In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we ana...In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we analyze the challenges of developing GaN-based ultraviolet laser diodes,and the approaches to improve the performance of ultraviolet laser diode are reviewed.With these techniques,room temperature(RT)pulsed oscillation of AlGaN UVA(ultraviolet A)LD has been realized,with a lasing wavelength of 357.9 nm.Combining with the suppression of thermal effect,the high output power of 3.8 W UV LD with a lasing wavelength of 386.5 nm was also fabricated.展开更多
Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen t...Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen to be higher than the bandgap energy of the sample.To the best of our knowledge,the highest energy of pumping laser in reported PR systems is 5.08 eV(244 nm),not yet in the vacuum ultraviolet(VUV)region.In this work,we report the design and construction of a PR system pumped by VUV laser of 7.0 eV(177.3 nm).At the same time,dual-modulated technique is applied and a dual channel lock-in-amplifier is integrated into the system for efficient PR measurement.The system’s performance is verified by the PR spectroscopy measurement of well-studied semiconductors,which testifies its ability to probe critical-point energies of the electronic band in semiconductors from ultraviolet to near-infrared spectral region.展开更多
We develop a picosecond widely tunable laser in a deep-ultraviolet region from 175 nm to 210 nm,generated by two stages of frequency doubling of a 80-MHz mode-locked picosecond Ti:sapphire laser.A β-BaB2O4 walk-off c...We develop a picosecond widely tunable laser in a deep-ultraviolet region from 175 nm to 210 nm,generated by two stages of frequency doubling of a 80-MHz mode-locked picosecond Ti:sapphire laser.A β-BaB2O4 walk-off compensation configuration and a KBe2BO3F2 prism-coupled device are adopted for the generation of second harmonic and fourth harmonics,respectively.The highest power is 3.72 mW at 193 nm,and the fluctuation at 2.85 mW in 130 min is less than ±2%.展开更多
In recent years,because of their small size,high efficiency and environment-friendly advantages,Ⅲ-nitride based ultraviolet(UV)light-emitting diodes(LEDs)have been widely used in many areas to substitute for mercury ...In recent years,because of their small size,high efficiency and environment-friendly advantages,Ⅲ-nitride based ultraviolet(UV)light-emitting diodes(LEDs)have been widely used in many areas to substitute for mercury lamps,such as in 3D printing,curing and sterilization.Ⅲ-nitride alloys cover the whole UV spectrum which is comprised of UV-A(320–400 nm),UV-B(280–320 nm)and UV-C(200–280 nm)by controlling Al/Ga/In content.In addition,Ⅲ-nitride based UV laser diodes(LDs)also have some potential applications in the case of high-power-density,narrow-spectrum,good-directional lighting.However,Ⅲ-nitride based UV laser diodes still have many challenges such as poor crystal quality and low hole concentration in p-type AlGaN.展开更多
Proton acceleration induced by a high-intensity ultraviolet laser interaction with a thin foil target was studied on an ultra-short KrF laser amplifier called LLG50 in China Institute of Atomic Energy(CIAE).The ultrav...Proton acceleration induced by a high-intensity ultraviolet laser interaction with a thin foil target was studied on an ultra-short KrF laser amplifier called LLG50 in China Institute of Atomic Energy(CIAE).The ultraviolet laser produced pulses with a high-contrast of 109,duration of 500 fs and energy of 30 mJ.The p-polarized laser was focused on a 2.1 μm gold foil by an of-axis parabola mirror(OAP) at an incident angle of 45°.The laser intensity was 1.2×1017W/cm2.The divergence angle for proton energy of 265 keV or higher was 30°,which was recorded by a CR39 detector covered with 2 μm aluminum foil in the target normal direction.The maximum proton energy recorded by a CR39 detector covered with a 4 μm aluminum foil was 440 keV,and the proton energy spectrum was measured by a proton spectrometer.The ultraviolet laser acquires a relatively lower hot electron temperature,which can be ascribed to the proportional relationship of Iλ2,but a higher hot electron density because of the higher laser absorption and critical density.Higher electron density availed to strengthen the sheath electric field,and increased the proton acceleration.展开更多
