A 1.7-at.%Er:CaF_(2)crystal was synthesized by temperature gradient method.The Er:CaF_(2)crystal was applied in acousto-optically Q-switched laser at mid-infrared region for the first time.Using a Te O_(2)-based cryst...A 1.7-at.%Er:CaF_(2)crystal was synthesized by temperature gradient method.The Er:CaF_(2)crystal was applied in acousto-optically Q-switched laser at mid-infrared region for the first time.Using a Te O_(2)-based crystal as Q-switcher,we obtained a laser diode(LD)end-pumped Er:CaF_(2)laser with the highest single pulse energy up to 0.49 mJ and maximum peak power of 0.56 kW under 6.34-W absorbed pump power.The implication of these results is that the low-doped Er:CaF_(2)crystal exhibits promising optical properties in solid-state lasers.展开更多
Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This st...Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.展开更多
With the development of mid-infrared (MIR) photoelectric devices, mid-infrared spectroscopy has become one of the important methods for non-invasive detection of blood glucose. The mid-infrared region (4000 - 400 cm&l...With the development of mid-infrared (MIR) photoelectric devices, mid-infrared spectroscopy has become one of the important methods for non-invasive detection of blood glucose. The mid-infrared region (4000 - 400 cm<sup>-1</sup>) has the well-known fingerprint region (1200 - 800 cm<sup>-1</sup>) of glucose, which has clearer characteristic absorption peaks and better specificity. There is a lot of molecular information about glucose in the MIR. The non-invasive detection of blood glucose by mid-infrared spectroscopy needs to achieve certain accuracy, and the quantitative model is an important factor affecting the accuracy of glucose detection. In this paper, the samples of imitation solution containing only glucose and the samples of imitation mixed solution are taken as the research objects, and the mid-infrared spectral data of the samples are collected. The full spectrum partial least squares Regression (PLSR) model, SNV + Ctr-PLSR model, MSC + Ctr-PLSR model, and convolutional neural networks (CNN) model of 3000 - 900 cm<sup>-1</sup> band were constructed. Full spectrum PLS model and CNN model of 1200 - 900 cm<sup>-1</sup> band were constructed. The experimental results show that the optimal model of the two bands is CNN, then the correlation coefficient of prediction set (Rp) of 3000 - 900 cm<sup>-1</sup> band is 0.95, and the root mean square error of pre-diction set (RMSEP) value is 22.10. The Rp of 1200 - 900 cm<sup>-1</sup> band is 0.95, and the RMSEP value is 22.54. The research results show that CNN is a promising method, which has higher accuracy than PLSR, and is especially suitable for modeling human complex environment. In addition, the study provides a theoretical and practical basis for CNN in feature selection and model interpretation.展开更多
In recent years,there has been a significant transformation in the field of incoherent imaging with new possibilities of compressing three-dimensional(3D)information into a two-dimensional intensity distribution witho...In recent years,there has been a significant transformation in the field of incoherent imaging with new possibilities of compressing three-dimensional(3D)information into a two-dimensional intensity distribution without two-beam interference(TBI).Most of the incoherent 3D imagers without TBI are based on scattering by a random phase mask exhibiting sharp autocorrelation and low cross-correlation along the depth.Consequently,during reconstruction,high lateral and axial resolutions are obtained.Imaging based on scattering requires an astronomical photon budget and is therefore precluded in many power-sensitive applications.In this study,a proof-of-concept 3D imaging method without TBI using deterministic fields has been demonstrated.A new reconstruction method called the Lucy-Richardson-Rosen algorithm has been developed for this imaging concept.We believe that the proposed approach will cause a paradigm-shift in the current state-of-the-art incoherent imaging,fluorescence microscopy,mid-infrared fingerprinting,astronomical imaging,and fast object recognition applications.展开更多
This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. C...This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.展开更多
A compact prototype based on mid-infrared wavelength modulation spectroscopy(WMS)is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers(QCLs)with central fre...A compact prototype based on mid-infrared wavelength modulation spectroscopy(WMS)is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers(QCLs)with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.展开更多
