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In this paper, we propose and numerically demonstrate a chaotic watermarking encryption and secure transmission scheme based on two synchronized response lasers (RLs) subject to identical injection from a driving laser (DL). In this proposed system, the chaos signals from DL can be optimized after passing through a phase modulator and a dispersion component, then the chaotic signal with large bandwidth and low TDS is obtained. Simultaneously injecting this chaotic signal into two identical RLs, high-quality chaos synchronization between two RLs can be realized. Both synchronized chaotic signals are respectively divided into two parts. One is used to generate shared keys required by the watermarking encryption, and the other is used as chaotic carrier to realize the secure message transmission. After introducing the synchronized optical chaos into the watermarking encryption algorithm, the normalized correlation of the extracted watermark without long-distance transmission is 0.9554 and can still maintain above 0.9 over 200km transmission fiber. The message transmission and watermark extraction have good robustness to the fiber parameter mismatches, and excellent performances can be maintained even within 20% mismatches range. Moreover, the security of the watermarking encryption algorithm and the message transmission can be guaranteed simultaneously.

Based on chaos synchronization of two response lasers (RLs) injected by the common chaos signals from a driving laser (DL) with double optical feedback (DOF) and an additional neural network (NN), a bidirectional chaotic secure communication system with machine learning capability is proposed and the long-distance digital image transmission and recognition performances are numerically investigated. The simulated results show that the time delay signature (TDS) of the driving chaotic signals from DL with DOF is greatly weakened under suitable operation conditions. Two RLs can generate chaos signals with low TDS and broad bandwidth, and the high-quality chaos synchronization between two RLs can be achieved while the synchronization quality between DL and any one of RLs is extremely bad, which is helpful to realize the secure communication. Using the synchronized chaos output signals from two RLs as chaos carriers and chaos masking (CM) encoding method, the bidirectional 10 Gb/s secure communication over 140 km fiber channel can be realized and the effects of the fiber parameters on the communication performances are discussed. After adopting an additional NN, a long-distance digital image transmission and recognition based on this proposed secure communication system can be realized and the communication distance can be extended to 220 km.

As data volumes grow rapidly, distributed computations are widely employed in data-centers to provide cheap and efficient methods to process large-scale parallel datasets. Various computation models have been proposed to improve the abstraction of distributed datasets and hide the details of parallelism. However, most of them follow the single-layer partitioning method, which limits developers to express a multi-level partitioning operation succinctly. To overcome the problem, we present the NDD (Nested Distributed Dataset) data model. It is a more compact and expressive extension of Spark RDD (Resilient Distributed Dataset), in order to remove the burden on developers to manually write the logic for multi-level partitioning cases. Base on the NDD model, we develop an open-source framework called Bigflow, which serves as an optimization layer over computation engines from most widely used processing frameworks. With the help of Bigflow, some advanced optimization techniques, which may only be applied by experienced programmers manually, are enabled automatically in a distributed data processing job. Currently, Bigflow is processing about 3 PB data volumes daily in the data-centers of Baidu. According to customer experience, it can significantly save code length and improve performance over the intuitive programming style.

Comparison of defect formation in tungsten samples exposed only to a helium plasma and those exposed to both helium plasma and subsequent deuterium plasmas is performed via Doppler broadening spectroscopy in the positron annihilation technique (DBS-PA). The S parameters of tungsten samples after helium plasma exposure increased with the increase of the incident fluence, which indicates that low energy helium plasma could induce the formation of defects such as nano-sized helium bubbles and dislocations in tungsten. The S parameters of samples exposed to helium incident fluence of 7.9 × 1021 He/m2 enhanced after deuterium plasmas exposure, indicating that low energy deuterium plasmas could form defects in tungsten too. Unexpectedly, deuterium plasmas exposure did not significantly influence the S parameters of the tungsten sample with helium incident fluence of 3.9 × 1022 He/m2, and reduced the S parameters of the tungsten sample with helium incident fluence of 7.9 × 1022 He/m2. These variations of S parameters could be associated with the occupation of nano-sized helium bubbles by deuterium atoms. This indicates possible competition between the increased density of vacancy-type defects by deuterium plasmas exposure and the filling of nano-sized helium bubbles by deuterium atoms, reducing detectability of these defects.

