A high-resolution two-photon spectrum of 5S1/2 → 5P3/2 → 5D5/2 transitions in a thermal SSRb vapor cell is presented by using an optical frequency comb and a cw laser. The fluorescence of 6P3/2 → 5S1/2 spontaneous ...A high-resolution two-photon spectrum of 5S1/2 → 5P3/2 → 5D5/2 transitions in a thermal SSRb vapor cell is presented by using an optical frequency comb and a cw laser. The fluorescence of 6P3/2 → 5S1/2 spontaneous emission is detected when the cw laser frequency is scanned from the 5S1/2 ground state to 5P3/2 hyperfine levels and the optical frequency comb repetition rate is fixed. The hyperfine splittings （Ff = 2-5） of the 5D5/2 excited state are well resolved. The dependences of fluorescence intensities on the cw laser intensity and temperature of SSRb vapor eel1 are studied, respectively. The experimental results are in good agreement with the theoretical analyses.展开更多
The synchronously periodic re-melting of molten pool was firstly introduced in additive manufacturing to promote the epitaxial growth of columnar structure using a novel quasi-continuous-wave(QCW)laser.The epitaxial g...The synchronously periodic re-melting of molten pool was firstly introduced in additive manufacturing to promote the epitaxial growth of columnar structure using a novel quasi-continuous-wave(QCW)laser.The epitaxial growth of columnar structure was intensified and the single-crystal-like sample with highly oriented "zigzag" columnar grains was produced.The modified molten-pool geometry and the synchronously high-frequency re-melting of the molten pool contribute to the formation of singlecrystal-like structure.This work reports a new route to promote the continuously epitaxial growth of dendrites for fabrication of single-crystal-like sample.展开更多
Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of su...Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material.However,the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost.In this work,we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam.By changing the spatial offset,combined beams with different lengths along the major axis can be created.We observe over 20%improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power.Additionally,both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.展开更多
We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor.A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor,whi...We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor.A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor,which drives the atoms from the 5S1/2 state to the 5D5/2 state with monochromatic two-photon transition.The frequency up-conversion laser is generated by the parametric four-wave mixing process under the phase matching condition.This coherent laser is firstly certified by the knife-edge method and a narrow range grating spectrometer.Then the generated laser power is investigated in terms of the power and frequency of the incoming beam as well as the density of the atoms.Finally,a 420 nm coherent laser with power of 19μW and beam quality of Mx^2=1.32,My^2=1.37 is obtained with optimal experimental parameters.This novel laser shows potential prospects in the measurement of material properties,information storage,and underwater optical communication.展开更多
This paper describes what is thought to be the first generation of a continuous wave deep ultraviolet laser at 275 nm by efficient frequency doubling of a blue-diode-pumped Pr:YLF laser at 550 nm.By employing a novel ...This paper describes what is thought to be the first generation of a continuous wave deep ultraviolet laser at 275 nm by efficient frequency doubling of a blue-diode-pumped Pr:YLF laser at 550 nm.By employing a novel fast-axis collimated blue semiconductor laser as the pump source,combined with a folded cavity and innovation coating technology,and utilizing a Brewster-cut BBO crystal for intracavity frequency doubling,TEM00 mode deep UV laser radiation at 275 nm with an output power of 351 mW is obtained.This marks the first report of achieving 275 nm laser generation based on Pr:LiYF4 to date.展开更多
Er:CaF_(2) crystals are crucial gain media for producing 3μm mid-infrared (MIR) lasers pumped by 976 nm continuouswave (CW) lasers owing to their low phonon energy and high conversion efficiency.This study investigat...Er:CaF_(2) crystals are crucial gain media for producing 3μm mid-infrared (MIR) lasers pumped by 976 nm continuouswave (CW) lasers owing to their low phonon energy and high conversion efficiency.This study investigated the damage characteristics and mechanism of Er:CaF_(2) crystals irradiated with a 976 nm CW laser.The laser-induced damage threshold of Er:CaF_(2) crystals with different Er^(3+) doping levels was tested;the damage morphology consists of a series of regular 70? cracks related to the angle of the crystal slip system on the surface.A finite-element model was used to calculate the temperature and stress fields of the crystals.The results indicated that the damage can be attributed to surface tensile stresses caused by the temperature gradient,and crystals with higher doping concentrations were more susceptible to damage owing to stronger light absorption.These findings provide valuable insights into the development of high-power MIR lasers.展开更多
