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Realizing high average power nanosecond pulsed single longitudinal mode laser sources around 1.6 μm are of intense interest for applications as diverse as range finding, remote sensing, and environmental monitoring. Herein, we first demonstrate a high average power and high beam quality nanosecond pulsed eye-safe diamond Raman laser at 1634 nm, which is intracavity driven by an acousto-optic Q-switched two-crystal Nd:YVO4 laser at 1342 nm. By exploiting the subtly designed dynamically stable resonator and the thoroughly optimized acousto-optic modulator, excellent beam quality and substantial power improvement have been confirmed. Under the incident pump power of 60.9 W, the highest multimode average output power of 6.92 W has been achieved with the repetition rate of 25 kHz and the duty cycle of 8%, corresponding to the pulse duration of 8.8 ns and the peak power of 31.5 kW. Subsequently, by inserting a fused silica etalon in the high-Q fundamental cavity, the average output power for single longitudinal mode operation has been creeping up to 2.56 W with the aid of the high precision temperature controlling and the enlarged beam diameter on diamond, where the pulse duration and the spectral linewidth are 8 ns and 180 MHz, respectively. The beam quality is maintained with M2 < 1.3 across the entire output power range.

Abstract Stable vortex lattices are basic dynamical patterns which have been demonstrated in physical systems including superconductor physics, Bose-Einstein condensates, hydrodynamics and optics. Vortex-antivortex (VAV) ensembles can be produced, self-organizing into the respective polar lattices. However, these structures are in general highly unstable due to the strong VAV attraction. Here, we demonstrate that multiple optical VAV clusters nested in the propagating coherent field can crystallize into patterns which preserve their lattice structures over distance up to several Rayleigh lengths. To explain this phenomenon, we present a model for effective interactions between the vortices and antivortices at different lattice sites. The observed VAV crystallization is a consequence of the globally balanced VAV couplings. As the crystallization does not require the presence of nonlinearities and appears in free space, it may find applications to high-capacity optical communications and multiparticle manipulations. Our findings suggest possibilities for constructing VAV complexes through the orbit-orbit couplings, which differs from the extensively studied spin-orbit couplings.

Abstract In recent years, related research has focused on how to safely transfer and protect the privacy of images in social network services while providing easy access by authorized users. To safeguard privacy, we suggest an image encryption scheme that combines data hiding and image encryption. The proposed scheme successfully decrypts images after JPEG compression attacks and preserves the privacy of secret regions through the use of block scrambling encryption based on region selection. Simultaneously, the scheme can handle nonuniform secret regions and obtain more sensitive secret keys because of the incorporation of a chaotic system. The enhanced deep learning-based data-hiding technology reduces algorithm complexity by enabling the encryption position to be determined in the decryption phase without the need for any information or equipment. However, this approach also increases algorithm security, because only when the right secret data are extracted can they be decrypted successfully. According to the experimental findings, the proposed scheme can correctly decrypt images via JPEG compression while maintaining visually acceptable quality. The proposed scheme can achieve greater robustness against image processing algorithms and a wider secret key space than traditional schemes.

Rabi oscillations express a phenomenon of periodic conversion between two wave states in a coupled system. The finding of Rabi oscillation has led to important applications in many different disciplines. Despite great progress, it is still unknown whether the Rabi oscillating state can be excited in the framework of the higher-order vector vortex regime. Here, we demonstrate in theory that the higher-order vector vortex light beams can be Rabi oscillating during evolution in an optical coupling system. This new classical oscillating state of light is characterized by a topologically shaped wavefront and coupled with spatially varying polarization. The vector vortex state exhibits a harmonic oscillatory property in the resonant and nonresonant conditions but differs greatly in Rabi oscillating frequencies. During Rabi oscillation, the complex state maintains its topology and intensity profile, while its intrinsic polarization pattern varies adiabatically in a periodic manner. We present an interpretation of the Rabi oscillation of the higher-order wave states in terms of the coupled-mode theory. Furthermore, we reveal a symmetry-protected transition between two Rabi oscillating modes, driven by a slowly varying phase mismatch. This Rabi transition has not been reported in either quantum mechanics or any other physical setting. This work advances the research of Rabi oscillation into the higher-order regime, and it may lead to novel applications in classical and quantum optics.

