We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We ...We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We show that the introduction of an air hollow into metal reflection plate beneath the scatterer does not induce an expected decrease but an abnormal increase of focal length of the TJ by as much as more than three times.This abnormal phenomenon takes place in case that the air hollow is shallow and there exists a critical hollow depth for a given lateral size of air hollow.Larger than the critical depth,the phenomenon no longer occurs.It is explained from viewpoints of both ray optics in terms of role of relative portion of central waves in TJ formation and electromagnetic field theory with regard to hollow-induced phase singularities.展开更多
We demonstrated a Kerr-lens mode-locked polycrystalline Cr：ZnS laser pumped by a narrow-linewidth linearpolarised monolithic Er：YAG nonplanar ring oscillator operated at 1645 nm. With a 5-mm-thick sapphire plate for...We demonstrated a Kerr-lens mode-locked polycrystalline Cr：ZnS laser pumped by a narrow-linewidth linearpolarised monolithic Er：YAG nonplanar ring oscillator operated at 1645 nm. With a 5-mm-thick sapphire plate for intracavity dispersion compensation, a compact and stable Kerr-lens mode-locking operation was realised. The oscillator delivered 125-fs pulses at 2347 nm with an average power of 80 m W. Owing to the special polycrystalline structure of the Cr：ZnS crystal, the second to fourth harmonic generation was observed by random quasi-phase-matching.展开更多
We present a new multi-scale geometrical analysis method for ophthalmic image contrast enhancement based on the contourlet transform. The contourlet transform has better performance in representing edges than wavelets...We present a new multi-scale geometrical analysis method for ophthalmic image contrast enhancement based on the contourlet transform. The contourlet transform has better performance in representing edges than wavelets due to its anisotropy and directionality,and is therefore well-suited for multiscale edge enhancement. We modify the contourlet coefficients in corresponding subband and take the noise into account for mere precise reconstruction and better visualization. We compare this approach with enhancement based on the ourvelet transform,and the traditional Histogram Stretching （HS）. Our findings are that contourlet based enhancement out-performs other enhancement methods on low contrast and dynamic range images,and can clearly identify the vessels and nerves in an ophthalmic image.展开更多
The Kirk test has good precision for measuring stray light in optical lithography and is the usual method of measuring stray light.However,Kirk did not provide a theoretical explanation to his simulation model.We atte...The Kirk test has good precision for measuring stray light in optical lithography and is the usual method of measuring stray light.However,Kirk did not provide a theoretical explanation to his simulation model.We attempt to give Kirk's model a kind of theoretical explanation and a little improvement based on the model of point spread function of scattering and the theory of statistical optics.It is indicated by simulation that the improved model fits Kirk's measurement data better.展开更多
An indium tin oxide(ITO) and silicon nitride(Si_(3)N_(4)) assisted compact TE-pass waveguide polarizer based on lithiumniobate-on-insulator is proposed and numerically analyzed.By properly designing the ITO and Si_(3)...An indium tin oxide(ITO) and silicon nitride(Si_(3)N_(4)) assisted compact TE-pass waveguide polarizer based on lithiumniobate-on-insulator is proposed and numerically analyzed.By properly designing the ITO and Si_(3)N_(4) assisted structure and utilizing the epsilon-near-zero effect of ITO,the TM mode is strongly confined in the ITO layer with extremely high loss,while the TE mode is hardly affected and passes through the waveguide with low loss.The simulation results show that the polarizer has an extinction ratio of 22.5 dB and an insertion loss of 0.8 dB at the wavelength of 1.55 μm,and has an operating bandwidth of about 125 nm(from 1540 nm to 1665 nm) for an extinction ratio of>20 dB and an insertion loss of<0.95 dB.Moreover,the proposed device exhibits large fabrication tolerances.More notably,the device is compact,with a length of only 7.5 μm,and is appropriate for on-chip applications.展开更多