Frequency-modulated continuous-wave radar enables the non-contact and privacy-preserving recognition of human behavior.However,the accuracy of behavior recognition is directly influenced by the spatial relationship be...Frequency-modulated continuous-wave radar enables the non-contact and privacy-preserving recognition of human behavior.However,the accuracy of behavior recognition is directly influenced by the spatial relationship between human posture and the radar.To address the issue of low accuracy in behavior recognition when the human body is not directly facing the radar,a method combining local outlier factor with Doppler information is proposed for the correction of multi-classifier recognition results.Initially,the information such as distance,velocity,and micro-Doppler spectrogram of the target is obtained using the fast Fourier transform and histogram of oriented gradients-support vector machine methods,followed by preliminary recognition.Subsequently,Platt scaling is employed to transform recognition results into confidence scores,and finally,the Doppler-local outlier factor method is utilized to calibrate the confidence scores,with the highest confidence classifier result considered as the recognition outcome.Experimental results demonstrate that this approach achieves an average recognition accuracy of 96.23%for comprehensive human behavior recognition in various orientations.展开更多
The intermodal nonlinear coefficient is an important parameter to analytically describe few-mode fiber(FMF) nonlinearity when the nonlinear interaction arising in the FMF is exploited for various applications. Here, w...The intermodal nonlinear coefficient is an important parameter to analytically describe few-mode fiber(FMF) nonlinearity when the nonlinear interaction arising in the FMF is exploited for various applications. Here, we experimentally characterize the intermodal nonlinear coefficient based on continuous-wave cross-phase modulation, without a priori knowledge of the intramodal nonlinear coefficient for the FMF under test. Based on the derived equation, we examine the impact of the pump modulation scheme and the wavelength spacing between the probe and pump on the precise measurement of the intermodal nonlinear coefficient. Compared with double sideband(DSB) modulation, the pump modulated with carrier-suppressed DSB scheme leads to an underestimation of measurement results, due to the coexistence of unnecessary nonlinear interactions. Finally, the intermodal nonlinear coefficient of a 1.9-km FMF supporting two mode groups is experimentally characterized and is in good agreement with the theoretically calculated values. Due to the random birefringence fluctuation, the average value of 4/3 to describe the intermodal nonlinear interaction arising in weakly coupled FMF by the commonly used Manakov equation is experimentally verified.展开更多
We reported on an efficient high-power continuous-wave laser operation on the^(3)H_(4)→^(3)H_(5) transition of Tm^(3+)ions in a diffusion-bonded composite YVO_(4)/Tm:GdVO_(4)crystal.Pumped by a laser diode at 794 nm,...We reported on an efficient high-power continuous-wave laser operation on the^(3)H_(4)→^(3)H_(5) transition of Tm^(3+)ions in a diffusion-bonded composite YVO_(4)/Tm:GdVO_(4)crystal.Pumped by a laser diode at 794 nm,a maximum output power of 7.5 W was obtained from a YVO_(4)/Tm:GdVO_(4)laser at 2.29μm,corresponding to a slope efficiency of 40.3%and exceeding the Stokes limit.To the best of our knowledge,this result represents the maximum power ever achieved from a Tm laser at 2.3μm.展开更多
Continuous-wave(CW)operated laser is a key component for photonic chips.It has been highly desired to develop low-threshold,high-efficiency,long-term operational,low-cost and easily integratable CW laser.As excellent ...Continuous-wave(CW)operated laser is a key component for photonic chips.It has been highly desired to develop low-threshold,high-efficiency,long-term operational,low-cost and easily integratable CW laser.As excellent optical gain materials,quantum dots(QDs)have been intensively investigated for on-chip CW lasers owing to their high photoluminescence quantum yields,tunable emission wavelengths and easy integration.Base on the difference of preparation processes,QDs can be classified into epitaxial QDs and solution-processed colloidal QDs(CQDs).In this mini-review,we summarize the research progresses of epitaxial III–V semiconductor QD and solution-processed CQD-based CW lasers.The challenges associated with the realization of CQD CW lasers are discussed in detail.In particular,the emerging perovskite-based CW lasers are highlighted.Finally,a short perspective of QD-based CW lasers is presented.展开更多
