Visual observation of photonic Floquet-Bloch oscillations

Bloch oscillations (BOs), an important transport phenomenon, have been studied extensively in static systems but remain mysterious in Floquet systems. Here, by harnessing notions from photonic analogy, we propose a generalization of the existing BOs in photonic Floquet lattices, namely the "photonic Floquet-Bloch oscillations", which refer to rescaled photonic Bloch oscillations with a period of extended least common multiple of the modulation period and the Bloch oscillation period. Next, we report the first visual observation of such photonic Floquet-Bloch oscillations (FBOs) by employing waveguide fluorescence microscopy. Most significantly, the FBOs surpass the existing BOs in Floquet systems and exhibit exotic properties on their own, including fractal spectrum and fractional Floquet tunneling. This new transport mechanism offers an intriguing method of wave manipulation that may contribute to rapidly developing fields in photonics, condensed matter physics, and quantum physics.

Functionalized gold nanoparticle enhanced nanorod hyperbolic metamaterial biosensor for highly sensitive detection of carcinoembryonic antigen

Hyperbolic metamaterial (HMM) biosensors based on metals have superior performance in comparison with conventional plasmonic biosensors in the detection of low concentrations of molecules. In this study, a nanorod HMM (NHMM) biosensor based on refractive index changes for carcinoembryonic antigen (CEA) detection is developed using secondary antibody modified gold nanoparticle (AuNP-Ab2) nanocomposites as signal amplification element for the first time. Numerical analysis based on finite element method is conducted to simulate the perturbation of the electric field of bulk plasmon polariton (BPP) supported by a NHMM in the presence of a AuNP. The simulation reveals an enhancement of the localized electric field, which arises from the resonant coupling of BPP to the localized surface plasmon resonance supported by AuNPs and is beneficial for the detection of changes of the refractive index. Furthermore, the AuNP-Ab2 nanocomposites-based NHMM (AuNP/Ab2-NHMM) biosensor enables CEA detection in the visible and near-infrared regions simultaneously. The highly sensitive detection of CEA with a wide linear range of 1-500 ng/mL is achieved in the near-infrared region. The detectable concentration of the AuNP/Ab2-NHMM biosensor has a 50-fold decrease in comparison with a NHMM biosensor. A low detection limit of 0.25 ng/mL (1.25 pM) is estimated when considering a noise level of 0.05 nm as the minimum detectable wavelength shift. The proposed method achieves high sensitivity and good reproducibility for CEA detection, which makes it a novel and viable approach for biomedical research and early clinical diagnostics.

[Analysis of influenza vaccination status and immunization strategy in high-risk population]

Influenza is a contagious respiratory disease caused by influenza viruses, and the burden of severe disease is commonly seen in high risk populations. Influenza vaccination is an effective way to prevent influenza and its complications, especially for high risk populations. Although some countries have included influenza vaccine in their national immunization programs, influenza vaccination rates remain low globally in high risk populations. The influenza vaccine in China is still a non-immunization program vaccine that is voluntarily vaccinated at its own expense, and the influenza vaccine immunization strategy is different across the country. There is still a gap between the vaccination rate of the influenza vaccine and that of developed countries. It is an urgent problem to further optimize the whole population immunization strategy of influenza vaccine in China, strengthen the publicity of the whole population immunization strategy of influenza vaccine, and reduce the disease burden of influenza in China.

Polychromatic photonic Floquet-Bloch oscillations

Photonic Floquet-Bloch oscillations (FBOs), a new type of Bloch-like oscillations in photonic Floquet lattices, have recently been observed as a typical discrete self-imaging effect. Here, we theoretically investigate the spectral range of approximate photonic Floquet-Bloch oscillations in arrays of evanescently coupled optical waveguides and show the adjustability of the spectral range. At an appropriate amplitude of the Floquet modulation, we have demonstrated approximate photonic FBOs over a broad spectral range, termed "polychromatic photonic Floquet-Bloch oscillations," which manifest as approximate self-imaging of polychromatic beams. Furthermore, by designing the functional form of the Floquet modulation, we can cascade two polychromatic photonic FBOs and further enhance the performance of polychromatic self-imaging. Our results provide a simple and novel mechanism for achieving polychromatic self-imaging in waveguide arrays and may find applications in polychromatic beam shaping and broadband optical signal processing.

Configurable SNAP microresonators induced by axial pre-strain-assisted CO2 laser exposure

Flexible engineering of the complex shapes of the surface nanoscale axial photonics (SNAP) bottle microresonators (SBMs) is challenging for future nanophotonic technology applications. Here, we experimentally propose a powerful approach for the one-step fabrication of SBMs with simultaneous negative and positive radius variations, exhibiting a distinctive "bump-well-bump" profile. It is executed by utilizing two focused and symmetrical CO2 laser beams exposed on the fiber surface for only several hundred milliseconds. The spectral characteristics of different eigenmodes are analyzed, providing deep insights into the complex physical processes during the CO2 laser exposure. The shapes of the SBMs can be flexibly adjusted by the exposure time, laser power, and applied pre-strains. As a proof of this technique, the developed approach enables the efficient production of a bat SBM, ensuring a uniform field amplitude of the bat mode over the length exceeding 120 µm with 7% deviation. Our proposed technique provides a powerful technique for the efficient fabrication of SBMs with predetermined shapes, laying the groundwork for its applications on microscale optical signal processing, quantum computing, and so on.

Few-mode fiber Bragg grating-based simultaneous multichannel CSRZ to NRZ format conversion scheme for LP01 and LP11

We propose what we believe is a novel format conversion scheme using a few-mode fiber Bragg grating (FM-FBG) that can perform multichannel format conversion from carrier-suppressed return-to-zero (CSRZ) to non-return-to-zero (NRZ) for both LP01 and LP11. The multichannel spectral response of FM-FBG is designed according to the algebraic difference between the CSRZ and NRZ spectra outlines. Additionally, the FM-FBG response spectra of LP11 are designed to shift with that of LP01 by the WDM-MDM channel spacing for filtering both modes together. Numerical results demonstrate the successful conversion of both LP01 and LP11 channels, carrying four channels of 200-GHz-spaced CSRZ signals at 40 Gbit/s, into NRZ signals with a high Q-factor (exceeding 14 dB), and the converted NRZ signals exhibit clean and open eye diagrams. Furthermore, the performance analysis also shown that our proposed FM-FBG is robust to central wavelength detuning.

