.Surface plasmons(SPs)have been admitted as another effective way allowing strong confinement of light at the nanoscale.The combination of GPs and SPs like localized surface plasmons(LSPs)and propagating surface plasmon polaritons(SPPs)will lead to a synergistic effect that could remarkably improve light-matter interactions,showing great potential for many applications for the improvement of solar cell efficiency,biosensor sensitivity,and the performance of photonic devices.In this study,the GPs were activated by placing graphene film onto a two-dimensional(2D)phase-changing crystalline Ge_(2)Sb_(1.5)Bi_(0.5)Te_(5)(cGSBT)nanograting structure,which also acts as an original source generating LSPs.The SPPs originated by laying the above structure onto an Au mirror.The combined effects of GPs,LSPs,and SPPs are epitomized in such a simple Gr/2D cGSBT gratings/Au heterostructure,which allows easy realization of an ultrafast mode-locked laser quite stable working at 1550 nm range due to the strong nonlinear optical absorption capability.This approach overcomes the heat and energy loss in metallic gratings or a Gr-based heterostructure,exhibiting great potential for applications in the design and fabrication of photonic devices.展开更多
Upconversion nanoparticles(UCNPs)have attracted considerable interest due to their large anti-Stokes shift,offering promising applications in lasing.Here,multi-wavelength upconversion whispering gallery mode(WGM)lasin...Upconversion nanoparticles(UCNPs)have attracted considerable interest due to their large anti-Stokes shift,offering promising applications in lasing.Here,multi-wavelength upconversion whispering gallery mode(WGM)lasing is demonstrated in silica microspheres coated with NaYF_(4)@NaYbF_(4):1%Tm^(3+)@NaYF_(4)nanoparticles and coupled with tapered fibers.Under continuous-wave 980 nm pumping,low-threshold lasing is achieved across Tm3+transitions from near-infrared to visible,with an ultra-low threshold of 0.61μWfor the 3H_(4)→3H_(6)transition.Additionally,upconversion laser output can also be achieved in Er^(3+)-and Ho^(3+)-activated microspheres.These results establish tapered fiber coupling as a versatile approach for enhancing upconversion microlasers.展开更多
Polygonal optical vortices—a new subset of optical vortices—uniquely enable numerous applications due to the new degrees of freedom offered and their customizable light intensity structure.So far,their generation ha...Polygonal optical vortices—a new subset of optical vortices—uniquely enable numerous applications due to the new degrees of freedom offered and their customizable light intensity structure.So far,their generation has only been reported for continuous wave.Here,we demonstrate the first femtosecond polygonal optical vortex pulses,which is also the first pulsed demonstration of such vortices in general.From a mode-locked Yb:KGW laser oscillator,femtosecond Hermit-Gaussian pulses at the quasi-frequency-degenerate state were generated and subsequently converted by astigmatic mode conversion to femtosecond polygonal optical vortices.They have light intensity distributions of square,pentagonal,and hexagonal shapes and carry orbital angular momentums.In all these variations,the average power and pulse duration are greater than one watt and less than 500 fs.These results open the way to new applications in the fields of femtosecond optical tweezer and three-dimensional microstructure fabrication.展开更多
Harmonic mode-locking,realized actively or passively,is an effective technique for increasing the repetition rate of ultrafast lasers.It is critically important to understand how a harmonically mode-locked pulse train...Harmonic mode-locking,realized actively or passively,is an effective technique for increasing the repetition rate of ultrafast lasers.It is critically important to understand how a harmonically mode-locked pulse train responds to external perturbations and noise,so as to make sure that it is stable and resistant to noise.Here,in a series of carefully designed experiments,we elucidate the retiming dynamics of laser pulses generated in a soliton fiber laser harmonically modelocked at GHz frequencies to the acoustic resonance in a photonic crystal fiber(PCF)core.We characterize the selfdriven optomechanical lattice,which is distributed along the PCF and provides the structure that supports harmonic mode-locking,using a homodyne setup.We reveal that,after an abrupt perturbation,each soliton in the lattice undergoes damped oscillatory retiming within its trapping potential,while the retiming is strongly coupled to soliton dissipation.In addition,we show,through statistical analysis of the intra-cavity pulse spacing,how the trapping potentials are effective for suppressing timing jtter.The measurements and the theory developed in this work lay the groundwork for studies of the general stability and noise performance of harmonically mode-locked lasers as well as providing valuable insight into generic multi-pulse phenomena in mode-locked lasers.展开更多
The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions.In comparison to multimode spatiotemporal mode-locked solitons,exp...The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions.In comparison to multimode spatiotemporal mode-locked solitons,expanding the wavelength dimension is also crucial for studying the dynamics of multi-dimensional solitons,with simpler characterization techniques。展开更多
The modes competition characteristics in birefringence cavity laser are studied in different regions of the gain curve. The mode＇s intensity modulation depth with modes competition is much deeper than that without mo...The modes competition characteristics in birefringence cavity laser are studied in different regions of the gain curve. The mode＇s intensity modulation depth with modes competition is much deeper than that without modes competition. When the average intensities of the two modes are comparable, the intensity modulation depth of either mode reaches its maximum. Modes competition can do more contribution to the mode＇s modulation depth than the percentage of light reflected back into the laser cavity does. These characteristics can be used to improve the sensitivity of an optical feedback system. A modes competition factor is introduced to either mode＇s intensity expression which describes the laser intensity more precisely.展开更多