A diode-pumped passively mode-locked Nd-doped La3Ga5SiO14 （Nd：LGS） laser is realized by using a semicon- ductor saturable absorber mirror. With the pump power of 2 W, we obtain a 532nm self-frequency doubling （SFD...A diode-pumped passively mode-locked Nd-doped La3Ga5SiO14 （Nd：LGS） laser is realized by using a semicon- ductor saturable absorber mirror. With the pump power of 2 W, we obtain a 532nm self-frequency doubling （SFD） laser together with a lO.9ps fundamental laser at the repetition rate of 173.7MHz. To the best of our knowledge, it is the first time for self-frequency doubling in the diode-pumped mode-locked Nd：LGS laser. Benefited from the diode lasers and its self-frequency doubling property, Nd：LGS could be a potential candidate for compact, stable and cheap ultrafast green laser sources.展开更多
In this work, a 90-nm critical dimension （CD） technological process in an ArF laser lithography system is simulated, and the swing curves of the CD linewidth changing with photoresist thickness are obtained in the a...In this work, a 90-nm critical dimension （CD） technological process in an ArF laser lithography system is simulated, and the swing curves of the CD linewidth changing with photoresist thickness are obtained in the absence and presence of bottom antireflection coating （BARC）. By analysing the simulation result, it can be found that in the absence of BARC the CD swing curve effect is much bigger than that in the presence of BARC. So, the BARC should be needed for the 90-nm CD manufacture. The optimum resist thickness for 90-nm CD in the presence of BARC is obtained, and the optimizing process in this work can be used for reference in practice.展开更多
A compact laser diode-pumped solid-state Nd：LuVO4 acousto-optic Q-switched laser is demonstrated at 916 nm of a quasi-three level for the first time. A pulse width of 130ns is observed when the pulse-repetition frequ...A compact laser diode-pumped solid-state Nd：LuVO4 acousto-optic Q-switched laser is demonstrated at 916 nm of a quasi-three level for the first time. A pulse width of 130ns is observed when the pulse-repetition frequency is 10 kHz. The laser experiment shows that the Nd：Lu VO4 crystal can be used for efficient diode-pumped Q-switched lasers.展开更多
We demonstrate a passively a Z-folded resonator. Using device, we achieve stable cw average output power under cw mode-locked Nd：LuVO4 laser operating on the quasi-three-level at 916nm with a semiconductor saturable ...We demonstrate a passively a Z-folded resonator. Using device, we achieve stable cw average output power under cw mode-locked Nd：LuVO4 laser operating on the quasi-three-level at 916nm with a semiconductor saturable absorber mirror （SESAM） as the passive mode-locking mode locking with 6.7ps pulse duration at repetition rate of 133 MHz and 88mW the pump power of 17.1 W.展开更多
We report an efficient diode-pumped Nd-doped Gadolinium gailium garnet （GGG） continuous-wave （CW） laser operating at 938nm. Laser action of 1.6at.% Nd-doped GGG crystais with different lengths and temperatures are...We report an efficient diode-pumped Nd-doped Gadolinium gailium garnet （GGG） continuous-wave （CW） laser operating at 938nm. Laser action of 1.6at.% Nd-doped GGG crystais with different lengths and temperatures are aiso investigated. The maximum output power of 620mW is obtained at the incident pump power of 5.0 W with a slope efficiency of 15%.展开更多
A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally.The symmetrical Au-cladding optical waveguid...A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally.The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films,which serve as the coupling layer and reflecting panel,respectively.The sensitivity of this sensor of 9.08 × 10^(-2) deg/℃,6.6 × 10^(-2) deg/℃ and 4.8 × 10^(-2) deg/℃ corresponding to 3238-order,3237-order and 3236-order modes,respectively,are obtained.Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.展开更多
The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg)...The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.展开更多