[Analysis of China's influenza vaccination policy based on the model of "behavioural and social drivers of vaccination"]

This article uses the "behavioural and social drivers of vaccination" model released by the World Health Organization (WHO) in 2022 to analyze influenza vaccine policy documents issued by the state and governments. This indicates that the current influenza vaccination policy in China has paid some attention to "publicity and mobilization", but it still pays insufficient attention to "vaccination convenience". It is recommended to continue to strengthen publicity and mobilization, explore ways to improve the convenience of vaccination, formulate corresponding plans to improve the convenience of vaccination, scientifically set vaccination rate targets, and encourage areas with conditions to carry out free vaccination projects for key populations.

Analysis of the value of echocardiographic parameters in the early diagnosis of preterm infants with bronchopulmonary dysplasia

OBJECTIVE

The objective of this study was to investigate the role of echocardiographic parameters in diagnosing bronchopulmonary dysplasia (BPD) in preterm infants.

PATIENTS AND METHODS

Ninety preterm infants with a gestational age of less than 32 weeks and a weight less than 1.5 kg, admitted to the neonatal intensive care unit of the hospital between January 2020 and January 2021, were selected for the study. The study subjects were divided into two groups: a BPD group (54 cases, observation group) and a non-BPD group (36 cases, control group). The correlation between tricuspid regurgitation (TR) velocity and BPD was investigated by detecting the cardiac function of preterm infants in both groups using a color Doppler ultrasound diagnostic instrument and analyzing the cardiac ultrasound results. The early prediction efficiency of TR velocity (m/s) for BPD was evaluated using the receiver operator characteristic (ROC) curve.

RESULTS

The incidence of patent ductus arteriosus (PDA) and pulmonary hypertension (PH) in the observation group was significantly higher than that in the control group. The levels of left ventricular ejection fraction (LVEF) and left ventricular shorting fraction (LVFS) were significantly lower than those in the control group (p < 0.05). The incidence of patent foramen ovale (PFO), atrial septal defect (ASD), and ventricular septal defect (VSD) in the observation group were not significantly different from the control group (p > 0.05). The proportion of tricuspid regurgitation in the observation group was significantly higher than that in the control group, and the TR velocity was significantly higher than that in the control group. The Spearman correlation analysis showed that TR velocity (m/s) was positively correlated to BPD severity (r = 0.379, p < 0.05). The area under the curve (AUC) for predicting BPD with TR velocity was 0.735. The sensitivity and specificity were 88.0% and 62.6%, respectively, when the TR velocity was 1.45 m/s.

CONCLUSIONS

Echocardiography is useful for understanding the degree of impaired cardiac function in preterm infants and for early detection of PH, which may reduce the mortality rate to a certain extent. The risk of BPD is significantly increased when TR velocity is higher than 1.45 m/s.

[Adult vaccination immunization strategies and research progress worldwide]

Vaccination is the most cost-effective measure to prevent infectious diseases in both children and adults. At present, the global burden of infectious diseases in adults is still heavy. With the continuous development and improvement of vaccines, vaccination has shown great potential to prevent infectious diseases, further reduce the morbidity and mortality of infectious diseases in adults and improve people's life quality. This article summarizes the current status of adult immunization, immunization strategies of representative countries, different adult vaccination strategies, and the advantages and challenges of adult immunization to provide reference for further exploring adult immunization strategies and improving adult vaccination recommendations. More attention should be paid to the immunization strategies for different adult populations, and effective measures should be taken to improve the vaccination coverage for the better protection of people's life and health.

Mode-locked fiber laser based on a small-period long-period fiber grating inscribed by femtosecond laser

We demonstrate stable mode-locked pulses in an erbium-doped fiber laser (EDFL) using a femtosecond laser-inscribed small-period long-period grating (SP-LPG). The SP-LPG has a period of 25 µm and a length of 2.5 mm. The polarization dependent loss (PDL) of the SP-LPG reaches 20 dB at the wavelength of 1556 nm and 25 dB at the wavelength of 1607 nm, which is sufficient to trigger the mode-locking mechanism. In addition, a mode-locked fiber laser (MLFL) based on the SP-LPG has been demonstrated to generate 1.58-ps pulses at 1577 nm with a bandwidth of 4 nm and a repetition rate of 1.54 MHz. The signal-to-noise ratio (SNR) of 50 dB shows the high stability of this system. This work indicates various potential applications of the SP-LPG in ultra-fast laser technologies due to its simple fabrication, compact structure, and high damage threshold.

Dual-step reconstruction algorithm to improve microscopy resolution by deep learning

Deep learning plays an important role in the field of machine learning, which has been developed and used in a wide range of areas. Many deep-learning-based methods have been proposed to improve image resolution, most of which are based on image-to-image translation algorithms. The performance of neural networks used to achieve image translation always depends on the feature difference between input and output images. Therefore, these deep-learning-based methods sometimes do not have good performance when the feature differences between low-resolution and high-resolution images are too large. In this paper, we introduce a dual-step neural network algorithm to improve image resolution step by step. Compared with conventional deep-learning methods that use input and output images with huge differences for training, this algorithm learning from input and output images with fewer differences can improve the performance of neural networks. This method was used to reconstruct high-resolution images of fluorescence nanoparticles in cells.

High-performance vector torsion sensor based on high polarization-dependent in-fiber Mach-Zehnder interferometer

We propose a high-performance vector torsion sensor based on an in-fiber Mach-Zehnder interferometer (MZI), which consists of a straight waveguide inscribed in the core-cladding boundary of the SMF by a femtosecond laser in only one step. The length of the in-fiber MZI is 5 mm, and the whole fabrication time does not exceed 1 min. The asymmetric structure makes the device have high polarization dependence, and the transmission spectrum shows a strong polarization-dependent dip. Since the polarization state of the input light entering the in-fiber MZI varies with the twist of the fiber, torsion sensing can be achieved by monitoring the polarization-dependent dip. Torsion can be demodulated by both the wavelength and intensity of the dip, and vector torsion sensing can be achieved by setting the appropriate polarization state of the incident light. The torsion sensitivity based on intensity modulation can reach 5763.96 dB/(rad/mm). The response of dip intensity to strain and temperature is weak. Furthermore, the in-fiber MZI retains the fiber coating, so it maintains the robustness of the complete fiber structure.

[Research progress of influenza vaccination, pneumococcal vaccination and COVID-19 vaccination among cancer patients]

This article reviews the relevant studies on the efficacy and safety of influenza, pneumococcal and COVID-19 vaccination among tumor patients worldwide in recent years. By combing and analyzing the retrieved literature, the results show that influenza and pneumococcal vaccination can significantly reduce the morbidity and hospitalization rate of infectious diseases in tumor patients, reduce the risk of cardiovascular events and death, and significantly improve survival prognosis. COVID-19 vaccination can also protect tumor patients, especially those who have completed full dose vaccination. Authoritative guidelines and consensuses worldwide all recommend that tumor patients receive influenza, pneumococcal and COVID-19 vaccines. We should carry out relevant researches, as well as take effective measures to strengthen patient education, so that tumor patients can fully experience the health protection brought by the vaccine to this specific group.

