Phosphor-in-glass(PiG)films have emerged as the preferred conversion materials for high-brightness laser-driven lighting due to their excellent thermal conductivity and superior optical performance.Screen printing tec...Phosphor-in-glass(PiG)films have emerged as the preferred conversion materials for high-brightness laser-driven lighting due to their excellent thermal conductivity and superior optical performance.Screen printing technology was employed to investigate the correlation between the reflective layer thickness and light conversion efficiency.A multilayer-structured Y_(3)Al_(3.5)Ga_(1.5)O_(12):Ce^(3+)(YAGG:Ce)-PiGTiO_(2)-aluminium nitride(AIN)film(YG-TAF)converter was constructed by efficiently coupling the optimal thickness of the reflective layer with the PiG layer and the AIN substrate.Notably,the YG-TAF shows an impressive thermal conductivity of 22.6 W/(m·K)and a maximum anti-laser power of 15.84 W,demonstrating superb thermal regulation capability.This anti-laser power of 15.84 W represents a breakthrough in current static laser performance research.Impressively,an YG-TAF phosphor color wheel was designed,which achieves an ultra-high-brightness 4375 lm of green light under 450 nm,88 W laser power excitation,close to that of commercial phosphor silicone color wheels.This advancement not only demonstrates the excellent performance of YG-TAF in high-brightness dynamic reflective laser applications but also indicates its strong feasibility for practical implementation.Furthermore,the developed YAGG:Ce-Y_(1.31)Ce_(0.09)Gd_(1.6)Al_5O_(12)-TAF spliced phosphor color wheel successfully mitigates the influence of photon reabsorption and achieves a color rendering index of 80.5,showing great potential for advancement of the field of reflective white light laser illumination.展开更多
Antimony tin oxide （ATO） nano-particles doped with different Sb contents were prepared by co-precipitation method, using SnCl4·5H2O and SbCl3 as main raw materials. Microstructure, morphology and reflectivity c...Antimony tin oxide （ATO） nano-particles doped with different Sb contents were prepared by co-precipitation method, using SnCl4·5H2O and SbCl3 as main raw materials. Microstructure, morphology and reflectivity curves were characterized by XRD, FESEM, UV-visible spectroscopy and laser, and the effects of Sb content on crystalline microstructure, crystal size and reflectivity curves of the ATO nano-particles were investigated systematically. The results show that the ATO nano-particles prepared by co-precipitation method have tetragonal rutile structure, with particle size distribution range of several decade nanometer. With the increase of Sb content, the grain size of ATO decreases, and the unit cell volume increases. Compared with the SnO2 particles without Sb, the 1.06 μm laser reflection of ATO nano-particles doped with Sb is obviously lower. With the increase of Sb content, the reflection increases first, then decreases;when the Sb content is 20%, 1.06μm laser reflection of ATO nano-particles is below 0.02%, and the laser reflection performance is the best.展开更多
By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser be...By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.展开更多
An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing wit...An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24(Pa·cm)/W to 1450.64(Pa·cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO2 photoacoustic sensors.展开更多
Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refrac...Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity（the degree of inhomogeneous is between -0.2 and 0.2） is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.展开更多
A novel 1064 tun laser stealth absorbent of SmzO2S was prepared by flux method. The effects of different calcining temperatures and fluxes on the reflective property of Sm2O2S were investigated. The phase composition,...A novel 1064 tun laser stealth absorbent of SmzO2S was prepared by flux method. The effects of different calcining temperatures and fluxes on the reflective property of Sm2O2S were investigated. The phase composition, morphology, and reflectivity of the powders were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and ultraviolet-visible spectrophotometer （UVPC）. The results showed that pure phase of Sm202S could be obtained with Na2CO3 as flux above 950~C, and the reflectivity decreased with the calcination temperature increasing. Compared with other samarium compounds, the reflectivity at 1064 nm of Sm2O2S was the lowest. Different fluxes had great impact on the phase composition, particle morphology, and reflectivity of the products. In short, Sm2O2S was suitable as a kind of absorbent against 1064 nm laser.展开更多
The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in s...The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored.The AZ31magnesium(Mg)alloy was used as the test materials.The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure.After the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth.Eventually,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably grows.During LW in subatmospheric environment,the weld penetration can be further greatly increased through power modulation.Besides,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams.Finally,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated.This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.展开更多