The fluorescence spectrum and thermal properties of the mixed crystal Nd：Luo.gvLa~.o1VO4 are determined. The strongest emission peak located at 1065.6 nm had a full width at half maximum （FWHM） of 2.1 nm. Continuou...The fluorescence spectrum and thermal properties of the mixed crystal Nd：Luo.gvLa~.o1VO4 are determined. The strongest emission peak located at 1065.6 nm had a full width at half maximum （FWHM） of 2.1 nm. Continuous-wave （CW） laser performance is demonstrated by a compact planar planar cavity that is end- pumped by a diode laser. The laser output characteristics are investigated by using output couplers with different transmissions. A maximum CW output power of 8.09 W was obtained at an incident pump power of 19.4 W, which corresponds to an optical-to-optical conversion efficiency of 41.7% and a slope efficiency of 54.6%. The dependence of optimum transmission on pump power is calculated theoretically and is found to be consistent with experimental results.展开更多
A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequenc...A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.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
Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials g...Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition(MOCVD).High interface quality structures designed for light emission at 8.5μm are achieved by optimizing and precise controlling of growth conditions.A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10μm-wide coated laser.Corresponding maximum wall-plug efficiency and threshold current density were 7.1%and 1.18 kA/cm2,respectively.The device can operate in CW mode up to 408 K with an output power of 160 mW.展开更多
We demonstrate an all-solid quasi-continuous-wave （QCW） narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal...We demonstrate an all-solid quasi-continuous-wave （QCW） narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd：YAG master oscillator power amplifier （MOPA） laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M^2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.展开更多
Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes.Microstructure,surface quality and mechanical properties were compared to evaluate the printing quality ...Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes.Microstructure,surface quality and mechanical properties were compared to evaluate the printing quality between these 2 laser beam modes.The results show that the application of pulsed wave could effectively eliminate cracking in the as-fabricated sample,despite 0.046%porosity generated.Further microstructure analysis revealed that the refinement of grains by the pulsed-wave laser beam was the main contributor in eliminating the cracks.And this refinement was ascribed to the higher cooling rate under the discontinuous radiation of laser beam proofed by the numerical simulation.And the pore formation was related to Rayleigh instability and residual bubbles in the sample under the pulsed-wave mode,while pores were less detrimental to the mechanical properties than cracks.Therefore,the part under the pulsed-wave mode exhibited superior mechanical performance compared to that under the continuous-wave mode.展开更多
We demonstrate a cw and actively Q-switched Er：LuAO laser resonantly dual-end-pumped by 1532nm fibre- coupled laser diodes. A maximum cw output power of 1.9W at 1650.3nm is obtained at a pump power of 25.5 W, corresp...We demonstrate a cw and actively Q-switched Er：LuAO laser resonantly dual-end-pumped by 1532nm fibre- coupled laser diodes. A maximum cw output power of 1.9W at 1650.3nm is obtained at a pump power of 25.5 W, corresponding to a slope efficiency of 43.3 %. In the Q-switched regime, the maximum pulse energy of 3.51 mJ is reached at a pulse repetition rate of 100 Hz, a pulse duration of 90.5ns and a pump power of 25.5 W. At the repetition rate of 400 Hz, the output energy is 2.12m J, corresponding to a pulse duration of 125.4 ns.展开更多
We demonstrate a kW continuous-wave ytterbium-doped all-fiber laser oscillator with M1 domestic fiber compo- nents： a 7× I fused fiber bundle combiner, a fiber Bragg grating and a double-clad gain fiber. The osc...We demonstrate a kW continuous-wave ytterbium-doped all-fiber laser oscillator with M1 domestic fiber compo- nents： a 7× I fused fiber bundle combiner, a fiber Bragg grating and a double-clad gain fiber. The oscillator operates at 1079.48nrn with 80.94% slope efficiency and shows no limit of temperature and nonlinear effects. These indicate that the passive fiber components and the gain fiber are all qualified for the high power environ- ment. No evidence of the signal power roll-over shows that this oscillator possesses the capacity to higher output with available pump power.展开更多