Long-Period Fiber Grating Sensors for Chemical and Biomedical Applications

Optical fiber biosensors (OFBS) are being increasingly proposed due to their intrinsic advantages over conventional sensors, including their compactness, potential remote control and immunity to electromagnetic interference. This review systematically introduces the advances of OFBS based on long-period fiber gratings (LPFGs) for chemical and biomedical applications from the perspective of design and functionalization. The sensitivity of such a sensor can be enhanced by designing the device working at or near the dispersion turning point, or working around the mode transition, or their combination. In addition, several common functionalization methods are summarized in detail, such as the covalent immobilization of 3-aminopropyltriethoxysilane (APTES) silanization and graphene oxide (GO) functionalization, and the noncovalent immobilization of the layer-by-layer assembly method. Moreover, reflective LPFG-based sensors with different configurations have also been introduced. This work aims to provide a comprehensive understanding of LPFG-based biosensors and to suggest some future directions for exploration.

Multi-wavelength random fiber laser based on a tilted parallel inscribed apodized fiber Bragg grating array

We propose and demonstrate a multi-wavelength random fiber laser (RFL) based on a novel, to the best of our knowledge, compact apodized fiber Bragg grating array (AFBGA). The AFBGA is fabricated by a femtosecond laser with the point-by-point tilted parallel inscription method. The characteristics of the AFBGA can be flexibly controlled in the inscription process. Hybrid erbium-Raman gain is used in the RFL and reduces the lasing threshold to sub-watt level. Stable emissions at two to six wavelengths are achieved with the corresponding AFBGAs, and more wavelengths are expected with higher pump power and AFBGAs containing more channels. A thermo-electric cooler is employed to improve the stability of the RFL, and the maximum wavelength and power fluctuations of a three-wavelength RFL are 64 pm and 0.35 dB, respectively. With flexible AFBGA fabrication and simple structure, the proposed RFL enriches the choice of multi-wavelength devices and has significant potential in practical applications.

Femtosecond laser-inscribed off-axis high-order mode long-period grating for independent sensing of curvature and temperature

We propose and demonstrate a novel curvature and temperature sensor based on an off-axis small-period long-period fiber grating (SP-LPG) which is inscribed in a single mode fiber by a femtosecond laser in one step. The total length of the SP-LPG is only 2.1 mm. The period of the SP-LPG is 30 µm, which is smaller than that of conventional long period fiber gratings. Essentially, the SP-LPG is a high-order mode long period fiber grating. Due to the off-axis structure, the SP-LPG can be used for two-dimensional vector bending sensing. The curvature can be demodulated by the intensity variation of the dips in the transmission spectrum. When the incident light is polarized, the instantaneous curvature sensitivity of the SP-LPG can exceed 20 dB/m^-1. Meanwhile, a series of Bragg resonant peaks can be observed in the reflection spectrum, which can be used to monitor the fluctuation of temperature. The transmission dip is insensitive to temperature and the reflection peak is insensitive to curvature, which allows the SP-LPG to measure curvature and temperature independently. The characteristics of high curvature sensitivity, two-dimensional bending direction identification, real-time temperature measurement, and compact structure make the device expected to be applied in the field of structural health monitoring and intelligent robotics.

Generation of different mode-locked states in a Yb-doped fiber laser based on nonlinear multimode interference

We demonstrated an ultrafast Yb-doped fiber laser with a single mode fiber-graded index multimode fiber-single mode fiber (SMF-GIMF-SMF) structure based saturable absorber. The GIMF was placed in the groove of an in-line fiber polarization controller to adjust its birefringence, enabling the SMF-GIMF-SMF structure to realize efficient saturable absorption based on nonlinear multimode interference without strict length restriction. By adjusting two intra-cavity polarization controllers, stable dissipation solitons and noise-like pulses were achieved in the 1030 nm waveband with pulse durations of 10.67 ps and 276 fs, respectively. We also realized Q-switched mode-locked pulses in the same fiber laser cavity. By the dispersive Fourier transform method, the real-time spectral evolution in the buildup process of the Q-switched mode-locked state was captured, which showed that the continuous-wave in this laser could gradually evolved into the stable Q-switched mode-locked pulses through unstable self-pulsation, relaxation oscillation and rogue Q-switching stage. To the best of our knowledge, our work reveals the buildup dynamics of the Q-switched mode-locked operation in a fiber laser for the first time. And we also studied the real-time spectral evolution of the stable Q-switched mode-locked pulses, which exhibited periodic breathing property.

[The effect of pregnant rats exposed to radio frequency electromagnetic field on the hippocampal morphology and nerve growth factor of offspring rats]

Objective: To explore the effects of exposure of pregnant rats to radio frequency electromagnetic field on the ultrastructure of hippocampus and the levels of obesity related protein (FTO) and nerve growth factor (NGF) in offspring rats. Methods: In September 2019, 36 healthy 7-week-old Wistar rats were selected, including 24 female rats (150-200 g) and 12 male rats (200-250 g) . The male and female mice were mated in the cage at 2: 1 ratio at 18: 00 every night. The smear results showed that the sperm was positive and the mating was successful. The day was regarded as the 0 day of pregnancy. Pregnant rats were randomly divided into 3 experimental groups and 3 control groups, with 4 rats in each group. The experimental group was exposed to 1 800 MHz, Wi-Fi and 1 800 MHz+Wi-Fi respectively, and the three control groups were exposed to virtual exposure. 12 hours a day for 21 days in three batches. After the end of exposure, the offspring of each group were raised for 7 weeks. The ultrastructural changes of the hippocampus were observed by transmission electron microscopy, the FTO level in the hippocampus was determined by Western blot, and the NGF level in the brain tissue was determined by ELISA. Results: Transmission electron microscopy showed that the nuclei of hippocampal tissue of female and male rats in the 1800 MHz group were slightly contracted, the cytoplasm was slightly edema, and the nuclei of male rats were obviously irregular. In the offspring of male and female rats in the Wi-Fi group, the nucleus of hippocampal tissue contracted seriously, the cell membrane was irregular, and the cytoplasm appeared obvious edema. In the 1800 MHz+Wi-Fi group, the nuclei of hippocampal tissue of both male and female offspring rats were severely contracted, the nuclear membrane was irregular, and the cytoplasm was severely edema. there was no significant difference in FTO level among the groups (P>0.05) . Compared with other groups, NGF content in hippocampus of offspring rats in the 1800 MHz+Wi-Fi group was significantly higher (P<0.05) . Conclusion: Exposure to radio frequency electromagnetic fields will damage the morphological structure of hippocampal tissue of offspring and stimulate the increase of NGF expression in the hippocampus.

