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We report the design and realization of the back focal plane (BFP) imaging for the light emission from a tunnel junction in a low-temperature ultrahigh-vacuum (UHV) scanning tunneling microscope (STM). To achieve the BFP imaging in a UHV environment, a compact "all-in-one" sample holder is designed and fabricated, which allows us to integrate the sample substrate with the photon collection units that include a hemisphere solid immersion lens and an aspherical collecting lens. Such a specially designed holder enables the characterization of light emission both within and beyond the critical angle and also facilitates the optical alignment inside a UHV chamber. To test the performance of the BFP imaging system, we first measure the photoluminescence from dye-doped polystyrene beads on a thin Ag film. A double-ring pattern is observed in the BFP image, arising from two kinds of emission channels: strong surface plasmon coupled emissions around the surface plasmon resonance angle and weak transmitted fluorescence maximized at the critical angle, respectively. Such an observation also helps to determine the emission angle for each image pixel in the BFP image and, more importantly, proves the feasibility of our BFP imaging system. Furthermore, as a proof-of-principle experiment, electrically driven plasmon emissions are used to demonstrate the capability of the constructed BFP imaging system for STM induced electroluminescence measurements. A single-ring pattern is obtained in the BFP image, which reveals the generation and detection of the leakage radiation from the surface plasmon propagating on the Ag surface. Further analyses of the BFP image provide valuable information on the emission angle of the leakage radiation, the orientation of the radiating dipole, and the plasmon wavevector. The UHV–BFP imaging technique demonstrated here opens new routes for future studies on the angular distributed emission and dipole orientation of individual quantum emitters in UHV. [ABSTRACT FROM AUTHOR]

In contrast to conventional anti‐counterfeiting technologies, which are susceptible to decryption and exhibit limited effectiveness, the utilization of light to dynamically configure soft materials in a fully reversible and programmable manner not only enhances data security but also improves anti‐counterfeiting performance. However, achieving precise control over reflection structural colors and laser wavelengths within a broad dynamic range remains a challenge. In this study, a UV‐responsive soft helical superstructure is established by combining a photochromic compound with chiral liquid crystals (LCs). By manipulating the Bragg reflection angle, structural reflection colors ranging from red to cyan are successfully achieved. The introduction of an anti‐counterfeiting technique that embeds diverse micro‐structures provides features such as color adjustability, erasability, and angle‐dependent stability. Using the unique properties of this soft helical superstructure, the implementation of a wavelength‐tunable LC bandgap laser through optically reconfigurable Förster resonance energy transfer processes is showcased. Furthermore, a straightforward prototype information encoder is developed to mimic the processes of information encoding and decoding, bypassing the need for complex algorithm design. This research underscores the practicality of LC helical soft systems, emphasizing their distinctive responsiveness to light and their applicability in optical programming photonics. [ABSTRACT FROM AUTHOR]

Liquid‐crystal random lasers (LCRLs) represent a burgeoning field in soft‐matter photonics, holding promise for ushering in an era of ultrathin, versatile laser sources. Such lasers encompass a multitude of remarkable features, including wide‐band tunability, large coherence area and, in some cases, multidirectional emission. In this paper, an LCRL is developed by doping a laser dye, pyrromethene 597 (PM597), into cholesteric LC, but achieving a wide‐range wavelength‐controllable (560–720 nm) bandgap lasing through voltage control. Bandgap lasing intriguingly occurs in media with extremely low dye gain, which is mainly contributed by the extremely high photon density of states (DOS) at the edge of the LC bandgap. In addition, the utilization rate of the fluorescence spectrum (550–750 nm) of laser dye PM597 is as high as 80%. The multivariate linear regression model is used to characterize the inherent relationship between the lasing intensity emitted by LC and the photon DOS, fluorescence quantum yield, and internal scattering under specific pumping energy. This model shows the potential to predict the critical conditions of laser emission accurately and provides the capability to design and fabricate large‐scale multifunctional responsive photonic crystals using a simple fabrication procedure. [ABSTRACT FROM AUTHOR]

Nanoscale optical sensing plays a crucial role in achieving high‐precision non‐contact distance and displacement measurements. As one of the promising alternatives, structured light can greatly simplify optical sensing systems. In this study, a novel optical phenomenon of a structured beam called the “Dumpling‐shaped Structured Light Field” (DSLF) is revealed, which forms during the focusing of cylindrical lens beams. The 3D DSLF comprises two mutually perpendicular primary and secondary foci, offering unique possibilities in micro/nano processing and sensing applications. A thorough investigation of the DSLF is conducted, revealing a correlation between the secondary foci and the phase status at the objective lens's entrance pupil. The propagation of DSLF under tight focus conditions has been verified and discussed through methods of femtosecond laser two‐photon polymerization and light field analysis. Finally, thanks to the unique 3D intensity distribution of 3D DSLF, the applicability of DSLF in high‐precision position and vibration sensing has been demonstrated. By detecting the horizontal and vertical dimensions of the reflected DSLF, position and vibration sensing is achieved with a Z‐direction accuracy of 10 nm (λ/80). This research contributes to understanding structured light, and offers practical applications in various fields, including micro/nano laser processing, optical imaging, sensing, etc. [ABSTRACT FROM AUTHOR]