We investigate the transverse mode pattern in GaN quantum-well （QW） laser diode （LD） by numerical calculation. We optimize the current GaN LD structure by varying the n-GaN layer thickness. The n-type GaN layer is...We investigate the transverse mode pattern in GaN quantum-well （QW） laser diode （LD） by numerical calculation. We optimize the current GaN LD structure by varying the n-GaN layer thickness. The n-type GaN layer is an important factor to determine the optical mode. Finally, we discuss the lasing performance of the GaN LD based on the transverse optical modes.展开更多
Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive.With the advantages of simple fabrication,full-color and high-quality-factor whispering gallery mode la...Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive.With the advantages of simple fabrication,full-color and high-quality-factor whispering gallery mode lasing inside a circular cross-section,polymer microfibers are attractive for photonic devices.However,polymer lasing microfibers for information encryption have never been reported.Herein,we propose a design of printable lasing microfiber encryption chip by in-situ tuning the effective refractive index of the microresonator arrays via a facile approach.Through inkjet printing high-refractive-index nanoparticles on the designated position of lasing microfiber arrays,the effective refractive index of the microcavities is regulated,and the ratio of wavenumber spacing between transverse electric and transverse magnetic mode to the free spectral range can be modulated,particularly with neglectable influence by the size factor.Thus,the programmable region selective encoding process can be conducted simply by a printing program within several minutes.Besides,the encoded microfiber arrays are encapsulated into polydimethylsiloxane to reduce the scattering loss and environmental interference,and a printable encryption chip is realized.This work is expected to provide a platform for the printable encrypted devices.展开更多
Optical coherence tomography(OCT)allows a direct and precise measurement of laser welding depth by coaxially measuring the keyhole depth and can be used for process monitoring and control.When OCT measurement was take...Optical coherence tomography(OCT)allows a direct and precise measurement of laser welding depth by coaxially measuring the keyhole depth and can be used for process monitoring and control.When OCT measurement was taken during single-beam laser welding,the keyhole instability of aluminum welding resulted in highly scattered OCT data and complicated the welding depth extraction methods.As a combination of an inner core beam and an outer ring beam,a novel adjustable ring mode(ARM)laser for producing a stable keyhole was applied to the OCT measurement.Different ARM laser power arrangements were conducted on aluminum and copper.The results indicated that the ring beam greatly improved the stability of the core beam-induced keyhole,and smooth welding depth can be extracted from the concentrated OCT data.展开更多
We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarize...We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarized input beam, a true 3-mode fiber and by applying the stress on a stripped piece of the optical waveguide. These generalizations are necessary in order to perform quantum information experiments and obtain reliable information on the stress imposed on the optical fiber.展开更多
Coiling technique is used to control the transverse mode of a large-mode-area （LMA） multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppre...Coiling technique is used to control the transverse mode of a large-mode-area （LMA） multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mm. It is found that as the coil radius decreases, the beam quality of a multimode fiber laser gets better but the slope efficiency drops for higher-order modes are discriminated. During the experiment, as the coil radius of multimode fiber changes, output characteristic of the laser has been measured. Meanwhile, the mode loss of different modes is calculated theoretically. It is proved that the experimental measured results fit well with the theoretically calculated results.展开更多
Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain （FDTD） technique. For a square resonator with refractive index of 3.2, side length of 4μm, and output ...Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain （FDTD） technique. For a square resonator with refractive index of 3.2, side length of 4μm, and output waveguide of 0.4μm width, we have got the quality factors （Q factors） of 6.7 ×10^2 and 7.3 × 10^3 for the fundamental and first-order transverse magnetic （TM） mode near the wavelength of 1.5μm, respectively. The simulated intensity distribution for the first-order TM mode shows that the coupling efficiency in the waveguide reaches 53%. The numerical simulation shows that the first-order transverse modes have fairly high Q factor and high coupling efficiency to the output waveguide. Therefore the square resonator with an output waveguide is a promising candidate to realize single-mode directional emission microcavity lasers.展开更多
An erbium-doped fiber （EDF） laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a...An erbium-doped fiber （EDF） laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a narrow linewidth of 5 kHz. The mode selection mechanisms of the un-pumped EDF and the ring resonator are theoretically and experimentally analyzed.展开更多
基金This work was supported by the National "863" Project of China. W. Gao's e-mail address is wdgao@mail.siom. ac.cn.