[Progress in research of influenza vaccine and 23 valent pneumococcal polysaccharide vaccine immunization in patients with chronic obstructive pulmonary disease]

A comprehensive review of the research of the effectiveness of influenza vaccine and 23 valent pneumococcal polysaccharide vaccine (PPV23) in patients with chronic obstructive pulmonary disease (COPD) both at home and abroad in recent years showed that influenza vaccine and PPV23 immunization can significantly reduce the risk for influenza and pneumonia in COPD patients, and reduce the acute exacerbation of disease and related hospitalization. In particular, the influenza vaccination can also reduce the risk for ischemic heart disease, acute coronary syndrome, ventricular arrhythmia, lung cancer, dementia and death in the patients, and the immunization of both vaccines has a more significant protective effect. It is recommended by authoritative guidelines both at home and abroad that COPD patients can receive influenza vaccine and PPV23. At present, the coverage of domestic influenza and pneumococcal vaccines are low, and there are less studies in the applications of both vaccines in patients with COPD. Effective measures should be taken to strengthen the health education and increase the vaccination coverage. Additionally, the clinical research of influenza vaccine and PPV23 for COPD patients, especially the analysis on clinical benefit of immunization of both vaccines, should be further strengthened to effectively improve the survival and prognosis of COPD patients.

Microsecond-resolved smartphone time-gated luminescence spectroscopy

Time-gated luminescence spectra are usually measured by laboratory instruments equipped with high-speed excitation sources and spectrometers, which are always bulky and expensive. To reduce the reliance on expensive laboratory instruments, we demonstrate the first, to the best of our knowledge, use of a smartphone for the detection of time-gated luminescence spectra. A mechanical chopper is used as the detection shutter and an optical switch is placed at the edge of the wheel to convert the chopping signal into a transistor-transistor logic (TTL) signal which is used to control the excitation source and achieve synchronization. The time-gated luminescence spectra at different delay times of Eu(TTA)₃ powder and the solutions of Eu-tetracycline complex are successfully detected with a temporal resolution of tens of microseconds by the proposed approach. We believe our approach offers a route toward portable instruments for the measurement of luminescence spectra and lifetimes.

[Analysis of China's influenza vaccine application policy based on the macro model of the health system]

This article uses the analysis framework of the macro model of the health system to analyze the influenza vaccine policy documents issued by the state and governments at all levels from three perspectives: structure, process and results, and provides a scientific basis for improving the application strategy of influenza vaccine. It is suggested that on the basis of continuing to strengthen publicity, mobilization and organizational guarantee, measures to promote the application of influenza vaccine in China by exploring multi-channel financing mechanisms, combining the experience of new crown vaccination to improve the convenience of influenza vaccination, and scientifically setting vaccination rate targets, improve preparedness for an influenza pandemic.

A Systematic Review and Meta-analysis of the Effect of Oral Exercises on Masticatory Function

The aim of the current systematic review was to summarize and to evaluate the available information on the effectiveness of oral exercise in improving the masticatory function of people ≥18 y. Electronic databases (Medline, Embase, CENTRAL) and gray literatures were searched (up to December 2020) for relevant randomized and nonrandomized controlled clinical trials. Two reviewers independently conducted the study selection, data extraction, and quality assessments. Meta-analysis was conducted for the comparison of bite force and masticatory performance using mean difference (MD) and standardized mean difference (SMD), respectively. GRADE (Grading of Recommendations Assessment, Development, and Evaluation) assessment was adopted for collective grading of the overall body of evidence. Of the 1,576 records identified, 18 studies (21 articles) were included in the analysis. Results of meta-analysis indicated that oral exercise could significantly improve the mean bite force of the participants (parallel comparison: MD, 41.2; 95% CI, 11.6-70.7, P = 0.006; longitudinal comparison: MD, 126.5; 95% CI, 105.2-144.9, P < 0.001). However, the improvement in masticatory performance was not significant (parallel comparison: SMD, 0.11; 95% CI, -0.20 to 0.42, P = 0.48; longitudinal comparison: SMD, 0.4; 95% CI, -0.11 to 0.91, P = 0.13). Results of meta-regression showed that greater improvements in bite force can be achieved among younger adults and with more intensive exercise. Chewing exercise is the most effective oral exercise, followed by clenching exercise, while simple oral exercise may not have a significant effect. Based on the results of the meta-analysis and GRADE assessment, a weak recommendation for people with declined masticatory function to practice oral exercise is made.

[Evaluation of safety of two inactivated COVID-19 vaccines in a large-scale emergency use]

Objective: To evaluate the safety of two inactivated COVID-19 vaccines in a large-scale emergency use. Methods: Based on the "Vaccination Information Collection System", the incidence data of adverse reactions in the population vaccinated with the inactivated COVID-19 vaccines developed by Beijing Institute of Biological Products Co., Ltd and Wuhan Institute of Biological Products Co., Ltd, respectively, in emergency use were collected, and the relevant information were analyzed with descriptive epidemiological and statistical methods. Results: By December 1, 2020, the vaccination information of 519 543 individuals had been collected. The overall incidence rate of adverse reactions was 1.06%, the incidence rate of systemic adverse reactions was 0.69% and the incidence rate of local adverse reactions was 0.37%. The main systemic adverse reactions included fatigue, headache, fever, cough and loss of appetite with the incidence rates of 0.21%, 0.14%, 0.06%, 0.05% and 0.05%, respectively; the main local adverse reactions were injection site pain and injection site swelling with the incidence rates of 0.24% and 0.05%, respectively. Conclusion: The two inactivated COVID-19 vaccines by Beijing Institute of Biological Products Co., Ltd and Wuhan Institute of Biological Products Co., Ltd showed that in the large-scale emergency use, the incidence rate of general reactions was low and no serious adverse reactions were observed after the vaccinations, demonstrating that the vaccines have good safety.

