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Bacteria are the primary cause of infectious diseases, making rapid and accurate identification crucial for timely pathogen diagnosis and disease control. However, traditional identification techniques such as polymerase chain reaction and loop-mediated isothermal amplification are complex, time-consuming, and pose infection risks. This study explores remote (~3 m) bacterial identification using laser-induced breakdown spectroscopy (LIBS) with a Cassegrain reflective telescope. Principal component analysis (PCA) was employed to reduce the dimensionality of the LIBS spectral data, and the accuracy of support vector machine (SVM) and Random Forest (RF) algorithms was compared. Multiple repeated experiments showed that the RF model achieved a classification accuracy, recall, precision, and F1-score of 99.81%, 99.80%, 99.79%, and 0.9979, respectively, outperforming the SVM model and providing more accurate remote bacterial identification. The method based on laser-induced plasma spectroscopy and machine learning has broad application prospects, supporting noncontact disease diagnosis, improving public health, and advancing medical research and technological development.
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The achievement of size uniformity and monodispersity in perovskite quantum dots (QDs) requires the implementation of precise temperature control and the establishment of optimal reaction conditions. Nevertheless, the accurate control of a range of reaction variables represents a considerable challenge. This study addresses the aforementioned challenge by employing manganese (Mn) doping to achieve size uniformity in CsPbBr3 perovskite QDs without the necessity for the precise control of the reaction conditions. By optimizing the Mn:Pb ratio, it is possible to successfully dope CsPbBr3 QDs with the appropriate concentrations of Mn²âº and achieve a uniform size distribution. The spectroscopic measurements on single QDs indicate that the appropriate Mn²âº concentrations can result in a narrower spectral linewidth, a longer photoluminescence (PL) lifetime, and a reduced biexciton Auger recombination rate, thus positively affecting the PL properties. This study not only simplifies the size control of perovskite QDs but also demonstrates the potential of Mn-doped CsPbBr3 QDs for narrow-linewidth light-emitting diode applications.
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In multistate non-Hermitian systems, higher-order exceptional points and exotic phenomena with no analogues in two-level systems arise. A paradigm is the exceptional nexus (EX), a third-order EP as the cusp singularity of exceptional arcs (EAs), that has a hybrid topological nature. Using atomic Bose-Einstein condensates to implement a dissipative three-state system, we experimentally realize an EX within a two-parameter space, despite the absence of symmetry. The engineered dissipation exhibits density dependence due to the collective atomic response to resonant light. Based on extensive analysis of the system's decay dynamics, we demonstrate the formation of an EX from the coalescence of two EAs with distinct geometries. These structures arise from the different roles played by dissipation in the strong coupling limit and quantum Zeno regime. Our Letter paves the way for exploring higher-order exceptional physics in the many-body setting of ultracold atoms.
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Precise synthesis of all-inorganic lead halide perovskite nanowire heterostructures and superlattices with designable modulation of chemical compositions is essential for tailoring their optoelectronic properties. Nevertheless, controllable synthesis of perovskite nanostructure heterostructures remains challenging and underexplored to date. Here, we report a rational strategy for wafer-scale synthesis of one-dimensional periodic CsPbCl3/CsPbI3 superlattices. We show that the highly parallel array of halide perovskite nanowires can be prepared roughly as horizontally guided growth on an M-plane sapphire. A periodic patterning of the sapphire substrate enables position-selective ion exchange to obtain highly periodic CsPbCl3/CsPbI3 nanowire superlattices. This patterning is further confirmed by micro-photoluminescence investigations, which show that two separate band-edge emission peaks appear at the interface of a CsPbCl3/CsPbI3 heterojunction. Additionally, compared with the pure CsPbCl3 nanowires, photodetectors fabricated using these periodic heterostructure nanowires exhibit superior photoelectric performance, namely, high ION/IOFF ratio (104), higher responsivity (49 A/W), and higher detectivity (1.51 × 1013 Jones). Moreover, a spatially resolved visible image sensor based on periodic nanowire superlattices is demonstrated with good imaging capability, suggesting promising application prospects in future photoelectronic imaging systems. All these results based on the periodic CsPbCl3/CsPbI3 nanowire superlattices provides an attractive material platform for integrated perovskite devices and circuits.