Abstract Rabi oscillation has been proven to be one of the cornerstones of quantum mechanics, triggering substantial investigations in different disciplines and various important applications both in the classical and quantum regimes. So far, two independent classes of wave states in the Rabi oscillations have been revealed as spin waves and orbital waves, while a Rabi wave state simultaneously merging the spin and orbital angular momentum has remained elusive. Here we report on the experimental and theoretical observation and control of spin–orbit-coupled Rabi oscillations in the higher-order regime of light. We constitute a pseudo spin-1/2 formalism and optically synthesize a magnetization vector through light-crystal interaction. We observe simultaneous oscillations of these ingredients in weak and strong coupling regimes, which are effectively controlled by a beam-dependent synthetic magnetic field. We introduce an electrically tunable platform, allowing fine control of transition between different oscillatory modes, resulting in an emission of orbital-angular-momentum beams with tunable topological structures. Our results constitute a general framework to explore spin–orbit couplings in the higher-order regime, offering routes to manipulating the spin and orbital angular momentum in three and four dimensions. The close analogy with the Pauli equation in quantum mechanics, nonlinear optics, etc., implies that the demonstrated concept can be readily generalized to different disciplines.

Objectives To evaluate the diagnostic performance of urine HIV antibody rapid test kits in screening diverse populations and to analyse subjects’ willingness regarding reagent types, purchase channels, acceptable prices, and self-testing.Designs Diagnostic accuracy studiesParticipants A total of 2606 valid and eligible samples were collected in the study, including 202 samples from female sex workers (FSWs), 304 persons with injection drug use (IDU), 1000 pregnant women (PW), 100 subjects undergoing voluntary HIV counselling and testing (VCT) and 1000 students in higher education schools or colleges (STUs). Subjects should simultaneously meet the following inclusion criteria: (1) being at least 18 years old and in full civil capacity, (2) signing an informed consent form and (3) providing truthful identifying information to ensure that the subjects and their samples are unique.Results The sensitivity, specificity and area under the curve (AUC) of the urine HIV-1 antibody rapid test kits were 92.16%, 99.92% and 0.960 (95% CI: 0.952 to 0.968, p

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

The kinetic process of the excited state population of Nd3+ ion in Nd: CaY0.9Gd0.1AlO4 (Nd: CYGA) crystal were studied in detail to estimate the optimal doping concentration, which maximize ~1 μm fluorescence emission from the 4F3/2 state to the 4I9/2 state of Nd3+. The analysis was accomplished by revealing the dependence of the excited state population on the doping concentration in a relatively convenient way in theory. After comparing the theoretical prediction results with the experimental findings and approximating the results obtained using the aforementioned method, the optimal relative doping concentration of Nd: CYGA was determined to be 2.1 at.%, which closely matched the 2.0 at.% obtained through experimental comparison. This verifies the effectiveness and accuracy of the proposed method. In particular, it is worth mentioning that in this method only one doping concentration of the crystal is required to obtain the optimal concentration, which may be used to guide the concentration optimization process for improving efficiency and saving resources.

Background: An unprecedented coronavirus disease 2019 (COVID-19) wave occurred in China between December 2022 and January 2023, challenging the efficacy of the primary series of COVID-19 vaccines. The attitudes toward future COVID-19 booster vaccines (CBV) after the massive breakthrough infection among healthcare workers remain unknown. This study aimed to explore the prevalence and determinants of future CBV refusal after the unprecedented COVID-19 wave among healthcare workers. Methods: Between 9 and 19 February 2023, a cross-sectional nationwide online survey was conducted using a self-administered questionnaire vaccine among healthcare workers in China. Sociodemographics, profession, presence of chronic medical conditions, previous COVID-19 infection, attitudes towards future CBV, and reasons for future CBV refusal were collected. We estimated odds ratio [OR] with 95% confidence interval [CI] using a multivariable logistic regression model to explore the factors associated with future CBV refusal. Results: Among the 1618 participants who completed the survey, 1511 respondents with two or more doses of COVID-19 vaccines were analyzed. A total of 648 (41.8%) of respondents were unwilling to receive a future CBV. Multivariable logistic regression analysis revealed the association of CBV refusal with profession (vs. other staff, physician-adjusted OR 1.17, 95%CI 0.79–1.72, nurse-adjusted OR 1.88, 95%CI 1.24−2.85, p = 0.008), history of allergy (adjusted OR 1.72, 95%CI 1.05–2.83, p = 0.032), a lower self-perceived risk of future COVID-19 infection (p < 0.001), and a lower belief in CBV effectiveness (p = 0.014), safety (p < 0.001), and necessities for healthcare workers and the public (p < 0.001, respectively). Conclusions: Our findings highlight that a considerable proportion of healthcare workers were against a future booster dose after an unprecedented COVID-19 wave. Self-perception of future COVID-19 risk, and potential harm or doubtful efficacy of vaccines are the main determinants. Our findings may help public health authorities to establish future COVID-19 vaccination programs.