SNAP structures fabricated by profile design of in-fiber inscribed regions with a femtosecond laser

Fabricating a surface nanoscale axial photonics (SNAP) microresonator with a specific profile is a challenging and important issue since its advent. We propose a powerful approach for the flexible fabrication of the SNAP structures with arbitrary profiles by a femtosecond laser. Our method is to design the profile of the length distribution of the inscribed lines to match the profile of the required SNAP microresonator, and to combine it with other fabrication parameters to precisely control the radius variation of the SNAP structure. In experiments, we demonstrate the design and fabrication of the SNAP structures with the parabolic, semi-parabolic, and bat profiles. The developed approach is expected to be universal for the fabrication of complex high Q-factor SNAP structures, which lays the groundwork for exploring the versatile performances of the SNAP devices.

Random fiber laser based on a partial-reflection random fiber grating for high temperature sensing

A stable single wavelength random fiber laser (RFL) with a partial-reflection random fiber grating (PR-RFG) for high temperature sensing is proposed and demonstrated for the first time, to the best of our knowledge. The PR-RFG is fabricated with the help of a femtosecond laser, with its highest reflection peak significantly higher than all other reflection peaks, which can ensure the stability of this filter-free RFL. Theoretical calculations also show that such a PR-RFG should be designed with reflectivity in the range of ∼30%-90% to obtain one reflection peak significantly higher than other peaks. The threshold of this laser is only 6.4 mW. In addition, the RFL realizes temperature sensing in the range from 25°C to 500°C and has an optical signal-to-noise ratio of up to 70 dB.

Accurate fabrication of SNAP microresonators via a femtosecond laser with multidimensional optimized parameters

Surface nanoscale axial photonics (SNAP) microresonators with nanoscale effective radius variations (ERVs) along the optical fiber axis can be fabricated by inscribing axially oriented lines inside the fiber with a femtosecond laser. Here, we propose the multi-dimensional fabrication parameter system for the femtosecond laser fabrication of SNAP devices and systematically investigate the relationships between the introduced ERV and the multidimensionally controllable fabrication parameters. Specifically, both the qualitative and quantitative processing principles are revealed. As a proof-of-principle, by multidimensionally optimizing the fabrication parameters, we realize a SNAP microresonator with the characteristics of both small axial size and maximal ERV. The achieved ERV is almost 5 times larger than the ERV achieved with the previous unoptimized method. Our work promotes the fs laser inscription technology to be a flexible and versatile approach for fabricating the SNAP devices with ultra-high precision, ultra-low loss and high robustness.

Mutations in CHMP4C cause dilated cardiomyopathy via dysregulation of autophagy

Background

Gene mutations have been implicated in DCM. However, due to the difficulty of clinical genetic diagnosis, more causal genes potentially related to DCM remain to be discovered.

Methods

We screened for gene mutations in more than 400 cases from families with hereditary cardiovascular disease using whole-exome sequencing. Then we validated biological functions of CHMP4C mutations in zebrafish models. To further assess the mechanism of CHMP4C mutations, we evaluated the potential signaling pathway in the cells.

Results

We identification of CHMP4C variants that segregated with DCM variants in four families from a total of 411 families via whole-exome sequencing. We further validate the function of CHMP4C in heart function in zebrafish models and found that over-expression of CHMP4C variants in zebrafish resulted in cardiac malformation, pericardial edema and increased heart rate, consistent with CHMP4C mutation-associated findings in DCM patients. Furthermore, we found that mutations in CHMP4C impaired autophagy and activated apoptosis in HEK293T cells, suggesting that the molecular mechanism of CHMP4C is involved in heart development.

Conclusions

CHMP4C is a novel candidate gene for DCM and may play a critical role in cardiac development by regulating autophagy.

Funding Acknowledgement

Type of funding source: None

Non-invasive myocardial workiIndices derived from left ventricular pressure-strain loops in predicting the response to cardiac resynchronization therapy

Background

Non-invasive left ventricular (LV) pressure-strain loops (PSLs) which generated by combining LV longitudinal strain with brachial artery blood pressure, provide a novel method of quantifying global and segmental myocardial work (MW) indices with potential advantages over conventional echocardiographic strain which is load-dependent. The method has been introduced in echocardiographic software recently, making MW calculations more effectively and rapidly. The aim was to evaluate the role of non-invasive MW indices derived from LV PSLs in the prediction of cardiac resynchronization therapy (CRT) response.

Methods

106 heart failure (HF) patients scheduled for CRT were included for MW analysis. Global and segmental (septal and lateral at the mid-ventricular level) MW indices were accessed before CRT. Response to CRT was defined as ≥15% reduction in LV end-systolic volume at 6-month follow-up in comparison with baseline value.

Results

CRT response was observed in 78 (74%) patients. At baseline, global work index (GWI) and global constructive work (GCW) were significant higher in CRT responders than in non-responders (both P&lt;0.05). Besides, responders exhibited a significantly higher Mid Lateral MW and Mid Lateral constructive work (CW) (both P&lt;0.001) but a significantly lower Mid Septal MW and Mid Septal myocardial work efficiency (MWE), as well as a significantly higher Mid Septal wasted work (WW) than non-responders (all P&lt;0.01). Baseline Mid Septal MWE (OR 0.975, 95% CI 0.959–0.990, P=0.002) and Mid Lateral MW (OR 1.003, 95% CI 1.002–1.004, P&lt;0.001) were identified as independent predictors of CRT response in multivariate regression analysis. Mid Septal MWE ≤42% combined with Mid Lateral MW ≥740 mm Hg% predicted CRT response with the optimal sensitivity of 79% and specificity of 82% (AUC = 0.830, P&lt;0.001).

Conclusion

Mid Septal MWE and Mid Lateral MW can successfully predict response to CRT, and their combination can further improve the prediction accuracy. Assessment of MW indices before CRT could identify the marked misbalance in LV myocardial work distribution and has the potential to be widely used as a reliable complementary tool for guiding patient selection in clinical practice.

Funding Acknowledgement

Type of funding source: None

Multi-wavelength random fiber laser with switchable wavelength interval

A random fiber laser with flexible wavelength interval switching is proposed and demonstrated through two switching methods. One is to change the effective structure of the laser cavity by controlling the switches of 980 nm pump laser diodes (LDs) for erbium-doped fibers (EDFs), which can achieve the switching of the wavelength interval from a single Brillouin frequency shift (BFS) of 0.088 nm to a double BFS of 0.176 nm. Another method is to manipulate the gain provided by the two EDF amplifiers by controlling the power of the three 980 nm LDs, thereby realizing the optical switching of the wavelength interval. This kind of wavelength interval switchable random fiber laser increases the flexibility and functionality of multi-wavelength light sources, and further expands the application range of the random fiber lasers. Furthermore, the alternative wavelength interval switching mechanisms with simple structure enable it to meet the application requirements of various occasions.