The high-speed advances in electromagnetic(EM)wave and laser detection technology have accelerated the innovation of absorbing materials toward specific multi-band compatibility.It is difficult to achieve dual absorpt...The high-speed advances in electromagnetic(EM)wave and laser detection technology have accelerated the innovation of absorbing materials toward specific multi-band compatibility.It is difficult to achieve dual absorption of EM waves and near-infrared lasers by absorbing materials in a single frequency band;the design of high-performance laser-EM wave multi-band compatible absorbing materials is imminent.Herein,ErBO_(3)@ATO(erbium borate/antimony-doped tin oxide)porous composite microspheres with an average size of 15-20μm are produced solvothermal method and self-assembly,which exhibit excellent laser-EM wave compatible absorption.The porous structure on the surface of ErBO_(3)microspheres provides heterogeneous nucleation sites for ATO particle deposition.The minimum reflectivity of the composite for1.06 and 1.54μm lasers is 9.59%and 4.79%,which is0.57%and 3.78%lower than those of pure ATO particles,respectively.The composites containing 70 wt%porous ErBO_(3)@ATO reveal the minimum reflection loss(RL)value of-31.6 dB,and an effective absorption band width reaches 2.08 GHz at 2.5 mm thickness.The mechanism of near-infrared laser and EM wave compatible absorption is the synergistic effect of the energy level transition of ErBO_(3)and the dielectric loss of ATO,coupled with the large surface area and porous structure of the micro spheres.Therefore,the designed porous ErBO_(3)@ATO composite microspheres can be an attractive choice for lasers and EM wave high-quality compatible absorption.展开更多
The paper puts forward a method of virtual keyboard key positioning based on infrared laser reflection and image processing technology. In this paper, the positioning principle is introduced first. And the experimenta...The paper puts forward a method of virtual keyboard key positioning based on infrared laser reflection and image processing technology. In this paper, the positioning principle is introduced first. And the experimental system is established based on image acquisition, image transformation, threshold selection and binarization processing and identification of key placement. Tested in the indoor environment, the method can achieve characters input efficiently and accurately. And the key positioning has high accuracy, validity and reliability. So the method which has a high practical value provides a good theoretical basis for design of virtual keyboard application.展开更多
Since numerous characteristic absorption lines caused by molecular vibration exist in the midinfrared(MIR)wavelength region,selective excitation or selective dissociation of molecules is possible by tuning the laser w...Since numerous characteristic absorption lines caused by molecular vibration exist in the midinfrared(MIR)wavelength region,selective excitation or selective dissociation of molecules is possible by tuning the laser wavelength to the characteristic absorption lines of target molecules.By applying this feature to the medical fields,less-invasive treatment and non-destructive diagnosis with absorption spectroscopy are possible using tunable MIR lasers.A high-energy nanosecond pulsed MIR tunable laser was obtained with difference-frequency generation(DFG)between a Nd:YAG and a tunable Cr:forsterite lasers.The MIR-DFG laser was tunable in a wavelength range of 5.5–10μm and generated laser pulses with energy of up to 1.4mJ,a pulse width of 5 ns,and a pulse repetition rate of 10 Hz.Selective removal of atherosclerotic lesion was successfully demonstrated with the MIR-DFG laser tuned at a wavelength of 5.75μm,which corresponds to the characteristic absorption of the ester bond in cholesterol esters in the atherosclerotic lesions.We have developed a non-destructive diagnostic probe with an attenuated total reflection(ATR)prism and two hollow optical fibers.An absorption spectrum of cholesterol was measured with the ATR probe by scanning the wavelength of the MIR-DFG laser,and the spectrum was in good agreement with that measured with a commercial Fourier transform infrared spectrometer.展开更多
According to the statistical description of direction distribution on wavy surface by Cox, we have set up a physical model of reflection and refraction of Gaussian beam on wavy surface, derived that a beam reflected a...According to the statistical description of direction distribution on wavy surface by Cox, we have set up a physical model of reflection and refraction of Gaussian beam on wavy surface, derived that a beam reflected and refracted by wavy surface is also a Gaussian beam when the incident beam is a Gaussian beam, and set up the relationship between Gaussian beam's light spot size and wind speed over sea surface.展开更多
