Quantum photonic integrated circuits offer enhanced stability and scalability for quantum communications,sensing, and computing. Transverse modes in multimode waveguides enable high-dimensional scalability and versati...Quantum photonic integrated circuits offer enhanced stability and scalability for quantum communications,sensing, and computing. Transverse modes in multimode waveguides enable high-dimensional scalability and versatile photon manipulation, but practical adoption requires compact and fabrication-tolerant quantum interference devices. Here, we present an ultra-compact taper-stepped beamsplitter that enables quantum interference between photon pairs in different transverse modes, and cascade it to realize NOON state interferometry. We experimentally achieve high visibilities of 93.9% for HOM interference and 86.5% for NOON state interference,demonstrating that efficient mode interference with active tuning can be realized on this platform.展开更多
The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from l...The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite–Gaussian(HG) and Laguerre–Gaussian(LG)modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite–LG(HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 2 in the Jordan–Schwinger map.Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials.Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by an astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes, but also a pedagogical insight into quantum physics.展开更多
Longitudinal polar modes generate a macroscopic electric field in piezoelectric crystals and cause an additional mechanism of Raman scattering. The classical theory holds that transverse polar modes cannot produce suc...Longitudinal polar modes generate a macroscopic electric field in piezoelectric crystals and cause an additional mechanism of Raman scattering. The classical theory holds that transverse polar modes cannot produce such an additional mechanism. Our quantum theory shows that there is an additional Raman scattering mechanism arising from the electro-optic effect of transverse polar modes.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
Spatial patterns are a significant characteristic of lasers.The knowledge of spatial patterns of structured laser beams is rapidly expanding,along with the progress of studies on laser physics and technology.Particula...Spatial patterns are a significant characteristic of lasers.The knowledge of spatial patterns of structured laser beams is rapidly expanding,along with the progress of studies on laser physics and technology.Particularly in the last decades,owing to the in-depth attention on structured light with multiple degrees of freedom,the research on spatial and spatiotemporal structures of laser beams has been promptly developed.Such beams have hatched various breakthroughs in many fields,including imaging,microscopy,metrology,communication,optical trapping,and quantum information processing.Here,we would like to provide an overview of the extensive research on several areas relevant to spatial patterns of structured laser beams,from spontaneous organization to multiple transformations.These include the early theory of beam pattern formation based on the Maxwell–Bloch equations,the recent eigenmodes superposition theory based on the time-averaged Helmholtz equations,the beam patterns extension of ultrafast lasers to the spatiotemporal beam structures,and the structural transformations in the nonlinear frequency conversion process of structured beams.展开更多
As for the Domino effect dv/dt and electromagnetic interference during the rapid switching course of single-chip switching power supply,this article firstly analyzes electromagnetic interference source,and then diagno...As for the Domino effect dv/dt and electromagnetic interference during the rapid switching course of single-chip switching power supply,this article firstly analyzes electromagnetic interference source,and then diagnoses the essential interaction relationship between interference and switching activity based on the timely and area measured waveform,analyzes and studies the production mechanism and coupling path of interference mode,and sets up circuit model according to the features of transverse mode interference and common mode interference.Put forward different suppression methods finally.展开更多
Inorganic perovskite lasers are of particular interest,with much recent work focusing on Fabry-P6rot cavity-forming nanowires.We demonstrate the direct observation of lasing from transverse electromagnetic(TEM)modes w...Inorganic perovskite lasers are of particular interest,with much recent work focusing on Fabry-P6rot cavity-forming nanowires.We demonstrate the direct observation of lasing from transverse electromagnetic(TEM)modes with a long coherence time-9.5ps in coupled CsPbBr_(3) quantum dots,which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms.Controlling the pump power allowed us tofine-tune the TEM mode structure to the emission wavelength,thus providing a degree of control over the properties of the lasing signal.The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak,importantly,maintained a constant full width at half maximum(FWHM)over the entire tuning range without mode-hopping.展开更多
We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length...We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction （blueshifts）. In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.展开更多