文摘The laser-induced damage behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running laser mode. The absorption measurement of such coatings has been performed by surface thermal lensing (STL) technique. The relationship between damage morphology and absorption under the two different laser modes was studied in detail. The explanation was given by the standing-wave distribution theory.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632801the National Key Research and Development Program under Grant No 2016YFB0402303+2 种基金the National Natural Science Foundation of China under Grant Nos61435014,61627822,61574136 and 61306058the Key Projects of Chinese Academy of Sciences under Grant No ZDRW-XH-2016-4the Beijing Natural Science Foundation under Grant No 4162060
文摘We report on the design and fabrication of λ-7.2μm distributed feedback quantum cascade lasers lot very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90℃. For a 2-mm-long and 10-μm-wide laser coated with high-reflectivity on the rear facet, more than 170mW of output power is obtained at 20℃ with a threshold power consumption of 2.4 W, corresponding to 30mW with a threshold power consumption of 3.9 W at 90℃. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11332011 and 11472276the Project of the Chinese Academy of Sciences,and the Defense Industrial Technology Development Program
文摘When laser ablation is subjected to supersonic flow, the influence mechanism of airflow on laser ablation behavior is still unclear. A coupled thermal-fluid-structure model is presented to investigate the influence of supersonic airflow on the development of a laser ablation pit. Results show that the aerodynamic convection cooling effect not only reduces the ablation velocity but also changes the symmetry morphology of the ablation pit due to the non-uniform convective heat transfer. Flow mode transition is also observed when the pit becomes deeper, and significant change in flow pattern and heat transfer behavior are found when the open mode is transformed into the closed mode.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61274046 and 61474111the National Basic Research Program of China under Grant No 2013AA014202
文摘Optimization of the high power single-lateral-mode double-trench ridge waveguide semiconductor laser based on InGaAsP/InP quantum-well heterostructures with a separate confinement layer is reported. Two different waveguide structures of Fabry-Perot lasers emitting at a wavelength of 1.55 μm are fabricated. The influence of an effective lateral refractive index step on the maximum output power is investigated. A cw single mode output power of 165mW is obtained for a 1-mm-long uncoated laser.
基金the support from the National Nature Science Foundation of China(NSFC),the grant number is 61275194.
文摘The fundamental transverse mode(TEM00)is preferable for experimental and theoretical study on the laser-induced retinal injury effect,for it can produce the minimal retinal image andestablish the most strict laser safety standards.But actually lasers with higher order mode werefrequently used in both earlier and recent studies.Generally higher order mode leads to largerretinal spot size and so higher damage threshold,but there are few quantitative analyses on thisproblem.In this paper,a four-surface schematic eye model is established for human and macaque.The propagation of 532-nm laser in schematic eye is analyzed by the ABCD law of Gaussianoptics.It is shown that retinal spot size increases with laser transverse mode order.For relativelower mode order,the retinal spot diameter will not exceed the minimum laser-induced retinallesion(25~30μm in diameter),and so has little effect on retinal damage threshold.While forhigher order mode,the larger'retinal spot requires more energy to induce injury and so the damage threshold increases.When beam divergence is lowered,the retinal spot size decreasescorrespondingly,so the efect of mode order can be compensated.The retinal spot size of macaqueis slightly smaller than that of human and the ratio bet ween them is independent of mode order.We conclude that the laser mode order has significant influence on retinal spot size but limitedinfluence on the retinal injury ffect.
