Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametr...Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.展开更多
The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additive...The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additives via vacuum sin-tering.A single-phase solid solution cubic structure of the ceramic was obtained with a relative density of 99.95%and an average grain size of 6.91±3.28μm.The grain boundary of the(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was clean with a thickness of only 1.3 nm.Further observations revealed uniform distribu-tion of all elements in the grains,and the presence of La and Zr segregation(1.5 nm thick)at few grain boundaries,but causing very little light scattering.The in-line transmittance of high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic reached 80%at 1100 nm,which was 98.7%of the theoretical value of Er_(2)O_(3) single crystal.Also,there were fluorescence emissions observed in the ultraviolet(311 nm),vis-ible(563,622 nm),and near-infrared(1032,1535 nm)regions.In addition,the intense red emission and weak green emission were detected,and the broad emission with a peak at 1.5μm was attributed to Stark splitting of Er3+ions,so the corresponding mechanism was discussed.Results obtained suggest that the highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic fabricated in this study could have broad application prospects in optical applications such as scintillators,up-conversion luminescent materials,and infrared lasers.展开更多
In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles we...In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature un-der a near-infrared photo source （980 nm） and UV-vis photo source, respectively.The results indicated thatα-TeO2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence. Theα-TeO2：Ho3＋/Yb3＋nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation, ascribed to the5S2→5I8 and5F5→5I8（Ho3＋） transitions, and weaker down-conversion emission at 545 nm under 455 nm excitation, ascribed to the5S2→5I8（Ho3＋） transitions. Theα-TeO2：Eu3＋nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation, attributed to the5D0→7F1 and 5D0→7F2 （Eu3＋） transitions. Possessing the advantages of these two luminescent materials, the as-prepared tri-doped samples ofα-TeO2：0.5Ho3＋/10Yb3＋/3Eu3＋ （mol.%）nanoparticles could successfully emit visible light via both up- and down-conversion modes.展开更多
Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single ph...Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single In As quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate（PPLN） waveguide and a 1.95 μmm pump laser, and the frequency conversion efficiency is ~40%. The singlephoton purity of quantum dot emission is preserved during the down-conversion process, i.e., g^（（2））（0）, only 0.22 at 1552 nm.This present technique advances the Ⅲ-Ⅴ semiconductor quantum dots as a promising platform for long-distance quantum communication.展开更多
We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variati...We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and splitting.We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth.Our study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.展开更多
By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the dege...By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.展开更多
We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achiev...We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achieved under typical dissipation conditions.To obtain a transparent understanding of the relevant physical process,we show that in the large detuned case,the cavity can be eliminated adiabatically,resulting in a parametric down-conversion(PDC)interaction between two phononic polariton modes.By tuning cavity detuning,the nonlinear interaction can be enhanced with the frequency-matching condition.Results from analytical treatment based on the effective PDC model agree with the numerical simulation.Such a system provides potential applications in nonlinear phononics.展开更多
A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- ti...A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.展开更多
In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodul...In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.展开更多
Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties ...Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.展开更多
Broadband photon pairs are highly desirable for quantum metrology,quantum sensing,and quantum communication.Such sources are usually designed through type-0 phase-matching spontaneous parametric down-conversion(SPDC)t...Broadband photon pairs are highly desirable for quantum metrology,quantum sensing,and quantum communication.Such sources are usually designed through type-0 phase-matching spontaneous parametric down-conversion(SPDC)that makes the photon pairs hard to separate in the frequency-degenerate case and thus limits their applications.In this paper,we design a broadband frequency-degenerate telecom-band photon pair source via the type-II SPDC in a dispersion-engineered thin-film lithium niobate waveguide,where the polarization modes of photon pairs are orthogonal and thus are easily separated deterministically.With a 5-mm-long waveguide,our design can achieve a bandwidth of 5.56 THz(44.8 nm),which is 8.6 times larger than that of the bulk lithium niobate,and the central wavelength can be flexibly adjusted.Our design is a promising approach towards high-quality integrated photon sources and may have wide applications in photonic quantum technologies.展开更多
