Laser Fabrication of Multi-Dimensional Perovskite Patterns with Intelligent Anti-Counterfeiting Applications.

Perovskites have gained widespread attention across various fields such as photovoltaics, displays, and imaging. Despite their promising applications, achieving precise and high-quality patterning of perovskite films remains a challenge. In this study, femtosecond laser direct writing technology is utilized to achieve rapid and highly precise micro/nanofabrication on perovskites. The study successfully fabricates multiple structured and emission-tunable perovskite patterns composed of A2(FA)n-1PbnX3n+1 (A represents a series of long-chain amine cations, and X = Cl, Br, I), encompassing 2D, quasi-2D, and 3D structures. The study delves into the intricate interplay between fabrication technology and the growth of multi-dimensional perovskites: higher repetition rates, coupled with appropriate laser power, prove more conducive to perovskite growth. By employing precise halogen element design, the simultaneous generation of two distinct color quick-response (QR) code patterns is achieved through one-step laser processing. These mirrored QR codes offer a novel approach to anti-counterfeiting. To further enhance anti-counterfeiting capabilities, artificial intelligence (AI)-based methods are introduced for recognizing patterned perovskite anti-counterfeiting labels. The combination of deep learning algorithms and a non-deterministic manufacturing process provides a convenient means of identification and creates unclonable features. This integration of materials science, laser fabrication, and AI offers innovative solutions for the future of security features.

Experimental evidence on the feasibility of employing a replica symmetry breaking classification random laser.

Replica symmetry breaking (RSB) has been introduced in a random laser to investigate the interactions between disorder and fluctuations. In this work, the dynamic difference between four non-energy transfer and Förster resonance energy transfer (FRET)-assisted random laser systems is investigated based on RSB. It is found that FRET is one of the key factors influencing RSB, and it is demonstrated that RSB in a random laser is not robust. This dynamic difference can be attributed to the different disorders induced by the gain mechanism in different random laser systems. This provides experimental evidence and theoretical support for the classification feasibility of RL with different emission mechanisms employing RSB.

Low-frequency electric field sensing via superposition orbital angular momentum light.

The polarization and orbital angular momentum (OAM) degrees of freedom carried by light have important applications in precision optical measurement and optical sensing. Here we show that the electro-optic Pockels effect of a magnesium-doped lithium niobate (MgO:LiNbO3) crystal can be used to measure a low-frequency electric field. By exploiting the rotation property of superposition OAM light, we experimentally observe that the minimum measured precision of electric field intensity is about 0.18 V/m. This study offers a method to perform low-frequency electric field sensing.

Non-invasive imaging using a low-spatial-coherence multimode random polymer fiber laser.

Random lasers (RLs), with their low spatial coherence, are ideal illumination sources for speckle-free imaging. However, it is still challenging for RLs to maintain low spatial coherence with the need for integration and directionality. Here, a disordered multimode random polymer fiber laser (RPFL) is proposed and implemented as a low-spatial-coherence light source. Compared to typical multimode optical fibers, the number of accommodated modes is increased by about 11×, the speckle contrast is reduced to 0.013, and the spatial coherence factor is reduced to 0.08. The low-spatial-coherence property enables RPFL to produce significantly superior imaging quality in both speckle-free imaging and non-invasive imaging through opacity. This study provides a strategy for an integrated speckle-free imaging system and paves the way for non-invasive imaging.

Simultaneous noninvasive ultrasensitive detection of prostate specific antigen and lncRNA PCA3 using multiplexed dual optical microfibers with strong plasmonic nanointerfaces.

Low accuracy of diagnosing prostate cancer (PCa) was easily caused by only assaying single prostate specific antigen (PSA) biomarker. Although conventional reported methods for simultaneous detection of two specific PCa biomarkers could improve the diagnostic efficiency and accuracy, low detection sensitivity restrained their use in extreme early-stage PCa clinical assay applications. In order to overcome above drawbacks, this paper herein proposed a multiplexed dual optical microfibers separately functionalized with gold nanorods (GNRs) and Au nanobipyramids (Au NBPs) nanointerfaces with strong localized surface plasmon resonance (LSPR) effects. The sensors could simultaneously detect PSA protein biomarker and long noncoding RNA prostate cancer antigen 3 (lncRNA PCA3) with ultrahigh sensitivity and remarkable specificity. Consequently, the proposed dual optical microfibers multiplexed biosensors could detect the PSA protein and lncRNA PCA3 with ultra-low limit-of-detections (LODs) of 3.97 × 10-15 mol/L and 1.56 × 10-14 mol/L in pure phosphorus buffer solution (PBS), respectively, in which the obtained LODs were three orders of magnitude lower than existed state-of-the-art PCa assay technologies. Additionally, the sensors could discriminate target components from complicated physiological environment, that showing noticeable biosensing specificity of the sensors. With good performances of the sensors, they could successfully assay PSA and lncRNA PCA3 in undiluted human serum and urine simultaneously, respectively. Consequently, our proposed multiplexed sensors could real-time high-sensitivity simultaneously detect complicated human samples, that providing a novel valuable approach for the high-accurate diagnosis of early-stage PCa individuals.