Early diagnosis is important to reduce the incidence and mortality rate of diabetes. The feasibility of early diagnosis of diabetes was studied via near-infrared spectra (NIRS) combined with a support vector machine (SVM) and aquaphotomics. Firstly, the NIRS of entire blood samples from the population of healthy, pre-diabetic, and diabetic patients were obtained. The spectral data of the entire spectra in the visible and near-infrared region (400–2,500 nm) were used as the research object of the qualitative analysis. Secondly, several preprocessing steps including multiple scattering correction, variable standardization, and first derivative and second derivative steps were performed and the best pretreatment method was selected. Finally, for the early diagnosis of diabetes, models were established using SVM. The first overtone of water (1,300–1,600 nm) was used as the research object for an aquaphotomics model, and the aquagram of the healthy group, pre-diabetes, and diabetes groups were drawn using 12 water absorption patterns for the early diagnosis of diabetes. The results of SVM showed that the highest accuracy was 97.22% and the specificity and sensitivity were 95.65 and 100%, respectively when the pretreatment method of the first derivative was used, and the best model parameters were c = 18.76 and g = 0.008583.The results of the aquaphotomics model showed clear differences in the 1,400–1,500 nm region, and the number of hydrogen bonds in water species (1,408, 1,416, 1,462, and 1,522 nm) was evidently correlated with the occurrence and development of diabetes. The number of hydrogen bonds was the smallest in the healthy group and the largest in the diabetes group. The suggested reason is that the water matrix of blood changes with the worsening of blood glucose metabolic dysfunction. The number of hydrogen bonds could be used as biomarkers for the early diagnosis of diabetes. The result show that it is effective and feasible to establish an accurate and rapid early diagnosis model of diabetes via NIRS combined with SVM and aquaphotomics.

We present the first demonstration of an actively Q-switched orthogonally polarized dual-wavelength Nd:YLF/YVO4 Raman laser to our knowledge. The gain competition of the orthogonally polarized dual-wavelength fundamental laser at 1047 and 1053 nm was ultimately avoided by incorporating two Nd:YLF crystals into two laser resonators. By adjusting the gain or loss difference of two resonators, the pulse synchronization of the orthogonally polarized dual-wavelength Raman laser was realized. Benefitting from the efficient thermal stress and energy-transfer upconversion management of Nd:YLF crystal, a maximum dual-wavelength Raman output power of 4.5 W was obtained with M2

β-Ga2O3 crystals have attracted great attention in the fields of photonics and photoelectronics because of their ultrawide band gap and high thermal conductivity. Here, a pure β-Ga2O3 crystal was successfully grown by the optical floating zone (OFZ) method, and was used as a saturable absorber to realize a passively Q-switched all-solid-state 1 μm laser for the first time. By placing the as-grown β-Ga2O3 crystal into the resonator of the Nd:GYAP solid-state laser, Q-switched pulses at the center wavelength of 1080.4 nm are generated under a output coupling of 10%. The maximum output power is 191.5 mW, while the shortest pulse width is 606.54 ns, and the maximum repetition frequency is 344.06 kHz. The maximum pulse energy and peak power are 0.567 μJ and 0.93 W, respectively. Our experimental results show that the β-Ga2O3 crystal has great potential in the development of an all-solid-state 1 μm pulsed laser.

An efficient enhancement of 2.78 μm emission from the transition of Er3+: 4I11/2 → 4I13/2 by Tm3+ introduction in the Er/Tm: PbF2 crystal was grown by the Bridgman technique for the first time. The spectroscopic properties, energy transfer mechanism, and first-principles calculations of as-grown crystals were investigated in detail. The co-doped Tm3+ ion can offer an appropriate sensitization and deactivation effect for Er3+ ion at the same time in PbF2 crystal under the pump of conventional 800 nm laser diodes (LDs). With the introduction of Tm3+ ion into the Er3+: PbF2 crystal, the Er/Tm: PbF2 crystal exhibited an enhancing 2.78 μm mid-infrared (MIR) emission. Furthermore, the cyclic energy transfer mechanism that contains several energy transfer processes and cross-relaxation processes was proposed, which would well achieve the population inversion between the Er3+: 4I11/2 and Er3+: 4I13/2 levels. First-principles calculations were performed to find that good performance originates from the uniform distribution of Er3+ and Tm3+ ions in PbF2 crystal. This work will provide an avenue to design MIR laser materials with good performance.