Efficient thermal radiation in the mid-infrared(M-IR)region is of supreme importance for many applications including thermal imaging and sensing,thermal infrared light sources,infrared spectroscopy,emissivity coatings...Efficient thermal radiation in the mid-infrared(M-IR)region is of supreme importance for many applications including thermal imaging and sensing,thermal infrared light sources,infrared spectroscopy,emissivity coatings,and camouflage.The ability to control light makes metasurfaces an attractive platform for infrared applications.Recently,different metamaterials have been proposed to achieve high thermal radiation.To date,broadening the radiation bandwidth of a metasurface emitter(meta-emitter)has become a key goal to enable extensive applications.We experimentally demonstrate a broadband M-IR thermal emitter using stacked nanocavity metasurface consisting of two pairs of circular-shaped dielectric(Si;N;)–metal(Au)stacks.A high thermal radiation can be obtained by engineering the geometry of nanocavity metasurfaces.Such a meta-emitter provides wideband and broad angular absorptance of both p-and s-polarized light,offering a wideband thermal radiation with an average emissivity of more than 80%in the M-IR atmospheric window of 8–14μm.The experimental illustration together with the theoretical framework establishes a basis for designing broadband thermal emitters,which,as anticipated,will initiate a promising avenue to M-IR sources.展开更多
Based on the rate equations describing the erbium-doped fluoride glass (ZBLAN) fibre lasers with different pumping configurations being taken into account, this paper presents theoretical calculations related to the...Based on the rate equations describing the erbium-doped fluoride glass (ZBLAN) fibre lasers with different pumping configurations being taken into account, this paper presents theoretical calculations related to the dynamic population density and the operation performance of a high power mid-infrared all-fibre erbium-doped ZBLAN fibre laser. It shows that the ground-state absorption, excited-state absorption and energy-transfer-upconversion processes co-exist and produce a population balance, causing the laser to operate stably at a continuous wave state. A good agreement between the theoretical results and recent experimental measurement is obtained. Furthermore, the laser structure parameters including fibre length, reflectance of output fibre Bragg grating and pumping configurations are quantitatively optimised to achieve the best performance. The results show, as expected, that the slope efficiency of the fibre laser can be improved significantly through optimisation, which then provides an important guide for the design of high-performance mid-infrared erbium-doped ZBLAN fibre lasers.展开更多
A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum (SC) is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial s...A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum (SC) is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial signal of the seed laser is provided by the incident pump light and amplified in the cavity. Based on this, we obtain a 2-μm pulsed laser with pulse repetition rate of 50 kHz and pulse width of 2 ns from the Tm-doped fiber laser. This 2-μm pulsed laser is amplified by two stages of fiber amplifiers, then the amplified laser is used for mid-infrared (mid-IR) SC generation in a 10-m length of ZrF4-BaF2-LaF3-AIF3-NaF (ZBLAN) fiber. An all-fiber-integrated mid-IR SC with spectrum ranging from 1.8 ~tm to 4.3 μm is achieved. The maximal average output power of the mid-IR SC from the ZBLAN fiber is 1.24 W (average output power beyond 2.5 μm is 340 mW), corresponding to an output efficiency of 6.6% with respect to the 790-nm pump power.展开更多
Cell wall composition in monocotyledonous grasses has been identified as a key area of research for developing better feedstocks for forage and biofuel production.Setaria viridis and its close domesticated relative Se...Cell wall composition in monocotyledonous grasses has been identified as a key area of research for developing better feedstocks for forage and biofuel production.Setaria viridis and its close domesticated relative Setaria italica have been chosen as suitable monocotyledonous models for plants possessing the C4 pathway of photosynthesis including sorghum,maize,sugarcane,switchgrass and Miscanthus×giganteus.Accurate partial least squares regression(PLSR)models to predict S.italica stem composition have been generated,based upon Fourier transform mid-infrared(FTIR)spectra and calibrated with wet chemistry determinations of ground S.italica stem material measured using a modified version of the US National Renewable Energy Laboratory(NREL)acid hydrolysis protocol.The models facilitated a high-throughput screening analysis for glucan,xylan,Klason lignin and acid soluble lignin(ASL)in a collection of 183 natural S.italica variants and clustered them into classes,some possessing unique chemotypes.The predictive models provide a highly efficient screening tool for large scale breeding programs aimed at identifying lines or mutants possessing unique cell wall chemotypes.Genes encoding key catalytic enzymes of the lignin biosynthesis pathway exhibit a high level of conservation with matching expression profiles,measured by RT-q PCR,among accessions of S.italica,which closely mirror profiles observed in the different developmental regions of an elongating internode of S.viridis by RNASeq.展开更多