In this paper Substrate Integrated Waveguide-basedfiltenna operating at Ku band is proposed.The model is designed on a low loss dielectric substrate having a thickness of 0.508 mm and comprises of shorting vias along ...In this paper Substrate Integrated Waveguide-basedfiltenna operating at Ku band is proposed.The model is designed on a low loss dielectric substrate having a thickness of 0.508 mm and comprises of shorting vias along two edges of the substrate walls.To realize a bandpassfilter,secondary shorting vias are placed close to primary shorting vias.The dimension and position of the vias are carefully analyzed for Ku band frequencies.The model is fabricated on Roger RT/duroid 5880 and the performance characteristics are measured.The proposed model achieves significant impedance characteristics with wider bandwidth in the Ku band.The model also achieves a maximum gain of 7.46 dBi in the operating band thus making it suitable for Ku-band applications.Substrate Integrated Waveguide(SIW)Structures possess most of the advantages over conventional radiofrequency waveguides since they have high power management capacity with self-consistent electrical shielding.The most noteworthy advantage of SIW,it can able to integrate all the components on the same substrate,both passive and active components.展开更多
Transverse mode instability(TMI),induced by nonlinear thermal-optical coupling,poses a primary challenge for the power scaling of fiber lasers.In the fiber oscillator,a sealed resonant cavity,TMI could become particul...Transverse mode instability(TMI),induced by nonlinear thermal-optical coupling,poses a primary challenge for the power scaling of fiber lasers.In the fiber oscillator,a sealed resonant cavity,TMI could become particularly complex due to the mode competition during the laser oscillation.While traditional theories of TMI predominantly address two-mode coupling,this paper explores the TMI phenomena in few-mode fiber oscillators utilizing a holistic approach that includes solving steady-state thermal-optic coupling equations.The simulation shows that there is a non-monotonic correlation between bending loss and the TMI threshold,which is contrary to the monotonic associations suggested by two-mode interaction theory.When one high-order mode experiences net gain,fluctuations of the TMI threshold would occur,leading to the amplification of a new mode within the uncoupled frequency region,thus affecting the gain saturation.By designing the linewidth of a low-reflection grating(LR),the modal power management in the uncoupled frequency domain can be achieved.An excessively broad LR linewidth exacerbates mode coupling within the shared frequency region,thus exacerbating TMI.To validate the theoretical simulation,we carefully fabricated LRs and optimized the fiber coiling to elevate the TMI threshold.Through careful optimization of LR linewidth and bending radii,we achieved a record-breaking laser output of 10.07kW using a monolithic fiber oscillator,with no observable evidence of TMI.Our work demonstrates that modal power redistribution in independent frequency domains offers a novel approach to mitigating TMI in high-power fiber lasers.Additionally,it provides new insights into mode decoupling strategies pertinent to fiber communications.展开更多
In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate ga...In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique,and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability(TMI)mitigation.Notably,the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments.It is found that the TMI threshold could be significantly affected by the seed laser mode purity.The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis.Finally,a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83,which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier.This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.展开更多
Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially des...Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially designed sandwich such as a microchip laser.The intracavity nonlinear frequency conversion process of a laser beam in a TML state to its second harmonic is theoretically and experimentally investigated,considering different relative phase and weight parameters between the basic modes in the TML beam.Comparison between the far-field SHG beam patterns of fundamental frequency transverse modes in coherently locked and incoherently superposed states demonstrates that the SHG of TML beams can carry more information.Various rarely observed far-field SHG beam patterns are obtained,and they are consistent with the theoretical analysis and numerical simulations.With the obtained SHG beams,the characteristics of the structured fundamental frequency beams can also be conversely investigated or predicted.This work may have important applications in optical 3D printing,optical trapping of particles,and free-space optical communication areas.展开更多
A laser-diode end-pumped Nd：YVO4 crystal laser is demonstrated to emit the first-order Laguerre- Gaussian （LGm） mode with 502-mW laser power and 22% slope efficiency. Tile LGm-mode is lased only when the pumping ar...A laser-diode end-pumped Nd：YVO4 crystal laser is demonstrated to emit the first-order Laguerre- Gaussian （LGm） mode with 502-mW laser power and 22% slope efficiency. Tile LGm-mode is lased only when the pumping area locates in the central part of the laser crystal＇s front surface, and thereafter the symmetrical LGm-HGol-TEM00 mode transition happens when laser crystal is moved laterally inside several-tens-micron area. The possible mechanism responsible for the phenomenon of symmetrical mode transition is also discussed.展开更多