In this study, down-conversion fluorescent powder of Sr2ZnSi2O7：Eu-（2＋）,Dy-（3＋）, SrAl2O4：Eu-（2＋）,Dy-（3＋） and Y2O2S：Eu-（3＋）,Mg-（2＋）,Ti-（4＋）, which were the common three primary colors materials ...In this study, down-conversion fluorescent powder of Sr2ZnSi2O7：Eu-（2＋）,Dy-（3＋）, SrAl2O4：Eu-（2＋）,Dy-（3＋） and Y2O2S：Eu-（3＋）,Mg-（2＋）,Ti-（4＋）, which were the common three primary colors materials with long afterglow, were synthesized by high temperature solid state method. The blends of rare earth（RE） luminescent materials have been of interest to reinvest the luminescent characteristics of polyethylene terephtahalate（PET） luminous fiber. The scanning electron microscopy（SEM） and an inversion fluorescence microscope were used to characterize the surface morphology and the dispersion of inclusion. Through analysis of microcosmic morphology, three typical dispersions of luminescent particles were summarized. The X-ray diffraction indicated that the phase structure of fiber samples and crystal structure of luminescence materials kept complete after prilling and spinning. From the fluorescence spectra and CIE 1931 coordinates, it could be found that different combinations of luminous fibers were desired to obtain divers colors emission luminous fiber. And the fiber samples were a light sensation which could induct different excitation wavelengths and convert it down to different colors. The afterglow decay curve and its differential curve were summarized indicating the three decay stages. The decay curve and decay rate curve showed that the contents of Sr2ZnSi2O7：Eu-（2＋）,Dy-（3＋）, SrAl2O4：Eu-（2＋）,Dy-（3＋） and Y2O2S：Eu-（3＋）,Mg-（2＋）,Ti-（4＋） had obvious influence on the afterglow of fiber samples.展开更多
A series of YNbO_(4):Bi^(3+) and YNbO_(4):Bi^(3+)/Er^(3+) phosphors were prepared by a conventional high temperature solid-state reaction method.The results of XRD and Rietveld refinement confirm that monoclinic phase...A series of YNbO_(4):Bi^(3+) and YNbO_(4):Bi^(3+)/Er^(3+) phosphors were prepared by a conventional high temperature solid-state reaction method.The results of XRD and Rietveld refinement confirm that monoclinic phase YNbO_(4)samples are achieved.The down-/up-conversion luminescence of Er^(3+) ions was investigated under the excitation of ultraviolet light(327 nm)and near infrared light(980 nm).Under 327 nm excitation,broad visible emission band from Bi^(3+) ions and characteristic green emission peaks from Er^(3+) ions are simultaneously observed,while only strong green emissions from Er^(3+) ions are detected upon excitation of 980 nm.Remarkable emission enhancement is observed in down-/up-conversion luminescence processes by introducing Bi^(3+) ions into Er^(3+)-doped YNbO_(4)phosphors.Pumped current versus up-conversion emission intensity study shows that two-photon processes are responsible for both the green and the red up-conversion emissions of Er^(3+)ion.Through the study of the temperature sensing property of Er^(3+) ion,it is affirmed that the temperature sensitivity is sensitive to the doping concentration of Bi^(3+) ions.By comparing the experimental values of the radiative transition rate ratio of the two green emission levels of Er^(3+) ions and the theoretical values calculated by Judd-Ofelt(J-O)theory,it is concluded that the temperature sensing property of Er^(3+) ions is greatly affected by the energy level splitting.展开更多
We propose a simple scheme to generate an arbitrary photon-added coherent state of a travelling optical field by combining an array of degenerate parametric amplifiers and corresponding single-photon detectors. Partic...We propose a simple scheme to generate an arbitrary photon-added coherent state of a travelling optical field by combining an array of degenerate parametric amplifiers and corresponding single-photon detectors. Particularly, when the single-photon-added coherent state is observed by developing the novel technique of Zavatta et al （2004 Science 306 660）, we can simultar/eously obtain the generalized N-qubit W state.展开更多
In this work,calcium niobium gallium garnet(Ca_(3)Nb_(1.6875)Ga_(3.1875)O_(12)-CNGG)ceramic samples singledoped with Tb^(3+)and co-doped with Tb^(3+)and Yb^(3+)ions were sintered by the solid-state reaction method.The...In this work,calcium niobium gallium garnet(Ca_(3)Nb_(1.6875)Ga_(3.1875)O_(12)-CNGG)ceramic samples singledoped with Tb^(3+)and co-doped with Tb^(3+)and Yb^(3+)ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb^(3+)ions corresponding to the maximum luminescence in the green spectral range in CNGG:x at%Tb(x=0.1,0.5,1,2,3,4,and 5)was determined to be 4 at%.The timeresolved luminescence of the^(5)D_(4)level(Tb^(3+))in the CNGG:x at%Tb samples was analysed to explore the quenching mechanisms involved in the Tb^(3+)green emission.Co-doped CNGG:4 at%Tb,y at%Yb(y=0.5,2,4,6,8,and 10)ceramics were