Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with dr...Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mellow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.展开更多
As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been invest...As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.展开更多
The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The m...The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.展开更多
Wide-field linear structured illumination microscopy(LSIM)extends resolution beyond the diffraction limit by moving unresolvable high-frequency information into the passband of the microscopy in the form of moiré...Wide-field linear structured illumination microscopy(LSIM)extends resolution beyond the diffraction limit by moving unresolvable high-frequency information into the passband of the microscopy in the form of moiréfringes.However,due to the diffraction limit,the spatial frequency of the structured illumination pattern cannot be larger than the microscopy cutoff frequency,which results in a twofold resolution improvement over wide-field microscopes.This Letter presents a novel approach in point-scanning LSIM,aimed at achieving higher-resolution improvement by combining stimulated emission depletion(STED)with point-scanning structured illumination microscopy(ps SIM)(STED-ps SIM).The according structured illumination pattern whose frequency exceeds the microscopy cutoff frequency is produced by scanning the focus of the sinusoidally modulated excitation beam of STED microscopy.The experimental results showed a 1.58-fold resolution improvement over conventional STED microscopy with the same depletion laser power.展开更多
Stimulated photoluminescence (PL) emission has been observed from an oxide structure of silicon when optically excited by a radiation of 514nm laser. Sharp twin peaks at 694 and 692nm are dominated by stimulated emi...Stimulated photoluminescence (PL) emission has been observed from an oxide structure of silicon when optically excited by a radiation of 514nm laser. Sharp twin peaks at 694 and 692nm are dominated by stimulated emission, which can be demonstrated by its threshold behaviour and linear transition of emission intensity as a function of pump power. The oxide structure is formed by laser irradiation on silicon and its annealing treatment. A model for explaining the stimulated emission is proposed, in which the trap states of the interface between an oxide of silicon and porous nanocrystal play an important role.展开更多
This paper studies power dependent photoluminescence spectra, the stimulated emission occurring at ultraviolet (UV) band instead of the green emission band of ZnO nanowires, which are prepared with a chemical reduct...This paper studies power dependent photoluminescence spectra, the stimulated emission occurring at ultraviolet (UV) band instead of the green emission band of ZnO nanowires, which are prepared with a chemical reduction method. The dynamics of the UV emission and green emission is given to demonstrate the reason of stimulated emission occurring at UV band but not the green emission band under high excitation, which indicates that the slow decay rate of trap state makes it easy to be fully filled and saturated, while the fast decay rate of near-band-edge exciton state makes the UV emission dominate the radiative recombination under high excitation. The UV emission, as well as the corresponding stimulated emission, occurs in competition with the green deep-trap emission. In addition, when pump fluence further increases, the multiple lasing modes appear. The dependence of these lasing modes on the pump fluence is first discussed. This diagram should be helpful to understand and design the optical nanodevices of ZnO nanowires.展开更多
Stimulated emission can be controlled by a material molecular energy band and the intensity of a pump laser, which can provide some population inversion and promote ground electron transition, respectively. We use a m...Stimulated emission can be controlled by a material molecular energy band and the intensity of a pump laser, which can provide some population inversion and promote ground electron transition, respectively. We use a metallic optofluidic resonator to enhance stimulated emission intensity. The quality factor Q and the spontaneous emission coupling factor β of the metallic optofluidic resonator are discussed in detail to explain the enhancement mechanism. Experimental data demonstrate that the operated emission from rhodamin 6G solution can be observed due to the enhancement of stimulated emission from the optofluidic resonator.展开更多
As an essential part in the toolbox of super-resolution microscopy,stimulated emission depletion(STED)nanoscopy has been widely explored in revealing the substructure and bioactivities in fluorescence imaging.Among th...As an essential part in the toolbox of super-resolution microscopy,stimulated emission depletion(STED)nanoscopy has been widely explored in revealing the substructure and bioactivities in fluorescence imaging.Among the applied STED fluorophores,silicon-substituted rhodamines(SiRs)belong to one of the most extensively employed fluorophores.The carboxy-SiR was favored in STED bioimaging with many advantages,including reliable photostability,cell permeability,tunable fluorogenicity,feasible structural decoration and so on.We reviewed the research of carboxy-SiR in the STED nanoscopy and hopefully this can inspire more efforts in the design and application of STED fluorophores.展开更多