The effect of transverse mode instability (TMI) is currently the main limitation for thefurther average-power scaling of fiber laser systems with diffraction-limited beamquality. In this work a main driving force for ...The effect of transverse mode instability (TMI) is currently the main limitation for thefurther average-power scaling of fiber laser systems with diffraction-limited beamquality. In this work a main driving force for TMI in fiber amplifiers is identified. Ourexperiments and simulations illustrate that the performance of fiber laser systems interms of their diffraction-limited output power can be significantly reduced whenthe pump or seed radiation exhibit intensity noise. This finding emphasizes the factthat the TMI threshold is not only determined by the active fiber but, rather, by thewhole system. In the experiment an artificially applied pump intensity-noise of 2.9%led to a reduction of the TMI threshold of 63%, whereas a similar seed intensitynoisedecreased it by just 13%. Thus, even though both noise sources have animpact on the TMI threshold, the pump intensity-noise can be considered as themain driver for TMI in saturated fiber amplifiers. Additionally, the work unveils thatthe physical origin of this behavior is linked to the noise transfer function insaturated fiber amplifiers. With the gained knowledge and the experimental andtheoretical results, it can be concluded that a suppression of pump-noise frequenciesbelow 20 kHz could strongly increase the TMI threshold in high-power fiber lasersystems.展开更多
1064 nm semiconductor lasers are crucial for optical communication,but the multitransverse‐mode nature of vertical‐cavity surface‐emitting laser(VCSEL)degrades beam quality over long distances.Traditional methods t...1064 nm semiconductor lasers are crucial for optical communication,but the multitransverse‐mode nature of vertical‐cavity surface‐emitting laser(VCSEL)degrades beam quality over long distances.Traditional methods to achieve fundamental transverse mode often limit power output and modulation band-width.We propose a two‐junction 1064 nm VCSEL with double embedded antiresonant oxide islands embedded in the top distributed Bragg reflector(DBR).By varying the oxide island count,aperture size,and position,we explore the behaviors of threshold current and output power for different transverse modes.This simulation‐based design achieves a maximum funda-mental transverse mode output power of 36.2 mW,a power conversion effi-ciency of 54.8%,and a 3 dB bandwidth of 33.06 GHz using oxide islands with 4 and 6μm radii at the second and eighth pairs of the top DBR.The enhanced modal discrimination raises the threshold current for higher‐order modes,thereby improving the fundamental mode output power,making this VCSEL structure promising for long‐distance optical communication.展开更多
The localized surface plasmon resonance metasurface is a research hotspot in the sensing field since it can enhance the light-matter interaction in the nanoscale,but the wavelength sensitivity is far from comparable w...The localized surface plasmon resonance metasurface is a research hotspot in the sensing field since it can enhance the light-matter interaction in the nanoscale,but the wavelength sensitivity is far from comparable with that of prism-coupled surface plasmon polariton(SPP).Herein,we propose and demonstrate an ultrasensitive angular interrogation sensor based on the transverse electric mode surface lattice resonance(SLR)mechanism in an all-metal metasurface.In theory,we derive the sensitivity function in detail and emphasize the refraction effect at the air-solution interface,which influences the SLR position and improves the sensitivity performance greatly in the wide-angle.In the measurement,a broadband light source substitutes the single-wavelength laser generally used in traditional angular sensing,and the measured SLR wavelength of broadband illuminant at normal incidence is defined as the single wavelength,avoiding the sensitivity loss from the large angle.The experimental sensitivity can reach 4304.35°/RIU,promoting an order of magnitude compared to those of SPP-sensors.This research provides a novel theory as well as the corresponding crucial approach to achieving ultrasensitive angular sensing.展开更多
High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simul...High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simultaneous achievement of kilowatt-level output power and diffraction-limited beam quality has remained elusive in all reported single-frequency fiber laser systems to date,primarily due to limitations imposed by the stimulated Brillouin scattering(SBS)effect and transverse mode instability(TMI)effect.In this study,we demonstrate the design and manufacturing of an ultra-low numerical aperture(NA)functional Yb-doped fiber featuring a bat-type refractive index distribution,specifically engineered for single-frequency laser amplification.In the fabrication,we implemented multiple chelate gas filling and particle deposition iterations,leading to an active fiber with a bat-type refractive index distribution.The unique capabilities of this large mode area and high-order modes leakage fiber(HOMLF)were demonstrated by stably amplifying the single-frequency laser with more than one kilowatt output power and near single mode beam quality(M_(x)^(2)=1.10,M_(x)^(2)=1.18)for the first time.This fiber design advances the leap forward in single-frequency fiber lasers,which could contribute as a novel and efficient laser amplification technique for the next generation of gravitational wave detection systems.展开更多
