Highly sensitive sensing of a magnetic field and temperature based on two open ring channels SPR-PCF.

A surface plasmon resonance (SPR) sensor comprising photonic crystal fiber (PCF) is designed for magnetic field and temperature dual-parameter sensing. In order to make the SPR detection of magnetic field and temperature effectively, the two open ring channels of the proposed sensor are coated with gold and silver layers and filled with magnetic fluid (MF) and Polydimethylsiloxane (PDMS), respectively. The sensor is analyzed by the finite element method and its mode characteristics, structure parameters and sensing performance are investigated. The analysis reveals when the magnetic field is a range of 40-310 Oe and the temperature is a range of 0-60 °C, the maximum magnetic field sensitivity is 308.3 pm/Oe and temperature sensitivity is 6520 pm/°C. Furthermore, temperature and magnetic field do not crosstalk with each other's SPR peak. Its refractive index sensing performance is also investigated, the maximum sensitivity and FOM of the left channel sensing are 16820 nm/RIU and 1605 RIU-1, that of the right channel sensing are 13320 nm/RIU and 2277 RIU-1. Because of its high sensitivity and special sensing performance, the proposed sensor will have potential application in solving the problems of cross-sensitivity and demodulation due to nonlinear changes in sensitivity of dual-parameter sensing.

Spectral diagnosis of in situ plasma cleaning in large-aperture optical components: reactive species characterization and prediction of cleaning.

The damage of large-aperture optical components caused by organic contamination limits the performance improvement of high-power laser facilities. We propose an in situ plasma cleaning technology to remove the organic contaminants on large-aperture optical components, demonstrated by the simulated equipment. The cleaning characteristics of the equipment were investigated by spectral diagnosis. The cleaning capability coefficient was defined to evaluate the performance of the plasma equipment. Then diffusion properties of reactive species along the surface of optical components were elucidated under various charge parameters, including powers, source frequencies, and gas pressures. We discuss the underlying cleaning mechanism for removing organic contaminants. A new plasma cleaning model is established to predict the treatment time with the cleaning capability coefficient.

A Novel Airborne Molecular Contaminants Sensor Based on Sagnac Microfiber Structure.

The impact of airborne molecular contaminants (AMCs) on the lifetime of fused silica UV optics in high power lasers (HPLs) is a critical issue. In this work, we demonstrated the on-line monitoring method of AMCs concentration based on the Sagnac microfiber structure. In the experiment, a Sagnac microfiber loop with mesoporous silica coating was fabricated by the microheater brushing technique and dip coating. The physical absorption of AMCs in the mesoporous coating results in modification of the surrounding refractive index (RI). By monitoring the spectral shift in the wavelength domain, the proposed structure can operate as an AMCs concentration sensor. The sensitivity of the AMCs sensor can achieve 0.11 nm (mg/m3). By evaluating the gas discharge characteristic of four different low volatilization greases in a coarse vacuum environment, we demonstrated the feasibility of the proposed sensors. The use of these sensors was shown to be very promising for meeting the requirements of detecting trace amounts of contaminants.

An Ultra-Sensitive Multi-Functional Optical Micro/Nanofiber Based on Stretchable Encapsulation.

Stretchable optical fiber sensors (SOFSs), which are promising and ultra-sensitive next-generation sensors, have achieved prominent success in applications including health monitoring, robotics, and biological-electronic interfaces. Here, we report an ultra-sensitive multi-functional optical micro/nanofiber embedded with a flexible polydimethylsiloxane (PDMS) membrane, which is compatible with wearable optical sensors. Based on the effect of a strong evanescent field, the as-fabricated SOFS is highly sensitive to strain, achieving high sensitivity with a peak gauge factor of 450. In addition, considering the large negative thermo-optic coefficient of PDMS, temperature measurements in the range of 30 to 60 °C were realized, resulting in a 0.02 dBm/°C response. In addition, wide-range detection of humidity was demonstrated by a peak sensitivity of 0.5 dB/% RH, with less than 10% variation at each humidity stage. The robust sensing performance, together with the flexibility, enables the real-time monitoring of pulse, body temperature, and respiration. This as-fabricated SOFS provides significant potential for the practical application of wearable healthcare sensors.

High Sensitivity Refractometer Based on Reflective Smf-Small Diameter No Core Fiber Structure.

A high sensitivity refractive index sensor based on a single mode-small diameter no core fiber structure is proposed. In this structure, a small diameter no core fiber (SDNCF) used as a sensor probe, was fusion spliced to the end face of a traditional single mode fiber (SMF) and the end face of the SDNCF was coated with a thin film of gold to provide reflective light. The influence of SDNCF diameter and length on the refractive index sensitivity of the sensor has been investigated by both simulations and experiments, where results show that the diameter of SDNCF has significant influence. However, SDNCF length has limited influence on the sensitivity. Experimental results show that a sensitivity of 327 nm/RIU (refractive index unit) has been achieved for refractive indices ranging from 1.33 to 1.38, which agrees well with the simulated results with a sensitivity of 349.5 nm/RIU at refractive indices ranging from 1.33 to 1.38.

The application of human-derived cell lines in neurotoxicity studies of environmental pollutants.