A rapid and accurate diagnostic modality is essential to prevent the spread of SARS-CoV-2. In this study, we proposed a SARS-CoV-2 detection sensor based on surface-enhanced Raman scattering (SERS) to achieve rapid and ultrasensitive detection. The sensor utilized spike protein deoxyribonucleic acid aptamers with strong affinity as the recognition entity to achieve high specificity. The spherical cocktail aptamers-gold nanoparticles (SCAP) SERS substrate was used as the base and Au nanoparticles modified with the Raman reporter molecule that resonates with the excitation light and spike protein aptamers were used as the SERS nanoprobe. The SCAP substrate and SERS nanoprobes were used to target and capture the SARS-CoV-2 S protein to form a sandwich structure on the Au film substrate, which can generate ultra-strong “hot spots” to achieve ultrasensitive detection. Analysis of SARS-CoV-2 S protein was performed by monitoring changes in SERS peak intensity on a SCAP SERS substrate-based detection platform. This assay detects S protein with a LOD of less than 0.7 fg mL−1 and pseudovirus as low as 0.8 TU mL−1 in about 12 min. The results of the simulated oropharyngeal swab system in this study indicated the possibility of it being used for clinical detection, providing a potential option for rapid and accurate diagnosis and more effective control of SARS-CoV-2 transmission.

In this paper, we propose and numerically demonstrate a security-enhanced high-speed chaotic communication system by introducing phase modulation and phase-to-intensity conversion. The driving laser (DL) with delayed optical feedback can be used to generate the chaotic driving signal, which is simultaneously injected into two response lasers (RLs) through a phase modulator (PM) and a dispersion component (De). The simulated results show that, due to the phase modulation and phase-tointensity conversion, TDS of injected chaos signal from DL can be effectively suppressed and its bandwidth can be increased to 39.6 GHz under suitable parameter conditions. Simultaneously injecting the chaos signal into two identical RLs, high-quality chaos signals with weakened TDS and enhanced bandwidth between two RLs can be achieved even under certain parameter mismatches, but the synchronization quality between DL and any one of RLs is extremely bad. Based on the system synchronization, secure transmission of 20 Gbit/s messages can be realized and the transmission distance can be over 200km.

Based on a master-slave frame, we propose and numerically simulate a scheme for generating frequency-modulated continuous-wave (FMCW) signals with broad bandwidth. In such a master-slave system, a semiconductor laser under current modulation with single-tone electrical signal is taken as the master laser (ML), and its output optical signal with modulated power is injected into another semiconductor laser (taken as the slave laser, SL) for generating FMCW. The simulated results show that, under suitable operating condition, the bandwidth and the sweep rate of generated FMCW signal can reach 15.4 GHz and 4.83 GHz/ns, respectively. Through further introducing optoelectronic feedback into SL for suppressing the phase noise, the contrast of the frequency comb in the FMCW signal can be increased by 20.22 dB.

Frequency-modulated continuous-wave (FMCW) can be acquired by using a distributed feedback semiconductor laser (DFB-SL) operating at period-one (P1) oscillation under an optical injection modulated by a Mach–Zehnder modulator (MZM). In this work, through introducing another MZM to establish cascade-modulated optical injection, an improved photonic scheme for generating high-quality FMCW is proposed and experimentally demonstrated. The experimental results indicate that, under appropriate injection parameters, the central frequency of the generated FMCW is widely tunable, and the bandwidth is larger than that obtained under a single MZM modulation. Further introducing optical feedback for suppressing the phase noise, the frequency comb contrast of the generated FMCW can be improved obviously.