Frequency up-conversion is an effective method of mid-infrared(MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light c...Frequency up-conversion is an effective method of mid-infrared(MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light carrying orbital angular momentum(OAM) from a difference frequency generation process and perform up-conversion on it via sum frequency conversion in a bulk quasi-phase-matching crystal. The maximum quantum conversion efficiencies from MIR to visible are 34.0%, 10.4%, and 3.5% for light with topological charges of 0, 1, and 2, respectively, achieved by utilizing an optimized strong pump light. We also verify the OAM conservation with a specially designed interferometer, and the results agree well with the numerical simulations. Our study opens up the possibilities for generating, manipulating, and detecting MIR light that carries OAM, and will have great potential for optical communications and remote sensing in the MIR regime.展开更多
We demonstrate a high-emciency mid-infrared picosecond optical parametric oscillator (OPO) based on MgO doped periodically poled lithium niobate (MgO:PPLN) with a laser diode array (LDA) pumped Innoslab amplifi...We demonstrate a high-emciency mid-infrared picosecond optical parametric oscillator (OPO) based on MgO doped periodically poled lithium niobate (MgO:PPLN) with a laser diode array (LDA) pumped Innoslab amplifier as the pumping source. Under a 16 W synchronously pumping power, 4.5 W of idler light at 2896nm is obtained. A tuning range of idler light from 2688nm to 3016nm is achieved, within which the highest optical-optical conversion ettlciency from pump power to OPO output is 35.1%. Moreover, a signal light of -500mW from 1644 to 1700nm with a repetition rate of 233.8 MHz is generated.展开更多
We study a laser wakefield acceleration driven by mid-infrared (mid-IR) laser pulses through two-dimensional particle-in-cell simulations. Since a mid-IR laser pulse can deliver a larger ponderomotive force as compa...We study a laser wakefield acceleration driven by mid-infrared (mid-IR) laser pulses through two-dimensional particle-in-cell simulations. Since a mid-IR laser pulse can deliver a larger ponderomotive force as compared with the usual 0.8 μm wavelength laser pulse, it is found that electron self-injection into the wake wave occurs at an earlier time, the plasma density threshold for injection becomes lower, and the electron beam charge is substantially enhanced. Meanwhile, our study also shows that quasimonoenergetic electron beams with a narrow energy-spread can be generated by using mid-IR laser pulses. Such a mid-IR laser pulse can provide a feasible method for obtaining a high quality and high charge electron beam. Therefore, the current efforts on constructing mid-IR terawatt laser systems can greatly benefit the laser wakefield acceleration research.展开更多
InGaSb/AlGaAsSb double-quantum-well diode lasers emitting around 2 μm are demonstrated. The AlGaAsSb barriers of the lasers are grown with digital alloy techniques consisting of binary AlSb/AlAs/GaSb short-period pai...InGaSb/AlGaAsSb double-quantum-well diode lasers emitting around 2 μm are demonstrated. The AlGaAsSb barriers of the lasers are grown with digital alloy techniques consisting of binary AlSb/AlAs/GaSb short-period pairs. Peak power conversion efficiency of 26% and an efficiency higher than 16% at 1 W are achieved at continuous-wave operation for a 2-mm-long and 100-μm-wide stripe laser. The maximum output power of a single emitter reaches to 1.4 W at 7 A.19-emitter bars with maximum efficiency higher than 20% and maximum power of 16 W are fabricated. Lasers with the short-period-pair barriers are proved to have improved temperature properties and wavelength stabilities. The characteristic temperature(T_0) is up to 140?C near room temperature(25–55?C).展开更多
Supercontinuum generation(SCG) and its application on all-optical quantization of all-optical analog-to-digital conversions(AOADCs) at the mid-infrared region in an Al GaAs strip waveguide are investigated numerically...Supercontinuum generation(SCG) and its application on all-optical quantization of all-optical analog-to-digital conversions(AOADCs) at the mid-infrared region in an Al GaAs strip waveguide are investigated numerically. The simulation results show that when the parabolic pulse is input, not only broader and higher-coherence SCG is obtained and a higher effective number of bits(ENOB) can be achieved, compared with the input pulse with hyperbolic-secant and Gaussian shaping. A four-bit quantization resolution is achieved along with a signal-to-noise ratio of 24.02 dB and an ENOB of3.99 bit, and the required input peak power is 760 mW.展开更多
We report on a chalcogenide glass fiber doped with Pr^(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform an...We report on a chalcogenide glass fiber doped with Pr^(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr^(3+) ion concentration at 4.22 × 10^(25) ions/m^3,fiber length at 0.94 m, and fiber background loss at 3 dB/m.展开更多