基金supported by the National Natural Science Foundation of China(Grant No.61205111)the Open Foundation of State Key Laboratory of Millimeter Waves,China(Grant No.K201219)the Natural Science Foundation of Chongqing Normal University,China(Grant No.2011XLZ06)
文摘In this paper, we observe experimentally the optical bistability induced by the side-mode injection power and wave- length detuning in a single mode Fabry-P6rot laser diode （SMFP-LD）. Results show that the bistability characteristics of the dominant and injected modes are strongly dependent on the injected input optical power and wavelength detuning in an SMFP-LD. We observe three types of hysteresis loops： counterclockwise, clockwise, and butterfly hysteresis with various loop widths. In the case of a bistability loop caused by injection power, the transition from counterclockwise to clockwise in the hysteresis direction with the wavelength detuning from 0.028 nm to 0.112 nm is observed in a way of butterfly hys- teresis for the dominant mode by increasing the wavelength detuning. The width of hysteresis loop, induced by wavelength detuning is also changed while the injection power is enhanced from -7 dBm to -5 dBm.
基金National Key Research and Development Program of China(2023YFF0715802)National Natural Science Foundation of China(62305299,62205296 and12475006)+1 种基金Natural Science Foundation of Zhejiang Province(Z24F050008,LQ23F050004,LQ22F050007)Natural Science Basic Research Program of Shaanxi(2023-JC-YB-563)。
文摘Mode-locked fiber lasers are excellent platforms for soliton generation.Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity.Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser.The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity,thereby enabling indepth observation and manipulation of soliton evolution along the dispersion map.The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution.Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics,fostering advancements in nonlinear and ultrafast optics.
基金National Natural Science Foundation of China(62404116)Natural Science Foundation of Shandong Province(ZR2023QE216)Youth Innovation Team Project of Shandong Province(2023KJ235)。
文摘Owing to the dynamic tunability and strong confinement,graphene plasmons(GPs)have emerged as an excellent candidate for the manipulation of light-matter interaction.Surface plasmons(SPs)have been admitted as another effective way allowing strong confinement of light at the nanoscale.The combination of GPs and SPs like localized surface plasmons(LSPs)and propagating surface plasmon polaritons(SPPs)will lead to a synergistic effect that could remarkably improve light-matter interactions,showing great potential for many applications for the improvement of solar cell efficiency,biosensor sensitivity,and the performance of photonic devices.In this study,the GPs were activated by placing graphene film onto a two-dimensional(2D)phase-changing crystalline Ge_(2)Sb_(1.5)Bi_(0.5)Te_(5)(cGSBT)nanograting structure,which also acts as an original source generating LSPs.The SPPs originated by laying the above structure onto an Au mirror.The combined effects of GPs,LSPs,and SPPs are epitomized in such a simple Gr/2D cGSBT gratings/Au heterostructure,which allows easy realization of an ultrafast mode-locked laser quite stable working at 1550 nm range due to the strong nonlinear optical absorption capability.This approach overcomes the heat and energy loss in metallic gratings or a Gr-based heterostructure,exhibiting great potential for applications in the design and fabrication of photonic devices.
基金National Natural Science Foundation of China(62122027,62075063,62205109,62405092,52202004)Postdoctoral Fellowship Program of CPSF(GZC20230852)+1 种基金State Key Laboratory of Luminescent Materials and Devices(Skllmd-2024-12)China Scholarship Council Grant(202406150002)。
文摘Upconversion nanoparticles(UCNPs)have attracted considerable interest due to their large anti-Stokes shift,offering promising applications in lasing.Here,multi-wavelength upconversion whispering gallery mode(WGM)lasing is demonstrated in silica microspheres coated with NaYF_(4)@NaYbF_(4):1%Tm^(3+)@NaYF_(4)nanoparticles and coupled with tapered fibers.Under continuous-wave 980 nm pumping,low-threshold lasing is achieved across Tm3+transitions from near-infrared to visible,with an ultra-low threshold of 0.61μWfor the 3H_(4)→3H_(6)transition.Additionally,upconversion laser output can also be achieved in Er^(3+)-and Ho^(3+)-activated microspheres.These results establish tapered fiber coupling as a versatile approach for enhancing upconversion microlasers.