Heteroepitaxial GaN films are grown on sapphire （0001） substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that th...Heteroepitaxial GaN films are grown on sapphire （0001） substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that the growth mode of GaN transformed from three-dimensional （3D） island mode to two-dimensional （2D） layer-by-layer mode with the increase of thickness. This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns. Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm. The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode. The ll0-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes. The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films.展开更多
Nanostructured, sub-wavelength anti-reflection layers (NALs) have attracted much attention as a new generation of anti-reflection surfaces. Among different designs, sub-wavelength periodic nanostructures are capable o...Nanostructured, sub-wavelength anti-reflection layers (NALs) have attracted much attention as a new generation of anti-reflection surfaces. Among different designs, sub-wavelength periodic nanostructures are capable of enhancing transmission of coherent light through an interface without inducing scattering. In this work, we have explored a new profile for periodic NALs capable of transmitting IR light with higher efficiency compared to NALs based on a parabolic profile. To achieve high transmission and low diffraction, the profile and pitch of the nanostructured NALs are calculated using a combination of a multi-layer modeling and Rigorous Coupled Wave (RCWA) analysis.展开更多
Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical v...Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical value to enhance mechanical stability can highly reduce the transmission efficiency. Here, using Rigorous Couples Wave Analysis (RCWA), we find the minimum height for over 99% transmission and effect of height on transmission bandwidth. Then, during a one-step plasma etching, two samples with different heights have been generated and their efficiency is evaluated using RCWA.展开更多
The blades on the plane are one of the most important parts of the engine,in the course of service,due to high temperature,strong vibration and great centrifugal force and so on.The using environment is very bad,so it...The blades on the plane are one of the most important parts of the engine,in the course of service,due to high temperature,strong vibration and great centrifugal force and so on.The using environment is very bad,so it is easy to produce fatigue cracks in the welding site and the near surface of the root,which will seriously affect the blade of the work intensity and fatigue life,and even the safety of aircraft structure,causing a huge security risk.Therefore,it must be tested.In order to solve the problem of the rapid detection of aircraft engine in situ cracks,and gett the rela-tionship between feature information and detect depth,the laboratory experimental platform was built,laser was used to excite laser ultrasonic signals on a range of aviation aluminum plates with different depth defects,the collected sig-nal was processed by wavelet de-noising,and the band energy distribution of the reflected echo signal was studied by using wavelet packet.The results show that the energy of reflected echo signal is mainly concentrated in the S80~So7 band.When the depth of defect is 0.2 mm to 0.4 mm,the energy is mainly concentrated in the adjacent bands.When the depth of defect is 0.5 mm to 0.7 mm,the energy is mainly concentrated in the two bands.This method provides a way to quantify surface micro-defects by ultrasonic signals,which will lay a foundation for the future analysis of crack depth from band energy.In order to avoid the interference of other irregular cracks,the cracks of the aviation aluminum parts are used as ar-tificial way for producing.The overall size of the specimen is 200 mmx80 mmx100 mm,the width of the defect is 0.15 mm,the range of the defect depth is 0.2 mm~0.7 mm,step size is 0.1 mm,and the total number of the specimen is six.After the experimental data is proposed,choosing the reflected echo signal for analysis,performing wavelet packet transform,the decomposition layer is 8.The percentage in the Sao~Sa7band is 89.77%、91.82%、91.41%、90.94%、90.19%、and 87.86%.The result shows that most of the energy is concentrated in the first eight bands.Therefore,the paper selects the first eight bands for analysis.In order to analyze the distribution characteristics of the different depth defect and the band energy,the energy dis-tribution of the first four bands of the defect depth of 0.2 mm to 0.4 mm is plotted in Fig,according to the spectrum,getting the center frequency were 3.14 MHz,2.58 MHz,2.17 MHz.These frequencies are located in the S83,S82,S82 band,respectively,which are the largest energy band,but the energy distribution in the adjacent segment Ss:also ac-counts for a larger proportion.When the depth of the defect increases from 0.2 mm to 0.4 mm,the center frequency decreases gradually,and the sum of the energy of the center frequency band and the adjacent higher energy band in-creases gradually.展开更多