Luminescent solar concentrators(LSCs)offer a sustainable approach to power generation using fluorescent glasses,yet their green industrialization is impeded by the limited production scale and non-recyclability of emb...Luminescent solar concentrators(LSCs)offer a sustainable approach to power generation using fluorescent glasses,yet their green industrialization is impeded by the limited production scale and non-recyclability of embedded nanocrystals.Here,we introduce a lead-free perovskite derivative ETP_(2)SbCl_(5)(ETP=(C_(6)H_(5))_(3)PC_(2)H_(5))with a reversible transition between powder and glass states.Through molecular dynamics and density functional theory,we elucidate the possible structural distortions of[SbCl_(5)]pyramids and their impact on luminescence.The fabricated LSCs,utilizing such fluorescent glasses with an efficient absorption for<420 nm,achieve the highest power conversion and optical efficiencies of~5.56%and~32.5%,respectively.In addition to self-healing by reheating at~200℃,impressively,it could be mass recycled to phosphor by ethanol or heating treatments,which still maintains nearly initial fluorescent performance and could be repurposed like freshly synthesized samples.This work presents a paradigm for the sustainable use of fluorescent materials and offers a reliable path toward low-carbon globalization.展开更多
Fringe projection profilometry has been increasingly sought and applied in dynamic three dimensional(3D)shape measurement.In this work,a robust,high-efficiency 3D measurement based on Gray-coded light is proposed.Unli...Fringe projection profilometry has been increasingly sought and applied in dynamic three dimensional(3D)shape measurement.In this work,a robust,high-efficiency 3D measurement based on Gray-coded light is proposed.Unlike the traditional method,a tripartite phase unwrapping method is proposed to avoid the jump errors on the boundary of code words,which are mainly caused by the defocusing of the projector and the motion of the tested object.Subsequently,the time overlapping coding strategy is presented to greatly increase the coding ef-ficiency,decreasing the projected number in each group from seven(i.e.,3+4)to four(i.e.,3+1)for one restored 3D frame.The combination of two proposed techniques allows the reconstruction of a pixel-wise and unambiguous 3D geometry of dynamic scenes with strong noise using every four projected patterns.To the best of our knowledge,the presented techniques for the first time preserve the high anti-noise ability of a method based on the Gray code while overcoming the drawbacks of jump errors and low coding efficiency.Experiments have demonstrated that the proposed method can achieve robust,high efficiency 3D shape measurement of high speed dynamic scenes even polluted by strong noise.展开更多
A novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of ...A novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of bottom electrode, support part, and mirror plate, in which a T-shaped beam structure is used to support the mirror plate. It can provide mirror with vertical movement and rotation around two horizontal axes. The test results show that the maximum deflection along the vertical direction of the mirror plate is 2 μm, while the rotation angles around x and y axes are±2.3° and ±1.45°, respectively.展开更多
A new phase unwrapping method based on dual-frequency fringe is proposed to improve both high accuracy and large measurement range of three-dimensional shape measurement by synthesizing the projected dual-frequency fr...A new phase unwrapping method based on dual-frequency fringe is proposed to improve both high accuracy and large measurement range of three-dimensional shape measurement by synthesizing the projected dual-frequency fringes obtaining higher and lower frequencies.The lower-frequency one is their phase difference,which can help unwrap the wrapped phase of the higher-frequency one from their phase sum.In addition,the relationship between the measuring accuracy and the frequencies of the projected fringes is studied to guide the frequency selection in actual measurement.It is found that the closer the two frequencies are,the higher the measurement accuracy will be.The computer simulation and experiment results show the viability of this method.展开更多
A high-repetition-rate eye-safe optical parametric oscillator （OPO）, using a non-critically phase-matched KTP crystal intracavity pumped by a passively Q-switched Nd：GdVO4/Cr^4＋ ：YAG laser, is experimentally demo...A high-repetition-rate eye-safe optical parametric oscillator （OPO）, using a non-critically phase-matched KTP crystal intracavity pumped by a passively Q-switched Nd：GdVO4/Cr^4＋ ：YAG laser, is experimentally demonstrated. The conversion efficiency for the average power is 7% from pump diode input to OPO signal output and the slope efficiency is up to 10.3%. With an incident pump power of 7,3 W, the compact intracavity OPO （IOPO） cavity, operating at 15 kHz, produces an average power of 0.57 W at 1570 nm with a pulse width as short as 6 ns. The peak power at 1570 nm is higher than 6.3 kW.展开更多