A scheme for generating wideband optical frequency comb (OFC) is proposed and experimentally investigated based on a master-slave system. In such a system, a tunable optical resource and a distributed feedback semiconductor laser are utilized as master lasers (MLs), and their outputs provide dual optical injection (DOI) into a slave laser (SL) which is a 1550 nm multi-transverse mode vertical-cavity surface-emitting laser (1550 nm-VCSEL) operating at gain-switched state. For the 1550 nm-VCSEL biased at a relatively high current, two low-order transverse modes LP01 and LP11 can simultaneously lase and possess comparable powers. After loaded a large signal modulation, the 1550 nm-VCSEL can be driven into gain-switched state, and two separated sub-combs originating from two transverse modes can be generated. Through further introducing DOI to the gain-switched 1550 nm-VCSEL, the two sub-combs can link up to form an overall OFC under suitable operation parameters. The experimental results show that, through selecting optimized operating parameters, the bandwidth of the integral OFC within 10 dB amplitude variation can achieve 150.0 GHz. Additionally, the effects of the wavelengths of the two injection lights on the bandwidth of the overall OFC are also analyzed.

Photonic generation of a low-phase-noise microwave signal based on period-one (P1) dynamics of an optically injected semiconductor laser (OISL) subject to subharmonic modulation from an optoelectronic oscillator (OEO) is firstly proposed and experimentally demonstrated. Under suitable injection parameters, an OISL can be driven into period-one (P1) dynamics, which can be regarded as a photonic microwave with a relatively large linewidth. By further introducing an OEO with a frequency of 1/2 P1 frequency to directly modulate the OISL, a low-phase-noise photonic microwave with P1 frequency can be obtained. For an OISL operating at P1 oscillation with a frequency of 16.96 GHz, after imposing a 1/2 subharmonic modulation of 8.48 GHz on the OISL by an OEO, the photonic microwave linewidth is reduced from 5.23 MHz to less than 1 kHz, and the single sideband (SSB) phase noise of the final photonic microwave is -102.5 dBc/Hz@10 kHz, which is close to the SSB phase noise of the OEO signal (-104.3 dBc/Hz@10 kHz).

Taking the broadband chaotic output from a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under filtered feedback as a chaotic entropy source, we propose and experimentally demonstrate a scheme for generating fast physical random bits (PRBs) at a rate up to 240 Gbits/s. First, we investigate the dependence of the dynamical properties of the filtered feedback WRC-FPLD on the system parameters, and determine the optimized parameter region for generating wavelength-tunable and broadband chaotic signals. Second, a broadband chaotic signal with a bandwidth beyond 20 GHz output from the WRC-FPLD is sampled and transferred to a digital bit sequence by an 8-bit analog-to-digital converter at a rate of 40 GS/s. Finally, by utilizing multi-bit post-processing method, PRBs is generated at a rate up to 240 Gbits/s, which can pass all the 15 NIST statistics tests and meet the strict criteria of the statistical bias and the serial correlation coefficient.

Based on the spiking dynamics of the electrically controlled vertical-cavity surface-emitting laser with an embedded saturable absorber (VCSEL-SA), we propose an image transmission system using two unidirectionally coupled VCSEL-SAs and numerically investigate the binary-to-spike (BTS) conversation characteristics and the image transmission performance. The simulation results show that, through electrically injecting the binary data to VCSEL-SA, the BTS conversation can be realized and the conversion rate of BTS highly depends on the injection strength and bias current. Thus, the image transmission can be realized in the proposed system. Moreover, the parameter mismatches between these two VCSEL-SAs have some effects on the image transmission performance, but the encoded images are still successfully decoded even under certain parameter mismatches. In addition, spiking patterns can be also stored and transmitted in the cascaded system with optoelectronic feedback loop.