Auto-Phase-Locked Time-Resolved Luminescence Detection: Principles, Applications, and Prospects

Time-resolved luminescence measurement is a useful technique which can eliminate the background signals from scattering and short-lived autofluorescence. However, the relative instruments always require pulsed excitation sources and high-speed detectors. Moreover, the excitation and detecting shutter should be precisely synchronized by electronic phase matching circuitry, leading to expensiveness and high-complexity. To make time-resolved luminescence instruments simple and cheap, the automatic synchronization method was developed by using a mechanical chopper acted as both of the pulse generator and detection shutter. Therefore, the excitation and detection can be synchronized and locked automatically as the optical paths fixed. In this paper, we first introduced the time-resolved luminescence measurements and review the progress and current state of this field. Then, we discussed low-cost time-resolved techniques, especially chopper-based time-resolved luminescence detections. After that, we focused on auto-phase-locked method and some of its meaningful applications, such as time-gated luminescence imaging, spectrometer, and luminescence lifetime detection. Finally, we concluded with a brief outlook for auto-phase-locked time-resolved luminescence detection systems.

Dual interference effects in a line-by-line inscribed fiber Bragg grating

Fiber Bragg grating (FBG) usually can be seen as a stack of Fabry-Perot (FP) cavities, which result in strong Bragg resonance through multi-cavity FP interference. In this Letter, we report surprising and interesting dual interference effects in a line-by-line (LBL) inscribed FBG with a femtosecond laser. Besides the well-known FP effect, the equivalent Mach-Zehnder interference (MZI) effect caused by mode interference can also be observed in the LBL FBG simultaneously. The experimental results of the comparison between the LBL FBGs and the point-by-point inscribed FBGs show that the dual interference effects are merely observed in the LBL FBGs. Meanwhile, the achieved MZI exhibits a strong polarization dependence. Sharing the merits of the FBG and MZI simultaneously, the achieved optical fiber device may find potential applications in optical fiber communication, fiber lasers, and multi-parameter sensor systems.

Mode-locked and Q-switched mode-locked fiber laser based on a ferroferric-oxide nanoparticles saturable absorber

We demonstrated an ultrafast erbium-doped fiber laser (EDFL) based on ferroferric-oxide (Fe₃O₄) nanoparticles as a saturable absorber (SA). The investigated SA was based on magnetic fluid deposited on the end face of a fiber ferrule connector. When the SA was inserted into an EDFL cavity, a stable 2.93 ps mode-locked pulse can be achieved by adjusting the intra-cavity polarization controller. The pulse had a central wavelength of 1572.39 nm and a 3 dB bandwidth of 1.39 nm. We also obtained Q-switched mode-locked pulses at 1593.4 nm. The repetition frequency and the temporal width of the Q-switched pulse envelope varied with the pump power. When the pump power reached 225 mW, the maximum average output power and the pulse envelope energy were up to 4.51 mW and 235.5 nJ. To the best of our knowledge, this is the first time that mode-locked and Q-switched mode-locked pulses have been obtained in a fiber laser based on Fe₃O₄ nanoparticles.

Dark solitons in the exploding pulsation of the bright dissipative soliton in ultrafast fiber lasers

Soliton explosion is an extremely pulsating behavior of the bright dissipative soliton (DS) in ultrafast lasers. By numerical simulation, we find that the dark soliton (DAS) can coexist with the bright soliton during the exploding process. The collapsed temporal structure of the exploding soliton is induced by the DASs. We reveal the birthing, evolving, and decaying of the DASs inside the bright DS. The time-frequency analysis of the exploding soliton helps us better understand the temporal and spectral structures of the exploding soliton, which might be useful for real-time spectroscopy of the coexisting dark and bright solitons during the soliton explosion.

Spectrally resolved luminescence lifetime detection for measuring the energy splitting of the long-lived excited states

Molecular motion plays an important role in the reverse intersystem crossing of thermally activated delayed fluorescence (TADF) materials, since the conformation varies as the molecule vibrates, leading to potential changes in the energies of excited states. Although many theoretical simulations have researched the relationship between the excited states and the molecular conformations, there are still few experimental results showing the energy level difference between different long-lived excited states. Herein, a novel method for measuring spectrally resolved luminescence lifetimes is proposed to detect the energy splitting of the long-lived excited states of a classical TADF molecule, BTZ-DMAC. A set of the time-gated luminescence spectra with different delay times were captured by a spectrograph equipped on an auto-phase-locked system, and then used for lifetime analysis at each wavelength. Unlike traditional measurement techniques, the proposed novel method does not require ultrafast laser, high-speed detector and any phase matching circuitry, thus significantly reducing the cost. This method revealed a definite energy gap between the two excited states of BTZ-DMAC with different lifetimes, indicating different conformations caused by molecular vibration. This low-cost method could be also used to detect many other luminescence materials for investigating the detail mechanisms of multiple excited states.

Rectangular SNAP microresonator fabricated with a femtosecond laser

Surface nanoscale axial photonics (SNAP) microresonators, which are fabricated by nanoscale effective radius variation (ERV) of the optical fiber with subangstrom precision, can be potentially used as miniature classical and quantum signal processors, frequency comb generators, and ultraprecise microfluidic and environmental optical sensors. Many of these applications require the introduction of nanoscale ERV with a large contrast α, which is defined as the maximum shift of the fiber cutoff wavelength introduced per unit length of the fiber axis. The previously developed fabrication methods of SNAP structures, which used focused CO₂ and femtosecond laser beams, achieved α∼0.02  nm/μm. Here we develop a new, to the best of our knowledge, fabrication method of SNAP microresonators with a femtosecond laser, which allows us to demonstrate a 50-fold improvement of previous results and achieve α∼1  nm/μm. Furthermore, our fabrication method enables the introduction of ERV that is several times larger than the maximum ERV demonstrated previously. As an example, we fabricate a rectangular SNAP resonator and investigate its group delay characteristics. Our experimental results are in good agreement with theoretical simulations. Overall, the developed approach allows us to reduce the axial scale of SNAP structures by an order of magnitude.