In order to balance the suppression of stimulated Raman scattering(SRS)and transverse mode instability(TMI)in high-power fiber lasers,in this Letter,a new type of spindle-shaped ytterbium-doped fiber(YDF)with asymmetr...In order to balance the suppression of stimulated Raman scattering(SRS)and transverse mode instability(TMI)in high-power fiber lasers,in this Letter,a new type of spindle-shaped ytterbium-doped fiber(YDF)with asymmetric longitude distribution was designed and produced,which had a small-sized input end,large-sized transmission section,and moderate output end,enabling a good fit with a seed laser and mitigating SRS as well as TMI effects.A counter-pumped fiber laser amplifier was established using this YDF,and two kinds of laser diodes(LDs)were adopted for increasing the TMI threshold.Finally,the maximum output power reached 6 kW,and the beam quality(M~2factors)indicated near-single-mode output.The SRS suppression ratio under 6 kW output power was 36 dB,and no dynamic TMI was observed,which revealed that further enhancement of output power was limited only by pump power.展开更多
Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a c...Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a constant cladding and tapered core(CCTC)along its axis direction.The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering(SRS)threshold and suppress higher-order mode resonance in the laser cavity.The CCTC YDF was fabricated successfully with a modified chemical vapor deposition(MCVD)method combined with solution doping technology,which has a cladding diameter of 400µm and a varying core with a diameter of~24μm at both ends and~31μm in the middle.To test the performance of the CCTC fiber during high-power operation,an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally.As a result,a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%,although the TMI effect was observed at an output power of~3.12 kW.The measured beam quality(M^(2)factor)was~1.7,and no sign of the Raman component was observed in the spectrum.We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects,and further power scaling is promising by optimizing the structure of the YDF.展开更多
Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimu...Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimulated Brillouin scattering effect.Nevertheless,over the past two decades much effort has been devoted to improving the power scaling and performance of high-power single-frequency fiber amplifiers.These amplifiers are mostly driven by applications,such as high precision detection and metrology,and have benefited from the long coherence length,low noise,and excellent beam quality of this type of laser source.In this paper,we review the overall development of high-power single-frequency fiber amplifiers by focusing on its progress and challenges,specifically,the strategies for circumventing the stimulated Brillouin scattering and transverse mode instability effects that,at present,are the major limiting factors of the power scaling of the single-frequency fiber amplifiers.These factors are also thoroughly discussed in terms of free-space and all-fiber coupled architecture.In addition,we also examine the noise properties of single-frequency fiber amplifiers,along with corresponding noise reducing schemes.Finally,we briefly envision the future development of high-power single-frequency fiber amplifiers.展开更多
基金supported by the National Key Research and Development Program of China (Grant No.2022YFB2803100)the National Major Scientific Research Instrument Development Project(Grant No.22127901)+6 种基金the National Natural Science Foundation of China (Grant No.62305367)the Shanghai Natural Science Foundation (Grant No.25ZR1401379)the Natural Science Foundation of Zhejiang Province,China (Grant No.LZ24F050001)the Innovation Program for Quantum Science and Technology (Grant Nos.2021ZD0301500 and 2021ZD0303200)the National Natural Science Foundation of China (Grant Nos.T2325022,U23A2074,62061160487,and 62275240)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-049)the Fundamental Research Funds for the Central Universities。
文摘Quantum photonic integrated circuits offer enhanced stability and scalability for quantum communications,sensing, and computing. Transverse modes in multimode waveguides enable high-dimensional scalability and versatile photon manipulation, but practical adoption requires compact and fabrication-tolerant quantum interference devices. Here, we present an ultra-compact taper-stepped beamsplitter that enables quantum interference between photon pairs in different transverse modes, and cascade it to realize NOON state interferometry. We experimentally achieve high visibilities of 93.9% for HOM interference and 86.5% for NOON state interference,demonstrating that efficient mode interference with active tuning can be realized on this platform.
