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In this research, optical absorption regulation of Ag nanodisc arrays in a monolayer MoS2 hybrid system is investigated using the FDTD technique. Ag nanodisc arrays are designed on monolayer MoS2 on SiO2/Si and Au/SiO2 substrates. For Ag/1L MoS2/SiO2/Si, two absorption peaks near 620 nm and 670 nm are showed, with different intensification amplitudes of absorption peaks and slight shifts in peak position changing diameters or spacing of Ag nanodiscs. When the diameter is 220 nm, the strongest absorption peak is displayed at 745 nm. When the spacing s is 300 nm, the absorption peak at 759 nm has the highest intensity. When the thickness of the SiO2 film increases from 90 to 280 nm and 300 nm, the intensity of the absorption peak near 620 nm increases by 1.7 times, and the peak blueshifts to 585 nm. In the band from 550 to 700 nm, the presence of the Ag nanodisc array significantly enhances the absorption of the film system, when the thickness of the SiO2 film is 300 nm, and the enhancement amplitude of the absorption peak near 620 nm reaches three times. For Ag/1L MoS2/Au/SiO2, when the diameter or spacing of the Ag nanodisc increases from 100 to 220 nm every 30 nm, the peak positions of 620 nm and 670 nm are changed. When the diameter of the Ag nanodisc is 100 nm and 220 nm, the normalized absorption rates at 686 nm and 707 nm are 0.95 and 0.96, respectively. When the spacing s is 200 nm and 400 nm, the normalized absorption rates at 562 nm and 686 nm are 0.94 and 0.96, respectively. By comparing the optical absorption with and without the Ag nanodisc array, the absorption of the monolayer MoS2 hybrid system is greatly enhanced. When the surrounding medium is changed from air to water, the absorption peaks of 641 nm and 686 nm become 587 nm and 775 nm, the distance between peak positions is enlarged, and the intensity is obviously weakened, which is due to the weakening of the surface plasmon effect of the Ag nanodisc array. [ABSTRACT FROM AUTHOR]

Highlights: A flexible tribotronic artificial synapse with bioinspired neurosensory behaviour was demonstrated, which establishes an active interaction mechanism with the environment. The device can well exhibit tuneable synaptic behaviours by changing the mechanical input modes, including excitatory postsynaptic current, paired-pulse facilitation, and the hierarchical memorial process. The device has excellent mechanical flexibility that can exhibit stable synaptic functions even under strain conditions with a bending radius of 20 mm after 1000 bending cycles. As key components of artificial afferent nervous systems, synaptic devices can mimic the physiological synaptic behaviors, which have attracted extensive attentions. Here, a flexible tribotronic artificial synapse (TAS) with bioinspired neurosensory behavior is developed. The triboelectric potential generated by the external contact electrification is used as the ion-gel-gate voltage of the organic thin film transistor, which can tune the carriers transport through the migration/accumulation of ions. The TAS successfully demonstrates a series of synaptic behaviors by external stimuli, such as excitatory postsynaptic current, paired-pulse facilitation, and the hierarchical memory process from sensory memory to short-term memory and long-term memory. Moreover, the synaptic behaviors remained stable under the strain condition with a bending radius of 20 mm, and the TAS still exhibits excellent durability after 1000 bending cycles. Finally, Pavlovian conditioning has been successfully mimicked by applying force and vibration as food and bell, respectively. This work demonstrates a bioinspired flexible artificial synapse that will help to facilitate the development of artificial afferent nervous systems, which is great significance to the practical application of artificial limbs, robotics, and bionics in future. [ABSTRACT FROM AUTHOR]

Carbon materials have become a research hotspot in many fields because of their unique properties. In this paper, carbon nanowires (CNWs) were constructed with the finite-difference time-domain (FDTD) technique, and the effects of different structural parameters on the optical absorption properties of CNWS arrays at 350–810 nm were investigated. The results show that different lengths, diameters and spacings of the nanowires lead to different absorption properties of the arrays. In addition to a sharp decrease in the absorption at high incidence or viewing angles, the arrays have strong absorption properties at other angles. However, the array absorption at high incidence or viewing angles can be enhanced to some extent by varying the lengths of the nanowires. The wavelength and polarization direction of the excitation light have little effect on the absorption properties of the arrays. It is very important to determine the corresponding structural parameters of CNWs with the strongest absorption for the fabrication of nanowire arrays and their applications in stealth technologies, nanolight-emitting devices, photoelectric sensors and photovoltaic cells. [ABSTRACT FROM AUTHOR]

Self-trapped modes suffer critical collapse in two-dimensional cubic systems. To overcome such a collapse, linear periodic potentials or competing nonlinearities between self-focusing cubic and self-defocusing quintic nonlinear terms are often introduced. Here, we combine both schemes in the context of an unconventional and nonlinear fractional Schrödinger equation with attractive-repulsive cubic–quintic nonlinearity and an optical lattice. We report theoretical results for various two-dimensional trapped solitons, including fundamental gap and vortical solitons as well as the gap-type soliton clusters. The latter soliton family resembles the recently-found gap waves. We uncover that, unlike the conventional case, the fractional model exhibiting fractional diffraction order strongly influences the formation of higher band gaps. Hence, a new route for the study of self-trapped modes in these newly emergent higher band gaps is suggested. Regimes of stability and instability of all the soliton families are obtained with the help of linear-stability analysis and direct simulations. Stabilising localised solitons in higher dimensions is more challenging than their one dimensional counterpart due to the onset of critical collapse. Here, competing nonlinear terms are added to a linearly-modulated optical lattice to predict regimes of stability for different soliton families. [ABSTRACT FROM AUTHOR]

The effective photonic control is one of the key issues in photo-physics. Significant advancement in photonic crystals, quantum optics, ultrafast optics as well as micro-nano-optics gives rise to new opportunities to manipulate the emission and propagation in optical fields, leading to a number of new and interesting discoveries, e.g., ultrashort light pulse storage and efficient energy conversion. This paper reviews the latest research progress in storage, release and energy conversion for ultrashort laser pulses in periodical arrays of absorbing medium. Techniques to fabricate such devices are also presented. [ABSTRACT FROM AUTHOR]

In this work, conical cavities with a fixed top diameter and varied bottom diameter have been utilized to improve the signal intensity, signal-to-noise ratio (SNR), and signal stability of laser-induced breakdown spectroscopy (LIBS). It is observed that the postponement of the maximum enhancement of spectral intensity and SNR occurs abnormally with decreasing the bottom diameter due to the energy dissipation from the plasma to the cavity walls. Optimization of the cavity size indicates that the conical cavity is superior to the widely-used cylindrical cavity in improving the performance of LIBS. It is also found that the emission enhancement in the conical cavity with larger bottom diameters is attributed to the increase in plasma temperature and electron number density, but the enhancement in the conical cavity with smaller bottom diameters is ascribed to the growth of electron number density. For the first time, the exact efficiencies of conical cavities suppressing the total number density fluctuation are acquired to evaluate the performance of improving signal stability through analysis of the signal uncertainty composition. [ABSTRACT FROM AUTHOR]