MXene Supported Surface Plasmon Polaritons for Optical Microfiber Ammonia Sensing.

The properties of surface plasmons are notoriously dependent on the supporting materials system. However, new capabilities cannot be obtained until the technique of surface plasmon enabled by advanced two-dimensional materials is well understood. Herein, we present the experimental demonstration of surface plasmon polaritons (SPPs) supported by single-layered MXene flakes (Ti3C2Tx) coating on an optical microfiber and its application as an ammonia gas sensor. Enabled by its high controllability of chemical composition, unique atomistically thin layered structure, and metallic-level conductivity, MXene is capable of supporting not only plasmon resonances across a wide range of wavelengths but also a selective sensing mechanism through frequency modulation. Theoretical modeling and optics experiments reveal that, upon adsorbing ammonia molecules, the free electron motion at the interface between the SiO2 microfiber and the MXene coating is modulated (i.e., the modulation of the SPPs under applied light), thus inducing a variation in the evanescent field. Consequently, a wavelength shift is produced, effectively realizing a selective and highly sensitive ammonia sensor with a 100 ppm detection limit. The MXene supported SPPs open a promising path for the application of advanced optical techniques toward gas and chemical analysis.

Stably suppressing laser relative intensity noise on a 3 × 3 coupler interferometric system.

A 3 × 3 coupler multiphase demodulation scheme is proposed to eliminate the impact of working point drifting and the laser relative intensity noise (RIN) on a 3 × 3 coupler interferometric system. An ellipse-fitting algorithm (EFA) is applied to fit the two interference signals of the 3 × 3 coupler in order, then the ATAN algorithm is applied to obtain three noise-containing signals with specific trigonometric relationships. By averaging the three signals, the demodulated phase noise induced from RIN can be effectively eliminated. The experimental results show that compared with the asymmetric demodulation scheme without intensity noise control, the noise floor of the proposed scheme decreases from 4.5 to 1 µrad/√Hz at 1 kHz and 2.7 to 0.8 µrad/√Hz at 3 kHz. At high frequencies, the average noise floor level is reduced from 10 to 0.9 µrad/√Hz, a reduction of about 21 dB. Furthermore, the variation range of the average noise floor is reduced from 5.4 to 0.17 µrad /√Hz within 100 s.

High precision 3 × 3 coupler demodulation algorithm with an additional phase shift judgment module.

Ellipse fitting algorithms (EFAs) have been widely used in 3×3 coupler demodulation systems to reduce the requirement for symmetry of the 3×3 couplers. Based on the relative stability of the splitting ratio and phase difference after the establishment of the 3×3 coupler demodulation system, we solve the problem that EFA fails to work when the stimulating signal is small. Depending on the existence of a symmetry point about the origin, an additional phase shift judgment module is used to determine whether the Lissajous figure is larger than π rad. If the elliptical arc exceeds π rad, the EFA is executed. Otherwise, the previous parameters are used to correct the ellipse. Parameters are updated in real time to ensure high precision. The experimental results show that the total harmonic distortion (THD) of the ameliorated algorithm is improved by 1.28% compared to the EFA without the judgment module with a stimulus amplitude of 30 mV. The proposed scheme can effectively improve the dynamic range of the 3×3 coupler demodulation to reach 125.64 dB @ 1 kHz and 1% THD. The algorithm ensures the effective operation of the EFA under small phase shift conditions and improves the accuracy of phase demodulation.

High-Precision and Real-Time Measurement of Water Isotope Ratios Based on a Mid-Infrared Optical Sensor.

A compact spectrometer based on a mid-infrared optical sensor has been developed for high-precision and real-time measurement of water isotope ratios. The instrument uses laser absorption spectroscopy and applies the weighted Kalman filtering method to determine water isotope ratios with high precision and fast time response. The precision of the measurements is 0.41‰ for δ18O and 0.29‰ for δ17O with a 1 s time. This is much faster than the standard running average technique, which takes over 90 s to achieve the same level of precision. The successful development of this compact mid-infrared optical sensor opens up new possibilities for its future applications in atmospheric and breath gas research.