Ultraviolet(UV)and deep-UV light emitters are prom-ising for various applications including bioagent detection,wa-ter and air purification,dermatology,high-density optical stor-age,and lithography.However,to achieve s...Ultraviolet(UV)and deep-UV light emitters are prom-ising for various applications including bioagent detection,wa-ter and air purification,dermatology,high-density optical stor-age,and lithography.However,to achieve shorter UV laser di-odes(LDs),especially for the LDs with lasing wavelength less than 360 nm,requires high AlN mole fraction AlGaN clad-ding layer(CL)and waveguide(WG)layers,which usually leads to generate cracks in AlGaN epilayer due to lack of lat-tice-matched substrates.Meanwhile,due to high resistivity of high AlN mole fraction Mg doped AlGaN layers,only few groups have reported GaN-based LDs with emission wavelength shorter than 360 nm[1−8],and up to now,there is no room temperature continuous-wave(CW)operation UV LDs with a lasing wavelength shorter than 360 nm ever repor-ted.Previously,we have reported a UV LD with lasing wavelength of 366 nm[9].In this paper,a higher AlN mole frac-tion of AlGaN WG layers is employed to shorten the LD emis-sion wavelength to less than 360 nm.A lasing wavelength of 357.9 nm is achieved.展开更多
This paper studies supersonic jet-cooled 1-fluoronaphthalene(1FN) clusters by ultraviolet(UV) laser ionization at 281 nm in a time-of-flight mass spectrometer.The(1FN) + n(n=1-3) series cluster ions are observed where...This paper studies supersonic jet-cooled 1-fluoronaphthalene(1FN) clusters by ultraviolet(UV) laser ionization at 281 nm in a time-of-flight mass spectrometer.The(1FN) + n(n=1-3) series cluster ions are observed where the signal intensity decreases with increasing cluster size.The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured.Using density functional theory calculations,it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds.The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first "shell" in geometric structure while the larger clusters are generated based on this fundamental unit.展开更多
In order to suppress the electron leakage to p-type region of near-ultraviolet GaN/In_xGa_(1-x )N/GaN multiple-quantumwell(MQW) laser diode(LD), the Al composition of inserted p-type AlxGa_(1-x)N electron blocking lay...In order to suppress the electron leakage to p-type region of near-ultraviolet GaN/In_xGa_(1-x )N/GaN multiple-quantumwell(MQW) laser diode(LD), the Al composition of inserted p-type AlxGa_(1-x)N electron blocking layer(EBL) is optimized in an effective way, but which could only partially enhance the performance of LD. Here, due to the relatively shallow GaN/In_(0.04)Ga_(0.96)N/GaN quantum well, the hole leakage to n-type region is considered in the ultraviolet LD. To reduce the hole leakage, a 10-nm n-type Al_xGa_(1-x)N hole blocking layer(HBL) is inserted between n-type waveguide and the first quantum barrier, and the effect of Al composition of Al_xGa_(1-x)N HBL on LD performance is studied. Numerical simulations by the LASTIP reveal that when an appropriate Al composition of Al_xGa_(1-x)N HBL is chosen, both electron leakage and hole leakage can be reduced dramatically, leading to a lower threshold current and higher output power of LD.展开更多
Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or...Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or quasi-Gaussian distribution will carry the pattern on DMD to etch the resin. It provides a method of precise control of laser beam shapes and?photon-induced curing behavior of resin. This technology provides an accurate micro-fabrication of microstructures used for micro-systems. As a virtual mask generator and a binary-amplitude spatial light modulator, DMD is equivalent to the masks in the conventional exposure system. As the virtual masks and shaped laser beam can be achieved flexibly, it is a good method of precision soft lithography for 2D/3D microstructures.展开更多
A novel hybrid process for surface fluorination of polymers is being introduced. The process is based on ultra violet (UV) laser radiation, which on the one hand forms radicals out of an atmosphere of a partially fluo...A novel hybrid process for surface fluorination of polymers is being introduced. The process is based on ultra violet (UV) laser radiation, which on the one hand forms radicals out of an atmosphere of a partially fluorinated benzene, and on the other hand activates a polymer surface in the areas where the UV radiation hits the surface. The radicals can react with the polymer surface, hence altering the surface energy. With this process, a fluorine content of over 30% on the surface of bulk polystyrene can be achieved, while the smallest possible structure size was smaller than 1 mm.展开更多