The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment ...The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment on the seeds was done, intervals from 10 s to 15 min （approximately）, by using a diode laser output power of 12 mW at 904 nm wavelength or with He-Ne laser with output power of 50 mW and 632.8 nm wavelength. Before irradiation seeds were divided into groups （wet and dry, and then in subgroups-irradiated or control groups）. We used maize hybrids, Amilacea and Identata and wheat （Triticum aestivum）. The reflection coefficient in visible range was done for maize varieties. Obtained data show the influence of laser beam to better plant growth. Better results are obtained for dry seed irradiation than for wet. In order to investigate the effect of laser beam and in general to clarify a lot of unsolved photo processes related to bioorganisms at macroscopic and microscopic levels, some optical constants of selected plant families were researched. At the same time, the influence of laser beams of common wavelengths to the selected plants was monitored. Morphological processes of plants （seeds and leaves） irradiated under different conditions and plant growing dynamics were contemplated. The definite correlation analyses of obtained results were made, clearly speaking about the influence of small-dose radiation to characteristics （quantitative and other genetic, bio-stimulating effects） of future plant growth.展开更多
基金Project supported by the National Natural Science Foundation of China(1237040868)。
文摘Phosphor-in-glass(PiG)films have emerged as the preferred conversion materials for high-brightness laser-driven lighting due to their excellent thermal conductivity and superior optical performance.Screen printing technology was employed to investigate the correlation between the reflective layer thickness and light conversion efficiency.A multilayer-structured Y_(3)Al_(3.5)Ga_(1.5)O_(12):Ce^(3+)(YAGG:Ce)-PiGTiO_(2)-aluminium nitride(AIN)film(YG-TAF)converter was constructed by efficiently coupling the optimal thickness of the reflective layer with the PiG layer and the AIN substrate.Notably,the YG-TAF shows an impressive thermal conductivity of 22.6 W/(m·K)and a maximum anti-laser power of 15.84 W,demonstrating superb thermal regulation capability.This anti-laser power of 15.84 W represents a breakthrough in current static laser performance research.Impressively,an YG-TAF phosphor color wheel was designed,which achieves an ultra-high-brightness 4375 lm of green light under 450 nm,88 W laser power excitation,close to that of commercial phosphor silicone color wheels.This advancement not only demonstrates the excellent performance of YG-TAF in high-brightness dynamic reflective laser applications but also indicates its strong feasibility for practical implementation.Furthermore,the developed YAGG:Ce-Y_(1.31)Ce_(0.09)Gd_(1.6)Al_5O_(12)-TAF spliced phosphor color wheel successfully mitigates the influence of photon reabsorption and achieves a color rendering index of 80.5,showing great potential for advancement of the field of reflective white light laser illumination.
基金Project(10KJB430008)supported by the Natural Science Foundation of Colleges in Jiangsu Province,ChinaProjects(2013(CXZZ13_0421),2012(CXLX12_0425))supported by Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),ChinaResearch and Innovation Program for College Graduates of Jiangsu Province,China
文摘Antimony tin oxide （ATO） nano-particles doped with different Sb contents were prepared by co-precipitation method, using SnCl4·5H2O and SbCl3 as main raw materials. Microstructure, morphology and reflectivity curves were characterized by XRD, FESEM, UV-visible spectroscopy and laser, and the effects of Sb content on crystalline microstructure, crystal size and reflectivity curves of the ATO nano-particles were investigated systematically. The results show that the ATO nano-particles prepared by co-precipitation method have tetragonal rutile structure, with particle size distribution range of several decade nanometer. With the increase of Sb content, the grain size of ATO decreases, and the unit cell volume increases. Compared with the SnO2 particles without Sb, the 1.06 μm laser reflection of ATO nano-particles doped with Sb is obviously lower. With the increase of Sb content, the reflection increases first, then decreases;when the Sb content is 20%, 1.06μm laser reflection of ATO nano-particles is below 0.02%, and the laser reflection performance is the best.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474257 and 61605183
文摘By employing three reflecting volume Bragg gratings, a near-infrared 4-channel spectral-beam-combining system is demonstrated to present 720 W combined power with a combining efficiency of 94.7%. The combined laser beam is near-diffraction-limited with a beam factor M^2-1.54. During this 4-channel beam-combining process, no special active cooling measures are used to evaluate the volume Bragg gratings as combining elements are under the higher power laser operation. Thermal expansion and period distortion are verified in a 2 k W 2-channel beam-combining process, and the heat issue in the transmission case is found to be more remarkable than that in the diffraction e-se. Transmitted and diffracted beams experience wave-front aberrations with different degrees, thus leading to distinct beam deterioration.