prepared and investigated.It is shown that CNGG:4 at%Tb,y at%Yb phosphors exhibit intense green luminescence under ultra-violet(UV),visible(VIS),and near-infrared(NIR)excitation,thus demonstrating the presence of simultaneous down-conversion(DC)and upconversion(UC)processes.The dependence of the UC luminescence intensity on the diode laser pumping power was measured and the results indicate a two-photon process based on cooperative energy transfer(CET).Under UV excitation,the lifetime of the^(5)D_(4)(Tb^(3+))level slowly increases with increase of Yb^(3+)concentration,suggesting the energy transfer from Yb^(3+)to Tb^(3+)ions,while under NIR excitation,the lifetime of the^(5)D_(4)(Tb^(3+))level decreases with increase of Yb^(3+)ions concentration,indicating the presence of a strong energy transfer from Tb^(3+)to Yb^(3+)ions.The highest energy transfer efficiency ofη_(ET)≈42%was determined for the CNGG:4 at%Tb,10 at%Yb sample.The obtained results indicate that CNGG:(Tb^(3+),Yb^(3+))could be efficient new yellowish-green-emitting phosphors.展开更多
The cavity-enhanced spontaneous parametric down-conversion far below threshold can be used to generate a narrow-band photon pair efficiently. Previous experiments on the cavity-enhanced spontaneous parametric down- co...The cavity-enhanced spontaneous parametric down-conversion far below threshold can be used to generate a narrow-band photon pair efficiently. Previous experiments on the cavity-enhanced spontaneous parametric down- conversion almost always utilize continuous wave pump light, but the pulse pumped case is rarely reported. One disadvantage of the continuous wave case is that the photon pair is produced randomly within the coherence time of the pump, which limits its application in the quantum information realm. However, a pulse pump can help to solve this problem. In this paper, we theoretically analyze pulse pumped cavity-enhanced spontaneous parametric down- conversion in detail and show how the pump pulse affects the multi-photon interference visibility, two-photon waveform, joint spectrum and spectral brightness.展开更多
We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz convers...We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz conversion at the transmitter end and an ultrabroadband packaged thin-film lithium niobate Mach-Zehnder modulator(MZM)to convert the THz signal to the optical signal at the receiver end.This system successfully realized the transmission of 33-Gbaud 16-quadrature amplitude modulation(QAM)and 31-Gbaud probabilistic shaping-64-QAM signals through 10-km standard singlemode fiber(SSMF),0.6-m wireless distance,and the subsequent 5-km SSMF,achieving net data rates of 116.03 and123.72 Gbps,respectively.展开更多
Nanomaterials have emerged as an active area of research.This is because of their broad spectrum of applications such as sensors,white light emitting diodes(LEDs),electronic displays,and other optoelectronic devices i...Nanomaterials have emerged as an active area of research.This is because of their broad spectrum of applications such as sensors,white light emitting diodes(LEDs),electronic displays,and other optoelectronic devices in the optics and electronic industries owing to their size-and shape-dependent properties.The synthesis technique plays a crucial role in tuning the size and shape of the materials.Herein,we briefly describe these nanomaterials'fundamental aspects,properties,and applications.Various nanomaterial synthesis methods are discussed.Their advantages and disadvantages are highlighted in conjunction with the criteria for selecting a synthesis method.The principle underlying the sonochemical method and its applicability in synthesizing diverse sub-15 nm size nanoparticles(NPs)are presented.The main objective of this article is to review recent studies on lanthanide-doped nanophosphors and the various parameters that play key roles in achieving optimum luminescence emission.Both down-conversion and up-conversion mechanisms are discussed.The importance of the combinations and concentrations of the synthesizer/activator,color tuning,and host material are emphasized.展开更多
We report a broadband energy-time entangled photon-pair source based on a fiber-pigtailed periodically poled lithium niobate[PPLN]waveguide,designed for applications in the quantum secure network.Utilizing the spontan...We report a broadband energy-time entangled photon-pair source based on a fiber-pigtailed periodically poled lithium niobate[PPLN]waveguide,designed for applications in the quantum secure network.Utilizing the spontaneous parametric down-conversion nonlinear optical process,the source generates entangled photon pairs within a wavelength range of64 nm in the telecom band at a pump wavelength of 770.3 nm.Photon pairs from eight paired International Telecommunication Union[ITU]channels are selected,and their correlation and entanglement properties are characterized.The measured coincidence counts of photon pairs from eight paired ITU channels are larger than 152.9 kHz when the coincidence-to-accidental ratios are greater than 260.Entanglement properties are measured through two-photon interference in the Franson interferometer,with all visibilities of interference curves exceeding 98.13%.Our demonstration provides a broadband energy-time entangled photon-pair source,contributing to the development of a large-scale quantum secure network.展开更多