Background: To evaluate the impact of embryo quality and quantity, specifically a poor quality embryo (PQE) in combination with a good quality embryo (GQE), by double embryo transfer (DET) on the live birth rate (LBR) and neonatal outcomes in patients undergoing frozen-thawed embryo transfer (FET) cycles. Methods: A study on a cohort of women who underwent a total of 1462 frozen-thawed cleavage or blastocyst embryo transfer cycles with autologous oocytes was conducted between January 2018 and December 2021. To compare the outcomes between single embryo transfer (SET) with a GQE and DET with a GQE and a PQE, propensity score matching (PSM) was applied to control for potential confounders, and a generalized estimating equation (GEE) model was used to determine the association between the effect of an additional PQE and the outcomes. Subgroup analysis was also performed for patients stratified by female age. Results: After PS matching, DET-GQE + PQE did not significantly alter the LBR (adjusted odds ratio [OR] 1.421, 95% CI 0.907–2.228) compared with SET-GQE in cleavage-stage embryo transfer but did increase the multiple birth rate (MBR, [OR] 3.917, 95% CI 1.189–12.911). However, in patients who underwent blastocyst-stage embryo transfer, adding a second PQE increased the live birth rate by 7.8% ([OR] 1.477, 95% CI 1.046–2.086) and the multiple birth rate by 19.6% ([OR] 28.355, 95% CI 3.926–204.790), and resulted in adverse neonatal outcomes. For patients who underwent cleavage-stage embryo transfer, transferring a PQE with a GQE led to a significant increase in the MBR ([OR] 4.724, 95% CI 1.121–19.913) in women under 35 years old but not in the LBR ([OR] 1.227, 95% CI 0.719–2.092). The increases in LBR and MBR for DET-GQE + PQE compared with SET-GQE in women older than 35 years were nonsignificant toward. For patients who underwent blastocyst-stage embryo transfer, DET-GQE + PQE had a greater LBR ([OR] 1.803, 95% CI 1.165–2.789), MBR ([OR] 24.185, 95% CI 3.285–178.062) and preterm birth rate (PBR, [OR] 4.092, 95% CI 1.153–14.518) than did SET-GQE in women under 35 years old, while no significant impact on the LBR ([OR] 1.053, 95% CI 0.589–1.884) or MBR (0% vs. 8.3%) was observed in women older than 35 years. Conclusions: The addition of a PQE has no significant benefit on the LBR but significantly increases the MBR in patients who underwent frozen-thawed cleavage-stage embryo transfer. However, for patients who underwent blastocyst-stage embryo transfer, DET-GQE + PQE resulted in an increase in both the LBR and MBR, which may lead to adverse neonatal outcomes. Thus, the benefits and risks of double blastocyst-stage embryo transfer should be balanced. In patients younger than 35 years, SET-GQE achieved satisfactory LBR either in cleavage-stage embryo transfer or blastocyst-stage embryo transfer, while DET-GQE + PQE resulted in a dramatically increased MBR. Considering the low LBR in women older than 35 years who underwent single cleavage-stage embryo transfer, selective single blastocyst-stage embryo transfer appears to be a more promising approach for reducing the risk of multiple live births and adverse neonatal outcomes. [ABSTRACT FROM AUTHOR]

• Based on the dye-doped hydrogel material, a low-threshold flexible film as well as a fiber random laser were realized. • Both random lasers in this paper can tune the wavelength of the random laser under the condition of changing the temperature. • Both hydrogel films and fiber random lasers have excellent flexibility and mechanical toughness, and the threshold of random lasers can be reduced by bending or stretching them. Hydrogel materials have great applications in biomedical and flexible optical sensors due to their good flexibility and biocompatibility. In this paper, two hydrogel structures of dye-doped poly(acrylamide-co-poly(ethylene glycol) diacrylate) (p(AM-co-PEGDA)) films and optical fibers were prepared to obtain low threshold and flexible random lasers. The random laser is attributed to the light scattering from the porous structure of the hydrogel, and the random lasing wavelength can be tuned of ∼ 7 nm and ∼ 11.8 nm for the hydrogel film and fiber in the temperature range of 25 to 85 °C, respectively. In addition, the hydrogel film can be bent repeatedly, and the bending strain has a positive effect on the random laser, and the random laser threshold is reduced by 10 μJ/mm2 when the bending strain reaches 47 % for hydrogel film. When the hydrogel optical fiber is stretched to 15 % of its original length, the random laser threshold can be reduced by 12 μJ/mm2.The p(AM-co-PEGDA) hydrogel optical fiber structure has better temperature sensing performance and excellent flexibility than the thin film structure. This work paves a way to extend random laser applications to photothermal therapy, ion detection, and biosensing. [ABSTRACT FROM AUTHOR]