Observation of the photonic Hall effect and photonic magnetoresistance in random lasers.

Modulation of scattering in random lasers (RLs) by magnetic fields has attracted much attention due to its rich physical insights. We fabricate magnetic gain polymer optical fiber to generate RLs. From macroscopic experimental phenomena, with the increase of the magnetic field strength, the magnetic transverse photocurrent exists in disordered multiple scattering of RLs and the emission intensity of RLs decreases, which is the experimental observation of photonic Hall effect (PHE) and photonic magnetoresistance (PMR) in RLs. At the microscopic level, based on the field dependence theory of magnetic disorder in scattered nanoparticles and the replica symmetry breaking theory, the magnetic-induced transverse diffusion of photons reduces the scattering disorder, and then decreases the intensity fluctuation disorder of RLs. Our work establishes a connection between the above two effects and RLs, visualizes the influence of magnetic field on RL scattering at the microscopic level, which is crucial for the design of RLs.

Nonlinear error elimination using the fusion of PGC-DCM, geometric fitting, and Atan algorithms.

A phase generated carrier (PGC) demodulation scheme is always accompanied by nonlinear errors. We propose a fusion of PGC differential and cross multiplying (PGC-DCM), geometric fitting, and arctangent (Atan) algorithms for fiber optic interferometric sensors to eliminate nonlinear errors. The output amplitude of the PGC-DCM algorithm is used to judge whether the Lissajous figure of quadrature signals is larger than 1/2 ellipse arc. When the Lissajous figure exceeds 1/2 ellipse arc, the contaminated quadrature signals are corrected by the ellipse correction parameters calculated from the geometric fitting; otherwise, the previous fitting parameters are employed for correction. Geometric fitting is realized by minimizing the Sampson error, and its failure problem under small signals is solved by using the temporary stability of fitting results. Finally, desired signals are extracted from the corrected quadrature signals by the Atan algorithm. Experimental results show that the fusion combines the merits of the three algorithms and expands the application of the geometric fitting in PGC demodulation schemes.

Ameliorated 3 × 3 coupler-based demodulation algorithm using iteratively reweighted ellipse specific fitting.

Passive demodulation scheme using 3 × 3 coupler has been widely used in phase-sensitive optical time-domain reflectometry (φ-OTDR), interrogation of fiber Bragg gratings or fiber optic interferometric sensors, and sensor multiplexing. However, the asymmetry of the 3 × 3 coupler in real applications affects the demodulation performance seriously. We proposed an ameliorated 3 × 3 coupler-based demodulation algorithm using iteratively reweighted ellipse specific fitting (IRESF) to overcome the drawback. IRESF combines iterative reweight technology with ellipse specific fitting, which decreases the weights of high noise points and always outputs ellipse solutions. Any two output signals from the 3 × 3 coupler-based interferometer are fitted by the IRESF and then corrected as a pair of quadrature signals. The stability of the fitting parameters is utilized to resolve the failures of IRESF under small signals. A real-time 1/4 ellipse arc judging module is designed, if the Lissajous figure is larger than 1/4 ellipse arc, IRESF is executed to offer ellipse correction parameters. Otherwise, the fixed parameters preset in the algorithm are used. The fixed parameters are mean values of the fitting parameters of IRESF under a large stimulus. The desired phase signal is finally extracted from the corrected quadrature signals. Experimental results show that the ameliorated algorithm does not require strict symmetry of the 3 × 3 coupler and can work under small signals. The noise floor of the proposed algorithm is -112 dB re rad/√Hz and the demodulated amplitude is 23.15 dB (14.37 rad) at 1 kHz when THD is 0.0488%. Moreover, the response linearity is as high as 99.999%. Compared to the algorithm using direct least squares, the proposed demodulation algorithm is more robust and precise, which has broad application prospects.

Laser Velocimetry for the In Situ Sensing of Deep-Sea Hydrothermal Flow Velocity.