A stimulated emission depletion is capable of breaking the diffraction limit by exciting fluorescent molecules with a solid Gaussian beam and quenching the excited molecules with another donut beam through stimulated ...A stimulated emission depletion is capable of breaking the diffraction limit by exciting fluorescent molecules with a solid Gaussian beam and quenching the excited molecules with another donut beam through stimulated emission.The coincidence degree of these two beams in three dimensions will significantly influence the spatial resolution of the microscope.However,the conventional alignment approach based on raster scanning of gold nanoparticles by the two laser beams separately suffers from a mismatch between fluorescence and scattering modes.To circumvent the above problems,we demonstrate a fast alignment design by scanning the second beam over the fabricated sample,which is made of aggregation-induced emission(AIE)dye resin.The relative positions of solid and donut laser beams can be represented by the fluorescent AIE from the labeled spots in the dye resin.This design achieves ultra-high resolutions of 22 nm in the x/y relative displacement and 27 nm in the z relative displacement for fast spatial matching of the two laser beams.This study has potential applications in scenarios that require the spatial matching of multiple laser beams,and the field of views of different objectives,for example,in a microscope with high precision.展开更多
Near-infrared stimulated emission from a high-quality InN layer under optical pumping was observed with a threshold excitation power density of 0.3 and 4 kW cm^(−2) at T=8 and 77 K,respectively.To achieve such a low t...Near-infrared stimulated emission from a high-quality InN layer under optical pumping was observed with a threshold excitation power density of 0.3 and 4 kW cm^(−2) at T=8 and 77 K,respectively.To achieve such a low threshold power density,vicinal GaN substrates were used to reduce the edge-component threading dislocation(ETD)density of the InN film.Cross-sectional transmission electron microscopy images reveal that the annihilation of ETDs can be divided into two steps,and the ETD density can be reduced to approximately 5×10^(8) cm^(−2) near the surface of the 5-μm-thick film.The well-resolved phonon replica of the band-to-band emission in the photoluminescence spectra at 9 K confirm the high quality of the InN film.As a result,the feasibility of InN-based photonic structures and the underlying physics of their growth and emission properties are demonstrated.展开更多
An extraordinary(X-mode)electromagnetic wave,injected into the ionosphere by the ground-based heating facility at Tromsφ,Norway,was utilized to modify the ionosphere on November 6,2017.The high-power high-frequency t...An extraordinary(X-mode)electromagnetic wave,injected into the ionosphere by the ground-based heating facility at Tromsφ,Norway,was utilized to modify the ionosphere on November 6,2017.The high-power high-frequency transmitter facility located at Tromsφ belongs to the European Incoherent Scatter Scientific Association.In the experiment,stimulated electromagnetic emission(SEE)spectra were observed.A narrow continuum occurred under cold-start conditions and showed an overshoot effect lasting several seconds.Cascading peaks occurred on both sides of the heating frequency only in the preconditioned ionosphere and also showed an overshoot effect.These SEE features are probably related to the ponderomotive process in the X-mode heating experiment and are helpful for understanding the physical mechanism that generated them during the X-mode heating experiment.The features observed in the X-mode heating experiments are novel and require further investigation.展开更多
Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence (PL) emission with the stimulated emission observed at about 700 nm. It is difficult t...Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence (PL) emission with the stimulated emission observed at about 700 nm. It is difficult to distinguish between the photoluminescence peaks emitted from samples prepared in different atmospheres. The reason for the appearance of similar peaks may be the similar distribution of the localised states in the gap for different samples when silicon dangling bonds of quantum dots are passivated by nitrogen or oxygen. It is revealed that both the kind and the density of passivated bonds on quantum dot surface prepared in oxygen or nitrogen have a strong influence on the enhancement of PL emission.展开更多