In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Yb doped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved wh...In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Yb doped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulated Brillouin scattering （SBS）. When the pump power achieves the SBS threshold, the fiber laser changes from the start resonator to the SBS resonator. With different reflectivities of the second mirror, stable dual-wavelength pulses with the pulse width range from 10 ns to less than 2 ns are obtained. The result was explained theoretically by birefringency （including stochastic birefringency and bend birefringency）. OCIS codes： 140.3510, 290.5900, 320.4240, 260.1440.展开更多
The twisted Laguerre-Gaussian beam was generated by transforming of Hermite-Gaussian beams through an optical system consisting of three rotated cylindrical lenses. The intensity distribution and phase structure of th...The twisted Laguerre-Gaussian beam was generated by transforming of Hermite-Gaussian beams through an optical system consisting of three rotated cylindrical lenses. The intensity distribution and phase structure of the twisted hollow beam were theoretically analyzed by using Collins diffraction integral. By utilizing the method of mode decomposition, the theory of transformation was analyzed. In the experiment, micro particles were trapped and rotated by this twisted beam.展开更多
Influence of thermal-mechanical properties on the features of the panda polarization-maintaining optical fiber (PMF-) in fabrication process is studied in detail by finite element method (FEM). The stress birefringenc...Influence of thermal-mechanical properties on the features of the panda polarization-maintaining optical fiber (PMF-) in fabrication process is studied in detail by finite element method (FEM). The stress birefringence is 2.13443×10-4 obtained by the static analysis and 2.1269×10-4 by dynamic analysis. The difference in simulation by two methods is around 0.4%. The non-uniformity of stress birefringence in the fiber core is about 1.6%. Predicted results demonstrate that effect of the thermal conductive parameter on fiber thermal stress dominates. The high and uniform stress birefringence in the fiber core is obtained by appropriately selecting suitable stress region area and position.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61875148)the Key Awards Program of Cultivating Outstanding Innovative Postgraduates in Arts and Sciences of Tianjin University(Grant No.C1-2022002)+3 种基金the Talent Project of Anhui Science and Technology University(Grant No.DQYJ202304)the University-Level Research Project of Tianjin Sino-German University of Applied Sciences(Grant No.zdkt2018-007)China Association for Science and Technology Young Talent Support Project Doctoral Special Programthe National High-level University Scholarship Program for Graduate Students of China Scholarship Council(Grant No.202406250166)。
文摘We report an interesting and abnormal electromagnetic phenomenon with regard to a terajet(TJ)that is generated in a reflection mode,which is realized by placing a dielectric scatterer onto a metal reflection plate.We show that the introduction of an air hollow into metal reflection plate beneath the scatterer does not induce an expected decrease but an abnormal increase of focal length of the TJ by as much as more than three times.This abnormal phenomenon takes place in case that the air hollow is shallow and there exists a critical hollow depth for a given lateral size of air hollow.Larger than the critical depth,the phenomenon no longer occurs.It is explained from viewpoints of both ray optics in terms of role of relative portion of central waves in TJ formation and electromagnetic field theory with regard to hollow-induced phase singularities.
基金supported by the National Natural Science Foundation of China(Grant Nos.61205130,61465012,and 61564008)
文摘We demonstrated a Kerr-lens mode-locked polycrystalline Cr：ZnS laser pumped by a narrow-linewidth linearpolarised monolithic Er：YAG nonplanar ring oscillator operated at 1645 nm. With a 5-mm-thick sapphire plate for intracavity dispersion compensation, a compact and stable Kerr-lens mode-locking operation was realised. The oscillator delivered 125-fs pulses at 2347 nm with an average power of 80 m W. Owing to the special polycrystalline structure of the Cr：ZnS crystal, the second to fourth harmonic generation was observed by random quasi-phase-matching.