As industrial and societal advancements progress, an increasing number of environmental pollutants linked to human existence have been substantiated to elicit neurotoxicity and developmental neural toxicity. For research in this field, human-derived neural cell lines have become excellent in vitro models. This study examines the utilization of immortalized cell lines, specifically the SH-SY5Y human neuroblastoma cell line, and neural cells derived from human pluripotent stem cells, in the investigation of neurotoxicity and developmental neural toxicity caused by environmental pollutants. The study also explores the culturing techniques employed for these cell lines and provides an overview of the standardized assays used to assess various biological endpoints. The environmental pollutants involved include a variety of organic compounds, heavy metals, and microplastics. The utilization of cell lines derived from human sources holds significant significance in elucidating the neurotoxic effects of environmental pollutants and the underlying mechanisms. Finally, we propose the possibility of improving the in vitro model of the human nervous system and the toxicity detection methods.

The Characterization of Laser-Induced Particles Generated from Aluminum Alloy in High Power Laser Facility.

Aerosol particle contamination in high-power laser facilities has become a major cause of internal optical component damage resistance and service life reduction. In general, contaminating particles primarily originate from stray light; therefore, it is crucial to investigate the mechanism and dynamics of the dynamic contaminating particle generation to control the cleanliness level. In this study, corresponding research was conducted on experiments and theory. We investigated the particle generation and surface composition modification under the action of a laser. We employed various surface analytical methods to identify the possible variations in the aluminum alloy surface during laser irradiations. A theoretical model for particle ejection from aluminum alloy surfaces was established by taking the adhesion force and laser cleaning force (due to thermal expansion) into account. The results show that the threshold energies for contamination particle generation and damage are around 0.1 and 0.2 J/cm2, respectively. Subsurface impurities are the primary source of particles, and particle adhesion density is related to surface roughness. Pollution particle generation and splashing processes include temperature increases, phase changes, impact diffusion, and adhesion. The results provide a reference for the normal operation of high-energy laser systems. The results also suggest that the laser irradiation pretreatment of aluminum alloy surfaces is essential to improve the cleanliness level.

[The study on supercontinuum generation of femtosecond pulse propagating in fused silica].

Starting from Nonlinear Schrodinger's equation and using the split-step Fourier method, the authors studied the characters of the supercontinuum generation of femtosecond laser pulse propagating in fused silica, and many physical factors were included such as propagation distance, input pulse peak power, diffraction effect, dispersion effect andnonlinear effect etc. The results show that when the femtosecond pulse propagated inside the fused silica, the process of supercontinuum generation could be divided into two main stages: the pulse compression stage, which was induced by the self-focus and other third nonlinear effects of the fused silica; and the pulse split stage, which was caused by the self-phase modulation and the group velocity dispersion of the fused silica. When the femtosecond pulse propagated inside the fused silica with high input peak power, the 3rd-order nonlinear effect of material induced pulse compression and then the subpulses were produced, so that new frequency components were introduced. At the same time, the authors also studied the spectral distribution of the pulse at different spacial locations, and there are new frequencies around the central frequency. Finally, some experiments were done to demonstrate the supercontinuum generation.

A simple all-fiber comb filter based on the combined effect of multimode interference and Mach-Zehnder interferometer.

A polarization-dependent all-fiber comb filter based on a combination effect of multimode interference and Mach-Zehnder interferometer was proposed and demonstrated. The comb filter was composed with a short section of multimode fiber (MMF) fusion spliced with a conventional single mode fiber on the one side and a short section of a different type of optical fiber on the other side. The second type of optical fiber is spliced to the MMF with a properly designed misalignment. Different types and lengths of fibers were used to investigate the influence of fiber types and lengths on the performance of the comb filter. Experimentally, several comb filters with free spectral range (FSR) values ranging from 0.236 to 1.524 nm were achieved. The extinction ratio of the comb filter can be adjusted from 6 to 11.1 dB by varying polarization states of the input light, while maintaining the FSR unchanged. The proposed comb filter has the potential to be used in optical dense wavelength division multiplexing communication systems.

Quantitative correlation between facets defects of RDX crystals and their laser sensitivity.

In this work, the {210} facets of cyclotrimethylenetrinitramine (RDX) single crystals with different quality were studied by scanning electron microscopy and atomic force microscopy. Their laser sensitivity was then assessed using a direct laser ignition test irradiated with ultraviolet laser (wavelength: 355nm, pulse width: 6.4ns). Quantitative relationships between laser sensitivity and surface defects of RDX (210) and (2¯1¯0) facets were investigated. It is determined that the laser sensitivity exhibits significant correlation with the surface roughness, size of which is comparable with scales of laser wavelength. 3D FDTD simulations disclose that this relationship can be well explained with light intensity modulation effects induced by micro-defects on the initial plane wave.

Ultraviolet Laser-induced ignition of RDX single crystal.

The RDX single crystals are ignited by ultraviolet laser (355 nm, 6.4 ns) pulses. The laser-induced damage morphology consisted of two distinct regions: a core region of layered fracture and a peripheral region of stripped material surrounding the core. As laser fluence increases, the area of the whole crack region increases all the way, while both the area and depth of the core region increase firstly, and then stay stable over the laser fluence of 12 J/cm(2). The experimental details indicate the dynamics during laser ignition process. Plasma fireball of high temperature and pressure occurs firstly, followed by the micro-explosions on the (210) surface, and finally shock waves propagate through the materials to further strip materials outside and yield in-depth cracks in larger surrounding region. The plasma fireball evolves from isotropic to anisotropic under higher laser fluence resulting in the damage expansion only in lateral direction while maintaining the fixed depth. The primary insights into the interaction dynamics between laser and energetic materials can help developing the superior laser ignition technique.