Laser Doppler velocimetry (LDV) based on a differential laser Doppler system has been widely used in fluid mechanics to measure particle velocity. However, the two outgoing lights must intersect strictly at the measurement position. In cross-interface applications, due to interface effects, two beams of light become easily disjointed. To address the issue, we present a laser velocimeter in a coaxial arrangement consisting of the following components: a single-frequency laser (wavelength λ = 532 nm) and a Twyman-Green interferometer. In contrast to previous LDV systems, a laser velocimeter based on the Twyman-Green interferometer has the advantage of realizing cross-interface measurement. At the same time, the sensitive direction of the instrument can be changed according to the direction of the measured speed. We have developed a 4000 m level laser hydrothermal flow velocity measurement prototype suitable for deep-sea in situ measurement. The system underwent a withstand voltage test at the Qingdao Deep Sea Base, and the signal obtained was normal under a high pressure of 40 MPa. The velocity contrast measurement was carried out at the China Institute of Water Resources and Hydropower Research. The maximum relative error of the measurement was 8.82% when compared with the acoustic Doppler velocimeter at the low-speed range of 0.1-1 m/s. The maximum relative error of the measurement was 1.98% when compared with the nozzle standard velocity system at the high-speed range of 1-7 m/s. Finally, the prototype system was successfully evaluated in the shallow sea in Lingshui, Hainan, with it demonstrating great potential for the in situ measurement of fluid velocity at marine hydrothermal vents.

Phase noise suppression technique based on an improved reference interferometer scheme.

The reference interferometer scheme is an effective noise reduction method, but the optical path length difference (OPD) of the two interferometers must be strictly equal, which limits its application in practical environments. In this paper, an improved reference interferometer demodulation technique without strictly equal OPDs is proposed to suppress phase noise. By introducing a reference interferometer, the phase noise can be removed from the demodulation results. The combination of the differential self-multiplication algorithm and the fitted phase modulation depth calculation formula can evaluate the phase modulation depth of both interferometers in real time and simultaneously eliminate the nonlinear distortion caused by phase modulation depth drift and the effect of different OPDs on the reference interferometer scheme. The experimental results show that the technique can obtain highly stable and accurate demodulation results even if the OPDs of the two reference interferometers are different. The phase modulation depth calculation error is less than 0.57%, the maximum phase noise reduction is 15 dB, the average reduction is 9 dB, the minimum total harmonic distortion is 0.17%, and the SINAD reaches 35.90 dB.

Neuroprotective effect of 1,25­dihydroxyvitamin D3 against hyperoxia­induced brain injury in premature rats.

Studies have shown that vitamin D plays a crucial role in brain development, brain metabolism and neuroprotection. There is little evidence for the neuroprotective effect of 1, 25­dihydroxyvitamin D3 (1,25­(OH)2D3) on various brain injury models. The aim of this study was to investigate the neuroprotection effect of 1,25­(OH)2D3 against hyperoxia­induced brain injury in premature rats. Sprague­Dawley rats were exposed to 95% oxygen or room air for 24 h and treated with 1,25­(OH)2D3 or normal saline for 14 consecutive days. The histopathological changes of optic chiasma tissue were observed by hematoxylin­eosin staining. Immunohistochemistry, qRT­PCR, and western blot were performed to detect the expression of integrin­ß1 and yes­associated protein (YAP) in the organization of the optic chiasm. Histopathological sections of optic chiasma showed visible optic nerve swelling, expanded nerve fiber space, uneven staining, obvious oligodendrocyte proliferation and disordered cell arrangement accompanied by inflammatory cell infiltration and exudation after 7 days and 14 days of hyperoxia exposure. The hyperoxia group treated with 1,25­(OH)2D3 were showed improvement of brain injury with reduced inflammatory exudation, uniform nerve fiber staining and less obvious oligodendrocyte proliferation. Immunohistochemical staining, qRT­PCR and western blot indicated that 1,25­(OH)2D3 treatment upregulated the expression of integrin­ß1 and YAP in the hyperoxia group on day 7. However, the expression of YAP was significantly increased compared with control group and treatment with 1,25­(OH)2D3 reduced the expression of YAP in the hyperoxic group on day 14. 1,25­(OH)2D3 may regulate the expression of integrin­ß1 and YAP to alleviate hyperoxia­induced brain injury in premature rats.

Improved topography measurement with a high dynamic range using phase difference sensing technology.

Phase difference sensing technology (PDST) is employed for topography measurement, and two interference structures are proposed to achieve upper-limit adjustment and high resolution in the measurement range: a dual-wavelength system with a single Fabry-Perot (FP) cavity and a single-wavelength system with dual FP cavities. The phase difference between the two interference signals is determined by an elliptic fitting algorithm (EFA), and this change in phase difference is utilized to characterize the step height. Experimental results indicate that the measurement upper-limit can be adjusted to either 410 µm, 187 µm, or 108 µm by varying the wavelength difference in the dual-wavelength system, which gives a measurement error of 2.96%. In contrast, while offering a measurement resolution of 3.47 nm, the single-wavelength system exhibits a measurement error of 5.38%. The proposed method is capable of satisfying the measurement requirements during micro-electromechanical system (MEMS) processing with proficiency.