International audience; Kesterite quaternary material Cu2ZnSnS4, (CZTS)-based thin-film solar cells have attracted intensive attention owing to their earth-abundant nature, stable thermodynamic structure, and large potential for high power conversion efficiency (PCE) defined by their suitable optoelectronic properties. As a widely used thin film preparation method, pulsed laser deposition (PLD) has not been fully studied in CZTS thin-film solar cell. Herein, a promising route based on PLD from a quaternary target and post-sulphuration for CZTS thin film was achieved. Through systematical investigation and optimization of substrate temperature, laser pulse energy, and sulfurization temperature, the CZTS thin films showed single kesterite structure, high (112) orientation, and dense polycrystalline grains with controlled composition. The CZTS thin-film solar cell exhibited a record PCE of 6.62%, the highest reported value when using pulsed laser deposited and sulfurized process, due to its lower series resistance, reduced grain boundary effects, superior interface quality, and a suitable depletion width. This research offers a facile and robust preparation method for CZTS films with enhanced photovoltaic properties and increased efficiency.

A security-enhanced bidirectional chaotic secure communication system is proposed and numerically investigated. In which, the high-quality chaos synchronization between two response lasers (RLs) is achieved via the common chaos signals injection from a driving laser (DL) with double optical feedback (DOF). The simulated results show that, the time delay signature (TDS) of the driving chaotic signals from DL with DOF is greatly weakened under suitable operation conditions. Two RLs can generate chaos signals with low TDS and broad bandwidth, and the high quality chaos synchronization between two RLs can be achieved while the synchronization quality between DL and any one of RLs is extremely bad, which can enhance the security of messages transmission in this proposed system. Using the synchronized chaos output signals from two RLs as chaos carriers and chaos masking (CM) encoding method, the bidirectional 10 Gb/s image messages transmission can be successfully realized.

Photonic generation of frequency-modulated continuous wave (FMCW) based on period-one (P1) oscillation of an optically injected semiconductor laser (OISL) is numerically investigated. A modulated optical injection can drive an OISL into P1 oscillation for generating an FMCW signal, and an optical feedback is further introduced to reduce the phase noise of the generated signal. The influences of operation parameters on the performance of the generated FMCW signal are discussed. The numerical results show that under proper operating conditions, a photonic FMCW signal with a sweep range of 12.41 GHz can be obtained. After adopting optical feedback, the frequency comb contrast can be increased to a level more than 30 dB.

Le-jing Lian,1 Bin Lin,2 Xiao Cui,1 Jie He,1 Zhe Wang,1 Xiao-dong Lin,1 Wei-jian Ye,1 Rui-jie Chen,1 Wei Sun1 1Department of Pharmacy, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Wenzhou 325027, People’s Republic of China; 2Department of Clinical Pharmacy, Changxing People’s Hospital, Changxing 313100, People’s Republic of ChinaCorrespondence: Wei Sun; Rui-jie Chen Tel +8613968803162; +8613806890233Email 33sunwei@163.com; crj@wzhealth.comPurpose: Precise and timely detection of methotrexate (MTX) concentration played a key role in high-dose MTX individualization therapy in acute lymphoblastic leukemia (ALL) children to avoid serious adverse effects or nonresponse. This report described a sensibility and validation of ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for therapeutic drug monitoring (TDM) of methotrexate concentration in children’s plasma.Methods: One-step protein precipitation of samples was accomplished by adding 200 μL of acetonitrile to 100 μL of plasma sample. The separation of plasma samples was carried out on a ZORBAX Eclipse Plus C18 Rapid Resolution HD column with gradient elution using a mobile phase constituted of acetonitrile and 1% formic acid. The detection was executed by electrospray ionization (ESI) of triple quadrupole tandem mass spectrometer (TQMS) in the multiple reaction monitoring (MRM) mode with the transitions m/z 455.2 → 307.9 for methotrexate and m/z 458.2 → 311.2 for IS, separately. Linear concentration range of the calibration curve was 44– 11,000 nmol/L and 44 nmol/L was the lower limit of quantification.Results: The methotrexate elution time was at 1.577 min, and the overall running time was only 3.3 min. The intra- and interday precision for all the analysis results was within 11.24%, and mean recoveries rate of methotrexate exceeded 87.98%.Conclusion: The described and fully validated UHPLC-MS/MS method was successfully applied in clinical TDM after infusion of high-dose methotrexate 1– 5 g/m2 to 41 childpatients.Keywords: high-dose methotrexate, UHPLC-MS/MS, therapeutic drug monitoring, children, acute lymphoblastic leukemia

