Abstract
The ability of simultaneous polarization filter and wavefront shaping is very important for many applications, especially for polarization imaging. However, traditional methods rely on ...complex combinations of bulky optical components, which not only hinder the miniaturization and integration but also reduce the efficiency and imaging quality. Metasurfaces have shown extraordinary electromagnetic properties to manipulate the amplitude, polarization, and wavefront. Unfortunately, multi-layer metasurfaces with complex fabrication are often required to realize complex functions. Here, a platform of monolayer all-dielectric metasurfaces is proposed to simultaneously achieve polarization filtering and wavefront shaping, based on the principle of local polarization-selective constructive or destructive interference. The transmission efficiency surpassing 0.75 and polarization extinction ratio exceeding 11.6 dB are achieved by the proposed metasurface at the wavelength of 10.6 μm. These results are comparable to those of multi-layer metasurfaces. Considering these good performances, this work may prove new ideas for the generation of complex optical field and find wide applications in polarization imaging.
Imaging polarimetry is one of the most widely used analytical technologies for object detection and analysis. To date, most metasurface-based polarimetry techniques are severely limited by narrow ...operating bandwidths and inevitable crosstalk, leading to detrimental effects on imaging quality and measurement accuracy. Here, we propose a crosstalk-free broadband achromatic full Stokes imaging polarimeter consisting of polarization-sensitive dielectric metalenses, im-plemented by the principle of polarization-dependent phase optimization. Compared with the single-polarization optimiza-tion method, the average crosstalk has been reduced over three times under incident light with arbitrary polarization ran-ging from 9 μm to 12 μm, which guarantees the measurement of the polarization state more precisely. The experimental results indicate that the designed polarization-sensitive metalenses can effectively eliminate the chromatic aberration with polarization selectivity and negligible crosstalk. The measured average relative errors are 7.08％, 8.62％, 7.15％, and 7.59％ at 9.3, 9.6, 10.3, and 10.6 μm, respectively. Simultaneously, the broadband full polarization imaging capability of the device is also verified. This work is expected to have potential applications in wavefront detection, remote sensing, light-field imaging, and so forth.
Nano-silica particles were prepared using chlorosilane residual liquid as raw materials in an inverse microemulsion system formed by three different surfactants (TX-100, CTAB, SDS) with
n
-hexanol, ...cyclohexane, and ammonia. The phase behavior of inverse microemulsions and the preparation of nano-silica were investigated. The results showed that the system composed of non-ionic surfactant TX-100 had a larger inverse microemulsion region than other two system and was more suitable for the preparation of nano-silica. The prepared nano-silica had uniform sphericity and good dispersibility, the average particle diameter of 31 nm, and the variance of 1 nm. XRD, FT-IR, N
2
adsorption/desorption experiments and TG-DSC analysis were used to characterize the prepared nano-silica. The results showed that the prepared nano-silica was amorphous mesoporous silica with a BET specific surface area of 472.5 m
2
/g. They have a good thermal stability, and the phase structure and main chemical functional groups of nano-silica would not change after calcination at 600 °C, but the nano-silica would undergo a phase change at 1135 °C, which changed from amorphous to crystalline. The new technology not only broadened the source of preparation of nano-silica materials, but also provided new ideas for the treatment of chlorosilane residual liquid and the sustainable development of polysilicon industry.
Terahertz (THz) absorbers have attracted considerable attention due to their potential applications in high-resolution imaging systems, sensing, and imaging. However, the limited bandwidth of THz ...absorbers limits their further applications. Recently, the dispersion management of metasurfaces has become a simple strategy for the bandwidth extension of THz devices. In this paper, we used the capability of dispersion management to extend the bandwidth of THz absorbers. As a proof-of-concept, a dual metasurface-based reflective device was proposed for broadband near-unity THz absorber, which was composed of two polarization-independent metasurfaces separated from a metallic ground by dielectric layers with different thickness. Benefiting from the fully released dispersion management ability in adjusting the dimensions of the metasurfaces, we obtained an absorbance above 90% in the frequency range from 0.52 to 4.4 THz and the total thickness for the bandwidth approaching the theoretical Rozanov limit. The experimental results verified the ability of dispersion management in designing broadband absorbers and the performance of the designed absorber. The underlying physical mechanism of dispersion management was interpreted in the general equivalent circuit theory and transmission line model. In addition, the catenary optical model was used to further interpret the physics behind this dual metasurface. Moreover, we found that the alignment deviations between the dual metasurface had little impact on the performance of the designed absorber, which indicates that the dual-metasurface does not require center alignment and is easy to be fabricated. The results of this work could broaden the application areas of THz absorbers.