High-power continuous-wave ultraviolet lasers are useful for many applications.As ultraviolet laser sources,the wavelength switching capability and compact structure are very important to extend the applicability and ...High-power continuous-wave ultraviolet lasers are useful for many applications.As ultraviolet laser sources,the wavelength switching capability and compact structure are very important to extend the applicability and improve the flexibility in practical applications.In this work,we present two simple and relatively compact schemes by laser diode pumping to obtain a watt-level single-wavelength 348.7-nm laser and discrete wavelength tunable ultraviolet lasers around 349 nm(from 334.7 to 364.5 nm)by intracavity frequency doubling based on Pr^(3+):YLF andβ-BBO crystals.The maximum output power of the single-wavelength 348.7-nm laser is 1.033 W.The output powers of the discrete wavelength tunable lasers are at the level of tens of milliwatts,except for two peaks at 348.7 and 360.3 nm with output powers of approximately 500 mW.In addition,simulations are carried out to explain the experimental results and clarify the tuning mechanisms.展开更多
We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on ...We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on the emission spectra centered around 6.7 nm from thin-film Gd targets were first investigated.It is found that the conversion efficiency of the produced plasma is saturated when the laser intensity goes beyond 2×10^(11)W cm^(-2).We have systematically compared the emission spectra of the laser-produced plasma with the changes in the thicknesses of the thin-film Gd targets.It is proved that a minimum-mass target with a thickness of 400 nm is sufficient to provide the maximum conversion efficiency,which also implies that this thickness is the ablation depth for the targets.These findings should be helpful in the exploration of next-generation EUV sources,as the thin-film Gd targets will reduce the debris during the plasma generation process compared with the bulk targets.展开更多
Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a v...Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a variety of analysis programs for battlefield targets to traditional weapons have been developed,but a comprehensive assessment methodology for targets'vulnerability to laser is still missing.Based on the shotline method,this paper proposes a method that equates laser beam to shotline array,an efficient vulnerability analysis program of target to laser is established by this method,and the program includes the circuit board and the wire into the vulnerability analysis category,which improves the precision of the vulnerability analysis.Taking the UAV engine part as the target of vulnerability analysis,combine with the"life-death unit method"to calculate the laser penetration rate of various materials of the UAV,and the influence of laser weapon system parameters and striking orientation on the killing probability is quantified after introducing the penetration rate into the vulnerability analysis program.The quantitative analysis method proposed in this paper has certain general expansibility,which can provide a fresh idea for the vulnerability analysis of other targets to laser.展开更多
Liquid-phase exfoliation was employed to synthesize Sr_(2)Nb_(3)O_(10) perovskite nanosheets with thicknesses down to 1.76 nm.Transmission electron microscopy(TEM),atomic force microscope(AFM),X-ray photoelectron spec...Liquid-phase exfoliation was employed to synthesize Sr_(2)Nb_(3)O_(10) perovskite nanosheets with thicknesses down to 1.76 nm.Transmission electron microscopy(TEM),atomic force microscope(AFM),X-ray photoelectron spectrometer(XPS),and other characterization techniques were used to evaluate the atomic structure and chemical composition of the exfoliated nanosheets.A UV photodetector based on individual Sr_(2)Nb_(3)O_(10) nanosheets was prepared to demonstrate the application of an ultraviolet(UV) photodetector.The UV photodetector exhibited outstanding photocurrent and responsivity with a responsivity of 3×10^(5) A·W^(-1) at 5 V bias under 280 nm illumination,a photocurrent of 60 nA,and an on/off ratio of 3×10^(2).展开更多
Ultraviolet radiation by its wavelength is divided into: UVA, UVB and UVC. Only UVA and UVB manage to penetrate the ozone layer, but due to anthropological activities, all of them are capable of interacting with human...Ultraviolet radiation by its wavelength is divided into: UVA, UVB and UVC. Only UVA and UVB manage to penetrate the ozone layer, but due to anthropological activities, all of them are capable of interacting with humans to a greater or lesser extent, and can generate adverse effects such as cellular stress when interacting with intra-and extracellular biomolecules. The skin is the first organ in contact with UV radiation, and the stress it generates can be analyzed by the expression of a bioindicator of cellular damage such as Hsp70. Therefore, the