In this work, a novel optoelectronic oscillator (OEO) structure is proposed for generating widely tunable photonic microwave. In this structure, an optical injection semiconductor laser (OISL) functions as an active tunable microwave photonic filter (MPF). Through controlling the injection power and frequency detuning, the OISL is driven into period-one dynamics whose oscillation frequency can be widely tuned from 10.43 to 65.82 GHz. As a result, the OISL can be regarded as a widely tunable active MPF. By introducing an optical feedback loop, the filtered bandwidth of the widely tunable active MPF can be further reduced. Taking the OISL under optical feedback as a widely tunable narrow-bandwidth MPF and a seeding laser source to establish an OEO structure, widely tunable narrow-linewidth photonic microwave can be generated. The experimental results demonstrate that widely tunable photonic microwaves ranging from 10.43 to 39.10 GHz with linewidths below 0.1 MHz and phase variances below 10-2 (rad2) can be achieved.

To solve the problems of high roughness and defects on the surface of thin film prepared by the conventional pulsed laser deposition method (PLD), the optimized shadow masked pulsed laser deposition method (SMPLD) was proposed in this work to prepare the copper zinc tin sulfur (CZTS) thin film. Comparative analysis was carried out on the CZTS thin films and solar cells prepared by these two PLD methods. The film prepared by SMPLD is compact and even, and the surface roughness decreases by one order of magnitude. The efficiency of the CZTS thin film solar cell prepared by SMPLD is approximately 4.4%. This value is 1.3% higher than that prepared by the conventional PLD method.

3003 aluminum melt was treated with efficient purification, and it was deformed by isothermal compression in the range of deformation temperature 300-500 °C at strain rate 0.0l-10.0 s-1 with Gleeble-1500 thermal simulator. The results show that efficient purification treatment can significantly reduce the impurities, and make inclusion size smaller, uniform distribution. Room temperature mechanical properties were significantly improved. At the same strain rate, the flow stress of 3003 aluminum alloy decreases with the increase of deformation temperature. The flow stress increases with the increase of strain rate under the same deformation temperature. Two kinds of 3003 aluminum alloys with different purification treatments both have dynamic recrystallization characteristics. Especially when the strain rate reaches 10.0 s-1, the rheological curve appears sawtooth fluctuation and the alloy may have discontinuous dynamic recrystallization.

Cr-coated Zr alloy claddings, prepared via physical vapor deposition (PVD), were used to study the damage evolution under a series of high-temperature steam oxidation conditions. Through-thickness cracks were initially produced within the Cr coat by internal pressure creep test. The Cr-coated samples with cracks were then oxidized at temperatures from 800 °C to 1200 °C in water steam environment. Microstructures of the samples before and after oxidation were characterized in comparison by scanning electronic microscopy, transmission electronic microscopy and energy dispersion spectrometry. The results showed that a large proportion of cracks would be self-healed when the temperature increased to 1000 °C. At the places where the cracks have survived, the corresponding Zr substrate regions were oxidized to form semi-spherical or fan-shaped ZrO2. However, the maximum depth of ZrO2 under the unhealed cracks was smaller than that of the uncoated claddings at the same oxidation conditions.

Based on the well-known Fabry–Pérot approach, after taking into account the variation of bias current of the vertical-cavity semiconductor optical amplifier (VCSOA) according to the present synapse weight, we implement the optical spike timing dependent plasticity (STDP) with weight-dependent learning window in a VCSOA with double optical spike injections, and numerically investigate the corresponding weight-dependent STDP characteristics. The simulation results show that, the bias current of VCSOA has significant effect on the optical STDP curve. After introducing an adaptive variation of the bias current according to the present synapse weight, the optical weight-dependent STDP based on VCSOA can be realized. Moreover, the weight training based on the optical weight-dependent STDP can be effectively controlled by adjusting some typical external or intrinsic parameters and the excessive adjusting of synaptic weight is avoided, which can be used to balance the stability and competition among synapses and pave a way for the future large-scale energy efficient optical spiking neural networks based on the weight-dependent STDP learning mechanism.