Hematologic malignancies are one of the most common malignant tumors caused by the clonal proliferation and differentiation of hematopoietic and lymphoid stem cells.The examination of bone marrow cells combined with i...Hematologic malignancies are one of the most common malignant tumors caused by the clonal proliferation and differentiation of hematopoietic and lymphoid stem cells.The examination of bone marrow cells combined with immunodeficiency typing is of great significance to the diagnostic type,treatment and prognosis of hematologic malignancies.Super-resolution fluorescence microscopy(SRM)is a special kind of optical microscopy technology,which breaks the resolution limit and was awarded the Nobel Prize in Chemistry in 2014.With the development of SRM,many related technologies have been applied to the diagnosis and treatment of clinical diseases.It was reported that a major type of SRM technique,single molecule localization microscopy(SMLM),is more sensitive than flow cytometry(FC)in detecting cell membrane antigens'expression,thus enabling better chances in detecting antigens on hematopoietic cells than traditional analytic tools.Furthermore,SRM may be applied to clinical pathology and may guide precision medicine and personalized medicine for clone hematopoietic cell diseases.In this paper,we mainly discuss the application of SRM in clone hematological malignancies.展开更多
A stimulated emission depletion (STED) microscopy scheme using axially symmetric polarized vortex beams is pro- posed based on unique focusing properties of such kinds of beams. The concept of axially symmetric pola...A stimulated emission depletion (STED) microscopy scheme using axially symmetric polarized vortex beams is pro- posed based on unique focusing properties of such kinds of beams. The concept of axially symmetric polarized vortex beams is first introduced, and the basic principle about the scheme is described. Simulation results for several typical beams are then shown, including radially polarized vortex beams, azimuthally polarized vortex beams, and high-order axi- ally symmetric polarized vortex beams. The results indicate that sharper doughnut spots and thus higher resolutions can be achieved, showing more flexibility than previous schemes based on flexible modulation of both phase and polarization for incident beams.展开更多
Ridge InGaN multi-quantum-well-structure (MQW) edge-emitting laser diodes (LDs) were grown on (0001) sapphire substrates by low-pressure metal-organic chemical vapour deposition (MOCVD). The dielectric TiO2/Si...Ridge InGaN multi-quantum-well-structure (MQW) edge-emitting laser diodes (LDs) were grown on (0001) sapphire substrates by low-pressure metal-organic chemical vapour deposition (MOCVD). The dielectric TiO2/SiO2 front and back facet coatings as cavity mirror facets of the LDs have been deposited with electron-beam evaporation method. The reflectivity of the designed front coating is about 50% and that of the back high reflective coating is as high as 99.9%. Under pulsed current injection at room temperature, the influences of the dielectric facets were discussed. The threshold current of the ridge GaN-based LDs was decreased after the deposition of the back high reflective dielectric mirrors and decreased again after the front facets were deposited. Above the threshold, the slope efficiency of the LDs with both reflective facets was larger than those with only back facets and without any reflective facets. It is important to design the reflectivity of the front facets for improving the performance of GaN-based LDs.展开更多
On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ...On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ratios and stimulated emission integrated cross sections between the two excited J manifolds of Tm 3+ , and discussed potentiality for the usage of this crystal as a laser material.展开更多
Far-¯eld°uorescence microscopy has made great progress in the spatial resolution,limited by light diffraction,since the super-resolution imaging technology appeared.And stimulated emission depletion(STED)mic...Far-¯eld°uorescence microscopy has made great progress in the spatial resolution,limited by light diffraction,since the super-resolution imaging technology appeared.And stimulated emission depletion(STED)microscopy and structured illumination microscopy(SIM)can be grouped into one class of the super-resolution imaging technology,which use pattern illumination strategy to circumvent the di®raction limit.We simulated the images of the beads of SIM imaging,the intensity distribution of STED excitation light and depletion light in order to observe effects of the polarized light on imaging quality.Compared to¯xed linear polarization,circularly polarized light is more suitable for SIM on reconstructed image.And right-handed circular polarization(CP)light is more appropriate for both the excitation and depletion light in STED system.Therefore the right-handed CP light would be the best candidate when the SIM and STED are combined into one microscope.Good understanding of the polarization will provide a reference for the patterned illumination experiment to achieve better resolution and better image quality.展开更多
.In the past decade,lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode,solar cell,photodetector,and laser,due to their low-cost synthesis method,tunable ba....In the past decade,lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode,solar cell,photodetector,and laser,due to their low-cost synthesis method,tunable bandgap,high quantum yield,large absorption,gain coefficient,and low trap-state densities.In this review,we present a comprehensive discussion of lead halide perovskite applications,with an emphasis on recent advances in synthetic strategies,morphology control,and lasing performance.In particular,the synthetic strategies of solution and vapor progress and the morphology control of perovskite nanocrystals are reviewed.Furthermore,we systematically discuss the latest development of perovskite laser with various fundamental performances,which are highly dependent on the dimension and size of nanocrystals.Finally,considering current challenges and perspectives on the development of lead halide perovskite nanocrystals,we provide an outlook on achieving high-quality lead perovskite lasers and expanding their practical applications.展开更多