objective of the project was: to determine the effect of UVA, UVB and UVC radiation on HaCaT epithelial cells, by analyzing the expression of Hsp70. Materials and methods: HaCaT cells were cultured in vitro, which were irradiated with UVA, UVB and UVC light at different doses, to subsequently determine the degree of Hsp70 expression by Immunodetection by PAGE-SDS and Western Blot. Results: Basal expression of Hsp70 was observed in no irradiated HaCaT cells. When HaCaT cells were irradiated with UVA, UVB, UVC, an increase in this Hsp70 protein was observed. With UVA, a higher degree of expression was observed at a time of 30 minutes of irradiation. With UVB the highest expression shifted to a time of 20 minutes. With UVC, overexpression was observed after 10 minutes. Conclusion: UV radiation generates cellular stress on HaCaT cells, evaluated by the stress bioindicator Hsp70. According to the wavelength of UV radiation, those that have a shorter wavelength have a greater potential for cellular damage, such as UVC.展开更多
240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge ef...240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.展开更多
We report a high-average-power acousto-optic(AO)Q-switched intracavity frequency-doubled red laser based on a high-efficiency light-emitting-diode(LED)pumped two-rod Nd,Ce:YAG laser module.Under quasi-continuous wave ...We report a high-average-power acousto-optic(AO)Q-switched intracavity frequency-doubled red laser based on a high-efficiency light-emitting-diode(LED)pumped two-rod Nd,Ce:YAG laser module.Under quasi-continuous wave operation conditions,a maximum output power of 1319.08 nm wavelength was achieved at 11.26 W at a repetition rate of 100 Hz.展开更多
The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM)....The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.展开更多
We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a reg...We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC.The dynamics of broadband BFC generation changing with the pump power(EDF and Raman)and Brillouin pump(BP)wavelength are investigated in detail,respectively.Under suitable conditions,the bidirectional BRRFL proposed can produce a flatamplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm,and built-in 242-order Brillouin Stokes lines(BSLs)with double Brillouin-frequency-shift spacing.Moreover,the linewidth of single BSL is experimentally measured to be about 2.5 kHz.The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication,optical sensing,spectral measurement,and so on.展开更多
A time-dependent analytical solution is found for the velocity of a plane ionization wave generated under nanosecond laser pulse action on the surface of a flat layer of low-Z porous substance with density less than t...A time-dependent analytical solution is found for the velocity of a plane ionization wave generated under nanosecond laser pulse action on the surface of a flat layer of low-Z porous substance with density less than the critical density of the produced plasma.With corrections for the two-dimensional nature of the problem when a laser beam of finite radius interacts with a flat target,this solution is in quantitative agreement with measurements of ionization wave velocity in various experiments.The solution compared with experimental data covering wide ranges of performance conditions,namely,(3-8)×10^(14)W cm^(−2)for laser pulse intensity,0.3-3 ns for pulse duration,0.35-0.53μm for laser wavelength,100-1000μm for laser beam radius,380-950μm for layer thickness,4.5-12 mg cm^(−3)for average density of porous substance,and 1-25μm for average pore size.The parameters of the laser beam that ensure the generation of a plane ionization wave in a layer of subcritical porous matter are determined for the problem statements and are found to meet the requirements of practical applications.展开更多
基金This work was supported by the National Key R&D Program of China(2022YFB3605104)National Natural Science Foundation of China(62250038,61904172,61974162,62034008,62074142,and 62074140)+1 种基金Strategic Priority Research Program of Chinese Academy of Sciences(XDB43030101)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(2022SX-TD016).
文摘In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we analyze the challenges of developing GaN-based ultraviolet laser diodes,and the approaches to improve the performance of ultraviolet laser diode are reviewed.With these techniques,room temperature(RT)pulsed oscillation of AlGaN UVA(ultraviolet A)LD has been realized,with a lasing wavelength of 357.9 nm.Combining with the suppression of thermal effect,the high output power of 3.8 W UV LD with a lasing wavelength of 386.5 nm was also fabricated.