基金supported by the Ministry of Science and Technology of Taiwan (Contract No. 108-2119-M-009-005)。
文摘The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite–Gaussian(HG) and Laguerre–Gaussian(LG)modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite–LG(HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 2 in the Jordan–Schwinger map.Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials.Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by an astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes, but also a pedagogical insight into quantum physics.
文摘Longitudinal polar modes generate a macroscopic electric field in piezoelectric crystals and cause an additional mechanism of Raman scattering. The classical theory holds that transverse polar modes cannot produce such an additional mechanism. Our quantum theory shows that there is an additional Raman scattering mechanism arising from the electro-optic effect of transverse polar modes.
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.
文摘Spatial patterns are a significant characteristic of lasers.The knowledge of spatial patterns of structured laser beams is rapidly expanding,along with the progress of studies on laser physics and technology.Particularly in the last decades,owing to the in-depth attention on structured light with multiple degrees of freedom,the research on spatial and spatiotemporal structures of laser beams has been promptly developed.Such beams have hatched various breakthroughs in many fields,including imaging,microscopy,metrology,communication,optical trapping,and quantum information processing.Here,we would like to provide an overview of the extensive research on several areas relevant to spatial patterns of structured laser beams,from spontaneous organization to multiple transformations.These include the early theory of beam pattern formation based on the Maxwell–Bloch equations,the recent eigenmodes superposition theory based on the time-averaged Helmholtz equations,the beam patterns extension of ultrafast lasers to the spatiotemporal beam structures,and the structural transformations in the nonlinear frequency conversion process of structured beams.
基金Tianjin Natunal science Foundation of China(No:05YFSYSF033)
文摘As for the Domino effect dv/dt and electromagnetic interference during the rapid switching course of single-chip switching power supply,this article firstly analyzes electromagnetic interference source,and then diagnoses the essential interaction relationship between interference and switching activity based on the timely and area measured waveform,analyzes and studies the production mechanism and coupling path of interference mode,and sets up circuit model according to the features of transverse mode interference and common mode interference.Put forward different suppression methods finally.
基金Basic Science Research Program and National Honor Scientist Program through the National Research Foundation of Korea(NRF)(Nos.2010-0020414,2018R1D1A1B07043676).T.F.acknowledges support from the Centre for Quantum Technologies,National University of Singapore.
文摘Inorganic perovskite lasers are of particular interest,with much recent work focusing on Fabry-P6rot cavity-forming nanowires.We demonstrate the direct observation of lasing from transverse electromagnetic(TEM)modes with a long coherence time-9.5ps in coupled CsPbBr_(3) quantum dots,which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms.Controlling the pump power allowed us tofine-tune the TEM mode structure to the emission wavelength,thus providing a degree of control over the properties of the lasing signal.The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak,importantly,maintained a constant full width at half maximum(FWHM)over the entire tuning range without mode-hopping.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11074176 and 10976019)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20100181110080)
文摘We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time- dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction （blueshifts）. In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.