Rare-earth(RE)based luminescent probes exhibit rich optical properties including upconversion and down-conversion luminescence spanning a broad spectral range from 300 to 3,000 nm,and have generated great scientific a...Rare-earth(RE)based luminescent probes exhibit rich optical properties including upconversion and down-conversion luminescence spanning a broad spectral range from 300 to 3,000 nm,and have generated great scientific and practical interest from telecommunication to biological imaging.While upconversion nanoparticles have been investigated for decades,down-conversion luminescence of RE-based probes in the second near-infrared(NIR-II,1,000-1,700 nm)window for in vivo biological imaging with sub-centimeter tissue penetration and micrometer image resolution has come into light only recently.In this review,we present recent progress on RE-based NIR-II probes for in vivo vasculature and molecular imaging with a focus on Er3+-based nanoparticles due to the down-conversion luminescence at the long-wavelength end of the NIR-II window(NIR-IIb,1,500-1,700 nm).Imaging in NIR-IIb is superior to imaging with organic probes such as ICG and IRDye800 in the^800 nm NIR range and the 1,000-1,300 nm short end of NIR-II range,owing to minimized light scattering and autofluorescence background.Doping by cerium and other ions and phase engineering of Er^3+-based nanoparticles,combined with surface hydrophilic coating optimization can afford ultrabright,biocompatible NIR-IIb probe towards clinical translation for human use.The Nd^3+-based probes with NIR-II emission at 1,050 and 1,330 nm are also discussed,including Nd^3+doped nanocrystals and Nd^3+-organic ligand complexes.This review also points out future directions for further development of multi-functional RE NIR-II probes for biological imaging.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 62075010)。
文摘Photon pairs with large nondegeneracy have recently attracted increasing interest, which gives rise to an urgent demand for revealing their complete and accurate spectral distribution. By thoroughly analyzing parametric down-conversion(PDC), we put forward a model to directly describe the spatial-spectral distribution of these photon pairs, which is experimentally demonstrated by a 532-nm pumped type-I PDC in a beta barium borate(BBO) crystal. The measured spectral curves show good agreement with the theoretical predictions over the entire spectral range. We further demonstrate that, as signal wavelength increases, the photon pairs are initially spectrally distinguishable, then partly indistinguishable, finally completely indistinguishable with a maximum bandwidth of approximately 500 nm. Utilizing photon-number-resolving single-photon detectors(SPD), we observe the average photon number decreases significantly more slowly than the spectral intensity as the wavelength deviates from the peak, and the photon numbers follow a quasi-Poisson distribution well for wavelengths around the peak, but a thermal distribution better describes the statistics near the spectral boundaries. Finally,we use the signal photons as the trigger to generate heralded Fock states up to 10 photons in near-infrared range, which are suitable for quantum simulation and quantum key distribution in optical fiber networks.
基金supported by the National Natural Science Foundation of China(No.51832002 and 52072077),Instrumental Analysis Center of Guangdong Unversity of Technology,Sinomate Institute of Materials Research(Guang Zhou)Co.,Ltd(SIMR)for assisting the TEM characterization.
文摘The highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was successfully fabri-cated by the addition of 3 at.%ZrO_(2) and 10 at.%La_(2)O_(3) introduced as sintering additives via vacuum sin-tering.A single-phase solid solution cubic structure of the ceramic was obtained with a relative density of 99.95%and an average grain size of 6.91±3.28μm.The grain boundary of the(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic was clean with a thickness of only 1.3 nm.Further observations revealed uniform distribu-tion of all elements in the grains,and the presence of La and Zr segregation(1.5 nm thick)at few grain boundaries,but causing very little light scattering.The in-line transmittance of high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic reached 80%at 1100 nm,which was 98.7%of the theoretical value of Er_(2)O_(3) single crystal.Also,there were fluorescence emissions observed in the ultraviolet(311 nm),vis-ible(563,622 nm),and near-infrared(1032,1535 nm)regions.In addition,the intense red emission and weak green emission were detected,and the broad emission with a peak at 1.5μm was attributed to Stark splitting of Er3+ions,so the corresponding mechanism was discussed.Results obtained suggest that the highly transparent novel high-entropy(Lu_(0.2)Y_(0.2)Gd_(0.2)Yb_(0.2)Er_(0.2))_(2)O_(3) ceramic fabricated in this study could have broad application prospects in optical applications such as scintillators,up-conversion luminescent materials,and infrared lasers.