We reported an ultrabroadband mid-infrared(MIR)emission in the range of 1800 nm-3100 nm at room temperature(RT)from a Cr^(2+):ZnSe-doped chalcogenide glasses(ChGs)and studied the emission-dependent properties on the d...We reported an ultrabroadband mid-infrared(MIR)emission in the range of 1800 nm-3100 nm at room temperature(RT)from a Cr^(2+):ZnSe-doped chalcogenide glasses(ChGs)and studied the emission-dependent properties on the doping methods.A series of Cr^(2+):ZnSe/As_(40)S_(57)Se_(3)(in unit wt.%)glass-ceramics were prepared by hot uniaxial pressing(HUP)and melt-quenching methods,respectively.The glass-ceramics with MIR emission bands greater than 1000 nm were successfully prepared by both methods.The effects of matrix glass composition and grain doping concentration on the optical properties of the samples were studied.The occurrence state,morphology of the grains,and the microscopic elemental distributions were characterized using x-ray diffraction(XRD),scanning electron microscope(SEM),and energy dispersive spectrometer(EDS)analyses.展开更多
We demonstrate a compact periodically poled MgO-doped lithium niobate(MgO:PPLN)-based optical parametric oscillator(OPO) quasi-synchronously pumped by a fiber laser system with burst-mode operation.The pump sourc...We demonstrate a compact periodically poled MgO-doped lithium niobate(MgO:PPLN)-based optical parametric oscillator(OPO) quasi-synchronously pumped by a fiber laser system with burst-mode operation.The pump source is a peak-power-selectable pulse-multiplied picosecond Yb fiber laser.The chirped pulses from a figure of eight-cavity modelocked fiber laser seed are narrowed to a duration of less than 50 ps using an FBG reflector and a circulator.The narrowed pulses are directed to pass through a pulse multiplier and to form pulse bunches,each of which is composed of 13 subpulses.The obtained pulse bunches are amplified by two-stage fiber pre-amplifiers:one-stage is core-pumped and the other is cladding-pumped.A fiberized acousto-optic modulator is inserted to control the pulse repetition rate(PRR) of the pulse bunches before they are power-amplified in the final amplifier stage with a large mode area(LMA) PM Yb-doped fiber.The maximum average powers from the final amplifier are 85 W,60 W,and 45 W,respectively,corresponding to the PRR of2.72 MHz,1.36 MHz,and 0.68 MHz.The amplified pulses are directed to pump an MgO:PPLN-based optical parametric oscillator(OPO).A maximum peak power at 3.45 μm is obtained approximately to be 8.4 kW.Detailed performance characteristics are presented.展开更多
Noninvasive,glucose-monitoring technologies using infrared spectroscopy that have been studied typically require a calibration process that involves blood collection,which renders the methods somewhat invasive.We deve...Noninvasive,glucose-monitoring technologies using infrared spectroscopy that have been studied typically require a calibration process that involves blood collection,which renders the methods somewhat invasive.We develop a truly noninvasive,glucose-monitoring technique using midinfrared spectroscopy that does not require blood collection for calibration by applying domain adaptation(DA)using deep neural networks to train a model that associates blood glucose concentration with mid-infrared spectral data without requiring a training dataset labeled with invasive blood sample measurements.For realizing DA,the distribution of unlabeled spectral data for calibration is considered through adversarial update during training networks for regression to blood glucose concentration.This calibration improved the correlation coeffcient between the true blood glucose concentrations and predicted blood glucose concentrations from 0.38 to 0.47.The result indicates that this calibration technique improves prediction accuracy for mid-infrared glucose measurements without any invasively acquired data.展开更多
Using a photonic crystal fiber with a zero dispersion wavelength of the fundamelItal mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation...Using a photonic crystal fiber with a zero dispersion wavelength of the fundamelItal mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases froul 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11974220,61925508,61905265,and 12104271)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2021LLZ008 and ZR2021QA030)+1 种基金the Fund from Science and Technology Commission of Shanghai Municipality(Grant No.20511107400)CAS Interdisciplinary Innovation Team(Grant No.JCTD-2019-12).
文摘A 1.7-at.%Er:CaF_(2)crystal was synthesized by temperature gradient method.The Er:CaF_(2)crystal was applied in acousto-optically Q-switched laser at mid-infrared region for the first time.Using a Te O_(2)-based crystal as Q-switcher,we obtained a laser diode(LD)end-pumped Er:CaF_(2)laser with the highest single pulse energy up to 0.49 mJ and maximum peak power of 0.56 kW under 6.34-W absorbed pump power.The implication of these results is that the low-doped Er:CaF_(2)crystal exhibits promising optical properties in solid-state lasers.