基金National Natural Science Foundation of China(Grant Nos.91644107,61575206,51904009,and 41905130)National Key Research and Development Program of China(Grant Nos.2017YFC0209401,2017YFC0209403,and 2017YFC0209902)the Outstanding Young Talents Program of Anhui University,China(Grant No.gxyq2019022).
文摘An NO2 photoacoustic sensor system with a high reflective mirror based on a low power blue diode laser is developed in this work. The excitation power is enhanced by increasing the number of reflections. Comparing with a traditional photoacoustic system, the pool constant is improved from 300.24(Pa·cm)/W to 1450.64(Pa·cm)/W, and the signal sensitivity of the photoacoustic sensor is increased from 0.016 μV/ppb to 0.2562 μV/ppb. The characteristics of temperature and humidity of the new photoacoustic sensor are also obtained, and the algorithm is adjusted to provide a quantitative response and drift of the resonance frequency. The results of this research provide a new method and concept for further developing the NO2 photoacoustic sensors.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61405145 and 61235011)the Natural Science Foundation of Tianjin,China(Grant No.15JCZDJC31900)the China Postdoctoral Science Foundation(Grant Nos.2015T80115 and 2014M560104)
文摘Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity（the degree of inhomogeneous is between -0.2 and 0.2） is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.
基金financially supported by the Natural Science Foundation of Jiangsu Province (No.BK2007724)Military Coordination Scientific Research Projects (No.JPPT-1486)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutions (No.CXZZ110333)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘A novel 1064 tun laser stealth absorbent of SmzO2S was prepared by flux method. The effects of different calcining temperatures and fluxes on the reflective property of Sm2O2S were investigated. The phase composition, morphology, and reflectivity of the powders were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and ultraviolet-visible spectrophotometer （UVPC）. The results showed that pure phase of Sm202S could be obtained with Na2CO3 as flux above 950~C, and the reflectivity decreased with the calcination temperature increasing. Compared with other samarium compounds, the reflectivity at 1064 nm of Sm2O2S was the lowest. Different fluxes had great impact on the phase composition, particle morphology, and reflectivity of the products. In short, Sm2O2S was suitable as a kind of absorbent against 1064 nm laser.
基金supported by National Natural Science Foundation of China(Grants No.52005393,51275391)National Thousand Talents Program of China(Grant No.WQ2017610446)。
文摘The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored.The AZ31magnesium(Mg)alloy was used as the test materials.The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure.After the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth.Eventually,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably grows.During LW in subatmospheric environment,the weld penetration can be further greatly increased through power modulation.Besides,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams.Finally,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated.This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.
基金financially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)"Qinglan Project"Young and Middle-aged Academic Leaders Program of Jiangsu Province。
文摘The high-speed advances in electromagnetic(EM)wave and laser detection technology have accelerated the innovation of absorbing materials toward specific multi-band compatibility.It is difficult to achieve dual absorption of EM waves and near-infrared lasers by absorbing materials in a single frequency band;the design of high-performance laser-EM wave multi-band compatible absorbing materials is imminent.Herein,ErBO_(3)@ATO(erbium borate/antimony-doped tin oxide)porous composite microspheres with an average size of 15-20μm are produced solvothermal method and self-assembly,which exhibit excellent laser-EM wave compatible absorption.The porous structure on the surface of ErBO_(3)microspheres provides heterogeneous nucleation sites for ATO particle deposition.The minimum reflectivity of the composite for1.06 and 1.54μm lasers is 9.59%and 4.79%,which is0.57%and 3.78%lower than those of pure ATO particles,respectively.The composites containing 70 wt%porous ErBO_(3)@ATO reveal the minimum reflection loss(RL)value of-31.6 dB,and an effective absorption band width reaches 2.08 GHz at 2.5 mm thickness.The mechanism of near-infrared laser and EM wave compatible absorption is the synergistic effect of the energy level transition of ErBO_(3)and the dielectric loss of ATO,coupled with the large surface area and porous structure of the micro spheres.Therefore,the designed porous ErBO_(3)@ATO composite microspheres can be an attractive choice for lasers and EM wave high-quality compatible absorption.