The diode-pumped Nd:YxGd1-xVO4 crystal continuous wave (CW) laser operating at 1.06 μm with a simple plane-concave cavity and a V-shaped folded cavity for intracavity frequency-doubling have been studied. With the in...The diode-pumped Nd:YxGd1-xVO4 crystal continuous wave (CW) laser operating at 1.06 μm with a simple plane-concave cavity and a V-shaped folded cavity for intracavity frequency-doubling have been studied. With the incident pump power of 8 W, an output power (1.06 μm) of 3.4 W was achieved, giving an optical conversion efficiency of 42.5%. 884 mW of stable green radiation was generated with the incident pump power of 5.9 W, giving an optical conversion efficiency of 15%.展开更多
We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the ...We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).展开更多
基金Supported by the National Basic Research Program of China under Grant No 2012CB921603the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China under Grant No IRT13076the National Natural Science Foundation of China under Grant Nos 61378049,10934004,61575116 and 61505100
文摘A high-resolution two-photon spectrum of 5S1/2 → 5P3/2 → 5D5/2 transitions in a thermal SSRb vapor cell is presented by using an optical frequency comb and a cw laser. The fluorescence of 6P3/2 → 5S1/2 spontaneous emission is detected when the cw laser frequency is scanned from the 5S1/2 ground state to 5P3/2 hyperfine levels and the optical frequency comb repetition rate is fixed. The hyperfine splittings （Ff = 2-5） of the 5D5/2 excited state are well resolved. The dependences of fluorescence intensities on the cw laser intensity and temperature of SSRb vapor eel1 are studied, respectively. The experimental results are in good agreement with the theoretical analyses.
基金supported financially by the National Natural Science Foundation of China(No.51875190)the Natural Science Foundation of Hunan Province(No.2020JJ5075)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110274)the China Postdoctoral Science Foundation(No.2018M642973)the Science and Technology Planning Project of Hunan Province(No.2016JC2006)State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body at Hunan University(No.31875004)。
文摘The synchronously periodic re-melting of molten pool was firstly introduced in additive manufacturing to promote the epitaxial growth of columnar structure using a novel quasi-continuous-wave(QCW)laser.The epitaxial growth of columnar structure was intensified and the single-crystal-like sample with highly oriented "zigzag" columnar grains was produced.The modified molten-pool geometry and the synchronously high-frequency re-melting of the molten pool contribute to the formation of singlecrystal-like structure.This work reports a new route to promote the continuously epitaxial growth of dendrites for fabrication of single-crystal-like sample.
基金This study was supported by Princeton University Eric and Wendy Schmidt Transformative Technology Fund.This simulation was funded by Comunidad de Madrid Project ADITIMAT-CM(S2018/NMT-4411)Universidad Politecnicade Madrid Research Grant(EST-PDI-19-A1JMBI-26-T4MNY9).The authors also want to thank Luc Deike for valuable discussions.The authors acknowledge the use of Princeton's Imaging and Analysis Center,which is partially supported by the Princeton Center for Complex Materials,a National Science Foundation(NSF)MRSEC program(DMR-1420541),for the SEM image acquisition.
文摘Laser polishing is widely employed to reduce the surface roughness of products with complex geometries.Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material.However,the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost.In this work,we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam.By changing the spatial offset,combined beams with different lengths along the major axis can be created.We observe over 20%improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power.Additionally,both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.
基金Project supported by the National R&D Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61875112,61705122,91736209,and 61728502)+2 种基金the Program for Sanjin Scholars of Shanxi Province,China,the Applied Basic Research Project of Shanxi Province,China(Grant No.201701D221004)the Key Research and Development Program of Shanxi Province for International Cooperation,China(Grant No.201803D421034)1331KSC。
文摘We demonstrate the generation of the coherent 420 nm laser via parametric four-wave mixing process in Rb vapor.A single 778 nm laser with circular polarization is directly injected into a high-density atomic vapor,which drives the atoms from the 5S1/2 state to the 5D5/2 state with monochromatic two-photon transition.The frequency up-conversion laser is generated by the parametric four-wave mixing process under the phase matching condition.This coherent laser is firstly certified by the knife-edge method and a narrow range grating spectrometer.Then the generated laser power is investigated in terms of the power and frequency of the incoming beam as well as the density of the atoms.Finally,a 420 nm coherent laser with power of 19μW and beam quality of Mx^2=1.32,My^2=1.37 is obtained with optimal experimental parameters.This novel laser shows potential prospects in the measurement of material properties,information storage,and underwater optical communication.