文摘In this paper Substrate Integrated Waveguide-basedfiltenna operating at Ku band is proposed.The model is designed on a low loss dielectric substrate having a thickness of 0.508 mm and comprises of shorting vias along two edges of the substrate walls.To realize a bandpassfilter,secondary shorting vias are placed close to primary shorting vias.The dimension and position of the vias are carefully analyzed for Ku band frequencies.The model is fabricated on Roger RT/duroid 5880 and the performance characteristics are measured.The proposed model achieves significant impedance characteristics with wider bandwidth in the Ku band.The model also achieves a maximum gain of 7.46 dBi in the operating band thus making it suitable for Ku-band applications.Substrate Integrated Waveguide(SIW)Structures possess most of the advantages over conventional radiofrequency waveguides since they have high power management capacity with self-consistent electrical shielding.The most noteworthy advantage of SIW,it can able to integrate all the components on the same substrate,both passive and active components.
基金support from the National Natural Science Foundation of China(NSFC)(62405373,11974427)the Science and Technology Innovation Program of Hunan Province(2021RC4027).
文摘Transverse mode instability(TMI),induced by nonlinear thermal-optical coupling,poses a primary challenge for the power scaling of fiber lasers.In the fiber oscillator,a sealed resonant cavity,TMI could become particularly complex due to the mode competition during the laser oscillation.While traditional theories of TMI predominantly address two-mode coupling,this paper explores the TMI phenomena in few-mode fiber oscillators utilizing a holistic approach that includes solving steady-state thermal-optic coupling equations.The simulation shows that there is a non-monotonic correlation between bending loss and the TMI threshold,which is contrary to the monotonic associations suggested by two-mode interaction theory.When one high-order mode experiences net gain,fluctuations of the TMI threshold would occur,leading to the amplification of a new mode within the uncoupled frequency region,thus affecting the gain saturation.By designing the linewidth of a low-reflection grating(LR),the modal power management in the uncoupled frequency domain can be achieved.An excessively broad LR linewidth exacerbates mode coupling within the shared frequency region,thus exacerbating TMI.To validate the theoretical simulation,we carefully fabricated LRs and optimized the fiber coiling to elevate the TMI threshold.Through careful optimization of LR linewidth and bending radii,we achieved a record-breaking laser output of 10.07kW using a monolithic fiber oscillator,with no observable evidence of TMI.Our work demonstrates that modal power redistribution in independent frequency domains offers a novel approach to mitigating TMI in high-power fiber lasers.Additionally,it provides new insights into mode decoupling strategies pertinent to fiber communications.
基金supported by the National Natural Science Foundation of China(62035015)the Innovative Research Groups of Hunan Province(2019JJ10005)the Hunan Provincial Innovation Construct Project(2019RS3018).
文摘In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique,and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability(TMI)mitigation.Notably,the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments.It is found that the TMI threshold could be significantly affected by the seed laser mode purity.The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis.Finally,a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83,which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier.This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.
基金the support of the National Natural Science Foundation of China (NSFC) (61805013)
文摘Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially designed sandwich such as a microchip laser.The intracavity nonlinear frequency conversion process of a laser beam in a TML state to its second harmonic is theoretically and experimentally investigated,considering different relative phase and weight parameters between the basic modes in the TML beam.Comparison between the far-field SHG beam patterns of fundamental frequency transverse modes in coherently locked and incoherently superposed states demonstrates that the SHG of TML beams can carry more information.Various rarely observed far-field SHG beam patterns are obtained,and they are consistent with the theoretical analysis and numerical simulations.With the obtained SHG beams,the characteristics of the structured fundamental frequency beams can also be conversely investigated or predicted.This work may have important applications in optical 3D printing,optical trapping of particles,and free-space optical communication areas.
基金supported by the National Natural Science Foundation of China(No.61275206)the National "973" Project of China(No.2014CB921300)
文摘A laser-diode end-pumped Nd：YVO4 crystal laser is demonstrated to emit the first-order Laguerre- Gaussian （LGm） mode with 502-mW laser power and 22% slope efficiency. Tile LGm-mode is lased only when the pumping area locates in the central part of the laser crystal＇s front surface, and thereafter the symmetrical LGm-HGol-TEM00 mode transition happens when laser crystal is moved laterally inside several-tens-micron area. The possible mechanism responsible for the phenomenon of symmetrical mode transition is also discussed.
