Ultrathin flat metalenses have emerged as promising alternatives to conventional diffractive lenses,offering new possibilities for myriads of miniaturization and interfacial applications.Graphene-based materials can a...Ultrathin flat metalenses have emerged as promising alternatives to conventional diffractive lenses,offering new possibilities for myriads of miniaturization and interfacial applications.Graphene-based materials can achieve both phase and amplitude modulations simultaneously at a single position due to the modification of the complex refractive index and thickness by laser conversion from graphene oxide into graphene like materials.In this work,we develop graphene oxide metalenses to precisely control phase and amplitude modulations and to achieve a holistic and systematic lens design based on a graphene-based material system.We experimentally validate our strategies via demonstrations of two graphene oxide metalenses:one with an ultra-long(~16λ)optical needle,and the other with axial multifocal spots,at the wavelength of 632.8 nm with a 200 nm thin film.Our proposed graphene oxide metalenses unfold unprecedented opportunities for accurately designing graphene-based ultrathin integratable devices for broad applications.展开更多
Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for ...Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for detecting small tumors, located deeply in human tissues, such as the breast. In this study, the sensitivity of existing ultrasonic detection systems has been compared experimentally with that by using thermoelastic waves as a broadband ultrasonic source. For the comparison, an optical stress transducer （OST）, a polyvinylidene difluoride （PVDF） sheet and a calibrated PVDF needle hydrophone were used. To ensure all of the detection systems interrogated by the same ultrasonic field, a small optical instrument that fixed the generating laser head was constructed. The sensitivity was evaluated by measuring signalto-noise ratios （SNRs） and noise equivalent pressures （NEPs）. The PVDF system, with a 4-kPa NEP has a 22 dB better performance than the OST. The OST showed nearly the same sensitivity as the hydrophone for detecting ultrasound waves at a 1-cm distance in water. PVDF detection system provides a useful tool for imaging of soft tissues because of its high sensitivity and broad detection range.展开更多
The effective detection depth of the needle-like optical probe is studied. The light transport model in highly scattering tissue is the diffusion equation and the boundary is Neuman. The sensitivity matrix is related ...The effective detection depth of the needle-like optical probe is studied. The light transport model in highly scattering tissue is the diffusion equation and the boundary is Neuman. The sensitivity matrix is related to the position of the light source and the detector. It can be used to evaluate the effective detection depth. The sensitivity matrix is defined as the multiplication of the source and detector hght distribution. Six different groups about ix parameters including the source diameter and detector fibers, the core-to-core distance between the source and detector fibers, the opotode depth, the absorption, and reduced scattering coefficient, are used as experimental models. The relationship between the six parameters and the effective detection depth is analyzed. Resuits can be used to study the spatial resolution and the depth of multi-fibers.展开更多
The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector ...The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.展开更多
Hypoxia is a disorder in which the tissues are not oxygenated adequately.The lack of oxygen may cause irreversible damage to the major organs such as the brain,heart and lungs.In severe cases,coma,seizures,and death m...Hypoxia is a disorder in which the tissues are not oxygenated adequately.The lack of oxygen may cause irreversible damage to the major organs such as the brain,heart and lungs.In severe cases,coma,seizures,and death may happen.In addition to the routine medication,acupuncture.treatment has been applied as a complementary treatment to counter hypoxia.In this paper,the optical fiber acupuncture needle was fabricated using the optical fiber imbedding into the metal capillary tube with needle tip,therefore made it easy to insert into the body for the laser treatment.The laser optical fiber needle treatment to the ST36 acupoint conducted with the laser.irradiation intra body.The normobaric hypoxia tolerance test results in mice show that the optical fber needle treatment to the ST36 acupoint with laser acupuncture appears to improve the tolerance to hypoxia.The mice treated with laser acupuncture expressed high level of IL-1βin serum.Our results suggest that laser optical fiber needle acupuncture may serve as a potential treatment for hypoxia.展开更多
In this study, a dielectric barrier discharge device with needle-plate electrodes was used to investigate the characteristics of the micro-discharge in argon at one atmospheric pressure by an optical method. The resul...In this study, a dielectric barrier discharge device with needle-plate electrodes was used to investigate the characteristics of the micro-discharge in argon at one atmospheric pressure by an optical method. The results show that there are two discharge modes in the dielectric barrier discharge, namely corona mode and filamentary mode. The corona discharge only occurs in the vicinity of the needle tip when the applied voltage is very low. However, the filamentary discharge mode can occur, and micro-discharge bridges the two electrodes when the applied voltage reaches a certain value. The extended area of micro-discharge on the dielectric plate becomes larger with the increase in applied voltage or decrease in gas pressure. The variance of the light emission waveforms is studied as a function of the applied voltage. Results show that very narrow discharge pulse only appears at the negative half cycle of the applied voltage in the corona discharge mode. However, broad hump （about several microseconds） can be discerned at both the negative half cycle and the positive half cycle for a high voltage in the filamentary mode. Furthermore, the inception voltage decreases and the width of the discharge hump increases with the increase in applied voltage. These experimental phenomena can be explained qualitatively by analyzing the discharge mechanism.展开更多