基金supported by the National Key Research and Development Program of China(2022YFC2203902)the National Natural Science Foundation of China(No.62335009)+2 种基金the Interdisciplinary Research Program of Hust(2023JCYJ041)the Key Research and Development Program of Ningbo(No.2024T007)Wuhan Knowledge Innovation Special Project(2023010201010052).
文摘Polygonal optical vortices—a new subset of optical vortices—uniquely enable numerous applications due to the new degrees of freedom offered and their customizable light intensity structure.So far,their generation has only been reported for continuous wave.Here,we demonstrate the first femtosecond polygonal optical vortex pulses,which is also the first pulsed demonstration of such vortices in general.From a mode-locked Yb:KGW laser oscillator,femtosecond Hermit-Gaussian pulses at the quasi-frequency-degenerate state were generated and subsequently converted by astigmatic mode conversion to femtosecond polygonal optical vortices.They have light intensity distributions of square,pentagonal,and hexagonal shapes and carry orbital angular momentums.In all these variations,the average power and pulse duration are greater than one watt and less than 500 fs.These results open the way to new applications in the fields of femtosecond optical tweezer and three-dimensional microstructure fabrication.
基金supported by the National Natural Science Foundation of China(Grant No.62375275 and 62275254)by Strategic Priority Research Program of the Chinese Academy of Science(XDB0650000)+1 种基金by Shanghai Science and Technology Plan Project Funding(Grant No.23JC1410100)by Fuyang High-level Talent Group Project.
文摘Harmonic mode-locking,realized actively or passively,is an effective technique for increasing the repetition rate of ultrafast lasers.It is critically important to understand how a harmonically mode-locked pulse train responds to external perturbations and noise,so as to make sure that it is stable and resistant to noise.Here,in a series of carefully designed experiments,we elucidate the retiming dynamics of laser pulses generated in a soliton fiber laser harmonically modelocked at GHz frequencies to the acoustic resonance in a photonic crystal fiber(PCF)core.We characterize the selfdriven optomechanical lattice,which is distributed along the PCF and provides the structure that supports harmonic mode-locking,using a homodyne setup.We reveal that,after an abrupt perturbation,each soliton in the lattice undergoes damped oscillatory retiming within its trapping potential,while the retiming is strongly coupled to soliton dissipation.In addition,we show,through statistical analysis of the intra-cavity pulse spacing,how the trapping potentials are effective for suppressing timing jtter.The measurements and the theory developed in this work lay the groundwork for studies of the general stability and noise performance of harmonically mode-locked lasers as well as providing valuable insight into generic multi-pulse phenomena in mode-locked lasers.
基金National Natural Science Foundation of China(12274238, 62205159, 61835006)Special Project for Cooperation in Basic Research of Beijing,Tianjin and Hebei (21JCZXJC00010)
文摘The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions.In comparison to multimode spatiotemporal mode-locked solitons,expanding the wavelength dimension is also crucial for studying the dynamics of multi-dimensional solitons,with simpler characterization techniques。
基金This work was supported by the National Nature Science Foundation of China under Grant No. 60437030.
文摘The modes competition characteristics in birefringence cavity laser are studied in different regions of the gain curve. The mode＇s intensity modulation depth with modes competition is much deeper than that without modes competition. When the average intensities of the two modes are comparable, the intensity modulation depth of either mode reaches its maximum. Modes competition can do more contribution to the mode＇s modulation depth than the percentage of light reflected back into the laser cavity does. These characteristics can be used to improve the sensitivity of an optical feedback system. A modes competition factor is introduced to either mode＇s intensity expression which describes the laser intensity more precisely.
基金supported by the"973"Program of China(No.TG2007CB307004)the"863"Program of China(No.863-2006AA03A113)the National Natural Science Foundation of China(No.60276034,60577030,and 60607003).
文摘We investigate the transverse mode pattern in GaN quantum-well （QW） laser diode （LD） by numerical calculation. We optimize the current GaN LD structure by varying the n-GaN layer thickness. The n-type GaN layer is an important factor to determine the optical mode. Finally, we discuss the lasing performance of the GaN LD based on the transverse optical modes.