文摘We present a new multi-scale geometrical analysis method for ophthalmic image contrast enhancement based on the contourlet transform. The contourlet transform has better performance in representing edges than wavelets due to its anisotropy and directionality,and is therefore well-suited for multiscale edge enhancement. We modify the contourlet coefficients in corresponding subband and take the noise into account for mere precise reconstruction and better visualization. We compare this approach with enhancement based on the ourvelet transform,and the traditional Histogram Stretching （HS）. Our findings are that contourlet based enhancement out-performs other enhancement methods on low contrast and dynamic range images,and can clearly identify the vessels and nerves in an ophthalmic image.
基金by the National Basic Research Program of China under Grant No 2007AA01Z333the National Special Program of China under Grant No 2009ZX02204-008.
文摘The Kirk test has good precision for measuring stray light in optical lithography and is the usual method of measuring stray light.However,Kirk did not provide a theoretical explanation to his simulation model.We attempt to give Kirk's model a kind of theoretical explanation and a little improvement based on the model of point spread function of scattering and the theory of statistical optics.It is indicated by simulation that the improved model fits Kirk's measurement data better.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61875148)。
文摘An indium tin oxide(ITO) and silicon nitride(Si_(3)N_(4)) assisted compact TE-pass waveguide polarizer based on lithiumniobate-on-insulator is proposed and numerically analyzed.By properly designing the ITO and Si_(3)N_(4) assisted structure and utilizing the epsilon-near-zero effect of ITO,the TM mode is strongly confined in the ITO layer with extremely high loss,while the TE mode is hardly affected and passes through the waveguide with low loss.The simulation results show that the polarizer has an extinction ratio of 22.5 dB and an insertion loss of 0.8 dB at the wavelength of 1.55 μm,and has an operating bandwidth of about 125 nm(from 1540 nm to 1665 nm) for an extinction ratio of>20 dB and an insertion loss of<0.95 dB.Moreover,the proposed device exhibits large fabrication tolerances.More notably,the device is compact,with a length of only 7.5 μm,and is appropriate for on-chip applications.
基金Supported by the National Major Equipment Development Project of the Ministry of Science and Technology of Chinathe National Natural Science Foundation of China under Grant Nos 2012YQ120047 and 11174361
文摘A diode-pumped passively mode-locked Nd-doped La3Ga5SiO14 （Nd：LGS） laser is realized by using a semicon- ductor saturable absorber mirror. With the pump power of 2 W, we obtain a 532nm self-frequency doubling （SFD） laser together with a lO.9ps fundamental laser at the repetition rate of 173.7MHz. To the best of our knowledge, it is the first time for self-frequency doubling in the diode-pumped mode-locked Nd：LGS laser. Benefited from the diode lasers and its self-frequency doubling property, Nd：LGS could be a potential candidate for compact, stable and cheap ultrafast green laser sources.
基金Project supported by the National Special Program of China (Grant No. 2009ZX02204-008)the National Basic Research Program of China (Grant No. 2007AA01Z333)
文摘In this work, a 90-nm critical dimension （CD） technological process in an ArF laser lithography system is simulated, and the swing curves of the CD linewidth changing with photoresist thickness are obtained in the absence and presence of bottom antireflection coating （BARC）. By analysing the simulation result, it can be found that in the absence of BARC the CD swing curve effect is much bigger than that in the presence of BARC. So, the BARC should be needed for the 90-nm CD manufacture. The optimum resist thickness for 90-nm CD in the presence of BARC is obtained, and the optimizing process in this work can be used for reference in practice.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60490280, 60225005 and 60478046.
文摘A compact laser diode-pumped solid-state Nd：LuVO4 acousto-optic Q-switched laser is demonstrated at 916 nm of a quasi-three level for the first time. A pulse width of 130ns is observed when the pulse-repetition frequency is 10 kHz. The laser experiment shows that the Nd：Lu VO4 crystal can be used for efficient diode-pumped Q-switched lasers.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60490280, 60621063, 50572054 and 50590401, and the National Basic Research Programme of China under Grant Nos 2007CB815104 and 2004CB619002.
