KEYWORDS: Reflection, Picosecond phenomena, Telecommunications, Spatial filtering, Numerical simulations, Signal processing, Matrices, Internet of things, Energy harvesting, Systems modeling
Simultaneous wireless information and power transfer (SWIPT) is an effective energy-saving technology, but its efficiency is hindered by environmental factors. The introduction of reconfigurable intelligent surfaces (RIS) has alleviated this issue, although it still faces significant constraints due to geographical limitations. This paper proposes a scheme that employs a simultaneously transmitting and reflecting (STAR)-RIS to assist SWIPT. It can overcome this limitation, achieve higher degrees of freedom (DoF), and provide better quality of service (QoS) for users on both sides of the ground. Meanwhile, we have considered a hybrid device based on a power splitting, which is capable of both energy harvesting and information decoding. We have proposed an efficient alternating optimization (AO) method to optimize the phase and amplitude vectors for reflection and transmission, beamforming and the optimal power splitting ratio, achieving an optimal balance between data rate and energy efficiency. Finally, simulation results demonstrate that the sum rate of the proposed model is superior to traditional RIS and other benchmark schemes.
Night is an inevitable scene for surveillance video. Due to the high image resolution, complex background, uneven illumination, and similarity between the target and the background of hawk-eye surveillance video, it is difficult for previous trackers to apply the tracking of a tiny object in such scenes. In this regard, this paper proposes to combine an online automatically and adaptively learning spatio-temporal regularized tracking algorithm with an efficient and effective low-light image enhancement algorithm to improve tracker performance. We constructed a new benchmark that includes 41 night surveillance sequences captured by Hawk-Eye cameras at night. Exhausted experiments have been conducted on this dataset, and the results show that by combining the two methods, the original algorithm can obtain better results in this dataset, and can meet the real-time object tracking, which contributes to the application of tiny object tracking in eagle-eye surveillance video at night.
Porous silicon has many advantages, such as biodegradability, biocompatibility, tunable pore size and active covalent and non-covalent surface chemical properties. One-dimensional porous silicon photonic crystal microcavity structure has the characteristics of porous silicon and optical microcavity, it is compatible with existing silicon micromachining technology and can be embedded into the sensitive chip so as to realize the function of micro-nano detection devices and integration. At present, there are many biosensors based on existing porous silicon microcavity, through controlling the pore size of porous silicon microcavities, the biological target molecules penetrate into the porous silicon microcavity structure, leading to increases of refractive index of porous silicon layers. In the practical test, we found that the penetration of biological molecules in the microcavity is not uniform, it is difficult to enter into the deeper porous silicon layers, according to this, the paper will explore the distributional characteristics of different biological molecules in the microcavity, and the variation of the sensing efficiency under the circumstance of nonuniform increase in refractive index. This study will be helpful to the accurate design and theoretical development of high efficiency porous silicon microcavity biosensor.
Various porous silicon-based photonic device structures has attracted more attention for use as biochemical optical
sensors. In this study, we have designed and characterized porous silicon-based two-dimensional photonic crystal
waveguide structure as an optical biosensor. Field intensity distribution of two-dimensional photonic crystal waveguide
was simulated using COMSOL Multiphysics. When the refractive index changes, the field strength changes greatly. This
study lays the theoretical foundation for further work.
An increased level of alpha-fetoprotein ( AFP) in the blood may be a sign of liver cancer. Porous silicon based optical
microcavities structure is prepared as a label-free immunosensor platform for detecting AFP. After the antigen-antibody
reaction, it is monitored that the red shift of the reflection spectrum of the immunosensor increases
Agriculture and animal husbandry area, such as Xinjiang, has high rates of hydatid disease. Protein P38 of Echinococcus granulosus has practical value in diagnosis of hydatid disease, and it may be used as a diagnostic marker and a prognostic index. In recent years, the development of biosensors based on porous silicon has been developed rapidly. In this experiment, the protein P38 detection based on fluorescence changes of porous silicon following protein P38 molecule adsorption. The results of the tests indicated that, with the increase of antigen concentration, the fluorescence decrease of porous silicon is also increasing. It is provided the foundation for the basic research of the molecular mechanism of P38, and diagnosis and treatment of cystic echinococcosis.
Aiming at the characteristics of remote sensing images with low-contrast, weak edge preservation, and poor resolution textual information, an image enhancement method that combines nonsubsampled shearlet transform (NSST) and guided filtering is presented. First, histogram equalization is applied to the remote sensing image. Second, the image is decomposed into a low frequency component and several high frequency components by NSST. Then, a linear stretch is adopted for the coefficients of the low-frequency component to improve the contrast of the original image; the threshold method is used to restrain the noise in the high-frequency components, then guided filtering is used for dealing with the high-frequency components, improving the detail information and edge-gradient retention ability. Finally, the final enhanced image is reconstructed by applying the inverse NSST to the processed low- and high-frequency components. The results show that the algorithm can significantly improve the visual impression of the image. Compared with the proposed algorithms in recent years, the average gradient and information entropy are significantly improved and the running time is shortened.
B ultrasound as a kind of ultrasonic imaging, which has become the indispensable diagnosis method in clinical medicine. However, the presence of speckle noise in ultrasound image greatly reduces the image quality and interferes with the accuracy of the diagnosis. Therefore, how to construct a method which can eliminate the speckle noise effectively, and at the same time keep the image details effectively is the research target of the current ultrasonic image de-noising. This paper is intended to remove the inherent speckle noise of B ultrasound image. The novel algorithm proposed is based on both wavelet transformation of B ultrasound images and data fusion of B ultrasound images, with a smaller mean squared error (MSE) and greater signal to noise ratio (SNR) compared with other algorithms. The results of this study can effectively remove speckle noise from B ultrasound images, and can well preserved the details and edge information which will produce better visual effects.
We have designed a novel evanescent field fiber optic biosensors with porous silicon dioxide cladding. The pore size of porous silicon dioxide cladding is about 100 nm in diameter. Biological molecules were immobilized to the porous silicon dioxide cladding used APTES and glutaraldehyde. Refractive index of cladding used Bruggemann's effective medium theory. We carried out simulations of changing in light intensity in optical fiber before and after chemical coupling of biomolecules. This novel optical fiber evanescent wave biosensor has a great potential in clinical chemistry for rapid and convenient determination of biological molecule.
Detection of protein kinases P38 of Echinococcus granulosus and its homologous antibody have great value for early diagnosis and treatment of hydatidosis hydatid disease. In this experiment, n-type mesoporous silicon microcavities have been successfully fabricated without KOH etching or oxidants treatment that reported in other literature. We observed the changes of the reflectivity spectrum before and after the antigen-antibody reaction by n-type mesoporous silicon microcavities. The binding of protein kinases P38 and its homologous antibody causes red shifts in the reflection spectrum of the sensor, and the red shift was proportional to the protein kinases P38 concentration with linear relationship.
Porous silicon material and device has attracted more attention for use as biochemical optical sensors. In this paper, A novel porous silicon-based multilayer dielectric-grating structures by adding high-reflectivity porous silicon stacks between the substrate and grating was fabricated, and the porous silicon grating height was set to be about 200 nm, the grating period was 4 μm, the air filling factor was 50%. A new better method of preparing this porous silicon-based multilayer dielectric-grating structures have also been employed.
We fabricated a one-dimensional nanoporous silicon photonic crystal on a silicon insulator substrate by a cost-effective electrochemical method as an optical biosensor for the detection of DNA hybridization. In the first step, a transfer matrix method was used to calculate the corresponding reflectivity spectrum for the design of nanoporous silicon photonic crystals. Then silicon-on-insulator-based photonic crystals were prepared by a novel simple electrochemical etching. Genes were hybridized inside the porous silicon (PS) pores by aminopropyltriethoxysilane and glutaraldehyde and detected through frequency resolved reflectance measurements. A detection sensitivity of 17.445 nm/μM is demonstrated with good specific detection. The linear response range covers a concentration range of antifreeze protein gene from 0.625 to 10.000 μM. This high responsivity indicates that the silicon-on-insulator-based PS photonic crystal has significant potential for application in biological micro-electro-mechanical-systems technologies.
Highly active and sensitive surface-enhanced Raman scattering (SERS) substrates were prepared by n -type (1 to 10 Ω⋅cm in resistivity) porous silicon (PS) substrates of Ag nanoparticles. SERS studies were carried on these substrates with R6G as a test molecule with a λ ex =785 nm laser. We optimized the fabrication procedure, which is easy and rapid, for nanostructured silver particles on the surface of PS. The maximum of SERS enhancement for R6G is observed for PS with an anodization current density of 6 mA/cm 2 and an etching time of 8 min. The detection limit for R6G absorbed on Ag-coated PS (Ag-PS) is 10 nM and SERS spectra show that the Ag-PS substrate has high SERS activity. The larger pore diameter of this new Ag-PS substrate is expected and the size of the pore diameter is about 1.2 μm, which permits better biomolecule infiltration. This new Ag-PS substrate can be applied in SERS in biochemical and biomedical fields.
We present a fast, novel method for building porous silicon-based silicon-on-insulator photonic crystals in which a periodic modulation of the refractive index is built by alternating different electrochemical etching currents. The morphology and reflectance spectra of the photonic crystals, prepared by the proposed method, are investigated. The scanning electron micrograph and atomic force microscopy images show a very uniform structure and the porous silicon demonstrates an 829 nm wide photonic band gap.
A prism coupled two-layer porous silicon waveguide beam splitter is presented. The component separates the input field
into two orthogonally polarized beams. The splitter has been designed through beam propagation analysis by employing
Finite-element method. Results obtained that the s and p polarization beams can be separated fully at a wavelength of
1.55μm.