The emission spectra of excited radicals（OH（A^2E）,O（3p^3 P）,Hα（3P）） and emissive species（N2^＋（B^2∑u^＋）,N2（C3Πu）） produced by positive pulsed high-voltage needle-plane corona discharges in atmospheri...The emission spectra of excited radicals（OH（A^2E）,O（3p^3 P）,Hα（3P）） and emissive species（N2^＋（B^2∑u^＋）,N2（C3Πu）） produced by positive pulsed high-voltage needle-plane corona discharges in atmospheric N2 and O2 flows wetted with 10%H2O at 80 ℃ are used to investigate the relative concentrations of the produced radicals.The results indicate that the tendencies of the concentrations of radicals with discharge conditions are similar to each other due to their similar excitation processes by electron collision.The influence of oxygen flow mixed with the nitrogen flow on the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2S）,N2＋（B^2∑u^＋ → X^2∑g＋0-0）,and N2（C^3Πu → B^3Πg 1-0） is presented.When the flow rate of oxygen addition is varied from 0-30 ml min^-1,the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2s）,and N2^＋（B^2∑u^＋ →X^2∑g 0-0） increase and reach a maximum.Then,if the oxygen flow rate increases further,the emission intensities tend to decrease.However,the intensity of N2（C^3Πu → B^3Πg1-0） decreases monotonously with the increasing oxygen flow,which indicates that the electron density decreases with the increasing oxygen flow.By the tendencies of the relative intensities to N2（C^3Πu → B^3Πg 1-0）,the concentrations of the total produced O,H,and N2^＋ are shown to increase with the oxygen flow.Based on the reactions for the production of H and O without and with the addition of O2,the analytic solutions for H and O production are derived in accordance with the experimental results.展开更多
基金Hongtao Wang acknowledges the support from National Key Research and Development Program of China(2017YFB0403602)China Scholarship Council.Baohua Jia acknowledges the support from the Australian Research Council through the Discovery Projects(DP150102972,DP190103186)+5 种基金the Industrial Transformation Training Centres scheme(Grant No.IC180100005)support from Defence Science Institute(DSI)and Defence Science and Technology Group(DSTG).C.W.Q.acknowledges the support from the National Research Foundation,Prime Minister’s Office,Singapore,under its Competitive Research Programme(CRP award NRF CRP22-2019-0006)Advanced Research and Technology Innovation Centre(ARTIC)under the grant(R-261-518-004-720)A STAR under Advanced Manufacturing and Engineering(AME)Individual Research Grant(IRG A2083c0060)Tian Lan acknowledges National Key Basic Research Program 973 Project(2013CB329202)National Major Scientific Instruments and Equipments Development Project supported by National Natural Science Foundation of China(No.61827814).
文摘Ultrathin flat metalenses have emerged as promising alternatives to conventional diffractive lenses,offering new possibilities for myriads of miniaturization and interfacial applications.Graphene-based materials can achieve both phase and amplitude modulations simultaneously at a single position due to the modification of the complex refractive index and thickness by laser conversion from graphene oxide into graphene like materials.In this work,we develop graphene oxide metalenses to precisely control phase and amplitude modulations and to achieve a holistic and systematic lens design based on a graphene-based material system.We experimentally validate our strategies via demonstrations of two graphene oxide metalenses:one with an ultra-long(~16λ)optical needle,and the other with axial multifocal spots,at the wavelength of 632.8 nm with a 200 nm thin film.Our proposed graphene oxide metalenses unfold unprecedented opportunities for accurately designing graphene-based ultrathin integratable devices for broad applications.
文摘Optoacoustic tomography （PAT） is a two-dimensional medical imaging method that has the advantage of optical contrast and resolution of ultrasonic waves. The detection systems with a high sensitivity can be used for detecting small tumors, located deeply in human tissues, such as the breast. In this study, the sensitivity of existing ultrasonic detection systems has been compared experimentally with that by using thermoelastic waves as a broadband ultrasonic source. For the comparison, an optical stress transducer （OST）, a polyvinylidene difluoride （PVDF） sheet and a calibrated PVDF needle hydrophone were used. To ensure all of the detection systems interrogated by the same ultrasonic field, a small optical instrument that fixed the generating laser head was constructed. The sensitivity was evaluated by measuring signalto-noise ratios （SNRs） and noise equivalent pressures （NEPs）. The PVDF system, with a 4-kPa NEP has a 22 dB better performance than the OST. The OST showed nearly the same sensitivity as the hydrophone for detecting ultrasound waves at a 1-cm distance in water. PVDF detection system provides a useful tool for imaging of soft tissues because of its high sensitivity and broad detection range.
基金Supported by the Natural Science Foundation of Jiangsu Province (BK2009371)the National High Technology Research and Development Program of China ("863" Program) (2008AA02Z438)~~
文摘The effective detection depth of the needle-like optical probe is studied. The light transport model in highly scattering tissue is the diffusion equation and the boundary is Neuman. The sensitivity matrix is related to the position of the light source and the detector. It can be used to evaluate the effective detection depth. The sensitivity matrix is defined as the multiplication of the source and detector hght distribution. Six different groups about ix parameters including the source diameter and detector fibers, the core-to-core distance between the source and detector fibers, the opotode depth, the absorption, and reduced scattering coefficient, are used as experimental models. The relationship between the six parameters and the effective detection depth is analyzed. Resuits can be used to study the spatial resolution and the depth of multi-fibers.