文摘Arson presents a challenging crime scene for fire investigators worldwide. Key to the investigation of suspected arson cases is the analysis of fire debris for the presence of accelerants or ignitable liquids. This study has investigated the application and method development of vapor phase mid-Infrared (mid-IR) spectroscopy using a field portable quantum cascade laser (QCL) based system for the detection and identification of accelerant residues such as gasoline, diesel, and ethanol in fire debris. A searchable spectral library of various ignitable fluids and fuel components measured in the vapor phase was constructed that allowed for real-time identification of accelerants present in samples using software developed in-house. Measurement of vapors collected from paper material that had been doused with an accelerant followed by controlled burning and then extinguished with water showed that positive identification could be achieved for gasoline, diesel, and ethanol. This vapor phase mid-IR QCL method is rapid, easy to use, and has the sensitivity and discrimination capability that make it well suited for non-destructive crime scene sample analysis. Sampling and measurement can be performed in minutes with this 7.5 kg instrument. This vibrational spectroscopic method required no time-consuming sample pretreatment or complicated solvent extraction procedure. The results of this initial feasibility study demonstrate that this portable fire debris analyzer would greatly benefit arson investigators performing analysis on-site.
文摘With the development of mid-infrared (MIR) photoelectric devices, mid-infrared spectroscopy has become one of the important methods for non-invasive detection of blood glucose. The mid-infrared region (4000 - 400 cm<sup>-1</sup>) has the well-known fingerprint region (1200 - 800 cm<sup>-1</sup>) of glucose, which has clearer characteristic absorption peaks and better specificity. There is a lot of molecular information about glucose in the MIR. The non-invasive detection of blood glucose by mid-infrared spectroscopy needs to achieve certain accuracy, and the quantitative model is an important factor affecting the accuracy of glucose detection. In this paper, the samples of imitation solution containing only glucose and the samples of imitation mixed solution are taken as the research objects, and the mid-infrared spectral data of the samples are collected. The full spectrum partial least squares Regression (PLSR) model, SNV + Ctr-PLSR model, MSC + Ctr-PLSR model, and convolutional neural networks (CNN) model of 3000 - 900 cm<sup>-1</sup> band were constructed. Full spectrum PLS model and CNN model of 1200 - 900 cm<sup>-1</sup> band were constructed. The experimental results show that the optimal model of the two bands is CNN, then the correlation coefficient of prediction set (Rp) of 3000 - 900 cm<sup>-1</sup> band is 0.95, and the root mean square error of pre-diction set (RMSEP) value is 22.10. The Rp of 1200 - 900 cm<sup>-1</sup> band is 0.95, and the RMSEP value is 22.54. The research results show that CNN is a promising method, which has higher accuracy than PLSR, and is especially suitable for modeling human complex environment. In addition, the study provides a theoretical and practical basis for CNN in feature selection and model interpretation.
基金European Union’s Horizon 2020 research and innovation programme under grant agreement No.857627(CIPHR).
文摘In recent years,there has been a significant transformation in the field of incoherent imaging with new possibilities of compressing three-dimensional(3D)information into a two-dimensional intensity distribution without two-beam interference(TBI).Most of the incoherent 3D imagers without TBI are based on scattering by a random phase mask exhibiting sharp autocorrelation and low cross-correlation along the depth.Consequently,during reconstruction,high lateral and axial resolutions are obtained.Imaging based on scattering requires an astronomical photon budget and is therefore precluded in many power-sensitive applications.In this study,a proof-of-concept 3D imaging method without TBI using deterministic fields has been demonstrated.A new reconstruction method called the Lucy-Richardson-Rosen algorithm has been developed for this imaging concept.We believe that the proposed approach will cause a paradigm-shift in the current state-of-the-art incoherent imaging,fluorescence microscopy,mid-infrared fingerprinting,astronomical imaging,and fast object recognition applications.
基金Project supported in part by the National Natural Science Foundation of China (Grant Nos 10474071, 60637010, 60671036 and60278001)Tianjin Applied Fundamental Research Project, China (07JCZDJC05900)
文摘This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO4 laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5 μm and the temperature of 140℃, the maximum idler output power of 155 mW at 3.86 μm has been achieved when the 808 nm pump power is 8.5 W, leading to an optical-to-optical conversion efficiency of 1.82%.
基金Project supported by the National Key Scientific Instrument and Equipment Development,China(Grant No.2014YQ060537)the National Key Research and Development Program,China(Grant No.2016YFC0201103)
文摘A compact prototype based on mid-infrared wavelength modulation spectroscopy(WMS)is developed for the simul-taneous monitoring of NO,NO2,and NH3 in the urban area.Three quantum cascade lasers(QCLs)with central frequencies around 1900.0 cm^-1,1600.0 cm^-1,and 1103.4 cm^-1are used for NO,NO2,and NH3detections,respectively,by timedivision multiplex.An open-path multi-pass cell of 60-m optical path length is applied to the instrument for high sensitivity and reducing the response time to less than 1 s.The prototype achieves a sub-ppb detection limit for all the three target gases with an average time of about 100 s.The instrument is installed in the Jiangsu environmental monitoring center to conduct performance tests on ambient air.Continuous 24-hour measurements show good agreement with the results of a reference instrument based on the chemiluminescence technique.