文摘The paper puts forward a method of virtual keyboard key positioning based on infrared laser reflection and image processing technology. In this paper, the positioning principle is introduced first. And the experimental system is established based on image acquisition, image transformation, threshold selection and binarization processing and identification of key placement. Tested in the indoor environment, the method can achieve characters input efficiently and accurately. And the key positioning has high accuracy, validity and reliability. So the method which has a high practical value provides a good theoretical basis for design of virtual keyboard application.
基金supported by Takeda Science Foundation,Japanese Foundation for Research and Promotion of Endoscopy,and Grants-in-Aid for Scientific Research(KAKENHI).
文摘Since numerous characteristic absorption lines caused by molecular vibration exist in the midinfrared(MIR)wavelength region,selective excitation or selective dissociation of molecules is possible by tuning the laser wavelength to the characteristic absorption lines of target molecules.By applying this feature to the medical fields,less-invasive treatment and non-destructive diagnosis with absorption spectroscopy are possible using tunable MIR lasers.A high-energy nanosecond pulsed MIR tunable laser was obtained with difference-frequency generation(DFG)between a Nd:YAG and a tunable Cr:forsterite lasers.The MIR-DFG laser was tunable in a wavelength range of 5.5–10μm and generated laser pulses with energy of up to 1.4mJ,a pulse width of 5 ns,and a pulse repetition rate of 10 Hz.Selective removal of atherosclerotic lesion was successfully demonstrated with the MIR-DFG laser tuned at a wavelength of 5.75μm,which corresponds to the characteristic absorption of the ester bond in cholesterol esters in the atherosclerotic lesions.We have developed a non-destructive diagnostic probe with an attenuated total reflection(ATR)prism and two hollow optical fibers.An absorption spectrum of cholesterol was measured with the ATR probe by scanning the wavelength of the MIR-DFG laser,and the spectrum was in good agreement with that measured with a commercial Fourier transform infrared spectrometer.
文摘According to the statistical description of direction distribution on wavy surface by Cox, we have set up a physical model of reflection and refraction of Gaussian beam on wavy surface, derived that a beam reflected and refracted by wavy surface is also a Gaussian beam when the incident beam is a Gaussian beam, and set up the relationship between Gaussian beam's light spot size and wind speed over sea surface.
基金supported by the Major State Basic Research Development Program of China (Grant No. 61363)the National Natural Science Foundation of China (Grant Nos. 50772019 and 61021061)
文摘Heteroepitaxial GaN films are grown on sapphire （0001） substrates using laser molecular beam epitaxy. The growth processes are in-situ monitored by reflection high energy electron diffraction. It is revealed that the growth mode of GaN transformed from three-dimensional （3D） island mode to two-dimensional （2D） layer-by-layer mode with the increase of thickness. This paper investigates the interfacial strain relaxation of GaN films by analysing their diffraction patterns. Calculation shows that the strain is completely relaxed when the thickness reaches 15 nm. The surface morphology evolution indicates that island merging and reduction of the island-edge barrier provide an effective way to make GaN films follow a 2D layer-by-layer growth mode. The ll0-nm GaN films with a 2D growth mode have smooth regular hexagonal shapes. The X-ray diffraction indicates that thickness has a significant effect on the crystallized quality of GaN thin films.
文摘Nanostructured, sub-wavelength anti-reflection layers (NALs) have attracted much attention as a new generation of anti-reflection surfaces. Among different designs, sub-wavelength periodic nanostructures are capable of enhancing transmission of coherent light through an interface without inducing scattering. In this work, we have explored a new profile for periodic NALs capable of transmitting IR light with higher efficiency compared to NALs based on a parabolic profile. To achieve high transmission and low diffraction, the profile and pitch of the nanostructured NALs are calculated using a combination of a multi-layer modeling and Rigorous Coupled Wave (RCWA) analysis.