Strong multi-order forward stimulated Brillouin scattering (SBS) has been observed in the backward pumped S-band distributed fiber Raman amplifier (PRA) with tunable narrow signal source (less than 100 MHz) when the p...Strong multi-order forward stimulated Brillouin scattering (SBS) has been observed in the backward pumped S-band distributed fiber Raman amplifier (PRA) with tunable narrow signal source (less than 100 MHz) when the pump power of FRA reached the SBS threshold. This does not obey the theory that only weak backward SBS lines exist according to the conservation of energy and momentum and the wave vector selected rule. This is because the sound waveguide characteristic weakens the wave vector rule, and the forward transmitted sound waveguide Brillouin scattering lines are generated and amplified in FRA. When the pump power is further increased, 11 orders of SBS lines and comb-like profile are observed. For the excited line, the frequency is 197.2296 THz and the power is 0 dBm. The even order SBS lines are stronger than odd order SBS lines, the power of the 2nd and 4th order SBS lines is 1.75 dBm, which is 16 dB higher than that of the 1st and 3rd order SBS lines. The odd order SBS lines are named Brillouin Rayleigh scattering lines.展开更多
Sm^(3+) ions incorporated Sm_(2)Si_(2)O_(7) crystalline phase formed in the aluminoborosilicate glass matrix synthesized via melting quenching technique followed by heat-treatment process is reported herewith.The prel...Sm^(3+) ions incorporated Sm_(2)Si_(2)O_(7) crystalline phase formed in the aluminoborosilicate glass matrix synthesized via melting quenching technique followed by heat-treatment process is reported herewith.The preliminary confirmation on the obtained glass ceramics was made through X-ray diffration(XRD) studies.Formation of non-bridging oxygens(NBOs) in the glass network and the modes of vibrations of network units we re analyzed through Fourier transform infrared spectroscopy(FTIR) studies.Surface morphology of heat-treated samples at varying temperatures was determined via a field emission scanning electron microscope(FESEM).The absorption studies on heat-treated samples signify the low bandgap values and high Urbach energy values due to improved crystallinity in the glass network.Judd-Ofelt intensity parameters identified for visible absorption transitions follow the trend of Ω_(4)>Ω_(2)>Ω_(6).Excitation and emission studies on heat-treated samples show improvement in their intensities compared to the unheated base glass.The thermal quenching is observed at higher temperatures(540 and 580℃ for 3 h) of heat-treated samples.Calculations based on luminescence spectra including radiative transition probability,stimulated emission cross-section and branching ratio show good results for glass ceramics prior to precursor glass.Longer lifetimes of Sm^(3+) ions(milliseconds) in the level ^(4)G_(5/2) are seen for glass ceramics.Color coordinates suggest the reddish-orange emissions from prepared glass ceramics.Thus,Sm^(3+) doped Sm_(2)Si_(2)O_(7) glass ceramics are favorable materials for solid-state lighting and laser applications.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10334010 10304001, 10521002, 10434020, 10328407 and 90501007). We are grateful to Professor Zhang J X for her helpful discussions.
文摘Absorption and refraction of the inner transition F2 ←→F3 of the closed four level N-type atom have been investigated under a weak field. The outer transitions F1←→F3 and F2←→F4 are resonantly interacted with drive field with frequency ωc and Rabi frequency Ωc, and saturation field with ωs and Ωs, respectively. For the suitable Rabi frequencies Ωc and Ωs, we obtain the Mellow absorption spectrum of probe field. The reason is that the drive field excites the atom to the upper level F3 and simultaneously the saturation field takes the atom out of the lower level F2, leading to the stimulated emission. Meanwhile, due to the dynamic energy splitting induced by the drive and saturation fields, the two- and four-peaked absorption spectra are observed. At the zero off-resonance detuning of probe field, we also find the transfer of dispersion from negative to positive with an increment of Ωs. Finally, the refractive index enhancement is predicted for a wide spectral region.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11672229 and 61378083)International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+4 种基金Major Research Plan of the National Natural Science Foundation of China(Grant No.91123030)Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110and 2013SZS03-Z01)Natural Science Basic Research Program of Shaanxi Province-Major Basic Research Project,China(Grant No.2016ZDJC-15)Young Scientist Fund of the National Natural Science Foundation of China(Grant No.11504294)the Youth Talent Plan of the Natural Science Foundation of Shaanxi Province of China(Grant No.2016JQ103)
文摘As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuous- wave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.