基金support from the National Key Research and Development Program of China(2019YFA0709100,2020YFA0714504)Fundamental Research Funds for the Central Universities(Nos.DUT20GF108,DUT20RC(3)007,DUT20RC(3)062,DUT19RC(3)010)the Program for Liaoning excellent Talents in University(Grant No.LJQ2015021)。
文摘Efficient thermal radiation in the mid-infrared(M-IR)region is of supreme importance for many applications including thermal imaging and sensing,thermal infrared light sources,infrared spectroscopy,emissivity coatings,and camouflage.The ability to control light makes metasurfaces an attractive platform for infrared applications.Recently,different metamaterials have been proposed to achieve high thermal radiation.To date,broadening the radiation bandwidth of a metasurface emitter(meta-emitter)has become a key goal to enable extensive applications.We experimentally demonstrate a broadband M-IR thermal emitter using stacked nanocavity metasurface consisting of two pairs of circular-shaped dielectric(Si;N;)–metal(Au)stacks.A high thermal radiation can be obtained by engineering the geometry of nanocavity metasurfaces.Such a meta-emitter provides wideband and broad angular absorptance of both p-and s-polarized light,offering a wideband thermal radiation with an average emissivity of more than 80%in the M-IR atmospheric window of 8–14μm.The experimental illustration together with the theoretical framework establishes a basis for designing broadband thermal emitters,which,as anticipated,will initiate a promising avenue to M-IR sources.
基金supported by the China Postdoctoral Science Foundation (Grant No. 20090451417)the China Postdoctoral Science Special Foundation (Grant No. 201003693)+1 种基金the Fundamental Research Funds for the Central Universities of China (Grant No. ZYGX2009J053)the National Natural Science Foundation of China (Grant No. 60736038)
文摘Based on the rate equations describing the erbium-doped fluoride glass (ZBLAN) fibre lasers with different pumping configurations being taken into account, this paper presents theoretical calculations related to the dynamic population density and the operation performance of a high power mid-infrared all-fibre erbium-doped ZBLAN fibre laser. It shows that the ground-state absorption, excited-state absorption and energy-transfer-upconversion processes co-exist and produce a population balance, causing the laser to operate stably at a continuous wave state. A good agreement between the theoretical results and recent experimental measurement is obtained. Furthermore, the laser structure parameters including fibre length, reflectance of output fibre Bragg grating and pumping configurations are quantitatively optimised to achieve the best performance. The results show, as expected, that the slope efficiency of the fibre laser can be improved significantly through optimisation, which then provides an important guide for the design of high-performance mid-infrared erbium-doped ZBLAN fibre lasers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61235008 and 61077076)
文摘A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum (SC) is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial signal of the seed laser is provided by the incident pump light and amplified in the cavity. Based on this, we obtain a 2-μm pulsed laser with pulse repetition rate of 50 kHz and pulse width of 2 ns from the Tm-doped fiber laser. This 2-μm pulsed laser is amplified by two stages of fiber amplifiers, then the amplified laser is used for mid-infrared (mid-IR) SC generation in a 10-m length of ZrF4-BaF2-LaF3-AIF3-NaF (ZBLAN) fiber. An all-fiber-integrated mid-IR SC with spectrum ranging from 1.8 ~tm to 4.3 μm is achieved. The maximal average output power of the mid-IR SC from the ZBLAN fiber is 1.24 W (average output power beyond 2.5 μm is 340 mW), corresponding to an output efficiency of 6.6% with respect to the 790-nm pump power.