基金supported by the National Natural Science Foundation of China(21075053)the"Challenge Cup"Undergraduate Extra-curriculum Academics,Science and Technology Works Competition and Student's Platform for Innovation and Entrepreneurship Training Program(201410559056)in Jinan University
文摘In this study,α-TeO2：Ho3＋/Yb3＋,α-TeO2：Eu3＋ andα-TeO2：Ho3＋/Yb3＋/Eu3＋ nanoparticles were prepared via a simple hydrothermal process. The up- and down-conversion properties of the as-prepared nanoparticles were tested at room temperature un-der a near-infrared photo source （980 nm） and UV-vis photo source, respectively.The results indicated thatα-TeO2 NPs were a kind of outstanding host material for both up- and down-conversion luminescence. Theα-TeO2：Ho3＋/Yb3＋nanoparticles showed sharp up-conversion emission at 545 and 660 nm under 980 nm excitation, ascribed to the5S2→5I8 and5F5→5I8（Ho3＋） transitions, and weaker down-conversion emission at 545 nm under 455 nm excitation, ascribed to the5S2→5I8（Ho3＋） transitions. Theα-TeO2：Eu3＋nanoparticles showed strong down-conversion emission at 592 and 615 nm under 395 nm excitation, attributed to the5D0→7F1 and 5D0→7F2 （Eu3＋） transitions. Possessing the advantages of these two luminescent materials, the as-prepared tri-doped samples ofα-TeO2：0.5Ho3＋/10Yb3＋/3Eu3＋ （mol.%）nanoparticles could successfully emit visible light via both up- and down-conversion modes.
基金Project supported by the National Key Technologies R&D Program of China(Grant No.2018YFA0306101)the Scientific Instrument Developing Project of Chinese Academy of Sciences(Grant No.YJKYYQ20170032)the National Natural Science Foundation of China(Grant No.61505196)
文摘Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single In As quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate（PPLN） waveguide and a 1.95 μmm pump laser, and the frequency conversion efficiency is ~40%. The singlephoton purity of quantum dot emission is preserved during the down-conversion process, i.e., g^（（2））（0）, only 0.22 at 1552 nm.This present technique advances the Ⅲ-Ⅴ semiconductor quantum dots as a promising platform for long-distance quantum communication.
基金Project supported by the National Key R&D Program of China(Grant No.2019YFA0705000)Leading-edge Technology Program of Jiangsu Natural Science Foundation,China(Grant No.BK20192001)the National Natural Science Foundation of China(Grant Nos.51890861,11690031,11974178,and 11627810).
文摘We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and splitting.We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth.Our study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.
基金supported by the National Natural Science Foundation of China under Grant Nos.40674076 and 40474064the Hunan Natural Science Foundation of China under Grant No.07JJ3123the Scientific Research Fund of Hunan Provincial Education Department under Grant Nos.06C163,05B023,and 06B004
文摘By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.
基金support from the NSFC(Grant No.12275331)the Penghuanwu Innovative Research Center(Grant No.12047503)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD031602)。
文摘We studied the process of polariton conversion in a 3-mode nonlinear optomechanical system.Compared with the standard 2-mode optomechanical system,we find a much larger conversion rate of polariton modes can be achieved under typical dissipation conditions.To obtain a transparent understanding of the relevant physical process,we show that in the large detuned case,the cavity can be eliminated adiabatically,resulting in a parametric down-conversion(PDC)interaction between two phononic polariton modes.By tuning cavity detuning,the nonlinear interaction can be enhanced with the frequency-matching condition.Results from analytical treatment based on the effective PDC model agree with the numerical simulation.Such a system provides potential applications in nonlinear phononics.
基金Supported by the National Key Basic Research Program of China under Grant Nos 2013CB933304 and 2014CB643904the National Natural Science Foundation of China under Grant Nos 61435012 and 61274125the Strategic Priority Research Program(B) of Chinese Academy of Sciences under Grant No XDB01010200
文摘A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.