文摘This paper describes what is thought to be the first generation of a continuous wave deep ultraviolet laser at 275 nm by efficient frequency doubling of a blue-diode-pumped Pr:YLF laser at 550 nm.By employing a novel fast-axis collimated blue semiconductor laser as the pump source,combined with a folded cavity and innovation coating technology,and utilizing a Brewster-cut BBO crystal for intracavity frequency doubling,TEM00 mode deep UV laser radiation at 275 nm with an output power of 351 mW is obtained.This marks the first report of achieving 275 nm laser generation based on Pr:LiYF4 to date.
基金supported by the Key Foreign Cooperation Projects of the Bureau of International Cooperation of the Chinese Academy of Sciences (No. 181231KYSB20210001)the National Key Laboratory of Infrared Detection Technologies (No. IRDT-23-11)+2 种基金the National Natural Science Foundation of China (Nos. 51972229,61925508 and 62205359)the Key Research and Development Program of the Ministry of Science and Technology (No. GG20210301)the National Defense Science and Technology 173 Program (No. 2021-JCJQ-JJ-0639)。
文摘Er:CaF_(2) crystals are crucial gain media for producing 3μm mid-infrared (MIR) lasers pumped by 976 nm continuouswave (CW) lasers owing to their low phonon energy and high conversion efficiency.This study investigated the damage characteristics and mechanism of Er:CaF_(2) crystals irradiated with a 976 nm CW laser.The laser-induced damage threshold of Er:CaF_(2) crystals with different Er^(3+) doping levels was tested;the damage morphology consists of a series of regular 70? cracks related to the angle of the crystal slip system on the surface.A finite-element model was used to calculate the temperature and stress fields of the crystals.The results indicated that the damage can be attributed to surface tensile stresses caused by the temperature gradient,and crystals with higher doping concentrations were more susceptible to damage owing to stronger light absorption.These findings provide valuable insights into the development of high-power MIR lasers.
基金the National Key Research and Development Program of China(No.2022YFC3601400)。
文摘Frequency-modulated continuous-wave radar enables the non-contact and privacy-preserving recognition of human behavior.However,the accuracy of behavior recognition is directly influenced by the spatial relationship between human posture and the radar.To address the issue of low accuracy in behavior recognition when the human body is not directly facing the radar,a method combining local outlier factor with Doppler information is proposed for the correction of multi-classifier recognition results.Initially,the information such as distance,velocity,and micro-Doppler spectrogram of the target is obtained using the fast Fourier transform and histogram of oriented gradients-support vector machine methods,followed by preliminary recognition.Subsequently,Platt scaling is employed to transform recognition results into confidence scores,and finally,the Doppler-local outlier factor method is utilized to calibrate the confidence scores,with the highest confidence classifier result considered as the recognition outcome.Experimental results demonstrate that this approach achieves an average recognition accuracy of 96.23%for comprehensive human behavior recognition in various orientations.
基金supported by the National Natural Science Foundation of China (No.U22A2087)the Guangdong Introducing Innovative and Entrepreneurial Teams of the Pearl River Talent Recruitment Program (No.2021ZT09X044)。
文摘The intermodal nonlinear coefficient is an important parameter to analytically describe few-mode fiber(FMF) nonlinearity when the nonlinear interaction arising in the FMF is exploited for various applications. Here, we experimentally characterize the intermodal nonlinear coefficient based on continuous-wave cross-phase modulation, without a priori knowledge of the intramodal nonlinear coefficient for the FMF under test. Based on the derived equation, we examine the impact of the pump modulation scheme and the wavelength spacing between the probe and pump on the precise measurement of the intermodal nonlinear coefficient. Compared with double sideband(DSB) modulation, the pump modulated with carrier-suppressed DSB scheme leads to an underestimation of measurement results, due to the coexistence of unnecessary nonlinear interactions. Finally, the intermodal nonlinear coefficient of a 1.9-km FMF supporting two mode groups is experimentally characterized and is in good agreement with the theoretically calculated values. Due to the random birefringence fluctuation, the average value of 4/3 to describe the intermodal nonlinear interaction arising in weakly coupled FMF by the commonly used Manakov equation is experimentally verified.