文摘Cell wall composition in monocotyledonous grasses has been identified as a key area of research for developing better feedstocks for forage and biofuel production.Setaria viridis and its close domesticated relative Setaria italica have been chosen as suitable monocotyledonous models for plants possessing the C4 pathway of photosynthesis including sorghum,maize,sugarcane,switchgrass and Miscanthus×giganteus.Accurate partial least squares regression(PLSR)models to predict S.italica stem composition have been generated,based upon Fourier transform mid-infrared(FTIR)spectra and calibrated with wet chemistry determinations of ground S.italica stem material measured using a modified version of the US National Renewable Energy Laboratory(NREL)acid hydrolysis protocol.The models facilitated a high-throughput screening analysis for glucan,xylan,Klason lignin and acid soluble lignin(ASL)in a collection of 183 natural S.italica variants and clustered them into classes,some possessing unique chemotypes.The predictive models provide a highly efficient screening tool for large scale breeding programs aimed at identifying lines or mutants possessing unique cell wall chemotypes.Genes encoding key catalytic enzymes of the lignin biosynthesis pathway exhibit a high level of conservation with matching expression profiles,measured by RT-q PCR,among accessions of S.italica,which closely mirror profiles observed in the different developmental regions of an elongating internode of S.viridis by RNASeq.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 92065101 and 11934013)Anhui Initiative In Quantum Information Technologies (Grant No. AHY020200)。
文摘Frequency up-conversion is an effective method of mid-infrared(MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light carrying orbital angular momentum(OAM) from a difference frequency generation process and perform up-conversion on it via sum frequency conversion in a bulk quasi-phase-matching crystal. The maximum quantum conversion efficiencies from MIR to visible are 34.0%, 10.4%, and 3.5% for light with topological charges of 0, 1, and 2, respectively, achieved by utilizing an optimized strong pump light. We also verify the OAM conservation with a specially designed interferometer, and the results agree well with the numerical simulations. Our study opens up the possibilities for generating, manipulating, and detecting MIR light that carries OAM, and will have great potential for optical communications and remote sensing in the MIR regime.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61275142,61308042,and 51321091the National Key Scientific Instrument and Equipment Development Project under Grant No 2011YQ030127the China Postdoctoral Science Foundation under Grant No 2014T70633
文摘We demonstrate a high-emciency mid-infrared picosecond optical parametric oscillator (OPO) based on MgO doped periodically poled lithium niobate (MgO:PPLN) with a laser diode array (LDA) pumped Innoslab amplifier as the pumping source. Under a 16 W synchronously pumping power, 4.5 W of idler light at 2896nm is obtained. A tuning range of idler light from 2688nm to 3016nm is achieved, within which the highest optical-optical conversion ettlciency from pump power to OPO output is 35.1%. Moreover, a signal light of -500mW from 1644 to 1700nm with a repetition rate of 233.8 MHz is generated.
基金Supported by the National Basic Research Program of China under Grant Nos 2013CBA01504the National Natural Science Foundation of China under Grant Nos 11475260,11374209 and 11375265
文摘We study a laser wakefield acceleration driven by mid-infrared (mid-IR) laser pulses through two-dimensional particle-in-cell simulations. Since a mid-IR laser pulse can deliver a larger ponderomotive force as compared with the usual 0.8 μm wavelength laser pulse, it is found that electron self-injection into the wake wave occurs at an earlier time, the plasma density threshold for injection becomes lower, and the electron beam charge is substantially enhanced. Meanwhile, our study also shows that quasimonoenergetic electron beams with a narrow energy-spread can be generated by using mid-IR laser pulses. Such a mid-IR laser pulse can provide a feasible method for obtaining a high quality and high charge electron beam. Therefore, the current efforts on constructing mid-IR terawatt laser systems can greatly benefit the laser wakefield acceleration research.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61790580 and 61435012)the National Basic Research Program of China(Grant No.2014CB643903)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YJKYYQ20170032)
文摘InGaSb/AlGaAsSb double-quantum-well diode lasers emitting around 2 μm are demonstrated. The AlGaAsSb barriers of the lasers are grown with digital alloy techniques consisting of binary AlSb/AlAs/GaSb short-period pairs. Peak power conversion efficiency of 26% and an efficiency higher than 16% at 1 W are achieved at continuous-wave operation for a 2-mm-long and 100-μm-wide stripe laser. The maximum output power of a single emitter reaches to 1.4 W at 7 A.19-emitter bars with maximum efficiency higher than 20% and maximum power of 16 W are fabricated. Lasers with the short-period-pair barriers are proved to have improved temperature properties and wavelength stabilities. The characteristic temperature(T_0) is up to 140?C near room temperature(25–55?C).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61307109 and 61475023)
文摘Supercontinuum generation(SCG) and its application on all-optical quantization of all-optical analog-to-digital conversions(AOADCs) at the mid-infrared region in an Al GaAs strip waveguide are investigated numerically. The simulation results show that when the parabolic pulse is input, not only broader and higher-coherence SCG is obtained and a higher effective number of bits(ENOB) can be achieved, compared with the input pulse with hyperbolic-secant and Gaussian shaping. A four-bit quantization resolution is achieved along with a signal-to-noise ratio of 24.02 dB and an ENOB of3.99 bit, and the required input peak power is 760 mW.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61605095)the Natural Science Foundation of Zhejiang Province,China(Grant No.LY19F050004)+2 种基金the Natural Science Foundation of Ningbo City(Grant No.2015A610038)the Open Fund of the Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices(South China University of Technology)(Grant No.2016-4)the K C Wong Magna Fund at Ningbo University
文摘We report on a chalcogenide glass fiber doped with Pr^(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr^(3+) ion concentration at 4.22 × 10^(25) ions/m^3,fiber length at 0.94 m, and fiber background loss at 3 dB/m.