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We present enhanced sensing of a radio frequency (RF) electric field (E-field) by the combined polarizability of Rydberg atoms and the optimized local oscillator (LO) field of a superheterodyne receiver. Our modified theoretical model reveals the dependencies of the sensitivity of E-field amplitude measurement on the polarizability of Rydberg states and the strength of the LO field. The enhanced sensitivities of the megahertz (MHz) E-field are demonstrated at the optimal LO field for three different Rydberg states ${\rm 43D}_{5/2}$, ${\rm 60S}_{1/2}$, and ${\rm 90S}_{1/2}$. The sensitivity of 63 MHz for the ${\rm 90S}_{1/2}$ state reaches 9.6 $\times 10^{-5}\rm \,V/m/\sqrt {Hz}$, which is approximately an order of magnitude higher than those already published. This result closely approaches the sensitivity limit of a 1 cm passive dipole antenna without using an impedance matching network. This atomic sensor based on the Rydberg Stark effect with heterodyne technique is expected to boost an alternative solution to electric dipole antennas.
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Determining the correlation between the size of a single quantum dot (QD) and its photoluminescence (PL) properties is a challenging task. In the study, we determine the size of each QD by measuring its absorption cross section, which allows for accurate investigation of size-dependent PL blinking mechanisms and volume scaling of the biexciton Auger recombination at the single-particle level. A significant correlation between the blinking mechanism and QD size is observed under low excitation conditions. When the QD size is smaller than their Bohr diameter, single CsPbI3 perovskite QDs tend to exhibit BC-blinking, whereas they tend to exhibit Auger-blinking when the QD size exceeds their Bohr diameter. In addition, by extracting bright-state photons from the PL intensity trajectories, the effects of QD charging and surface defects on the biexcitons are effectively reduced. This allows for a more accurate measurement of the volume scaling of biexciton Auger recombination in weakly confined CsPbI3 perovskite QDs at the single-dot level, revealing a superlinear volume scaling (τXX,Auger â σ1.96).
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Twisted stacking of two-dimensional materials with broken inversion symmetry, such as spiral MoTe2 nanopyramids and supertwisted spiral WS2, emerge extremely strong second- and third-harmonic generation. Unlike well-studied nonlinear optical effects in these newly synthesized layered materials, photoluminescence (PL) spectra and exciton information involving their optoelectronic applications remain unknown. Here, we report layer- and power-dependent PL spectra of the supertwisted spiral WS2. The anomalous layer-dependent PL evolutions that PL intensity almost linearly increases with the rise of layer thickness have been determined. Furthermore, from the power-dependent spectra, we find the power exponents of the supertwisted spiral WS2 are smaller than 1, while those of the conventional multilayer WS2 are bigger than 1. These two abnormal phenomena indicate the enlarged interlayer spacing and the decoupling interlayer interaction in the supertwisted spiral WS2. These observations provide insight into PL features in the supertwisted spiral materials and may pave the way for further optoelectronic devices based on the twisted stacking materials.
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This erratum corrects errors in Fig. 4(b) of the original paper, Appl. Opt.63, 1847 (2023)APOPAI0003-693510.1364/AO.510265. This correction does not affect any of the results or conclusions of the aforementioned paper.
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Transition strengths between states are fundamental physical properties of atomic spectra. The differences in fine structure splitting of certain states are mainly attributed to the angular momentum parts of transition dipole matrix elements. These can be calculated by integrating the wave-functions theoretically and can be accessed by selecting corresponding polarizations of the exciting lasers experimentally. We measured the transition strengths ratios of nD 5 / 2 /nD 3 / 2 via Rydberg electromagnetically induced transparency (EIT) by changing the powers and polarizations of probing and coupling lasers in a room temperature cesium vapor cell. The variation of the ratios on the principal quantum number n which ranges from 40 to 62 is also investigated. Theoretical and experimental results agreed with each other.