Association between methylenetetrahydrofolate reductase polymorphisms and non-syndromic cleft lip with or without palate susceptibility: an updated systematic review and meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms are thought to be involved in the development of cleft lip with or without cleft palate (NSCL/P), but published results are contradictory. We therefore designed an updated meta-analysis to pool eligible studies and to evaluate further the possible relations between MTHFR polymorphisms (c.677C>T and c.1298A>C) and susceptibility to NSCL/P. A comprehensive search based on PubMed, Medline, Web of Science, and Embase databases was made up to February 2018. Twenty-three case-control and 10 case-parent trio studies (including 1149 cases and 1161 controls) were retrieved. Odds ratio (OR) with 95% CI were used to estimate the pooled strength of association under different genetic models. The Q test and I² test were used to estimate heterogeneity among studies, the quality of which was assessed using the Newcastle-Ottawa scale. In the MTHFR c.677C>T polymorphism group, there were significant overall results for the recessive (OR 1.231, 95%CI 1.092 to 1.387) and homozygote (OR 1.252, 95%CI 1.078 to 1.456) models. Subgroup analysis by subjects and ethnicity identified only associations in European mothers for the recessive model and the homozygote model. For the c.1298A>C group, there were no significant results for either European or Asian patients for all genetic models. The MTHFR c.677C>T polymorphism might increase susceptibility to NSCL/P in European mothers, but was negatively associated in Asian patients, and the MTHFR c.1298A>C polymorphism is not involved in the development of NSCL/P in either European or Asian patients.

P6501Recurrent genetic aberrations in bicuspid aortic valve disease patients with isolated severe aortic regurgitation

Background

The etiology of bicuspid aortic valve disease (BAVD) is still unclear. Recent studies have demonstrated elevated prevalence of genetic defects in BAV patients with root phenotype, which includes aortic regurgitation and root-predominant dilatation.

Purpose

The present study intended to illustrate the feature of genetic defects among early-onset BAV patients with isolated severe aortic regurgitation.

Methods

From June 2015 to December 2017, whole exome sequencing was performed upon 27 BAVD patients with isolated severe aortic regurgitation under 45 years in our institution. Patients were categorized into right-left (R-L, n=16) and non-RL (n=11) cusp fusion types, and those with complex cardiac defects were excluded from the present study.

Results

Among 27 patients with a median age of 30.5 (18–44) years, only one was female with a rare left-non-coronary cusp fusion type. The prevalence of root phenotype was markedly higher in RL patients (56.3% vs 9.1%, p=0.018). In RL patients, the numbers of rare genetic variants (RGVs) were 15 in extracellular matrix genes, 8 in TGF-β signaling pathway genes, 2 in smooth muscle cell contraction apparatus genes, and 3 in familiar BAV related genes. In non-RL patients, the number of RGVs were 15, 3, 4, and 5, respectively. On the other hand, the number of RGVs in above gene clusters were 9, 6, 3, 2 in patients with a root phenotype, and 21, 5, 3, 6 in those without. Eight recurrent genetic variants were identified in 6 genes (see Table). An interesting observation was that ADAMTS2 variants were exclusively found among non-RL patients without root phenotype, as FBN2 variants among RL patients with root phenoype.

Recurrent Rare Genetic Variants Gene Reference sequence Variant 1000G 1000G-East Asia Patients TGFBR2 NM_001024847.2 p.Val216Ile/c.646G>A 0.004 0.018 A16, A23 TGFBR2 NM_001024847.2 p.Thr340Met/c.1019C>T 0.003 0.015 A03, A05, A07 ADAMTS2 NM_014244.4 p.Gly1169Val/c.3506G>T 0.0044 0.021 A03, A15 FBN2 NM_001999.3 p.Gly475Val/c.1424G>T 0.0004 0.002 A19, A24 ELN NM_001278939.1 p.Pro93Leu/c.278C>T 0.0014 0.0069 A22, A26 COL4A5 NM_033380.2 p.Gly953Val/c.2858G>T 0.0079 0.03 A11, A17 MYLK NM_053025.3 p.Ser243Trp/c.728C>G 0.0002 0.001 A01, A02 MYLK NM_053025.3 p.Asp717Tyr/c.2149G>T 0.0024 0.011 A04, A21

Conclusion

Recurrent genetic variants could be identified in a cohort of early-onset BAVD patients with isolated severe aortic regurgitation and staggering male predominance. The incidence and clinical relevance of these variants should be validated in an extended real-world BAV cohort.

P916The effect of a novel, user-friendly, transcatheter edge-to-edge mitral valve repair device in a porcine model of mitral regurgitation

Objective

A new technique has been devised to treat mitral regurgitation (MR) through the transapical route by replicating the edge-to-edge repair surgery. This system encompasses an easy-to-use leaflet clamp and a smaller-sized delivery system (14F–16F). We aimed to evaluate the effectiveness of this device in a porcine model of acute MR.

Methods

Acute MR was induced in 36 anesthetized porcine subjects by severing the major chordae supporting the corresponding segment of the leaflet. This device was then transapically implanted on the prolapsing segment under 3D epicardial echocardiographic guidance. All of the animals were killed 30 days after the procedure to verify the proper location of the implanted devices.

Results

Cutting the major chordae induced an eccentric MR jet (MR grade: 3+, 27.8%/4+, 72.2%) in all of the animals. Every single pig was then successfully implanted with one clamp. The duration of catheterization ranged from 18 to 40 minutes. Overt MR reduction was observed following the procedure through echocardiography; residual MR was mild in 8 cases, trivial in 19 cases, and absent in 9 cases. In terms of hemodynamic parameters, the mean and maximum mitral valve pressure gradients were increased significantly (p<0.01), but these values were less than 4 mmHg in all of the cases. Autopsy demonstrated that all but one device were precisely placed to clip the prolapsing segment of the mitral valve, and there was no evidence of thrombosis, thromboembolism or impairment of the cardiac structure.

Table 1. Changes in hemodynamic parameters, cardiac size, and functional parameters after the procedure Preoperation Postoperation P value MR-maxA (mm2) 7.27±2.13 1.54±1.29 0.000 MVPG-max (mmHg) 1.95±0.47 3.66±0.62 0.000 MVPG-mean (mmHg) 0.87±0.31 1.7±0.28 0.000 LVEDD (mm) 46.08±2.85 46.44±3.53 0.239 LVESD (mm) 29.11±3.44 29.08±3.62 0.940 LVEF (%) 66.53±6.4 67.14±4.93 0.256 LAD (mm) 35.75±2.24 36.42±1.99 0.057 LAA (mm2) 12.95±2.22 12.64±1.55 0.301

Figure 1

Conclusions

Transapical implantation of the novel mitral valve repair device is effective and safe in reducing acutely induced MR in pigs; thus, suggesting that it has great potential for clinical benefit in patients with MR.