基金Project supported by the National Development Project for Major Scientific Research Facility of China(Grant No.ZDYZ2012-2)the National Natural Science Foundation of China(Grant No.11874350)CAS Key Research Program of Frontier Sciences(Grant Nos.ZDBS-LY-SLH004 and XDPB22)。
文摘Photoreflectance(PR)spectroscopy is a powerful and non-destructive experimental technique to explore interband transitions of semiconductors.In most PR systems,the photon energy of the pumping beam is usually chosen to be higher than the bandgap energy of the sample.To the best of our knowledge,the highest energy of pumping laser in reported PR systems is 5.08 eV(244 nm),not yet in the vacuum ultraviolet(VUV)region.In this work,we report the design and construction of a PR system pumped by VUV laser of 7.0 eV(177.3 nm).At the same time,dual-modulated technique is applied and a dual channel lock-in-amplifier is integrated into the system for efficient PR measurement.The system’s performance is verified by the PR spectroscopy measurement of well-studied semiconductors,which testifies its ability to probe critical-point energies of the electronic band in semiconductors from ultraviolet to near-infrared spectral region.
基金supported by the State Key Program for Basic Research of China (Grant No. 2010CB630706)National High Technology Research and Development Program of Chinathe National Natural Science Foundation of China (Grant No. 61138004)
文摘We develop a picosecond widely tunable laser in a deep-ultraviolet region from 175 nm to 210 nm,generated by two stages of frequency doubling of a 80-MHz mode-locked picosecond Ti:sapphire laser.A β-BaB2O4 walk-off compensation configuration and a KBe2BO3F2 prism-coupled device are adopted for the generation of second harmonic and fourth harmonics,respectively.The highest power is 3.72 mW at 193 nm,and the fluctuation at 2.85 mW in 130 min is less than ±2%.
文摘In recent years,because of their small size,high efficiency and environment-friendly advantages,Ⅲ-nitride based ultraviolet(UV)light-emitting diodes(LEDs)have been widely used in many areas to substitute for mercury lamps,such as in 3D printing,curing and sterilization.Ⅲ-nitride alloys cover the whole UV spectrum which is comprised of UV-A(320–400 nm),UV-B(280–320 nm)and UV-C(200–280 nm)by controlling Al/Ga/In content.In addition,Ⅲ-nitride based UV laser diodes(LDs)also have some potential applications in the case of high-power-density,narrow-spectrum,good-directional lighting.However,Ⅲ-nitride based UV laser diodes still have many challenges such as poor crystal quality and low hole concentration in p-type AlGaN.
基金supported by the Key Project of Chinese National Programs for Fundamental Research(973 Program)(No.2011CB808104)National Natural Science Foundation of China(Nos.10834008,11105234)
文摘Proton acceleration induced by a high-intensity ultraviolet laser interaction with a thin foil target was studied on an ultra-short KrF laser amplifier called LLG50 in China Institute of Atomic Energy(CIAE).The ultraviolet laser produced pulses with a high-contrast of 109,duration of 500 fs and energy of 30 mJ.The p-polarized laser was focused on a 2.1 μm gold foil by an of-axis parabola mirror(OAP) at an incident angle of 45°.The laser intensity was 1.2×1017W/cm2.The divergence angle for proton energy of 265 keV or higher was 30°,which was recorded by a CR39 detector covered with 2 μm aluminum foil in the target normal direction.The maximum proton energy recorded by a CR39 detector covered with a 4 μm aluminum foil was 440 keV,and the proton energy spectrum was measured by a proton spectrometer.The ultraviolet laser acquires a relatively lower hot electron temperature,which can be ascribed to the proportional relationship of Iλ2,but a higher hot electron density because of the higher laser absorption and critical density.Higher electron density availed to strengthen the sheath electric field,and increased the proton acceleration.