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A method called the optimal demodulated Lorentzian spectrum is employed to precisely quantify the narrowness of a laser's linewidth. This technique relies on the coherent envelope demodulation of a spectrum obtained through short delayed self-heterodyne interferometry. Specifically, we exploit the periodic features within the coherence envelope spectrum to ascertain the delay time of the optical fiber. Furthermore, the disparity in contrast within the coherence envelope spectrum serves as a basis for estimating the laser's linewidth. By creating a plot of the coefficient of determination for the demodulated Lorentzian spectrum fitting in relation to the estimated linewidth values, we identify the existence of an optimal Lorentzian spectrum. The corresponding laser linewidth found closest to the true value is deemed optimal. This method holds particular significance for accurately measuring the linewidth of lasers characterized as narrow or ultranarrow.
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Quantum imaging based on entangled light sources exhibits enhanced background resistance compared to conventional imaging techniques in low-light conditions. However, direct imaging of dynamic targets remains challenging due to the limited count rate of entangled photons. In this paper, we propose a quantum imaging method based on quantum compressed sensing that leverages the strong correlation characteristics of entangled photons and the randomness inherent in photon pair generation and detection. This approach enables the construction of a compressed sensing system capable of directly imaging high-speed dynamic targets. The results demonstrate that our system successfully achieves imaging of a target rotating at a frequency of 10 kHz, while maintaining an impressive data compression rate of 10-6. This proposed method introduces a pioneering approach for the practical implementation of quantum imaging in real-world scenarios.
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Governed by the hairy ball theorem, classical antennas with isotropic responses to linearly polarized radio waves are unrealizable. Also, their calibrations face a causal dilemma. Therefore, radio wave measurements based on classical antennas are challenging to achieve high accuracy. This work shows that the antenna based on Rydberg atoms can theoretically achieve an ideal isotropic response to linearly polarized radio waves; that is, it has zero isotropic deviation. Although this conclusion is straightforward, it is not theoretically clear when complex atomic energy levels are taken into account. Experimental results of isotropic deviation within 5 dB and 0.3 dB possible with optimization in microwave and terahertz wave measurements support the theory and is at least 15 dB improvement than the classical omnidirectional antenna. Combined with the SI traceable and ultrawideband property, the ideal isotropic response will make radio wave measurement based on atomic antenna much more accurate and reliable than the traditional method. This isotropic atomic antenna is an excellent example of what a tailored quantum sensor can realize, but a classical sensor cannot. It has crucial applications in fields such as radio wave electrometry.
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There was an error in the original publication [...].
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Local density of states (LDOS) is emerging as powerful means of exploring classical-wave topological phases. However, the current LDOS detection method remains rare and merely works for static situations. Here, we introduce a generic dynamical method to detect both the static and Floquet LDOS, based on an elegant connection between dynamics of chiral density and local spectral densities. Moreover, we find that the Floquet LDOS allows to measure out Floquet quasienergy spectra and identify topological π modes. As an example, we demonstrate that both the static and Floquet higher-order topological phase can be universally identified via LDOS detection, regardless of whether the topological corner modes are in energy gaps, bands, or continuous energy spectra without band gaps. Our study opens a new avenue utilizing dynamics to detect topological spectral densities and provides a universal approach of identifying static and Floquet topological phases.
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Electro-optic modulators (EOMs) are essential devices of optical communications and quantum computing systems. In particular, ultra-compact EOMs are necessary for highly integrated photonic chips. Thin film lithium niobate materials are a promising platform for designing highly efficient EOMs. However, EOMs based on conventional waveguide structures are at a millimeter scale and challenging to scale down further, greatly hindering the capability of on-chip integration. Here, we design an EOM based on lithium niobate valley photonic crystal (VPC) structures for the first time. Due to the high effective refractive index introduced by the strong slow light effect, the EOM can achieve an ultra-compact size of 4 µm×14 µm with a half-wave voltage of 1.4 V. The EOM has a high transmittance of 0.87 in the 1068â nm because of the unique spin-valley locking effect in VPC structures. The design is fully compatible with current nanofabrication technology and immune to fabrication defects. Therefore, it opens a new possibility in designing lithium niobate electro-optic modulators and will find broad applications in optical communication and quantum photonic devices.