基金supported by the National Natural Science Foundation of China(Nos.52072351,12274263,12174223 and 12304466)the Qilu Young Scholar Program of Shandong Universitythe Taishan Scholar Foundation of Shandong Province。
文摘We reported on an efficient high-power continuous-wave laser operation on the^(3)H_(4)→^(3)H_(5) transition of Tm^(3+)ions in a diffusion-bonded composite YVO_(4)/Tm:GdVO_(4)crystal.Pumped by a laser diode at 794 nm,a maximum output power of 7.5 W was obtained from a YVO_(4)/Tm:GdVO_(4)laser at 2.29μm,corresponding to a slope efficiency of 40.3%and exceeding the Stokes limit.To the best of our knowledge,this result represents the maximum power ever achieved from a Tm laser at 2.3μm.
基金financially supported by the National Natural Science Foundation of China(61722502 and 61705009)BIT funds。
文摘Continuous-wave(CW)operated laser is a key component for photonic chips.It has been highly desired to develop low-threshold,high-efficiency,long-term operational,low-cost and easily integratable CW laser.As excellent optical gain materials,quantum dots(QDs)have been intensively investigated for on-chip CW lasers owing to their high photoluminescence quantum yields,tunable emission wavelengths and easy integration.Base on the difference of preparation processes,QDs can be classified into epitaxial QDs and solution-processed colloidal QDs(CQDs).In this mini-review,we summarize the research progresses of epitaxial III–V semiconductor QD and solution-processed CQD-based CW lasers.The challenges associated with the realization of CQD CW lasers are discussed in detail.In particular,the emerging perovskite-based CW lasers are highlighted.Finally,a short perspective of QD-based CW lasers is presented.
基金supported by the Natural Science Foundation of Shandong Province(No.ZR2010FM029)the Interdisciplinary Incubation Project Foundation of the Shandong University(No.2011JC025)
文摘The fluorescence spectrum and thermal properties of the mixed crystal Nd：Luo.gvLa~.o1VO4 are determined. The strongest emission peak located at 1065.6 nm had a full width at half maximum （FWHM） of 2.1 nm. Continuous-wave （CW） laser performance is demonstrated by a compact planar planar cavity that is end- pumped by a diode laser. The laser output characteristics are investigated by using output couplers with different transmissions. A maximum CW output power of 8.09 W was obtained at an incident pump power of 19.4 W, which corresponds to an optical-to-optical conversion efficiency of 41.7% and a slope efficiency of 54.6%. The dependence of optimum transmission on pump power is calculated theoretically and is found to be consistent with experimental results.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91436103 and 11204374
文摘A 194-nm cw laser is an essential part in the mercury ion optical frequency standard. We report the generation of over 2mW continuous-wave radiation at 194nm in a beta barium borate crystal using a simple sum frequency mixing （SFM） system. One source beams at 718nm is resonantly enhanced with a cavity and the other at 266mn makes a single pass. Considering the walk-off effect in SFM, the source beam waists are designed to be elliptical, thus the conversion efficiency can be promoted. The 266-nm beam produced by frequency doubling of 532-nm laser is shaped close to the diffraction limit to achieve better mode matching.
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The authors would thank Ping Liang and Ying Hu for their help with device fabrication.This work was supported by the National Key Research and Development Program of China(Grant No.2020YFB0408401)in part by the National Natural Science Foundation of China(Grant Nos.61991430,61774146,61790583,61734006,61835011,61674144,61774150,61805168)+1 种基金in part by Beijing Municipal Science&Technology Commission(Grant No.Z201100004020006)in part by the Key Projects of the Chinese Academy of Sciences(Grant Nos.2018147,YJKYYQ20190002,QYZDJ-SSW-JSC027,XDB43000000,ZDKYYQ20200006).
文摘Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition(MOCVD).High interface quality structures designed for light emission at 8.5μm are achieved by optimizing and precise controlling of growth conditions.A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10μm-wide coated laser.Corresponding maximum wall-plug efficiency and threshold current density were 7.1%and 1.18 kA/cm2,respectively.The device can operate in CW mode up to 408 K with an output power of 160 mW.