A distinguishing characteristic of normal and cancer cells is the difference in their nuclear chromatin content and distribution. This difference can be revealed by the transmission spectra of nuclei stained with a pH-sensitive stain. Here, we used hematoxylin–eosin (HE) to stain hepatic carcinoma tissues and obtained spectral–spatial data from their nuclei using hyperspectral microscopy. The transmission spectra of the nuclei were then used to train a support vector machine (SVM) model for cell classification. Especially, we found that the chromatin distribution in cancer cells is more uniform, because of which the correlation coefficients for the spectra at different points in their nuclei are higher. Consequently, we exploited this feature to improve the SVM model. The sensitivity and specificity for the identification of cancer cells could be increased to 99% and 98%, respectively. We also designed an image-processing method for the extraction of information from cell nuclei to automate the identification process.

In this study, a strain of E. faecium R1 with effective bacteriostatic activity, acid resistance, bile salt resistance, high-temperature resistance was screened. To study the effect of E. faecium R1 on lipopolysaccharide (LPS)-induced intestinal and liver injury in piglets, twenty-four weaned female piglets were randomly assigned into one of three groups (8 piglets per group). Piglets in the control group and LPS group were fed a basal diet, piglets in the E. faecium group were fed the basal diet supplemented with E. faecium R1 (6.5 × 106 CFU/g). On day 21 of the trial, piglets in the LPS group and E. faecium group were intraperitoneally administered LPS (100 μg/kg), piglets in the control group were administered the same volume of saline. Subsequently, blood samples were collected at 3 h, and intestinal, liver, and pancreas samples were collected at 6 h. Results showed that E. faecium R1 supplementation significantly decreased the diarrhea rate and feed to gain ratio, and dramatically reduced LPS-induced intestinal and liver injury in piglets. Compared with the LPS group, E. faecium R1 supplementation significantly increased the content of glucagon in plasma and IL-1β in the liver, and the mRNA levels of villin in jejunum and ileum and Bcl-xL and pBD-L in the ileum, and significantly decreased the contents of prostaglandin 2 and malondialdehyde in the liver and the activities of myeloperoxidase and aspartate aminotransferase in plasma in piglets. Moreover, E. faecium R1 improved the pancreatic antioxidant capacity in piglets, which was indicated by a significant increase in catalase activity and a decrease in total nitric oxide synthase activity. In summary, dietary supplementation with E. faecium R1 alleviates intestinal and liver injury in LPS-challenged piglets.

In the past few decades, the multifunctional optical crystals for all-solid-state Raman lasers have been widely studied by many scholars due to their compactness, convenience and excellent performance. In this review, we briefly show two kinds of multifunctional Raman crystals: self-Raman (laser and Raman effects) crystals and self-frequency-doubled Raman (frequency-doubling and Raman effects) crystals. We firstly introduce the properties of the self-Raman laser crystals, including vanadate, tungstate, molybdate and silicate doped with rare earth ions, as well as self-frequency-doubled Raman crystals, including KTiOAsO4 (KTA) and BaTeMo2O9 (BTM). Additionally, the domestic and international progress in research on multifunctional Raman crystals is summarized in the continuous wave, passively Q-switched, actively Q-switched and mode-locked regimes. Finally, we present the bottleneck in multifunctional Raman crystals and the outlook for future development. Through this review, we contribute to a general understanding of multifunctional Raman crystals.

In this research, a new method based on the hyperspectral imaging for searching the best decocting time of sun dried ginseng is reported. The spectral images at different decocting time of test sample have been taken by the staring hyperspectral fluorescence imaging system and the solubility of active ingredients have been discussed by analyzing the changes on the spectral curves. The spectral range of the system is 400–720nm and the spectral resolution is 5nm. In the decocting process, the active ingredients of nonsoaked ginseng was dissolved in the tissue fluid at first, and reached equilibrium condition at last after the precipitation–dissolution reciprocating process of boiling. At last, the experimental results show that the best decoction time of sun dried ginseng is about 60min after boiling.

The content of berberine hydrochloride (BH) in compound berberine tablets (CBTs) is subject to strict requirements. Its content is usually measured based on chemical analysis. In this paper, the fluorescence spectral imaging method was used to study the relative content of BH from a physics perspective. By comparing the relative fluorescence intensity of self-made CBTs with different mass percentages of BH, a linear positive relationship was observed between the BH content and the relative fluorescence intensity, and accordingly the quality of CBTs of different brands was evaluated. The results indicate that the fluorescence spectral imaging method can be a simple, fast and nondestructive semi-quantitative analysis method to determine the content of BH in CBTs, and this method has great potential in the quality control of CBTs.