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Tomography plays an important role in characterizing the three-dimensional structure of samples within specialized scenarios. In the paper, a masked attention network is presented to eliminate interference from different layers of the sample, substantially enhancing the resolution for photon-level single-pixel tomographic imaging. The simulation and experimental results have demonstrated that the axial resolution and lateral resolution of the imaging system can be improved by about 3 and 2 times respectively, with a sampling rate of 3.0 %. The scheme is expected to be seamlessly integrated into various tomography systems, which is conducive to promoting the tomographic imaging for biology, medicine, and materials science.
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Almost all colloidal quantum dots (QDs) exhibit undesired photoluminescence (PL) blinking, which poses a significant obstacle to their use in numerous luminescence applications. An in-depth study of the blinking behavior, along with the associated mechanisms, can provide critical opportunities for fabricating high-quality QDs for diverse applications. Here the blinking of a large series of colloidal QDs is investigated with different surface ligands, particle sizes, shell thicknesses, and compositions. It is found that the blinking behavior of single alloyed CdSe/ZnS QDs with a shell thickness of up to 2 nm undergoes an irreversible conversion from Auger-blinking to band-edge carrier blinking (BC-blinking). Contrastingly, single perovskite QDs with particle sizes smaller than their Bohr diameters exhibit reversible conversion between BC-blinking and more pronounced Auger-blinking. Changes in the effective trapping sites under different excitation conditions are found to be responsible for the blinking type conversions. Additionally, changes in shell thickness and particle size of QDs have a significant effect on the blinking type conversions due to altered wavefunction overlap between excitons and effective trapping sites. This study elucidates the discrepancies in the blinking behavior of various QD samples observed in previous reports and provides deeper understanding of the mechanisms underlying diverse types of blinking.
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The tunable optical display is vital for many application fields in telecommunications, sensors, and military devices. However, most optical materials have a strong wavelength dependence, which limits their spectral operation range. In this work, we develop an electrically reconfigurable optical medium based on graphene, demonstrating a cycle-controlled display covering the electromagnetic spectrum from the visible to the infrared wavelength. Through an electro-intercalation method, the graphene-based surface enables rich colors from gray to dark blue to dark red to yellow, and the response time is about 1 min from the start gray color to the final yellow color. Simultaneously, it exhibits a remarkable change in infrared emissivity (from 0.63 to 0.80 reduction to 0.20) with a response time of 1 s. This modification of optical properties of lithiated multilayer graphene (MLG) is the increase of Fermi energy (Ef) due to the charge transfer from lithium (Li) to graphene layers, which causes changes in interband and intraband electronic transitions. Our findings imply potential value in fabricating multispectral optical materials with high tunability.
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Quantum matter interacting with gauge fields, an outstanding paradigm in modern physics, underlies the description of various physical systems. Engineering artificial gauge fields in ultracold atoms offers a highly controllable access to the exotic many-body phenomena in these systems, and has stimulated intense interest. Here we implement a triangular flux ladder in the momentum space of ultracold 133Cs atoms, and study the chiral dynamics under tunable interactions. Through measurements of the site-resolved density evolutions, we reveal how the competition between interaction and flux in the frustrated triangular geometry gives rise to flux-dependent localization and biased chiral dynamics. For the latter in particular, the symmetry between the two legs is dynamically broken, which can be attributed to frustration. We then characterize typical dynamic patterns using complementary observables. Our work opens the avenue toward exploring correlated transport in frustrated geometries, where the interplay between interactions and gauge fields plays a key role.
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Realization of nonreciprocal transport is of great importance in the development of devices and systems that require the directional manipulation of signals or particles in information processing and modern physics. For ultracold atomic systems, the approaches based on synthetic dimensions have led to rapid advances in engineering quantum transport. Here, we use laser-coupled discrete momentum states of noninteracting ultracold atoms to synthesize a momentum lattice, and construct a closed ring with controllable tunneling phase in the momentum lattice. We measure the density evolution of atoms in the synthetic lattice with the single-site resolution, and observe the nonreciprocal dynamics by controlling the tunneling phase. We show the effect of both the applied phase and the coupling strength between two distinct population regions on the population distribution of atoms in the momentum lattice, and provide the optimal parameters for achieving the nonreciprocal transport.