We conducted an investigation on a flexible random laser (RL) device featuring non-noble plasmonic enhancement and scattering. The RL device was created by integrating copper nanowires (Cu NWs) and laser dyes (rhodamine 6G, R6G) into an acrylamide (AM) hydrogel matrix. The substantial overlap between the plasmonic resonance of Cu NWs and the emission of R6G effectively mitigates the requirements for lasing generation. Furthermore, the robust scattering induced by the three-dimensional distribution of Cu NWs contributes to a reduction in the laser threshold. Notably, the unique properties of the AM hydrogel ensure that the laser device exhibits excellent tensile recovery performance. The RL device is capable of maintaining stable lasing performance even after 100 % tensile deformation. This flexible laser device offers the advantages of a straightforward fabrication process, low cost, and robust lasing characteristics, thus paving the way for their advanced application in the future. [Display omitted] • A flexible hydrogel-based random laser that utilizes the plasmonic enhancement effect of non-noble metals was developed. • The threshold of random laser is effectively reduced by the local surface plasmon resonance effect of copper nanowires. • The random laser can maintain stable and high-quality laser output even after 100 % tensile deformation. [ABSTRACT FROM AUTHOR]

Near‐field optical trapping can be realized with focused evanescent waves that are excited at the water–glass interface due to the total internal reflection, or with focused plasmonic waves excited on the water–gold interface. Herein, the performance of these two kinds of near‐field optical trapping techniques is compared using the same optical microscope configuration. Experimental results show that only a single‐micron polystyrene bead can be trapped by the focused evanescent waves, whereas many beads are simultaneously attracted to the center of the excited region by focused plasmonic waves. This difference in trapping behavior is analyzed from the electric field intensity distributions of these two kinds of focused surface waves and the difference in trapping behavior is attributed to photothermal effects due to the light absorption by the gold film. [ABSTRACT FROM AUTHOR]

Fast, accurate, and real-time detection of nitrogen content in tobacco leaves is of great significance for monitoring the quality of tobacco leaves. Hyperspectral remote sensing (HRS) coupled with unmanned aerial vehicle (UAV) platform can provide unprecedented spectral information of field plants on a large scale. And with the support of various machine learning algorithms, a series of efficient models for leaf nitrogen content (LNC) assessment can be developed. This study aimed to develop a high-performance model to estimate the LNC of tobacco using UAV-borne HRS image data. Meanwhile, to cope with the heterogeneous performance problem of the individual model, ensemble learning strategies were applied to assemble multiple estimators, including multiple linear regression (MLR), decision tree regression (DTR), random forest (RF), adaptive boosting (Adaboost), and stacking to mine more valid data features. To accurately assess the performance of the established models, the coefficient of determination (R 2), root mean square error (RMSE), and mean absolute percentage error (MAPE) were introduced as the evaluation indicators, and partial least squares regression (PLSR) was selected as the baseline model. Results on the test set showed that all ensemble learning methods outperformed PLSR (R 2 =0.680, RMSE=5.402 mg/g, 19.72%). Specifically, the stacking-based models achieved the highest accuracy as well as relatively high stability (R 2 =0.745, RMSE=4.825 mg/g, 17.98%). This study provides a reference for efficient and non-destructive detection of LNC or other vegetation phenotypic traits using UAV-borne HRS technology. • A new attempt using drones-based hyperspectral for tobacco nitrogen estimation. • Three ensemble strategies performed well in predicting nitrogen content of tobacco leaves. • Exploring methods to improve the prediction accuracy and stability of the stacking strategy. [ABSTRACT FROM AUTHOR]

• In optic fiber sensing field, it shows the highest magnetic field sensitivity of 23.7425 nm/mT under magnetic field lower than 3mT. • The sensitivity is 250 times and 13.9 times than ordinary long period fiber grating and tapered fiber. • Dual-peaks-MTLPG (taper-long-period-fiber-grating-filled-with magnetic fluid) realizes the two parameters demodulation in the different range of magnetic field. The high sensitivity and dual parameters tapered-long-period-fiber-grating filled magnetic fluid (MTLPG) sensor is proposed in this paper. The tapered-long period fiber grating (TLPG) with double peaks was obtained by exposing periodically in the taper waist region of the taped fiber by using CO 2 laser. The magnetic fluid (MF)was wrapped on the taper cone surface of TLPG to obtain a magnetic field and temperature double responsive MTLPG sensor. According to the two resonance wavelengths responsive difference of MTLPG for the magnetic field and temperature, the sensitivity matrix including magnetic and temperature parameters can be constructed to solve the cross-sensitivity problem. The proposed MTLPG sensor has different responsive ranges and sensitivity according to the different MF concentrations and MTLPG cone diameters. The maximum sensitivity of our proposed sensor can reach to 23.72 nm/mT and 0.52 nm/℃, while the maximum responsive range can reach at 8.0 ∼ 16.0 mT and 25 ∼ 75 ℃. As far as we known, this is the highest magnetic sensitivity of optic fiber sensors in a weak magnetic field (below 3mT).Therefore, according the excellent characteristic for high sensitivity in a weak magnetic field and wide range temperature detection without crosstalk. [ABSTRACT FROM AUTHOR]