基金The authors would like to acknowledge the National Natural Science Foundation of China(NSFC)(Nos.52203252 and 61822501)the Beijing Natural Science Foundation(No.Z180015)for financial support.
文摘Lasing emissions with multiple and tunable modes are promising in coding field as a novel cryptographic primitive.With the advantages of simple fabrication,full-color and high-quality-factor whispering gallery mode lasing inside a circular cross-section,polymer microfibers are attractive for photonic devices.However,polymer lasing microfibers for information encryption have never been reported.Herein,we propose a design of printable lasing microfiber encryption chip by in-situ tuning the effective refractive index of the microresonator arrays via a facile approach.Through inkjet printing high-refractive-index nanoparticles on the designated position of lasing microfiber arrays,the effective refractive index of the microcavities is regulated,and the ratio of wavenumber spacing between transverse electric and transverse magnetic mode to the free spectral range can be modulated,particularly with neglectable influence by the size factor.Thus,the programmable region selective encoding process can be conducted simply by a printing program within several minutes.Besides,the encoded microfiber arrays are encapsulated into polydimethylsiloxane to reduce the scattering loss and environmental interference,and a printable encryption chip is realized.This work is expected to provide a platform for the printable encrypted devices.
基金supported by the National Natural Science Foundation of China(No.12002215)the China Postdoctoral Science Foundation(No.2022T150437)the National Key Research and Development Program of China(No.2019YFC1511102)。
文摘Optical coherence tomography(OCT)allows a direct and precise measurement of laser welding depth by coaxially measuring the keyhole depth and can be used for process monitoring and control.When OCT measurement was taken during single-beam laser welding,the keyhole instability of aluminum welding resulted in highly scattered OCT data and complicated the welding depth extraction methods.As a combination of an inner core beam and an outer ring beam,a novel adjustable ring mode(ARM)laser for producing a stable keyhole was applied to the OCT measurement.Different ARM laser power arrangements were conducted on aluminum and copper.The results indicated that the ring beam greatly improved the stability of the core beam-induced keyhole,and smooth welding depth can be extracted from the concentrated OCT data.
文摘We have coupled an upright HG mode into a fiber-optic waveguide and used the application of stress to generate a Laguerre-Gaussian laser mode. We have generalized previous results by McGloin et al. by using a polarized input beam, a true 3-mode fiber and by applying the stress on a stripped piece of the optical waveguide. These generalizations are necessary in order to perform quantum information experiments and obtain reliable information on the stress imposed on the optical fiber.
基金National Key Basic Research Project of China,the Shanghai Science & Technology Foundation(No.04DZ05120,05DZ22001)the Knowledge Innovation Project of Chinese Academy of Sciences.
文摘Coiling technique is used to control the transverse mode of a large-mode-area （LMA） multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mm. It is found that as the coil radius decreases, the beam quality of a multimode fiber laser gets better but the slope efficiency drops for higher-order modes are discriminated. During the experiment, as the coil radius of multimode fiber changes, output characteristic of the laser has been measured. Meanwhile, the mode loss of different modes is calculated theoretically. It is proved that the experimental measured results fit well with the theoretically calculated results.
基金This work was supported by the National Natural Science Foundation of China(No.60225011)and the MajorState Basic Research Program(No.2006CB302804).
文摘Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain （FDTD） technique. For a square resonator with refractive index of 3.2, side length of 4μm, and output waveguide of 0.4μm width, we have got the quality factors （Q factors） of 6.7 ×10^2 and 7.3 × 10^3 for the fundamental and first-order transverse magnetic （TM） mode near the wavelength of 1.5μm, respectively. The simulated intensity distribution for the first-order TM mode shows that the coupling efficiency in the waveguide reaches 53%. The numerical simulation shows that the first-order transverse modes have fairly high Q factor and high coupling efficiency to the output waveguide. Therefore the square resonator with an output waveguide is a promising candidate to realize single-mode directional emission microcavity lasers.
文摘An erbium-doped fiber （EDF） laser was configured with a fiber grating, a fiber ring resonator, and a saturable absorber by using un-pumped EDF as mode selection element. The laser showed single mode operation with a narrow linewidth of 5 kHz. The mode selection mechanisms of the un-pumped EDF and the ring resonator are theoretically and experimentally analyzed.