基金Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-416342637,416342891,GRK 2101(259607349)Fraunhofer Gesellschaft–Fraunhofer Cluster of Excellence“Advanced Photon Sources”.
文摘The effect of transverse mode instability (TMI) is currently the main limitation for thefurther average-power scaling of fiber laser systems with diffraction-limited beamquality. In this work a main driving force for TMI in fiber amplifiers is identified. Ourexperiments and simulations illustrate that the performance of fiber laser systems interms of their diffraction-limited output power can be significantly reduced whenthe pump or seed radiation exhibit intensity noise. This finding emphasizes the factthat the TMI threshold is not only determined by the active fiber but, rather, by thewhole system. In the experiment an artificially applied pump intensity-noise of 2.9%led to a reduction of the TMI threshold of 63%, whereas a similar seed intensitynoisedecreased it by just 13%. Thus, even though both noise sources have animpact on the TMI threshold, the pump intensity-noise can be considered as themain driver for TMI in saturated fiber amplifiers. Additionally, the work unveils thatthe physical origin of this behavior is linked to the noise transfer function insaturated fiber amplifiers. With the gained knowledge and the experimental andtheoretical results, it can be concluded that a suppression of pump-noise frequenciesbelow 20 kHz could strongly increase the TMI threshold in high-power fiber lasersystems.
基金National Key Research and Development Program of China,Grant/Award Number:2021YFA1401100National Natural Science Foundation of China,Grant/Award Numbers:52202165,52472148,62304031Natural Science Foundation of Sichuan Province,Grant/Award Number:2025ZNSFSC0351。
文摘1064 nm semiconductor lasers are crucial for optical communication,but the multitransverse‐mode nature of vertical‐cavity surface‐emitting laser(VCSEL)degrades beam quality over long distances.Traditional methods to achieve fundamental transverse mode often limit power output and modulation band-width.We propose a two‐junction 1064 nm VCSEL with double embedded antiresonant oxide islands embedded in the top distributed Bragg reflector(DBR).By varying the oxide island count,aperture size,and position,we explore the behaviors of threshold current and output power for different transverse modes.This simulation‐based design achieves a maximum funda-mental transverse mode output power of 36.2 mW,a power conversion effi-ciency of 54.8%,and a 3 dB bandwidth of 33.06 GHz using oxide islands with 4 and 6μm radii at the second and eighth pairs of the top DBR.The enhanced modal discrimination raises the threshold current for higher‐order modes,thereby improving the fundamental mode output power,making this VCSEL structure promising for long‐distance optical communication.
基金supported by the National Key R&D Program of China(Grant No.2021YFB3200100)the National Natural Science Foundation of China(Grant No.61931018 and 61974004)。
文摘The localized surface plasmon resonance metasurface is a research hotspot in the sensing field since it can enhance the light-matter interaction in the nanoscale,but the wavelength sensitivity is far from comparable with that of prism-coupled surface plasmon polariton(SPP).Herein,we propose and demonstrate an ultrasensitive angular interrogation sensor based on the transverse electric mode surface lattice resonance(SLR)mechanism in an all-metal metasurface.In theory,we derive the sensitivity function in detail and emphasize the refraction effect at the air-solution interface,which influences the SLR position and improves the sensitivity performance greatly in the wide-angle.In the measurement,a broadband light source substitutes the single-wavelength laser generally used in traditional angular sensing,and the measured SLR wavelength of broadband illuminant at normal incidence is defined as the single wavelength,avoiding the sensitivity loss from the large angle.The experimental sensitivity can reach 4304.35°/RIU,promoting an order of magnitude compared to those of SPP-sensors.This research provides a novel theory as well as the corresponding crucial approach to achieving ultrasensitive angular sensing.
基金support from the National Key Research and Development Program of China(2022YFB3606400).