文摘The intensity distribution in the focal region of a high-NA lens for the incident azimuthally polarized multi Gaussian beam transmitted through a multi belt spiral phase hologram is studied on the basis of the vector diffraction theory. Here we report a new method used to generate a needle of transversely polarized light beam with sub diffraction beam size of 0.366A that propagates without divergence over a long distance of about 22A in free space. We also expect that such a light needle of transversely polarized beam may find its applications in utilizing optical materials or instruments responsive to the transversal field only.
基金the Natural Science Foundation of China(NSFC)(61107076,61177088,61475095,61027015 and 31571430)Shanghai Pujiang Program(14PJ1407700)+2 种基金Health and Fam-ily Planning Commission Foundation of Shanghai(201440300)National Program(on Key Basic Research Project(973 Program,2012CB723405,2014CB541804)the Key Laboratory of Specialty Fiber Optics and Optical Access Networks(SKLSF02013-02 and SKLSFO2015-01).
文摘Hypoxia is a disorder in which the tissues are not oxygenated adequately.The lack of oxygen may cause irreversible damage to the major organs such as the brain,heart and lungs.In severe cases,coma,seizures,and death may happen.In addition to the routine medication,acupuncture.treatment has been applied as a complementary treatment to counter hypoxia.In this paper,the optical fiber acupuncture needle was fabricated using the optical fiber imbedding into the metal capillary tube with needle tip,therefore made it easy to insert into the body for the laser treatment.The laser optical fiber needle treatment to the ST36 acupoint conducted with the laser.irradiation intra body.The normobaric hypoxia tolerance test results in mice show that the optical fber needle treatment to the ST36 acupoint with laser acupuncture appears to improve the tolerance to hypoxia.The mice treated with laser acupuncture expressed high level of IL-1βin serum.Our results suggest that laser optical fiber needle acupuncture may serve as a potential treatment for hypoxia.
基金supported by National Natural Science Foundation of China (Nos. 10805013,51077035)the National Natural Science Foundation of Hebei Province,China (No.A2009000149)the Key Project of Chinese Ministry of Education (No. 210014)
文摘In this study, a dielectric barrier discharge device with needle-plate electrodes was used to investigate the characteristics of the micro-discharge in argon at one atmospheric pressure by an optical method. The results show that there are two discharge modes in the dielectric barrier discharge, namely corona mode and filamentary mode. The corona discharge only occurs in the vicinity of the needle tip when the applied voltage is very low. However, the filamentary discharge mode can occur, and micro-discharge bridges the two electrodes when the applied voltage reaches a certain value. The extended area of micro-discharge on the dielectric plate becomes larger with the increase in applied voltage or decrease in gas pressure. The variance of the light emission waveforms is studied as a function of the applied voltage. Results show that very narrow discharge pulse only appears at the negative half cycle of the applied voltage in the corona discharge mode. However, broad hump （about several microseconds） can be discerned at both the negative half cycle and the positive half cycle for a high voltage in the filamentary mode. Furthermore, the inception voltage decreases and the width of the discharge hump increases with the increase in applied voltage. These experimental phenomena can be explained qualitatively by analyzing the discharge mechanism.
基金supported by National Natural Science Foundation of China under Grant No.513377014
文摘The emission spectra of excited radicals（OH（A^2E）,O（3p^3 P）,Hα（3P）） and emissive species（N2^＋（B^2∑u^＋）,N2（C3Πu）） produced by positive pulsed high-voltage needle-plane corona discharges in atmospheric N2 and O2 flows wetted with 10%H2O at 80 ℃ are used to investigate the relative concentrations of the produced radicals.The results indicate that the tendencies of the concentrations of radicals with discharge conditions are similar to each other due to their similar excitation processes by electron collision.The influence of oxygen flow mixed with the nitrogen flow on the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2S）,N2＋（B^2∑u^＋ → X^2∑g＋0-0）,and N2（C^3Πu → B^3Πg 1-0） is presented.When the flow rate of oxygen addition is varied from 0-30 ml min^-1,the emission intensities of O（3p^5P → 3s^5S2^0.）,Hα（3P → 2s）,and N2^＋（B^2∑u^＋ →X^2∑g 0-0） increase and reach a maximum.Then,if the oxygen flow rate increases further,the emission intensities tend to decrease.However,the intensity of N2（C^3Πu → B^3Πg1-0） decreases monotonously with the increasing oxygen flow,which indicates that the electron density decreases with the increasing oxygen flow.By the tendencies of the relative intensities to N2（C^3Πu → B^3Πg 1-0）,the concentrations of the total produced O,H,and N2^＋ are shown to increase with the oxygen flow.Based on the reactions for the production of H and O without and with the addition of O2,the analytic solutions for H and O production are derived in accordance with the experimental results.