We investigate experimentally and theoretically the communication of inhibited spiking dynamics between two interlinked photonic neurons based upon the vertical-cavity surface-emitting lasers (VCSELs). We show that the sub-nanosecond speed spiking dynamics fired by a Transmitter-VCSEL (T-VCSEL) can be inhibited under the arrival of suitable external stimuli and that the inhibited spiking behaviors are propagated into another Receiver-VCSEL (R-VCSEL). Both VCSELs exhibit analogous inhibited spiking dynamics in response to stimuli with different temporal durations and strength. In addition, a very good agreement is found between theoretical simulations and experiments. These results offer greater prospects for future networks of VCSEL-based photonic neurons for neuromorphic computing platforms.

We experimentally demonstrate multi-channel physical random bits (PRBs) generation by utilizing chaotic outputs from two linear polarization modes in a vertical-cavity surface-emitting laser (VCSEL) under a chaotic optical injection. The polarization-resolved chaotic signal is obtained with a master-VCSEL subject to optical feedback, and then injects into a slave-VCSEL for driving its two linear polarization modes into chaotic state. We analyze the influences of injection parameters on bandwidth, complexity, and the correlation of two-channel chaotic signals. By using the two chaotic signal outputs from the slave-VCSEL under optimized parameters as entropy sources, we have obtained the PRBs at the dual-channel rate of 160 Gbits/s by adopting the $m$ least significant bits extraction with logical exclusive-OR (XOR) post-processing. Further utilizing the $n$ -bit cross-merging method, the PRB at a rate of 320 Gbits/s could be obtained.

We have experimentally demonstrated and characterized the generation of tunable and ultra-broadband microwave frequency combs (MFCs) based on a slave laser (SL) subject to regular pulse injection from a current modulated master laser (ML). Under modulation frequency fm = 1.2 GHz and modulation power Pm = 22 dBm, the current modulated ML is driven into a regular pulse state, and a seed MFC with 14.4 GHz bandwidth within a ±5 dB amplitude variation can be obtained. Such a seed MFC is then injected into the SL for producing final MFC with higher performances. For a fixed detuning frequency fi = 0 GHz and optimized injection power Pi = 2060 μW, the bandwidth of the final MFC is increased to 33.6 GHz, and the single-sideband phase noises of all comb lines of the MFC within the bandwidth can be decreased to below -90.9 dBc/Hz@10 kHz. Additionally, the influences of Pi and fm on the MFC bandwidth are also analyzed. The experimental results are in agreement with numerical simulations to a certain extent.

We propose and experimentally demonstrate a scheme to acquire a narrow-linewidth photonic microwave based on an optically injected semiconductor laser (OISL) modulated by a subharmonic microwave from an optoelectronic oscillation (OEO). The microwave frequency generated by the OEO is 7.62 GHz, and the period-one (P1) oscillation frequency of the OISL is close to twice of it. Through modulating the OISL by a 1/2 subharmonic microwave generated by the OEO, the photonic microwave is locked at 15.24 GHz with a 3-dB linewidth about 1 kHz and a SSB phase noise of -94 dBc/Hz at offset frequency 10 kHz.

The influence of intra-cavity propagation delay in message encoding and decoding using chaotic semiconductor lasers is numerically investigated. A message is encoded at the transmitter laser by a chaos shift keying scheme and is decoded at the receiver by comparing its output with the transmitter laser. The requisite intra-cavity propagation delay in achieving synchronization of optical chaos is estimated by cross-correlation analysis between the transmitter and receiver lasers&rsquo, output. The effect of intra-cavity propagation delay on the message recovery has been analyzed from the bit error rate performance. It is found that despite the intra-cavity propagation delay magnitude being less, it has an impact on the quality of message recovery. We also examine the dependency of injection rate, frequency detuning, modulation depth and bit rate on intra-cavity propagation delay and associated message recovery quality. We found that the communication performance has been adequately improved after incorporating intra-cavity propagation delay correction in the synchronization system.