文摘We demonstrate a passively a Z-folded resonator. Using device, we achieve stable cw average output power under cw mode-locked Nd：LuVO4 laser operating on the quasi-three-level at 916nm with a semiconductor saturable absorber mirror （SESAM） as the passive mode-locking mode locking with 6.7ps pulse duration at repetition rate of 133 MHz and 88mW the pump power of 17.1 W.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60490280, 60225005 and 60478046.
文摘We report an efficient diode-pumped Nd-doped Gadolinium gailium garnet （GGG） continuous-wave （CW） laser operating at 938nm. Laser action of 1.6at.% Nd-doped GGG crystais with different lengths and temperatures are aiso investigated. The maximum output power of 620mW is obtained at the incident pump power of 5.0 W with a slope efficiency of 15%.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10876022,60890200 and 10976017.
文摘A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally.The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films,which serve as the coupling layer and reflecting panel,respectively.The sensitivity of this sensor of 9.08 × 10^(-2) deg/℃,6.6 × 10^(-2) deg/℃ and 4.8 × 10^(-2) deg/℃ corresponding to 3238-order,3237-order and 3236-order modes,respectively,are obtained.Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.
文摘The thermal stability of oil gels formed by styrene-butadiene-styrene triblock copolymer (SBS) was improved by adding a small amount of poly(phenylene ether) (PPE), which has a higher glass transition temperature (Tg). In naphthenic oil which is a good solvent for the butadiene blocks, but a non-solvent for the styrene blocks and PPE, PPE was selectively included into styrene blocks in SBS, and induced the increase of the Tg of these blocks. The melting temperature determined by viscoelastic measurements and softening temperature of the gels were elevated by adding PPE, while no significant change was detected by adding polystyrene. The gel became opaque by adding PPE, and partially separated phases were observed by field emission scanning electron microscopy (FE-SEM). The dependence of the viscoelastic behavior on the PPE concentration can be explained by the structural change observed by FE-SEM.
基金financially supported by the National Natural Science Foundation of China(22275101).
文摘Luminescent solar concentrators(LSCs)offer a sustainable approach to power generation using fluorescent glasses,yet their green industrialization is impeded by the limited production scale and non-recyclability of embedded nanocrystals.Here,we introduce a lead-free perovskite derivative ETP_(2)SbCl_(5)(ETP=(C_(6)H_(5))_(3)PC_(2)H_(5))with a reversible transition between powder and glass states.Through molecular dynamics and density functional theory,we elucidate the possible structural distortions of[SbCl_(5)]pyramids and their impact on luminescence.The fabricated LSCs,utilizing such fluorescent glasses with an efficient absorption for<420 nm,achieve the highest power conversion and optical efficiencies of~5.56%and~32.5%,respectively.In addition to self-healing by reheating at~200℃,impressively,it could be mass recycled to phosphor by ethanol or heating treatments,which still maintains nearly initial fluorescent performance and could be repurposed like freshly synthesized samples.This work presents a paradigm for the sustainable use of fluorescent materials and offers a reliable path toward low-carbon globalization.
基金National Natural Science Foundation of China(61675141).
文摘Fringe projection profilometry has been increasingly sought and applied in dynamic three dimensional(3D)shape measurement.In this work,a robust,high-efficiency 3D measurement based on Gray-coded light is proposed.Unlike the traditional method,a tripartite phase unwrapping method is proposed to avoid the jump errors on the boundary of code words,which are mainly caused by the defocusing of the projector and the motion of the tested object.Subsequently,the time overlapping coding strategy is presented to greatly increase the coding ef-ficiency,decreasing the projected number in each group from seven(i.e.,3+4)to four(i.e.,3+1)for one restored 3D frame.The combination of two proposed techniques allows the reconstruction of a pixel-wise and unambiguous 3D geometry of dynamic scenes with strong noise using every four projected patterns.To the best of our knowledge,the presented techniques for the first time preserve the high anti-noise ability of a method based on the Gray code while overcoming the drawbacks of jump errors and low coding efficiency.Experiments have demonstrated that the proposed method can achieve robust,high efficiency 3D shape measurement of high speed dynamic scenes even polluted by strong noise.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 10476010.