文摘In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.
基金Project supported by the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB01030100 and XDB01030300)the National Key Research and Development Program of China(Grant No.2016YFA0302600)the National Natural Science Foundation of China(Grant Nos.61475148 and 61575183)
文摘Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.
基金Project supported by the National Key Research and Development Program of China(Grant No.2019YFA0705000)Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301500)+1 种基金Leading-edge Technology Program of Jiangsu Natural Science Foundation(Grant No.BK20192001)the National Natural Science Foundation of China(Grant Nos.51890861 and 11974178).
文摘Broadband photon pairs are highly desirable for quantum metrology,quantum sensing,and quantum communication.Such sources are usually designed through type-0 phase-matching spontaneous parametric down-conversion(SPDC)that makes the photon pairs hard to separate in the frequency-degenerate case and thus limits their applications.In this paper,we design a broadband frequency-degenerate telecom-band photon pair source via the type-II SPDC in a dispersion-engineered thin-film lithium niobate waveguide,where the polarization modes of photon pairs are orthogonal and thus are easily separated deterministically.With a 5-mm-long waveguide,our design can achieve a bandwidth of 5.56 THz(44.8 nm),which is 8.6 times larger than that of the bulk lithium niobate,and the central wavelength can be flexibly adjusted.Our design is a promising approach towards high-quality integrated photon sources and may have wide applications in photonic quantum technologies.
基金Project supported by the National Natural Science Foundation of China(51503082)the Fundamental Research Funds for the Central Universities(JUSRP51505,JUSRP116020)Jiangsu Province Ordinary University Academic Degree Graduate Student Scientific Research Innovation Projects(KYLX16-0791)
文摘In this study, down-conversion fluorescent powder of Sr2ZnSi2O7：Eu-（2＋）,Dy-（3＋）, SrAl2O4：Eu-（2＋）,Dy-（3＋） and Y2O2S：Eu-（3＋）,Mg-（2＋）,Ti-（4＋）, which were the common three primary colors materials with long afterglow, were synthesized by high temperature solid state method. The blends of rare earth（RE） luminescent materials have been of interest to reinvest the luminescent characteristics of polyethylene terephtahalate（PET） luminous fiber. The scanning electron microscopy（SEM） and an inversion fluorescence microscope were used to characterize the surface morphology and the dispersion of inclusion. Through analysis of microcosmic morphology, three typical dispersions of luminescent particles were summarized. The X-ray diffraction indicated that the phase structure of fiber samples and crystal structure of luminescence materials kept complete after prilling and spinning. From the fluorescence spectra and CIE 1931 coordinates, it could be found that different combinations of luminous fibers were desired to obtain divers colors emission luminous fiber. And the fiber samples were a light sensation which could induct different excitation wavelengths and convert it down to different colors. The afterglow decay curve and its differential curve were summarized indicating the three decay stages. The decay curve and decay rate curve showed that the contents of Sr2ZnSi2O7：Eu-（2＋）,Dy-（3＋）, SrAl2O4：Eu-（2＋）,Dy-（3＋） and Y2O2S：Eu-（3＋）,Mg-（2＋）,Ti-（4＋） had obvious influence on the afterglow of fiber samples.
基金Project supported by the National Natural Science Foundation of China(11774042,11704056)Fundamental Research Funds for the Central Universities(3132020177,3132019338)。
文摘A series of YNbO_(4):Bi^(3+) and YNbO_(4):Bi^(3+)/Er^(3+) phosphors were prepared by a conventional high temperature solid-state reaction method.The results of XRD and Rietveld refinement confirm that monoclinic phase YNbO_(4)samples are achieved.The down-/up-conversion luminescence of Er^(3+) ions was investigated under the excitation of ultraviolet light(327 nm)and near infrared light(980 nm).Under 327 nm excitation,broad visible emission band from Bi^(3+) ions and characteristic green emission peaks from Er^(3+) ions are simultaneously observed,while only strong green emissions from Er^(3+) ions are detected upon excitation of 980 nm.Remarkable emission enhancement is observed in down-/up-conversion luminescence processes by introducing Bi^(3+) ions into Er^(3+)-doped YNbO_(4)phosphors.Pumped current versus up-conversion emission intensity study shows that two-photon processes are responsible for both the green and the red up-conversion emissions of Er^(3+)ion.Through the study of the temperature sensing property of Er^(3+) ion,it is affirmed that the temperature sensitivity is sensitive to the doping concentration of Bi^(3+) ions.By comparing the experimental values of the radiative transition rate ratio of the two green emission levels of Er^(3+) ions and the theoretical values calculated by Judd-Ofelt(J-O)theory,it is concluded that the temperature sensing property of Er^(3+) ions is greatly affected by the energy level splitting.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10304020 and 10474117）, the State Key Development Program for Basic Research of China （Grant No 2001CB309309）, and also in part by the Sunshine Project of Wuhan, China.