Acknowledgement/Funding

Shanghai Science and Technology Committee

Spatially distributed delay line interferometer based on transmission Bragg scattering

A novel approach for a delay line interferometer (DLI) based on transmission Bragg scattering is proposed. We have numerically and experimentally demonstrated for the first time, to the best of our knowledge, that a Bragg grating (BG) can deliver the functionality of a DLI in its transmission mode along a single common interfering optical path, instead of the conventional DLI implementation with two interfering optical paths. As a proof of concept, phase-modulated fiber BGs have been designed and fabricated, showing the desired functionality in the transmission mode of the BG. The proposed approach is applicable to any kind of BG technology, such as volume BGs, dielectric mirrors, silicon photonics, and other optical waveguide-based Bragg structures.

Pulsating soliton with broadened Kelly sidebands in an ultrafast fiber laser

We experimentally observed a novel pulsating soliton state with broadened Kelly sidebands in an ultrafast laser. Through simulations, we found that the synchronized and unsynchronized resonant dispersive waves coexisted in the laser. The incoherent interaction between the unsynchronized dispersive waves and soliton resulted in oscillation of the intensity and central wavelength of the soliton. The frequencies of the Kelly sidebands oscillated with the soliton, resulting in their spectral broadening when measured by an optical spectrum analyzer. The numerical results agreed qualitatively well with the experiments. Our results are novel and useful for understanding the chaotic dynamics and designing of the ultrafast fiber laser.

Fiber Bragg grating sensor interrogation system based on an optoelectronic oscillator loop

In this article, we propose and experimentally demonstrate a fiber Bragg grating (FBG) sensor interrogation technique based on an optoelectronic oscillator (OEO). The main components of the OEO loop in this proposed scheme contains an electro-optic modulator (EOM), a section of dispersive element, an electric filter, and a photodiode (PD). The reflection signal of the FBG sensor is functioning as the optical source of the OEO. The oscillating frequency of the OEO is determined by the overall time delay of the OEO loop. Due to the dispersive element in the loop, time delay of the OEO loop is a function of the OEO optical source wavelength. As a result, the wavelength change of the FBG can be converted into the oscillating frequency shift of the OEO. A proof-of-concept FBG based axial strain sensing experiment is carried out. The experimental results show that the frequency of the OEO generated microwave signals have a good linear relationship with the axial strain applied to the FBG. The sensitivity is about 58 Hz/με when using dispersion compensation fiber (DCF) with dispersion of -120 ps/(nm*km) as the dispersive medium and tracking the microwave signal with frequency near 2056.4 MHz, which is consistent with the theoretical calculation. The proposed method can also be applied to interrogate optical sensors based on detecting the wavelength change of the optical signals.

Stable and low-threshold random fiber laser via Anderson localization

We report a stable and low-threshold Er-doped random fiber laser (RFL) based on a femtosecond-laser-inscribed random-distributed-grating array (RDGA) as the random feedback. The RDGA had a reflectivity of 93.5%, and its properties were numerically analyzed based on the transfer matrix method. The threshold of the laser was significantly reduced to 5.7 mW, and the linewidth was ~0.4 pm near the threshold as the Anderson localization effect existing in the RDGA significantly improved the laser quality factor (4 × 10⁶). In addition, we propose a method to select RFL lasing modes by stretching a fiber grating filter used in the cavity with different axial strains. The center wavelength hardly drifted and the maximum jitter value of the peak power was less than 0.12 dB over 1 hour for the selected three lasing modes, which indicated that our laser operation was quite stable.

Vitamin B6 catabolism and lung cancer risk: results from the Lung Cancer Cohort Consortium (LC3)

BACKGROUND

Increased vitamin B6 catabolism related to inflammation, as measured by the PAr index (the ratio of 4-pyridoxic acid over the sum of pyridoxal and pyridoxal-5'-phosphate), has been positively associated with lung cancer risk in two prospective European studies. However, the extent to which this association translates to more diverse populations is not known.

MATERIALS AND METHODS

For this study, we included 5323 incident lung cancer cases and 5323 controls individually matched by age, sex, and smoking status within each of 20 prospective cohorts from the Lung Cancer Cohort Consortium. Cohort-specific odds ratios (ORs) and 95% confidence intervals (CIs) for the association between PAr and lung cancer risk were calculated using conditional logistic regression and pooled using random-effects models.

RESULTS

PAr was positively associated with lung cancer risk in a dose-response fashion. Comparing the fourth versus first quartiles of PAr resulted in an OR of 1.38 (95% CI: 1.19-1.59) for overall lung cancer risk. The association between PAr and lung cancer risk was most prominent in former smokers (OR: 1.69, 95% CI: 1.36-2.10), men (OR: 1.60, 95% CI: 1.28-2.00), and for cancers diagnosed within 3 years of blood draw (OR: 1.73, 95% CI: 1.34-2.23).

CONCLUSION

Based on pre-diagnostic data from 20 cohorts across 4 continents, this study confirms that increased vitamin B6 catabolism related to inflammation and immune activation is associated with a higher risk of developing lung cancer. Moreover, PAr may be a pre-diagnostic marker of lung cancer rather than a causal factor.

Efficient postprocessing technique for fabricating surface nanoscale axial photonics microresonators with subangstrom precision by femtosecond laser

We demonstrated the subangstrom precise correction of surface nanoscale axial photonics (SNAP) micro-resonators by the femtosecond (fs) laser postprocessing technique for the first time. The internal stress can be induced by fs laser inscriptions in the fiber, causing nanoscale effective radius variation (ERV). However, the obtained ultraprecise fabrication usually undergoes multiple tries. Here, we propose a novel postprocessing technique based on the fs laser that significantly reduces the ERV errors and improves the fabrication precision without iterative corrections. The postexposure process is achieved at the original exposure locations using lower pulse energy than that in the initial fabrication process. The results show that the ERV is nearly proportional to the pulse energy of the postexposure process. The slope of the ERV versus the pulse energy is 0.07 Å/nJ. The maximum of the postprocessed ERV can reach 8.0 Å. The repeatability was experimentally verified by accomplishing the correction on three SNAP microresonators with the precision of 0.75 Å. The developed fabrication technique with fs laser enables SNAP microresonators with new breakthrough applications for optomechanics and filters.

Spatio-spectral dynamics of the pulsating dissipative solitons in a normal-dispersion fiber laser

For the first time, to the best of our knowledge, we observed the pulsating dissipative solitons in a mode-locked fiber laser at normal dispersion using the dispersive-Fourier transformation technology. The artificial saturable absorbers, as well as the birefringent filter formed by the nonlinear polarization rotation, make the polarization controller an effective component to adjust the laser state from stationary to pulsating. The pulsating dissipative solitons are accompanied with the spectrum breathing and oscillating structures due to the nonlinear pulse propagation. Our results can enhance the understanding of the pulsating solitons in the dissipative systems.