Voltage, thermal and magnetic field fiber sensors based on magnetic nanoparticles-doped photonic liquid crystal fibers.

In this article, highly sensitive voltage, thermal and magnetic field fiber sensors were obtained in magnetic nanoparticles-doped E7 liquid crystals filled into photonic crystal fibers (PLCF). The voltage and temperature sensitivity reached at 12.598 nm/V and -3.874 nm/°C, respectively. The minimum voltage response time is 48.2 ms. The phase transition temperature Tc of liquid crystal with magnetic dopant was reduced from 60 °C to 46 °C. The magnetic field sensor based on magnetic nanoparticles-doped PLCF were obtained with sensitivity of 118.2 pm/mT from 400 to 460 mT.

Metal-organic framework-based self-healing hydrogel fiber random lasers.

Metal-organic frameworks (MOFs), which have well-defined nanoporous skeletons and whose natural structure can work as optical resonant cavities, are emerging as ideal platforms for constructing micro/nanolasers. However, lasing generated from the light oscillating inside a defined MOFs' cavity usually suffers the drawback of the lasing performance being difficult to maintain once the cavity is destroyed. In this work, we report a MOF-based self-healing hydrogel fiber random laser (MOF-SHFRL) that can withstand extreme damage. The optical feedback of MOF-SHFRLs does not depend on the light reflection inside the MOF cavity but comes from the multiple scattering effects from the MOF nanoparticles (NPs). The hydrogel fiber's one-dimensional waveguide structure also permits confined directional lasing transmission. Based on such an ingenious design, a robust random lasing is achieved without worrying about the destruction of the MOF NPs. More interestingly, the MOF-SHFRL demonstrates excellent self-healing ability without any external stimulation: it can fully recover its initial morphology and lasing performance even when totally broken (e.g., cut into two parts). The lasing threshold also remains stable, and the optical transmission capability can recover by more than 90% after multiple breaks and self-healing processes. These results indicate that the MOF-SHFRL is a highly stable optical device that can be expected to play a significant role in environmental monitoring, intelligent sensing, and other aspects under extreme conditions.

Performance evaluation of plastic optical fiber communication using micro-lens coupling and computational temporal ghost imaging algorithm.

Plastic optical fiber communication (POFC) systems are particularly sensitive to signal performance and power budget. In this paper, we propose what we belive to be a novel scheme to jointly enhance the bit-error-ratio (BER) performance and coupling efficiency for multi-level pulse amplitude modulation (PAM-M) based POFC systems. The computational temporal ghost imaging (CTGI) algorithm is developed for PAM4 modulation for the first time to resist the system distortion. The simulation results reveal that enhanced BER performance and clear eye diagrams are acquired by using CTGI algorithm with an optimized modulation basis. Experimental results also investigate and show, with CTGI algorithm, the BER performance for 180 Mb/s PAM4 signals is enhanced from 2.2 × 10-2 to 8.4 × 10-4 over 10 m POF by using a 40 MHz photodetector. The POF link is equipped with micro-lenses at its end faces by using a ball-burning technique, which helps to increase the coupling efficiency from 28.64% to 70.61%. Both simulation and experimental results show that the proposed scheme is feasible to achieve a cost-effective and high-speed POFC system with short reach.

Line positions and effective line strengths of trans-HONO near 1280 cm-1.

The measurement of the line positions and effective line strengths of the ν3 fundamental band of trans-nitrous acid (trans-HONO) near 1280 cm-1 (7.8 µm) by tunable laser absorption spectroscopy (TLAS) utilizing a room temperature continuous-wave quantum cascade laser (cw-QCL) was reported. The effective line strengths of 30 well-resolved trans-HONO absorption lines in the range of 1279.8-1282.2 cm-1 were determined using the HONO line strength at 1280.3841 cm-1 as a scale. The maximum measurement uncertainty of 7.64% in the line strengths is mainly determined by the uncertainty of the referenced line strength, while the measurement precision of the line positions is better than 5.56 * 10-3 cm-1. The line positions and strengths of the trans-HONO absorption lines obtained in this work provide a reference for continuous gas monitoring and analysis of the sources and sinks of atmospheric HONO.