文摘We propose a simple scheme to generate an arbitrary photon-added coherent state of a travelling optical field by combining an array of degenerate parametric amplifiers and corresponding single-photon detectors. Particularly, when the single-photon-added coherent state is observed by developing the novel technique of Zavatta et al （2004 Science 306 660）, we can simultar/eously obtain the generalized N-qubit W state.
基金Project supported by the Romanian Ministry of Research and Innovation under grant agreement no.16N/2019 within Program NUCLEULAPLASⅥ(PN-Ⅲ-P1-1.1-PD-2019-0665,PN-Ⅲ-P4-ID-PCE-2020-2203)。
文摘In this work,calcium niobium gallium garnet(Ca_(3)Nb_(1.6875)Ga_(3.1875)O_(12)-CNGG)ceramic samples singledoped with Tb^(3+)and co-doped with Tb^(3+)and Yb^(3+)ions were sintered by the solid-state reaction method.The structural characterization of the samples was carried out by X-ray diffraction measurements.The optimal concentration of Tb^(3+)ions corresponding to the maximum luminescence in the green spectral range in CNGG:x at%Tb(x=0.1,0.5,1,2,3,4,and 5)was determined to be 4 at%.The timeresolved luminescence of the^(5)D_(4)level(Tb^(3+))in the CNGG:x at%Tb samples was analysed to explore the quenching mechanisms involved in the Tb^(3+)green emission.Co-doped CNGG:4 at%Tb,y at%Yb(y=0.5,2,4,6,8,and 10)ceramics were prepared and investigated.It is shown that CNGG:4 at%Tb,y at%Yb phosphors exhibit intense green luminescence under ultra-violet(UV),visible(VIS),and near-infrared(NIR)excitation,thus demonstrating the presence of simultaneous down-conversion(DC)and upconversion(UC)processes.The dependence of the UC luminescence intensity on the diode laser pumping power was measured and the results indicate a two-photon process based on cooperative energy transfer(CET).Under UV excitation,the lifetime of the^(5)D_(4)(Tb^(3+))level slowly increases with increase of Yb^(3+)concentration,suggesting the energy transfer from Yb^(3+)to Tb^(3+)ions,while under NIR excitation,the lifetime of the^(5)D_(4)(Tb^(3+))level decreases with increase of Yb^(3+)ions concentration,indicating the presence of a strong energy transfer from Tb^(3+)to Yb^(3+)ions.The highest energy transfer efficiency ofη_(ET)≈42%was determined for the CNGG:4 at%Tb,10 at%Yb sample.The obtained results indicate that CNGG:(Tb^(3+),Yb^(3+))could be efficient new yellowish-green-emitting phosphors.
基金supported by the National Natural Science Foundation of China(Grant No.10874171)the National Basic Research Program of China(Grant No.2009CB929601)+1 种基金the Innovation Fund from Chinese Academy of Sciencesthe Program for New Century Excellent Talents in University of China(Grant No.NCET-07-0791)
文摘The cavity-enhanced spontaneous parametric down-conversion far below threshold can be used to generate a narrow-band photon pair efficiently. Previous experiments on the cavity-enhanced spontaneous parametric down- conversion almost always utilize continuous wave pump light, but the pulse pumped case is rarely reported. One disadvantage of the continuous wave case is that the photon pair is produced randomly within the coherence time of the pump, which limits its application in the quantum information realm. However, a pulse pump can help to solve this problem. In this paper, we theoretically analyze pulse pumped cavity-enhanced spontaneous parametric down- conversion in detail and show how the pump pulse affects the multi-photon interference visibility, two-photon waveform, joint spectrum and spectral brightness.