文摘Periodic Nanostructured anti-reflection coatings (NALs) are a promising option for enhancing transmission of coherent light without inducing scattering. We’ve found that reducing the height of NALs below a critical value to enhance mechanical stability can highly reduce the transmission efficiency. Here, using Rigorous Couples Wave Analysis (RCWA), we find the minimum height for over 99% transmission and effect of height on transmission bandwidth. Then, during a one-step plasma etching, two samples with different heights have been generated and their efficiency is evaluated using RCWA.
文摘The blades on the plane are one of the most important parts of the engine,in the course of service,due to high temperature,strong vibration and great centrifugal force and so on.The using environment is very bad,so it is easy to produce fatigue cracks in the welding site and the near surface of the root,which will seriously affect the blade of the work intensity and fatigue life,and even the safety of aircraft structure,causing a huge security risk.Therefore,it must be tested.In order to solve the problem of the rapid detection of aircraft engine in situ cracks,and gett the rela-tionship between feature information and detect depth,the laboratory experimental platform was built,laser was used to excite laser ultrasonic signals on a range of aviation aluminum plates with different depth defects,the collected sig-nal was processed by wavelet de-noising,and the band energy distribution of the reflected echo signal was studied by using wavelet packet.The results show that the energy of reflected echo signal is mainly concentrated in the S80~So7 band.When the depth of defect is 0.2 mm to 0.4 mm,the energy is mainly concentrated in the adjacent bands.When the depth of defect is 0.5 mm to 0.7 mm,the energy is mainly concentrated in the two bands.This method provides a way to quantify surface micro-defects by ultrasonic signals,which will lay a foundation for the future analysis of crack depth from band energy.In order to avoid the interference of other irregular cracks,the cracks of the aviation aluminum parts are used as ar-tificial way for producing.The overall size of the specimen is 200 mmx80 mmx100 mm,the width of the defect is 0.15 mm,the range of the defect depth is 0.2 mm~0.7 mm,step size is 0.1 mm,and the total number of the specimen is six.After the experimental data is proposed,choosing the reflected echo signal for analysis,performing wavelet packet transform,the decomposition layer is 8.The percentage in the Sao~Sa7band is 89.77%、91.82%、91.41%、90.94%、90.19%、and 87.86%.The result shows that most of the energy is concentrated in the first eight bands.Therefore,the paper selects the first eight bands for analysis.In order to analyze the distribution characteristics of the different depth defect and the band energy,the energy dis-tribution of the first four bands of the defect depth of 0.2 mm to 0.4 mm is plotted in Fig,according to the spectrum,getting the center frequency were 3.14 MHz,2.58 MHz,2.17 MHz.These frequencies are located in the S83,S82,S82 band,respectively,which are the largest energy band,but the energy distribution in the adjacent segment Ss:also ac-counts for a larger proportion.When the depth of the defect increases from 0.2 mm to 0.4 mm,the center frequency decreases gradually,and the sum of the energy of the center frequency band and the adjacent higher energy band in-creases gradually.
文摘The paper presents a study on the effects of low intensity laser irradiation on morphological changes in plants sprouted from maize hybrid seeds （two hybrids） and wheat seeds. Pre-sowing laser irradiation treatment on the seeds was done, intervals from 10 s to 15 min （approximately）, by using a diode laser output power of 12 mW at 904 nm wavelength or with He-Ne laser with output power of 50 mW and 632.8 nm wavelength. Before irradiation seeds were divided into groups （wet and dry, and then in subgroups-irradiated or control groups）. We used maize hybrids, Amilacea and Identata and wheat （Triticum aestivum）. The reflection coefficient in visible range was done for maize varieties. Obtained data show the influence of laser beam to better plant growth. Better results are obtained for dry seed irradiation than for wet. In order to investigate the effect of laser beam and in general to clarify a lot of unsolved photo processes related to bioorganisms at macroscopic and microscopic levels, some optical constants of selected plant families were researched. At the same time, the influence of laser beams of common wavelengths to the selected plants was monitored. Morphological processes of plants （seeds and leaves） irradiated under different conditions and plant growing dynamics were contemplated. The definite correlation analyses of obtained results were made, clearly speaking about the influence of small-dose radiation to characteristics （quantitative and other genetic, bio-stimulating effects） of future plant growth.