基金supported by the National Natural Science Foundation of China(Grant Nos.62034008,6207414262074140,61974162,61904172,61874175)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2019115)+2 种基金Beijing Nova Program(Grant No202093)Beijing Municipal Science and Technology Project(Grant No.Z211100007921022)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No XDB43030101)。
文摘Ultraviolet(UV)and deep-UV light emitters are prom-ising for various applications including bioagent detection,wa-ter and air purification,dermatology,high-density optical stor-age,and lithography.However,to achieve shorter UV laser di-odes(LDs),especially for the LDs with lasing wavelength less than 360 nm,requires high AlN mole fraction AlGaN clad-ding layer(CL)and waveguide(WG)layers,which usually leads to generate cracks in AlGaN epilayer due to lack of lat-tice-matched substrates.Meanwhile,due to high resistivity of high AlN mole fraction Mg doped AlGaN layers,only few groups have reported GaN-based LDs with emission wavelength shorter than 360 nm[1−8],and up to now,there is no room temperature continuous-wave(CW)operation UV LDs with a lasing wavelength shorter than 360 nm ever repor-ted.Previously,we have reported a UV LD with lasing wavelength of 366 nm[9].In this paper,a higher AlN mole frac-tion of AlGaN WG layers is employed to shorten the LD emis-sion wavelength to less than 360 nm.A lasing wavelength of 357.9 nm is achieved.
文摘This paper studies supersonic jet-cooled 1-fluoronaphthalene(1FN) clusters by ultraviolet(UV) laser ionization at 281 nm in a time-of-flight mass spectrometer.The(1FN) + n(n=1-3) series cluster ions are observed where the signal intensity decreases with increasing cluster size.The effects of sample inlet pressures and ionization laser fluxes to mass spectral distribution are measured.Using density functional theory calculations,it obtains a planar geometric structure of 1FN dimer which is combined through two hydrogen bonds.The mass spectra indicate that the intensity of 1FN trimer is much weaker than that of 1FN dimer and this feature is attributed to the fact that the dimer may form the first "shell" in geometric structure while the larger clusters are generated based on this fundamental unit.
基金Project supported by the Science Challenge Project,China(Grant No.Z2016003)the National Key R&D Program of China(Grant Nos.2016YFB0400803and 2016YFB0401801)+1 种基金the National Natural Science Foundation of China(Grant Nos.61674138,61674139,61604145,61574135,61574134,61474142,61474110,61377020,and 61376089)the Beijing Municipal Science and Technology Project,China(Grant No.Z161100002116037)
文摘In order to suppress the electron leakage to p-type region of near-ultraviolet GaN/In_xGa_(1-x )N/GaN multiple-quantumwell(MQW) laser diode(LD), the Al composition of inserted p-type AlxGa_(1-x)N electron blocking layer(EBL) is optimized in an effective way, but which could only partially enhance the performance of LD. Here, due to the relatively shallow GaN/In_(0.04)Ga_(0.96)N/GaN quantum well, the hole leakage to n-type region is considered in the ultraviolet LD. To reduce the hole leakage, a 10-nm n-type Al_xGa_(1-x)N hole blocking layer(HBL) is inserted between n-type waveguide and the first quantum barrier, and the effect of Al composition of Al_xGa_(1-x)N HBL on LD performance is studied. Numerical simulations by the LASTIP reveal that when an appropriate Al composition of Al_xGa_(1-x)N HBL is chosen, both electron leakage and hole leakage can be reduced dramatically, leading to a lower threshold current and higher output power of LD.
文摘Laser shaping was introduced to maskless projection soft lithography by using digital micro-mirror device (DMD). The predesigned intensity pattern was imprinted onto the DMD and the input laser beam with a Gaussian or quasi-Gaussian distribution will carry the pattern on DMD to etch the resin. It provides a method of precise control of laser beam shapes and?photon-induced curing behavior of resin. This technology provides an accurate micro-fabrication of microstructures used for micro-systems. As a virtual mask generator and a binary-amplitude spatial light modulator, DMD is equivalent to the masks in the conventional exposure system. As the virtual masks and shaped laser beam can be achieved flexibly, it is a good method of precision soft lithography for 2D/3D microstructures.
文摘A novel hybrid process for surface fluorination of polymers is being introduced. The process is based on ultra violet (UV) laser radiation, which on the one hand forms radicals out of an atmosphere of a partially fluorinated benzene, and on the other hand activates a polymer surface in the areas where the UV radiation hits the surface. The radicals can react with the polymer surface, hence altering the surface energy. With this process, a fluorine content of over 30% on the surface of bulk polystyrene can be achieved, while the smallest possible structure size was smaller than 1 mm.