基金supported by the National Key Research and Development Program of China(No.2022YFB2903600)the National Natural Science Foundation of China(Nos.62235005,62171137,and 61925104)。
文摘We demonstrated a fiber-terahertz(THz)-fiber communication system at the D-band based on full photonic conversions,exploiting a modified unitraveling-carrier photodiode(MUTC-PD)module to achieve optical-to-THz conversion at the transmitter end and an ultrabroadband packaged thin-film lithium niobate Mach-Zehnder modulator(MZM)to convert the THz signal to the optical signal at the receiver end.This system successfully realized the transmission of 33-Gbaud 16-quadrature amplitude modulation(QAM)and 31-Gbaud probabilistic shaping-64-QAM signals through 10-km standard singlemode fiber(SSMF),0.6-m wireless distance,and the subsequent 5-km SSMF,achieving net data rates of 116.03 and123.72 Gbps,respectively.
文摘Nanomaterials have emerged as an active area of research.This is because of their broad spectrum of applications such as sensors,white light emitting diodes(LEDs),electronic displays,and other optoelectronic devices in the optics and electronic industries owing to their size-and shape-dependent properties.The synthesis technique plays a crucial role in tuning the size and shape of the materials.Herein,we briefly describe these nanomaterials'fundamental aspects,properties,and applications.Various nanomaterial synthesis methods are discussed.Their advantages and disadvantages are highlighted in conjunction with the criteria for selecting a synthesis method.The principle underlying the sonochemical method and its applicability in synthesizing diverse sub-15 nm size nanoparticles(NPs)are presented.The main objective of this article is to review recent studies on lanthanide-doped nanophosphors and the various parameters that play key roles in achieving optimum luminescence emission.Both down-conversion and up-conversion mechanisms are discussed.The importance of the combinations and concentrations of the synthesizer/activator,color tuning,and host material are emphasized.
基金supported by the Sichuan Science and Technology Program(Nos.2022YFSY0061,2023YFSY0061,2022YFSY0062,2022YFSY0063,2023YFSY0058,and2023YFSY0060)the National Natural Science Foundation of China(Nos.62405046,62475039,and 92365106)+1 种基金the Innovation Program for Quantum Science and Technology(No.2021ZD0301702)the Tianfu Jiangxi Laboratory(No.TFJX-ZD-2024-002)。
文摘We report a broadband energy-time entangled photon-pair source based on a fiber-pigtailed periodically poled lithium niobate[PPLN]waveguide,designed for applications in the quantum secure network.Utilizing the spontaneous parametric down-conversion nonlinear optical process,the source generates entangled photon pairs within a wavelength range of64 nm in the telecom band at a pump wavelength of 770.3 nm.Photon pairs from eight paired International Telecommunication Union[ITU]channels are selected,and their correlation and entanglement properties are characterized.The measured coincidence counts of photon pairs from eight paired ITU channels are larger than 152.9 kHz when the coincidence-to-accidental ratios are greater than 260.Entanglement properties are measured through two-photon interference in the Franson interferometer,with all visibilities of interference curves exceeding 98.13%.Our demonstration provides a broadband energy-time entangled photon-pair source,contributing to the development of a large-scale quantum secure network.
基金supported by the National Institutes of Health(grant no.DP1-NS-105737).
文摘Rare-earth(RE)based luminescent probes exhibit rich optical properties including upconversion and down-conversion luminescence spanning a broad spectral range from 300 to 3,000 nm,and have generated great scientific and practical interest from telecommunication to biological imaging.While upconversion nanoparticles have been investigated for decades,down-conversion luminescence of RE-based probes in the second near-infrared(NIR-II,1,000-1,700 nm)window for in vivo biological imaging with sub-centimeter tissue penetration and micrometer image resolution has come into light only recently.In this review,we present recent progress on RE-based NIR-II probes for in vivo vasculature and molecular imaging with a focus on Er3+-based nanoparticles due to the down-conversion luminescence at the long-wavelength end of the NIR-II window(NIR-IIb,1,500-1,700 nm).Imaging in NIR-IIb is superior to imaging with organic probes such as ICG and IRDye800 in the^800 nm NIR range and the 1,000-1,300 nm short end of NIR-II range,owing to minimized light scattering and autofluorescence background.Doping by cerium and other ions and phase engineering of Er^3+-based nanoparticles,combined with surface hydrophilic coating optimization can afford ultrabright,biocompatible NIR-IIb probe towards clinical translation for human use.The Nd^3+-based probes with NIR-II emission at 1,050 and 1,330 nm are also discussed,including Nd^3+doped nanocrystals and Nd^3+-organic ligand complexes.This review also points out future directions for further development of multi-functional RE NIR-II probes for biological imaging.