基金Project supported by the Key Research and Development Program of Zhejiang Province,China (Grant No. 2021C01025)the National Natural Science Foundation of China (Grant Nos. 61975086 and 61605095)+3 种基金the Zhejiang Provincial Natural Science Foundation of China (Grant No. LY19F050004)the National Key Research and Development Program of China (Grant No. 2016YFB0303803)the K. C. Wong Magna Fund at Ningbo Universitythe Natural Science Foundation of Ningbo (Grant No. 202003N4180)
文摘We reported an ultrabroadband mid-infrared(MIR)emission in the range of 1800 nm-3100 nm at room temperature(RT)from a Cr^(2+):ZnSe-doped chalcogenide glasses(ChGs)and studied the emission-dependent properties on the doping methods.A series of Cr^(2+):ZnSe/As_(40)S_(57)Se_(3)(in unit wt.%)glass-ceramics were prepared by hot uniaxial pressing(HUP)and melt-quenching methods,respectively.The glass-ceramics with MIR emission bands greater than 1000 nm were successfully prepared by both methods.The effects of matrix glass composition and grain doping concentration on the optical properties of the samples were studied.The occurrence state,morphology of the grains,and the microscopic elemental distributions were characterized using x-ray diffraction(XRD),scanning electron microscope(SEM),and energy dispersive spectrometer(EDS)analyses.
基金supported by the National Natural Science Foundation of China(Grant No.61078015)the National Basic Research Program of China(Grant No.2011CB311803)
文摘We demonstrate a compact periodically poled MgO-doped lithium niobate(MgO:PPLN)-based optical parametric oscillator(OPO) quasi-synchronously pumped by a fiber laser system with burst-mode operation.The pump source is a peak-power-selectable pulse-multiplied picosecond Yb fiber laser.The chirped pulses from a figure of eight-cavity modelocked fiber laser seed are narrowed to a duration of less than 50 ps using an FBG reflector and a circulator.The narrowed pulses are directed to pass through a pulse multiplier and to form pulse bunches,each of which is composed of 13 subpulses.The obtained pulse bunches are amplified by two-stage fiber pre-amplifiers:one-stage is core-pumped and the other is cladding-pumped.A fiberized acousto-optic modulator is inserted to control the pulse repetition rate(PRR) of the pulse bunches before they are power-amplified in the final amplifier stage with a large mode area(LMA) PM Yb-doped fiber.The maximum average powers from the final amplifier are 85 W,60 W,and 45 W,respectively,corresponding to the PRR of2.72 MHz,1.36 MHz,and 0.68 MHz.The amplified pulses are directed to pump an MgO:PPLN-based optical parametric oscillator(OPO).A maximum peak power at 3.45 μm is obtained approximately to be 8.4 kW.Detailed performance characteristics are presented.
文摘Noninvasive,glucose-monitoring technologies using infrared spectroscopy that have been studied typically require a calibration process that involves blood collection,which renders the methods somewhat invasive.We develop a truly noninvasive,glucose-monitoring technique using midinfrared spectroscopy that does not require blood collection for calibration by applying domain adaptation(DA)using deep neural networks to train a model that associates blood glucose concentration with mid-infrared spectral data without requiring a training dataset labeled with invasive blood sample measurements.For realizing DA,the distribution of unlabeled spectral data for calibration is considered through adversarial update during training networks for regression to blood glucose concentration.This calibration improved the correlation coeffcient between the true blood glucose concentrations and predicted blood glucose concentrations from 0.38 to 0.47.The result indicates that this calibration technique improves prediction accuracy for mid-infrared glucose measurements without any invasively acquired data.
基金Project supported by the National Key Basic Research Special Foundation of China (Grant Nos. 2010CB327605 and 2010CB328300)the Fundamental Research Funds for the Central Universities, China (Grant Nos. 2011RC0309 and 2011RC008)the Specialized Research Fund for the Doctoral Program of Beijing University of Posts and Telecommunications, China (Grant No. CX201023)
文摘Using a photonic crystal fiber with a zero dispersion wavelength of the fundamelItal mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases froul 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated.