We propose and demonstrate a symmetric step-apodized distributed feedback (DFB) fiber laser, which has an improved efficiency and a narrow linewidth. This special DFB laser cavity is based on a ...unique symmetric step-apodized π-phase-shifted fiber Bragg grating (FBG) directly inscribed in a heavily erbium-doped fiber. The symmetric step-apodized phase-shifted grating is equivalent to a weak uniform phase-shifted FBG embedded in a pair of strong FBGs, and this design could increase the effective cavity length of a DFB fiber laser. Moreover, the symmetric step-apodized DFB laser cavity proposed in this work has a phase shift located in the cavity center. It could simplify the design process significantly due to the symmetry in the laser cavity. Experimental results show that the slope efficiency of a symmetric step-apodized DFB fiber laser could be increased to 1.06%, which is significantly higher than that of a uniform DFB fiber laser (i.e., 0.45%) under the same cavity length and pump conditions. In addition, the proposed DFB fiber laser exhibits a high stability. The fluctuations in lasing wavelength and output power were less than 12 pm (corresponding to a frequency shift of 1.49 GHz) and 0.13 dB within 24 h, respectively. Moreover, the full-width at half-maximum linewidth of the symmetric step-apodized DFB fiber laser was ∼2.6 kHz, measured by the delayed self-heterodyne method with a 50-km fiber delayed line. As such, the proposed symmetric step-apodized DFB fiber laser could potentially be used as high-performance light source for fiber-optic sensors or coherent optical communication systems.
A novel, highly efficient terahertz fully polarized transmission line is designed by two-dimensional tellurium photonic crystals consisting of square lattice rod arrays with a complete photonic ...bandgap. The TE and TM photonic bandgaps of the tellurium photonic crystals, which are computed by plane wave expansion, happen to coincide, and the complete photonic bandgap covers from 2.894 to 3.025 THz. The function of the designed waveguide is simulated by the finite element method, and the transmission characteristics are optimized by accurately adjusting its structural parameters. The transmission efficiency of the waveguide for TE mode achieves a peak value of −0.34 dB at a central frequency of 2.950 THz and keeps above −3 dB from 2.82 THz to 3.02 THz, obtaining a broad relative bandwidth of about 6.84 percent. The operating bandwidth of the tellurium photonic crystals’ waveguide for TM mode is narrower than that of TE mode, whose relative bandwidth is about 4.39 percent or around 2.936 THz above −5 dB. The designed terahertz photonic crystals’ waveguide can transmit both TE and TM waves, and not only can it be used as a high-efficiency transmission line, but it also provides a promising approach for implementing fully polarized THz devices for future 6G communication systems.
In a multiple degrees of freedom motion system with rigid-flexible coupling, the flexible internal dynamics have a significant negative impact on performance because the degrees of freedom are ...coupled. Inspired by this problem, a multi-input multioutput state-space model based on modal coordinates is proposed to decouple the rigid body and flexible modes. The closed-loop subspace identification method based on orthogonal is utilized to develop an unbiased standard state-space model. Based on the similarity principle, a modal analysis method is proposed to transfer the standard state-space model to the proposed modal-decomposition-dependent state-space model. Controllability and observability criteria are met to guarantee the minimum realization of the proposed state-space model. Finally, a modeling and modal analysis experiment is conducted on a developed wafer stage of lithographic tool. The results verify the effectiveness and accuracy of the proposed modeling method, as well as the controllability and observability of the proposed model.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Abstract
Optical fibers are typically used in telecommunications services for data transmission, where the use of fiber tags is essential to distinguish between the different transmission fibers or ...channels and thus ensure the working functionality of the communication system. Traditional physical entity marking methods for fiber labeling are bulky, easily confused, and, most importantly, the label information can be accessed easily by all potential users. This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating (FBG) array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method. Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations. It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array, and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities. The proposed fiber tag technology can be used for applications in port identification, encrypted data storage, and transmission in fiber networks.
Highlights
Based on an encoded fiber Bragg grating (FBG) array fabricated using a point-by-point femtosecond laser pulse chain inscription method, an encrypted optical fiber tag is proposed and demonstrated experimentally.
A binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array, and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities.
The encrypted data are recovered via analysis of the backscattered light signal from the fiber tag. The featured grating information and the spatial distribution of the FBGs and the information carried in their specific channels can be recovered based on a code rule.
The proposed fiber tag technology can be used for applications in port identification, encrypted data storage, and transmission in fiber networks.
We demonstrate an ultrasensitive temperature sensor based on a unique fiber Fabry-Pérot interferometer (FPI) that was created by means of splicing a mercury-filled silica tube with a single-mode ...fiber. The air cavity of the fiber FPI was formed by the surface of the mercury column and the endface of the single-mode fiber. Moreover, the mercury-based fiber FPI exhibits an ultrahigh temperature-sensitivity of up to -41.9 nm/°C, which is about one order of magnitude higher than that of the ordinary FPI-based fiber-tip sensors reported so far. Hence, such a mercury-based fiber FPI temperature sensor could be used for highly sensitive ambient temperature sensing applications.