In this paper, nano-silica particles were prepared from chlorosilane residue liquid using an inverse micro-emulsions system formed from octylphenyl polyoxyethylene ether ...(TX-100)/n-hexanol/cyclohexane/ammonia. The influence of different reaction conditions on the morphology, particle size, and dispersion of nano-silica particles was investigated via single-factor analysis. When the concentration of chlorosilane residue liquid (0.08 mol/L), hydrophile-lipophilic-balance (HLB) values (10.50), and the concentration of ammonia (0.58 mol/L) were under suitable conditions, the nano-silica particles had a more uniform morphology, smaller particle size, and better dispersion, while the size of the nano-silica particles gradually increased with the increase in the molar ratio of water to surfactant (ω). The prepared nano-silica was characterized through XRD, FT-IR, N2 adsorption/desorption experiments, and TG-DSC analysis. The results showed that the prepared nano-silica was amorphous mesoporous silica, and that the BET specific surface area was 850.5 m2/g. It also had good thermal stability. When the temperature exceeded 1140 °C, the nano-silica underwent a phase transition from an amorphous form to crystalline. This method not only promoted the sustainable development of the polysilicon industry, it also provided new ideas for the protection of the ecological environment, the preparation of environmental functional materials, and the recycling of resources and energy.
In situ TEM mechanical stages based on micro-electromechanical systems (MEMS) have developed rapidly over recent decades. However, image-based quantification of MEMS mechanical stages suffers from ...the trade-off between spatial and temporal resolutions. Here, by taking in situ TEM nanoindentation as an example, we developed a novel method for image-based quantified in situ TEM mechanical tests with both high spatial and temporal resolutions. A reference beam was introduced to the close vicinity of the indenter–sample region. By arranging the indenter, the sample, and the reference beam in a micron-sized area, the indentation depth and load can be directly and dynamically acquired from the relative motion of markers on the three components, while observing the indentation process at a relatively high magnification. No alteration of viewing area is involved throughout the process. Therefore, no deformation events will be missed, and the collection rate of quantification data can be raised significantly.
With the continuous depletion of fossil resources and the deterioration of the global climate, it is particularly urgent to find green and sustainable renewable resources to replace non-renewable ...resources. Renewable biomass, which converts and stores light energy into chemical energy through photosynthesis by green plants, has received widespread attention due to its simultaneous resource and energy properties. Therefore, this article focuses on lignocellulose, an important component of biomass, in the fields of chemical conversion and high-value-added chemical preparation. A detailed review was conducted on the application of catalysts in biomass bio-char, bio-oil, bio-gas, and high-value added chemicals and their derivatives, represented by 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA). At the same time, the difficulties and challenges encountered by catalysts in biomass conversion were analyzed, and new ideas were proposed for future development directions, so as to provide new development pathways for efficient and green conversion of biomass into biomass energy and high-value-added chemicals.
Optical metasurfaces empower complete wavefront manipulation of electromagnetic waves and have been found in extensive applications, whereas most of them work in either transmission or reflection ...space. Here, we demonstrate that two independent and arbitrary phase profiles in transmission and reflection spaces could be produced by a monolayer all-dielectric metasurface based on the asymmetric photonic spin-orbit interactions, realizing full-space wavefront independent manipulation. Furthermore, the supercell-based non-local approach is employed to suppress crosstalk between adjacent nanopillars in one supercell for broadband and high-efficiency wavefront manipulation in full space. Compared with the conventional unit cell-based local approach, such a method could improve efficiency about 10%. As a proof of concept, two metadevices are designed, in which the maximum diffraction efficiencies are ∼95.53%/∼74.07% within the wavelength range of 1500-1600 nm in reflection/transmission space under circularly polarized light incidence. This configuration may offer an efficient way for 2π-space holographic imaging, augmented reality, virtual reality technologies, three-dimensional imaging, and so forth.
Metasurfaces can flexibly manipulate electromagnetic waves by engineering subwavelength structures, which have attracted enormous attention in holography, cloaking, and functional multiplexing. For ...structures with n-fold (n > 2) rotational symmetry, they have been utilized to realize broadband and high-efficiency wavefront manipulation with generalized Pancharatnam–Berry phase, whereas spin-selective wavefront manipulation is still a challenge limited by their symmetrical spin–orbit interactions. Here, we demonstrate the spin-selective wavefront manipulations with generalized Pancharatnam–Berry phase in the range of 560–660 nm with a metal–insulator–metal metasurface consisting of the chiral C3 logarithmic spiral nanostructures. As a proof of concept, two deflectors and a bifocal metalens are designed. This configuration may provide a platform for various applications in polarimetry, polarization-selective images, and nonlinear optical responses.
We propose a novel process for the preparation of silica and concentrated hydrochloric acid using chlorosilane residual liquid originating from the polysilicon production process. The process was ...designed and optimized after conducting pilot plant tests. The effects of circulating acid concentration, flow rate, chlorosilane residual liquid treatment load and other factors on silica products were studied. The results showed that the circulating acid flowrate can effectively control the formation of gel, and the amount of chlorosilane residual liquid has significant influence on the hydrolysis efficiency and operation of the hydrolysis tower. The prepared silica was characterized using XRD, XRF, FT-IR, SEM, DLS, TG-MS and N
2
adsorption/desorption experiments. The results indicated that silica consisted of amorphous particles, which were spherical, had surface hydroxyl, and showed heterogeneous distribution. The average particle size was 50-80 μm and had high specific surface area (565.049 m
2
g
−1
), large pore volume (0.449 cm
3
g
−1
), and a narrow pore size distribution (3.419 nm). The new technology provides a simple, efficient and environmentally friendly way for treating chlorosilane residual liquid, as well as a cost-effective method for the preparation of silica.
PDF