文摘The optical nonlinearity in polycrystalline zinc selenide(ZnSe),excited with 775 nm,1 kHz femtosecond laser pulses was investigated via the nonlinear transmission with material thickness and the Z scan technique.The measured two photon absorption coefficientβwas intensity dependent,inferring that reverse saturated absorption(RSA)is also relevant dur-ing high intensity excitation in ZnSe.At low peak intensity I<5 GW cm^(-2),we findβ=3.5 cm GW^(-1) at 775 nm.The spec-tral properties of the broad blueish two-photon induced fluorescence(460 nm-500 nm)was studied,displaying self-ab-sorption near the band edge while the upper state lifetime was measured to be τ_(e)~3.3 ns.Stimulated emission was ob-served when pumping a 0.5 mm thick polycrystalline ZnSe sample within an optical cavity,confirmed by significant line narrowing fromΔλ=11 nm(cavity blocked)toΔλ=2.8 nm at peak wavelength λ_(p)=475 nm while the upper state life-time also decreased.These results suggest that with more optimum pumping conditions and crystal cooling,polycrystal-line ZnSe might reach lasing threshold via two-photon pumping atλ=775 nm.
基金supported by the National Natural Science Foundation of China(Nos.62275168,62275164,61775148,and 61905145)the National Key Research and Development Program of China(No.2022YFA1206300)+5 种基金the Guangdong Natural Science Foundation and Province Project(Nos.2021A1515011916 and 2023A1515012250)the Foundation from Department of Science and Technology of Guangdong Province(No.2021QN02Y124)the Foundation from Department of Education of Guangdong Province(No.2023ZDZX2052)the Shenzhen Science and Technology R&D and Innovation Foundation(No.JCYJ20200109105608771)the Shenzhen Key Laboratory of Photonics and Biophotonics(No.ZDSYS20210623092006020)the Medical-Engineering Interdisciplinary Research Foundation of Shenzhen University。
文摘Wide-field linear structured illumination microscopy(LSIM)extends resolution beyond the diffraction limit by moving unresolvable high-frequency information into the passband of the microscopy in the form of moiréfringes.However,due to the diffraction limit,the spatial frequency of the structured illumination pattern cannot be larger than the microscopy cutoff frequency,which results in a twofold resolution improvement over wide-field microscopes.This Letter presents a novel approach in point-scanning LSIM,aimed at achieving higher-resolution improvement by combining stimulated emission depletion(STED)with point-scanning structured illumination microscopy(ps SIM)(STED-ps SIM).The according structured illumination pattern whose frequency exceeds the microscopy cutoff frequency is produced by scanning the focus of the sinusoidally modulated excitation beam of STED microscopy.The experimental results showed a 1.58-fold resolution improvement over conventional STED microscopy with the same depletion laser power.
基金supported by the National Natural Science Foundation of China (Grant No 10764002)
文摘Stimulated photoluminescence (PL) emission has been observed from an oxide structure of silicon when optically excited by a radiation of 514nm laser. Sharp twin peaks at 694 and 692nm are dominated by stimulated emission, which can be demonstrated by its threshold behaviour and linear transition of emission intensity as a function of pump power. The oxide structure is formed by laser irradiation on silicon and its annealing treatment. A model for explaining the stimulated emission is proposed, in which the trap states of the interface between an oxide of silicon and porous nanocrystal play an important role.
基金Project supported by the National Natural Science Foundation of China (Grant No 20173073), National 973 Project (Grant No 2002CB713802), Nano- and Bio-device Key Project of CAS, 985 Project of Hunan University.
文摘This paper studies power dependent photoluminescence spectra, the stimulated emission occurring at ultraviolet (UV) band instead of the green emission band of ZnO nanowires, which are prepared with a chemical reduction method. The dynamics of the UV emission and green emission is given to demonstrate the reason of stimulated emission occurring at UV band but not the green emission band under high excitation, which indicates that the slow decay rate of trap state makes it easy to be fully filled and saturated, while the fast decay rate of near-band-edge exciton state makes the UV emission dominate the radiative recombination under high excitation. The UV emission, as well as the corresponding stimulated emission, occurs in competition with the green deep-trap emission. In addition, when pump fluence further increases, the multiple lasing modes appear. The dependence of these lasing modes on the pump fluence is first discussed. This diagram should be helpful to understand and design the optical nanodevices of ZnO nanowires.
基金National Key R&D Program of China(2013CBA01703,2017YFA0303700)National Natural Science Foundation of China(NSFC)(11734011,61235009)
文摘Stimulated emission can be controlled by a material molecular energy band and the intensity of a pump laser, which can provide some population inversion and promote ground electron transition, respectively. We use a metallic optofluidic resonator to enhance stimulated emission intensity. The quality factor Q and the spontaneous emission coupling factor β of the metallic optofluidic resonator are discussed in detail to explain the enhancement mechanism. Experimental data demonstrate that the operated emission from rhodamin 6G solution can be observed due to the enhancement of stimulated emission from the optofluidic resonator.
基金supported by the Natural Science Foundation of Shanghai(Nos.19ZR1480000,20ZR1470200)National Natural Science Foundation of China(No.81830106)the Program for Professor of Special Appointment(Eastern Scholar,No.TP2017039)。
文摘As an essential part in the toolbox of super-resolution microscopy,stimulated emission depletion(STED)nanoscopy has been widely explored in revealing the substructure and bioactivities in fluorescence imaging.Among the applied STED fluorophores,silicon-substituted rhodamines(SiRs)belong to one of the most extensively employed fluorophores.The carboxy-SiR was favored in STED bioimaging with many advantages,including reliable photostability,cell permeability,tunable fluorogenicity,feasible structural decoration and so on.We reviewed the research of carboxy-SiR in the STED nanoscopy and hopefully this can inspire more efforts in the design and application of STED fluorophores.
基金supported by the National Key Research and Development Program of China(No.2018YFB0704103)National Natural Science Foundation of China(No.62175153)。
文摘A stimulated emission depletion is capable of breaking the diffraction limit by exciting fluorescent molecules with a solid Gaussian beam and quenching the excited molecules with another donut beam through stimulated emission.The coincidence degree of these two beams in three dimensions will significantly influence the spatial resolution of the microscope.However,the conventional alignment approach based on raster scanning of gold nanoparticles by the two laser beams separately suffers from a mismatch between fluorescence and scattering modes.To circumvent the above problems,we demonstrate a fast alignment design by scanning the second beam over the fabricated sample,which is made of aggregation-induced emission(AIE)dye resin.The relative positions of solid and donut laser beams can be represented by the fluorescent AIE from the labeled spots in the dye resin.This design achieves ultra-high resolutions of 22 nm in the x/y relative displacement and 27 nm in the z relative displacement for fast spatial matching of the two laser beams.This study has potential applications in scenarios that require the spatial matching of multiple laser beams,and the field of views of different objectives,for example,in a microscope with high precision.
基金partially supported by the National Natural Sci-ence Foundation of China(Grants No.61734001,61774004 and 61904002)the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH0120191000103)the Science Challenge Project(Grant No.TZ2018003).
文摘Near-infrared stimulated emission from a high-quality InN layer under optical pumping was observed with a threshold excitation power density of 0.3 and 4 kW cm^(−2) at T=8 and 77 K,respectively.To achieve such a low threshold power density,vicinal GaN substrates were used to reduce the edge-component threading dislocation(ETD)density of the InN film.Cross-sectional transmission electron microscopy images reveal that the annihilation of ETDs can be divided into two steps,and the ETD density can be reduced to approximately 5×10^(8) cm^(−2) near the surface of the 5-μm-thick film.The well-resolved phonon replica of the band-to-band emission in the photoluminescence spectra at 9 K confirm the high quality of the InN film.As a result,the feasibility of InN-based photonic structures and the underlying physics of their growth and emission properties are demonstrated.
基金supported by the National Natural Science Foundation of China(grant numbers 41204111,41574146,41774162,and 41704155)the China Postdoctoral Science Foundation(grant numbers 2017M622504 and2019T120679)supported through the Russian Education Ministry(project number3.1844.2017)
文摘An extraordinary(X-mode)electromagnetic wave,injected into the ionosphere by the ground-based heating facility at Tromsφ,Norway,was utilized to modify the ionosphere on November 6,2017.The high-power high-frequency transmitter facility located at Tromsφ belongs to the European Incoherent Scatter Scientific Association.In the experiment,stimulated electromagnetic emission(SEE)spectra were observed.A narrow continuum occurred under cold-start conditions and showed an overshoot effect lasting several seconds.Cascading peaks occurred on both sides of the heating frequency only in the preconditioned ionosphere and also showed an overshoot effect.These SEE features are probably related to the ponderomotive process in the X-mode heating experiment and are helpful for understanding the physical mechanism that generated them during the X-mode heating experiment.The features observed in the X-mode heating experiments are novel and require further investigation.
基金supported by the National Natural Science Foundation of China (Grant Nos.10764002 and 60966002)the National Key Laboratory of Surface Physics at Fudan University
文摘Silicon quantum dots fabricated by nanosecond pulsed laser in nitrogen, oxygen or air atmosphere have enhanced photoluminescence (PL) emission with the stimulated emission observed at about 700 nm. It is difficult to distinguish between the photoluminescence peaks emitted from samples prepared in different atmospheres. The reason for the appearance of similar peaks may be the similar distribution of the localised states in the gap for different samples when silicon dangling bonds of quantum dots are passivated by nitrogen or oxygen. It is revealed that both the kind and the density of passivated bonds on quantum dot surface prepared in oxygen or nitrogen have a strong influence on the enhancement of PL emission.
基金This work was supported by the Innovation Fund of WNLO(2018WNLOKF023)the Start-up Fund of Hainan University(KYQD(ZR)-20077).
文摘Hematologic malignancies are one of the most common malignant tumors caused by the clonal proliferation and differentiation of hematopoietic and lymphoid stem cells.The examination of bone marrow cells combined with immunodeficiency typing is of great significance to the diagnostic type,treatment and prognosis of hematologic malignancies.Super-resolution fluorescence microscopy(SRM)is a special kind of optical microscopy technology,which breaks the resolution limit and was awarded the Nobel Prize in Chemistry in 2014.With the development of SRM,many related technologies have been applied to the diagnosis and treatment of clinical diseases.It was reported that a major type of SRM technique,single molecule localization microscopy(SMLM),is more sensitive than flow cytometry(FC)in detecting cell membrane antigens'expression,thus enabling better chances in detecting antigens on hematopoietic cells than traditional analytic tools.Furthermore,SRM may be applied to clinical pathology and may guide precision medicine and personalized medicine for clone hematopoietic cell diseases.In this paper,we mainly discuss the application of SRM in clone hematological malignancies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61108047 and 61475021)the Natural Science Foundation of Beijing,China(Grant No.4152015)+2 种基金the Program for New Century Excellent Talents in Universities of China(Grant No.NCET-13-0667)the Top Young Talents Support Program of BeijingChina(Grant No.CIT&TCD201404113)
文摘A stimulated emission depletion (STED) microscopy scheme using axially symmetric polarized vortex beams is pro- posed based on unique focusing properties of such kinds of beams. The concept of axially symmetric polarized vortex beams is first introduced, and the basic principle about the scheme is described. Simulation results for several typical beams are then shown, including radially polarized vortex beams, azimuthally polarized vortex beams, and high-order axi- ally symmetric polarized vortex beams. The results indicate that sharper doughnut spots and thus higher resolutions can be achieved, showing more flexibility than previous schemes based on flexible modulation of both phase and polarization for incident beams.
基金supported by the National High Technology Program of China (Grant No 2007AA03Z403)the National Natural Science Foundation of China (Grant Nos 60776042 and 60477011)National Basic Research Program of China (Grand No2006CB921607)
文摘Ridge InGaN multi-quantum-well-structure (MQW) edge-emitting laser diodes (LDs) were grown on (0001) sapphire substrates by low-pressure metal-organic chemical vapour deposition (MOCVD). The dielectric TiO2/SiO2 front and back facet coatings as cavity mirror facets of the LDs have been deposited with electron-beam evaporation method. The reflectivity of the designed front coating is about 50% and that of the back high reflective coating is as high as 99.9%. Under pulsed current injection at room temperature, the influences of the dielectric facets were discussed. The threshold current of the ridge GaN-based LDs was decreased after the deposition of the back high reflective dielectric mirrors and decreased again after the front facets were deposited. Above the threshold, the slope efficiency of the LDs with both reflective facets was larger than those with only back facets and without any reflective facets. It is important to design the reflectivity of the front facets for improving the performance of GaN-based LDs.
文摘On the basis of the obtained intensity parameters Ω λ(λ =2,4,6) of Tm 3+ in the Na 5Tm(WO 4) 4 crystal, we performed calculations on the radiative transition probability, radiative lifetime, branching ratios and stimulated emission integrated cross sections between the two excited J manifolds of Tm 3+ , and discussed potentiality for the usage of this crystal as a laser material.
基金This work was partly supported by the National Key Basic Research Program of China (973 project)under Grant No.2015CB352006the National Natural Science Foundation of China under Grant Nos.61335011 and 61405035Program for Changjiang Scholars and Innovative Research Team in University under Grant No.IRT 15R10.
文摘Far-¯eld°uorescence microscopy has made great progress in the spatial resolution,limited by light diffraction,since the super-resolution imaging technology appeared.And stimulated emission depletion(STED)microscopy and structured illumination microscopy(SIM)can be grouped into one class of the super-resolution imaging technology,which use pattern illumination strategy to circumvent the di®raction limit.We simulated the images of the beads of SIM imaging,the intensity distribution of STED excitation light and depletion light in order to observe effects of the polarized light on imaging quality.Compared to¯xed linear polarization,circularly polarized light is more suitable for SIM on reconstructed image.And right-handed circular polarization(CP)light is more appropriate for both the excitation and depletion light in STED system.Therefore the right-handed CP light would be the best candidate when the SIM and STED are combined into one microscope.Good understanding of the polarization will provide a reference for the patterned illumination experiment to achieve better resolution and better image quality.
基金This work was supported by the National Key R&D Program of China(2018YFB2200500,2017YFE0123700)the National Natural Science Foundation of China(61975023,61875211,22072010,61925507,61905264,62005296,and 92050203)+5 种基金the Strategic Priority Research Program of CAS(XDB16030400)CAS Interdisciplinary Innovation Team,Program of Shanghai Academic/Technology Research Leader(Grant No.18XD1404200)China Postdoctoral Science Foundation(2020M681421)Chongqing Research Program of Basic Research and Frontier Technology(cstc2018jszxcyzdX0137)the Natural Science Foundation of Chongqing(cstc2019jcyj-msxmX0522)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN201900515).
文摘.In the past decade,lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode,solar cell,photodetector,and laser,due to their low-cost synthesis method,tunable bandgap,high quantum yield,large absorption,gain coefficient,and low trap-state densities.In this review,we present a comprehensive discussion of lead halide perovskite applications,with an emphasis on recent advances in synthetic strategies,morphology control,and lasing performance.In particular,the synthetic strategies of solution and vapor progress and the morphology control of perovskite nanocrystals are reviewed.Furthermore,we systematically discuss the latest development of perovskite laser with various fundamental performances,which are highly dependent on the dimension and size of nanocrystals.Finally,considering current challenges and perspectives on the development of lead halide perovskite nanocrystals,we provide an outlook on achieving high-quality lead perovskite lasers and expanding their practical applications.
文摘Strong multi-order forward stimulated Brillouin scattering (SBS) has been observed in the backward pumped S-band distributed fiber Raman amplifier (PRA) with tunable narrow signal source (less than 100 MHz) when the pump power of FRA reached the SBS threshold. This does not obey the theory that only weak backward SBS lines exist according to the conservation of energy and momentum and the wave vector selected rule. This is because the sound waveguide characteristic weakens the wave vector rule, and the forward transmitted sound waveguide Brillouin scattering lines are generated and amplified in FRA. When the pump power is further increased, 11 orders of SBS lines and comb-like profile are observed. For the excited line, the frequency is 197.2296 THz and the power is 0 dBm. The even order SBS lines are stronger than odd order SBS lines, the power of the 2nd and 4th order SBS lines is 1.75 dBm, which is 16 dB higher than that of the 1st and 3rd order SBS lines. The odd order SBS lines are named Brillouin Rayleigh scattering lines.
基金supported by Department of Science and Technology (DST)-Science and Engineering Research Board (SERB),Government of India(DST-SERB-EMR/2017/001548)。
文摘Sm^(3+) ions incorporated Sm_(2)Si_(2)O_(7) crystalline phase formed in the aluminoborosilicate glass matrix synthesized via melting quenching technique followed by heat-treatment process is reported herewith.The preliminary confirmation on the obtained glass ceramics was made through X-ray diffration(XRD) studies.Formation of non-bridging oxygens(NBOs) in the glass network and the modes of vibrations of network units we re analyzed through Fourier transform infrared spectroscopy(FTIR) studies.Surface morphology of heat-treated samples at varying temperatures was determined via a field emission scanning electron microscope(FESEM).The absorption studies on heat-treated samples signify the low bandgap values and high Urbach energy values due to improved crystallinity in the glass network.Judd-Ofelt intensity parameters identified for visible absorption transitions follow the trend of Ω_(4)>Ω_(2)>Ω_(6).Excitation and emission studies on heat-treated samples show improvement in their intensities compared to the unheated base glass.The thermal quenching is observed at higher temperatures(540 and 580℃ for 3 h) of heat-treated samples.Calculations based on luminescence spectra including radiative transition probability,stimulated emission cross-section and branching ratio show good results for glass ceramics prior to precursor glass.Longer lifetimes of Sm^(3+) ions(milliseconds) in the level ^(4)G_(5/2) are seen for glass ceramics.Color coordinates suggest the reddish-orange emissions from prepared glass ceramics.Thus,Sm^(3+) doped Sm_(2)Si_(2)O_(7) glass ceramics are favorable materials for solid-state lighting and laser applications.