文摘High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simultaneous achievement of kilowatt-level output power and diffraction-limited beam quality has remained elusive in all reported single-frequency fiber laser systems to date,primarily due to limitations imposed by the stimulated Brillouin scattering(SBS)effect and transverse mode instability(TMI)effect.In this study,we demonstrate the design and manufacturing of an ultra-low numerical aperture(NA)functional Yb-doped fiber featuring a bat-type refractive index distribution,specifically engineered for single-frequency laser amplification.In the fabrication,we implemented multiple chelate gas filling and particle deposition iterations,leading to an active fiber with a bat-type refractive index distribution.The unique capabilities of this large mode area and high-order modes leakage fiber(HOMLF)were demonstrated by stably amplifying the single-frequency laser with more than one kilowatt output power and near single mode beam quality(M_(x)^(2)=1.10,M_(x)^(2)=1.18)for the first time.This fiber design advances the leap forward in single-frequency fiber lasers,which could contribute as a novel and efficient laser amplification technique for the next generation of gravitational wave detection systems.
基金supported by the Hunan Outstanding Youth Fund(No.2023JJ10057)the Changsha Excellent Innovative Youth Training Program(Nos.kq2206006 and kq2206002)the National Natural Science Foundation of China(No.62005315)。
文摘In order to balance the suppression of stimulated Raman scattering(SRS)and transverse mode instability(TMI)in high-power fiber lasers,in this Letter,a new type of spindle-shaped ytterbium-doped fiber(YDF)with asymmetric longitude distribution was designed and produced,which had a small-sized input end,large-sized transmission section,and moderate output end,enabling a good fit with a seed laser and mitigating SRS as well as TMI effects.A counter-pumped fiber laser amplifier was established using this YDF,and two kinds of laser diodes(LDs)were adopted for increasing the TMI threshold.Finally,the maximum output power reached 6 kW,and the beam quality(M~2factors)indicated near-single-mode output.The SRS suppression ratio under 6 kW output power was 36 dB,and no dynamic TMI was observed,which revealed that further enhancement of output power was limited only by pump power.
基金the National Natural Science Foundation of China(Nos.61735007 and 61705266).
文摘Power scaling based on traditional ytterbium-doped fibers(YDFs)is limited by optical nonlinear effects and transverse mode instability(TMI)in high-power fiber lasers.Here,we propose a novel long tapered fiber with a constant cladding and tapered core(CCTC)along its axis direction.The tapered-core region of the fiber is designed to enhance the stimulated Raman scattering(SRS)threshold and suppress higher-order mode resonance in the laser cavity.The CCTC YDF was fabricated successfully with a modified chemical vapor deposition(MCVD)method combined with solution doping technology,which has a cladding diameter of 400µm and a varying core with a diameter of~24μm at both ends and~31μm in the middle.To test the performance of the CCTC fiber during high-power operation,an all-fiber laser oscillator based on a CCTC YDF was investigated experimentally.As a result,a maximum output power of 3.42 kW was achieved with an optical-to-optical efficiency of 55.2%,although the TMI effect was observed at an output power of~3.12 kW.The measured beam quality(M^(2)factor)was~1.7,and no sign of the Raman component was observed in the spectrum.We believe that CCTC YDF has great potential to simultaneously mitigate the SRS and TMI effects,and further power scaling is promising by optimizing the structure of the YDF.
基金supported by the National Key R&D Program of China(No.2020YFC2200401)the National Natural Science Foundation of China(Nos.62005316 and 62035015)。
文摘Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimulated Brillouin scattering effect.Nevertheless,over the past two decades much effort has been devoted to improving the power scaling and performance of high-power single-frequency fiber amplifiers.These amplifiers are mostly driven by applications,such as high precision detection and metrology,and have benefited from the long coherence length,low noise,and excellent beam quality of this type of laser source.In this paper,we review the overall development of high-power single-frequency fiber amplifiers by focusing on its progress and challenges,specifically,the strategies for circumventing the stimulated Brillouin scattering and transverse mode instability effects that,at present,are the major limiting factors of the power scaling of the single-frequency fiber amplifiers.These factors are also thoroughly discussed in terms of free-space and all-fiber coupled architecture.In addition,we also examine the noise properties of single-frequency fiber amplifiers,along with corresponding noise reducing schemes.Finally,we briefly envision the future development of high-power single-frequency fiber amplifiers.