文摘We demonstrate an all-solid quasi-continuous-wave （QCW） narrow-band source tunable to sodium D2a line at 589.159 nm. The source is based on sum-frequency mixing between lasers at 1064 nm and 1319 nm in a LBO crystal. The 1064 nm and 1319 nm lasers are produced from two diode side-pumped Nd：YAG master oscillator power amplifier （MOPA） laser systems, respectively. A 33 W output of 589 nm laser is obtained with beam quality factor M^2 = 1.25, frequency stability better than ±0.2 GHz and linewidth less than 0.44 GHz. A prototype 589 nm laser system is assembled, and a sodium laser guided star has been successfully observed in the field test.
基金financially supported by National Natural Science Foundation of China(No.91860131 and No.52074157)National Key Research and Development Program of China(No.2017YFB0702901)+1 种基金Shenzhen Science and Technology Innovation Commission under the Projects(No.JCYJ20170817111811303,No.KQTD20170328154443162 and ZDSYS201703031748354)joint Ph.D.program between SUSTech and UoB(No.FEFE/GAS1792)。
文摘Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes.Microstructure,surface quality and mechanical properties were compared to evaluate the printing quality between these 2 laser beam modes.The results show that the application of pulsed wave could effectively eliminate cracking in the as-fabricated sample,despite 0.046%porosity generated.Further microstructure analysis revealed that the refinement of grains by the pulsed-wave laser beam was the main contributor in eliminating the cracks.And this refinement was ascribed to the higher cooling rate under the discontinuous radiation of laser beam proofed by the numerical simulation.And the pore formation was related to Rayleigh instability and residual bubbles in the sample under the pulsed-wave mode,while pores were less detrimental to the mechanical properties than cracks.Therefore,the part under the pulsed-wave mode exhibited superior mechanical performance compared to that under the continuous-wave mode.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61308009 and 61405047the China Postdoctoral Science Foundation Funded Project under Grant No 2013M540288+2 种基金the Fundamental Research Funds for the Central Universities under Grant Nos HIT.NSRIF.2014044 and HIT.NSRIF.2015042the Science Fund for Outstanding Youths of Heilongjiang Province under Grant No JQ201310the Heilongjiang Postdoctoral Science Foundation Funded Project under Grant No LBH-Z14085
文摘We demonstrate a cw and actively Q-switched Er：LuAO laser resonantly dual-end-pumped by 1532nm fibre- coupled laser diodes. A maximum cw output power of 1.9W at 1650.3nm is obtained at a pump power of 25.5 W, corresponding to a slope efficiency of 43.3 %. In the Q-switched regime, the maximum pulse energy of 3.51 mJ is reached at a pulse repetition rate of 100 Hz, a pulse duration of 90.5ns and a pump power of 25.5 W. At the repetition rate of 400 Hz, the output energy is 2.12m J, corresponding to a pulse duration of 125.4 ns.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2013AA031501the Fundamental Research Funds for the Central Universities under Grant No 2014TS017
文摘We demonstrate a kW continuous-wave ytterbium-doped all-fiber laser oscillator with M1 domestic fiber compo- nents： a 7× I fused fiber bundle combiner, a fiber Bragg grating and a double-clad gain fiber. The oscillator operates at 1079.48nrn with 80.94% slope efficiency and shows no limit of temperature and nonlinear effects. These indicate that the passive fiber components and the gain fiber are all qualified for the high power environ- ment. No evidence of the signal power roll-over shows that this oscillator possesses the capacity to higher output with available pump power.
基金This work was supported by the National Natural Science Foundation of China under Grant No.60078011.
文摘The diode-pumped Nd:YxGd1-xVO4 crystal continuous wave (CW) laser operating at 1.06 μm with a simple plane-concave cavity and a V-shaped folded cavity for intracavity frequency-doubling have been studied. With the incident pump power of 8 W, an output power (1.06 μm) of 3.4 W was achieved, giving an optical conversion efficiency of 42.5%. 884 mW of stable green radiation was generated with the incident pump power of 5.9 W, giving an optical conversion efficiency of 15%.
基金Project supported by the National Natural Science Foundation of China(Grant No.61974141)Tianjin Municipal Science and Technology BureauScience and Technology Innovation Bureau of China-Singapore Tianjin Eco-City。
文摘We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).