文摘A novel hybrid surface micromachined segmented mirror array is described. This device is capable of scaling to large apertures for correcting time-varying aberrations in laser applications. Each mirror is composed of bottom electrode, support part, and mirror plate, in which a T-shaped beam structure is used to support the mirror plate. It can provide mirror with vertical movement and rotation around two horizontal axes. The test results show that the maximum deflection along the vertical direction of the mirror plate is 2 μm, while the rotation angles around x and y axes are±2.3° and ±1.45°, respectively.
基金supported by the National Natural Science Foundation of China(No.62075143)。
文摘A new phase unwrapping method based on dual-frequency fringe is proposed to improve both high accuracy and large measurement range of three-dimensional shape measurement by synthesizing the projected dual-frequency fringes obtaining higher and lower frequencies.The lower-frequency one is their phase difference,which can help unwrap the wrapped phase of the higher-frequency one from their phase sum.In addition,the relationship between the measuring accuracy and the frequencies of the projected fringes is studied to guide the frequency selection in actual measurement.It is found that the closer the two frequencies are,the higher the measurement accuracy will be.The computer simulation and experiment results show the viability of this method.
文摘A high-repetition-rate eye-safe optical parametric oscillator （OPO）, using a non-critically phase-matched KTP crystal intracavity pumped by a passively Q-switched Nd：GdVO4/Cr^4＋ ：YAG laser, is experimentally demonstrated. The conversion efficiency for the average power is 7% from pump diode input to OPO signal output and the slope efficiency is up to 10.3%. With an incident pump power of 7,3 W, the compact intracavity OPO （IOPO） cavity, operating at 15 kHz, produces an average power of 0.57 W at 1570 nm with a pulse width as short as 6 ns. The peak power at 1570 nm is higher than 6.3 kW.
基金This work was supported by the National Major Project Foundation of China under Grant No. 60137010.
文摘In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Yb doped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulated Brillouin scattering （SBS）. When the pump power achieves the SBS threshold, the fiber laser changes from the start resonator to the SBS resonator. With different reflectivities of the second mirror, stable dual-wavelength pulses with the pulse width range from 10 ns to less than 2 ns are obtained. The result was explained theoretically by birefringency （including stochastic birefringency and bend birefringency）. OCIS codes： 140.3510, 290.5900, 320.4240, 260.1440.
基金This work was partly supported by the National Natural Science Foundation of China (No. 69908001)the Characterization of Optical Company and Laser BeamsⅡof Germany and the internatioual cooperation agreed by DFG and NSFC.
文摘The twisted Laguerre-Gaussian beam was generated by transforming of Hermite-Gaussian beams through an optical system consisting of three rotated cylindrical lenses. The intensity distribution and phase structure of the twisted hollow beam were theoretically analyzed by using Collins diffraction integral. By utilizing the method of mode decomposition, the theory of transformation was analyzed. In the experiment, micro particles were trapped and rotated by this twisted beam.
文摘Influence of thermal-mechanical properties on the features of the panda polarization-maintaining optical fiber (PMF-) in fabrication process is studied in detail by finite element method (FEM). The stress birefringence is 2.13443×10-4 obtained by the static analysis and 2.1269×10-4 by dynamic analysis. The difference in simulation by two methods is around 0.4%. The non-uniformity of stress birefringence in the fiber core is about 1.6%. Predicted results demonstrate that effect of the thermal conductive parameter on fiber thermal stress dominates. The high and uniform stress birefringence in the fiber core is obtained by appropriately selecting suitable stress region area and position.