基金supported by the National Natural Science Foundation of China(NSFC)(No.61975168)
文摘High-power continuous-wave ultraviolet lasers are useful for many applications.As ultraviolet laser sources,the wavelength switching capability and compact structure are very important to extend the applicability and improve the flexibility in practical applications.In this work,we present two simple and relatively compact schemes by laser diode pumping to obtain a watt-level single-wavelength 348.7-nm laser and discrete wavelength tunable ultraviolet lasers around 349 nm(from 334.7 to 364.5 nm)by intracavity frequency doubling based on Pr^(3+):YLF andβ-BBO crystals.The maximum output power of the single-wavelength 348.7-nm laser is 1.033 W.The output powers of the discrete wavelength tunable lasers are at the level of tens of milliwatts,except for two peaks at 348.7 and 360.3 nm with output powers of approximately 500 mW.In addition,simulations are carried out to explain the experimental results and clarify the tuning mechanisms.
基金supported by National Natural Science Foundation of China(Nos.61427812,61805118,12104216 and 12241403)the Natural Science Foundation of Jiangsu Province of China(Nos.BK20192006,BK20180056 and BK20200307)。
文摘We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on the emission spectra centered around 6.7 nm from thin-film Gd targets were first investigated.It is found that the conversion efficiency of the produced plasma is saturated when the laser intensity goes beyond 2×10^(11)W cm^(-2).We have systematically compared the emission spectra of the laser-produced plasma with the changes in the thicknesses of the thin-film Gd targets.It is proved that a minimum-mass target with a thickness of 400 nm is sufficient to provide the maximum conversion efficiency,which also implies that this thickness is the ablation depth for the targets.These findings should be helpful in the exploration of next-generation EUV sources,as the thin-film Gd targets will reduce the debris during the plasma generation process compared with the bulk targets.
基金National Natural Science Foundation of China(Grant Nos.62005276,62175234)the Scientific and Technological Development Program of Jilin,China(Grant No.20230508111RC)to provide fund for this research。
文摘Laser anti-drone technology is entering the sequence of actual combat,and it is necessary to consider the vulnerability of typical functional parts of UAVs.Since the concept of"vulnerability"was proposed,a variety of analysis programs for battlefield targets to traditional weapons have been developed,but a comprehensive assessment methodology for targets'vulnerability to laser is still missing.Based on the shotline method,this paper proposes a method that equates laser beam to shotline array,an efficient vulnerability analysis program of target to laser is established by this method,and the program includes the circuit board and the wire into the vulnerability analysis category,which improves the precision of the vulnerability analysis.Taking the UAV engine part as the target of vulnerability analysis,combine with the"life-death unit method"to calculate the laser penetration rate of various materials of the UAV,and the influence of laser weapon system parameters and striking orientation on the killing probability is quantified after introducing the penetration rate into the vulnerability analysis program.The quantitative analysis method proposed in this paper has certain general expansibility,which can provide a fresh idea for the vulnerability analysis of other targets to laser.
基金Funded by the National Natural Science Foundation of China(Nos.51872214 and 52172124)the Fundamental Research Funds for the Central Universities(WUT:2021Ⅲ019JC and 2018Ⅲ041GX)。
文摘Liquid-phase exfoliation was employed to synthesize Sr_(2)Nb_(3)O_(10) perovskite nanosheets with thicknesses down to 1.76 nm.Transmission electron microscopy(TEM),atomic force microscope(AFM),X-ray photoelectron spectrometer(XPS),and other characterization techniques were used to evaluate the atomic structure and chemical composition of the exfoliated nanosheets.A UV photodetector based on individual Sr_(2)Nb_(3)O_(10) nanosheets was prepared to demonstrate the application of an ultraviolet(UV) photodetector.The UV photodetector exhibited outstanding photocurrent and responsivity with a responsivity of 3×10^(5) A·W^(-1) at 5 V bias under 280 nm illumination,a photocurrent of 60 nA,and an on/off ratio of 3×10^(2).