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•A novel Si-O-C hyperbranched polysiloxane with specific terminals was synthesized.•The curing processability of CE was enhanced by a 93.5 °C lower curing temperature.•The impact ...strength of the fabricated CE resins was greatly enhanced by 105.3%.•Synergism of hyperbranched structure and covalent bonds led to great enhancement.
High-performance electronic packaging materials with favorable processability are highly desirable to satisfy the booming of new generation communication technology. Herein, the bisphenol A cyanate ester (BADCy) resins containing Si-O-C hyperbranched polysiloxane were fabricated with facile curing process to achieve the application of electronic packaging. The fabricated BADCy resins exhibited not only significantly reduced curing temperature in favor of facile processability, but also dramatically enhanced toughness for prolonging the service life of packaging materials. The curing peak temperature was miraculously decreased by 93.5 °C. Meanwhile, the impact strength was significantly enhanced by 105.3%. Notably, the BADCy resins presented lower dielectric constant (ε of 2.59) and dielectric loss tangent values (tan δ of 0.0062) at 10 GHz. The results suggest that HSiEP possesses promising potential applications in the field of electronic packaging.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Cas12a can process multiple sgRNAs from a single transcript of CRISPR array, conferring advantages in multiplexed base editing when incorporated into base editor systems, which is extremely helpful ...given that phenotypes commonly involve multiple genes or single-nucleotide variants. However, multiplexed base editing through Cas12a-derived base editors has been barely reported, mainly due to the compromised efficiencies and restricted protospacer-adjacent motif (PAM) of TTTV for wild-type Cas12a. Here, we develop Cas12a-mediated cytosine base editor (CBE) and adenine base editor (ABE) systems with elevated efficiencies and expanded targeting scope, by combining highly active deaminases with Lachnospiraceae bacterium Cas12a (LbCas12a) variants. We confirm that these CBEs and ABEs can perform efficient C-to-T and A-to-G conversions, respectively, on targets with PAMs of NTTN, TYCN, and TRTN. Notably, multiplexed base editing can be conducted using the developed CBEs and ABEs in somatic cells and embryos. These Cas12a variant-mediated base editors will serve as versatile tools for multiplexed point mutation, which is notably important in genetic improvement, disease modeling, and gene therapy.
This paper focuses on augmenting the propulsion via commutation of coil array for the long-stroke magnetically levitated stage with moving coils, whose mechatronics structure have been defined. The ...used commutation of coil array is based on the analytical force/torque-decomposing model of the stage and it is characterized by bounding the coil currents. Through this current-bounded commutation, the 1-norm of commutated coil current vector is increased so that the propulsion can be augmented, and simultaneously the infinite norm of commutated coil current vector is limited so that the amplitudes of commutated coil currents are not beyond the capacity of selected coil power amplifiers. By the investigation example of a long-stroke magnetically levitated stage with moving coils, it is theoretically verified that the propulsion (acceleration) can be augmented by 125% as well as the commutated coil currents can be kept within the capacity of selected coil power amplifiers, 3 A. The study results indicate that the propulsion of a magnetically levitated stage can be augmented via current-bounded commutation of coil array rather than via reconfiguring the mechatronics structure of stage or reselecting coil power amplifiers of larger capacity.
Plastic combustion has adverse impacts on air quality and human health. In this work, a novel non-aromatic Si, P, N-containing hyperbranched flame retardant (HPNSi) was synthesized and proposed to ...epoxy resin. The modified epoxy exhibits not only reduced fire hazards and less smoke production in favor of eco-friendly, but also remarkable mechanical properties and lower curing temperature for facile processability. With 6 wt% incorporation, the peak heat release and total smoke production were reduced by 29.6% and 20.7%, respectively, and the time to ignition (TTI) increased as well as the fire growth rate (FIGRA) dropped off, which is of vital significance for saving lives in a fire. Meanwhile, the impact strength and flexural strength greatly enhanced by 72.9% and 22.0%, while its curing temperature was lower than that of controlled EP system. Interestingly, we also found that the solid carbon particles on the char surface apparently reduced from SEM image. The blending of its unique non-aromatic hyperbranched structure containing Si, P, N with epoxy architecture was responsible for the desirable integrated enhancement. The broad possibilities in the field of flame-retardant plastic with reduced fire hazards and excellent integrated performance enable the novel hyperbranched flame retardant a bright future for application.
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•Non-aromatic Si, P, N-hyperbranched FR was synthesized by facile polycondensation.•Significantly enhanced flame retardancy and low smoke release were achieved.•The HPNSi/EP exhibits outstanding mechanical properties and rapid curing rate.•Phosphorus group introduce to hyperbranched architecture led to great enhancement.•SEM show that HPNSi may inhibit carbon particle release on the char surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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