文摘Ultraviolet radiation by its wavelength is divided into: UVA, UVB and UVC. Only UVA and UVB manage to penetrate the ozone layer, but due to anthropological activities, all of them are capable of interacting with humans to a greater or lesser extent, and can generate adverse effects such as cellular stress when interacting with intra-and extracellular biomolecules. The skin is the first organ in contact with UV radiation, and the stress it generates can be analyzed by the expression of a bioindicator of cellular damage such as Hsp70. Therefore, the objective of the project was: to determine the effect of UVA, UVB and UVC radiation on HaCaT epithelial cells, by analyzing the expression of Hsp70. Materials and methods: HaCaT cells were cultured in vitro, which were irradiated with UVA, UVB and UVC light at different doses, to subsequently determine the degree of Hsp70 expression by Immunodetection by PAGE-SDS and Western Blot. Results: Basal expression of Hsp70 was observed in no irradiated HaCaT cells. When HaCaT cells were irradiated with UVA, UVB, UVC, an increase in this Hsp70 protein was observed. With UVA, a higher degree of expression was observed at a time of 30 minutes of irradiation. With UVB the highest expression shifted to a time of 20 minutes. With UVC, overexpression was observed after 10 minutes. Conclusion: UV radiation generates cellular stress on HaCaT cells, evaluated by the stress bioindicator Hsp70. According to the wavelength of UV radiation, those that have a shorter wavelength have a greater potential for cellular damage, such as UVC.
基金This work was supported by National Key R&D Program of China(2022YFB3605103)the National Natural Science Foundation of China(62204241,U22A2084,62121005,and 61827813)+3 种基金the Natural Science Foundation of Jilin Province(20230101345JC,20230101360JC,and 20230101107JC)the Youth Innovation Promotion Association of CAS(2023223)the Young Elite Scientist Sponsorship Program By CAST(YESS20200182)the CAS Talents Program(E30122E4M0).
文摘240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.
基金Nanjing University of Posts and Telecommunications Foundation(Grant Nos.JUH219002 and JUH219007)Key Laboratory of Functional Crystals and Laser Technology,TIPC,CAS Foundation(Grant No.FCLT 202201)。
文摘We report a high-average-power acousto-optic(AO)Q-switched intracavity frequency-doubled red laser based on a high-efficiency light-emitting-diode(LED)pumped two-rod Nd,Ce:YAG laser module.Under quasi-continuous wave operation conditions,a maximum output power of 1319.08 nm wavelength was achieved at 11.26 W at a repetition rate of 100 Hz.
基金supported by the National Key R&D Program of China,No.2022YFB4601201.
文摘The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62175116 and 91950105)the 1311 Talent Plan of Nanjing University of Posts and Telecommunications, Chinathe Postgraduate Research & Practice Innovation Program, Jiangsu Province, China (Grant No. SJCX21_0276)
文摘We present a Brillouin–Raman random fiber laser(BRRFL)with full-open linear cavity structure to generate broadband Brillouin frequency comb(BFC)with double Brillouin-frequency-shift spacing.The incorporation of a regeneration portion consisting of an erbium-doped fiber and a single-mode fiber enables the generation of broadband BFC.The dynamics of broadband BFC generation changing with the pump power(EDF and Raman)and Brillouin pump(BP)wavelength are investigated in detail,respectively.Under suitable conditions,the bidirectional BRRFL proposed can produce a flatamplitude BFC with 40.7-nm bandwidth ranging from 1531 nm to 1571.7 nm,and built-in 242-order Brillouin Stokes lines(BSLs)with double Brillouin-frequency-shift spacing.Moreover,the linewidth of single BSL is experimentally measured to be about 2.5 kHz.The broadband bidirectional narrow-linewidth BRRFL has great potential applications in optical communication,optical sensing,spectral measurement,and so on.
文摘A time-dependent analytical solution is found for the velocity of a plane ionization wave generated under nanosecond laser pulse action on the surface of a flat layer of low-Z porous substance with density less than the critical density of the produced plasma.With corrections for the two-dimensional nature of the problem when a laser beam of finite radius interacts with a flat target,this solution is in quantitative agreement with measurements of ionization wave velocity in various experiments.The solution compared with experimental data covering wide ranges of performance conditions,namely,(3-8)×10^(14)W cm^(−2)for laser pulse intensity,0.3-3 ns for pulse duration,0.35-0.53μm for laser wavelength,100-1000μm for laser beam radius,380-950μm for layer thickness,4.5-12 mg cm^(−3)for average density of porous substance,and 1-25μm for average pore size.The parameters of the laser beam that ensure the generation of a plane ionization wave in a layer of subcritical porous matter are determined for the problem statements and are found to meet the requirements of practical applications.