This study is to investigate a new representation of a partition of an image domain into a number of regions using a level set method derived from a statistical framework. The proposed model is composed of evolving simple closed planar curves by a region-based force determined by maximizing the posterior image densities over all possible partitions of the image plane containing three terms: a Bayesian term based on the prior probability, a regularity term adopted to avoid the generation of excessively irregular and small segmented regions, and a term based on a region merging prior related to region area, which is applied to allow the number of regions to vary automatically during curve evolution and therefore can optimize the objective functional implicitly with respect to the number of regions. This formulation leads to a system of coupled curve evolution equations, which is easily amenable to a level set implementation, and an unambiguous segmentation because the evolving regions form a partition of the image domain at all times during curve evolution. Given these advantages, the proposed method can get good performance and experiments show promising segmentation results on both synthetic and real images.
This study is to investigate a new representation of a partition of an image domain into a fixed but arbitrary number of regions via active contours and level sets. The proposed algorithm is composed of simple closed evolving planar curves by an explicit correspondence to minimize the energy functional containing three terms: multiregion fitting energy, regularization related to the length of the curve, and the distance regularizing term to penalize the deviation of the level set function from a signed distance function. This formulation leads to a system of coupled curve evolution equations, which is easily amenable to a level set implementation, and an unambiguous segmentation because the evolving regions form a partition of the image domain at all times during curve evolution. In order to increase the robustness of the method to noise and to reduce the computational cost, a multiresolution level set schema is proposed, which can perform the evolution curves of the partitioned image at a different resolution. Given these advantages, the proposed method can get good performance and experiments show promising segmentation results on both synthetic and real images.
The purpose of this study is to propose a novel method of a partition of an image domain into an adaptive number of regions using a multilayer foreground-filled method. First, two coupled curves based on a three-region Chan-Vese model, which is built based on the techniques of evolving simple closed planar curves by an explicit correspondence to minimize energy functional containing a fitting term and a regularization term, evolve simultaneously to segment images containing two objects and one background region in each image layer. Second, a foreground-filled technique is used to generate a new image and the three-region Chan-Vese model is repeated to segment the new image for the next image layer. To avoid the long iteration process for level set evolution, an efficient termination criterion is presented on the basis on the length change of an evolving curve. This iterative process is repeated until the background image layer is detected. Numerical experiments on some synthetic and real images have demonstrated the efficiency and robustness of our method.
We report the measurements of the nonlinear refractive index of a metal/porous silicon composite system as measured by the reflection Z-scan technique. The composite system is formed by using magnetron sputtering to deposit thin metallic films onto porous silicon anodized on p-type silicon. The experiment results indicate an enhancement over the nonlinear refractive index of the composite system, which suggests an opportunity to form new-type nonlinear-optical media consisting of porous silicon for nonlinear optical applications such as power limiting or optical switching.
Porous silicon has attracted a great deal of attention and research for biochemical sensing applications. In this study, we
report a novel porous silicon based resonant grating filters as an optical sensor platform. A narrow bandwidth in the
reflectance spectrum is shown of this porous silicon grating filters and this resonance dip shift obviously after little
infiltration. This research also played a potential role for the extensive applications in all-silicon biosensor.
We have designed and characterized a novel fractal Cantor multilayer porous silicon photonic crystal with a defect
embedded in its middle as an optical sensor for sensing of various chemical and biological species. Compared with the
common periodic structure one (such as Bragg) and some aperiodic structure (such as Thue-morse), it is more sensitive
because of the lower number of interfaces. This research lays the foundation for design all-silicon sensor for biochemical
sensing and can also be good applied in excellent filter.
Third order nonlinear properties of new composite materials obtained by embedding A new type π-conjugated poly
[2,1,3-benzoselenadiazole-(2,5-didodecyloxy-1,4-phenylene)ethynylene](PPE)in porous silicon are measured in 532nm.
The picoseconds measurements show a significant increase of nonlinear refractive index not only with respect to the
standard optical materials. The reason can be explained as follows, the Π-electron conjugation bond would be expected
to have a significant effect on the ground and excited state dipole moments and electronic transition energies of the
molecule and, consequently, could affect the third-order nonlinear optical property of the molecule. The result shows that
it is a promising candidate for further material development and possible photonic device applications.
We report the experimental demonstration of a novel label-free optical immunosensor based on porous silicon
microcavity for the detection of Hydroxysafflor yellow A (HYSA). HYSA antibodies were immobilized into the porous
silicon using standard amino-silane and glutaraldehyde chemistry. We monitor the shift of the resonance dip in the
reflectance spectrum when HYSA-BSA is attached to the porous silicon microcavity. The label-free immunosensor is
simple and exhibit excellent sensitivity for HYSA antibodies with a sensitivity of 0.91nm/ng.
The procedure of light-path calls for WDM all-optical network was analyzed without wavelength converting in
optical nodes based on L-hop path in Wavelength Routing WDM Networks, and blocking performance model was
proposed. Receivers configured in optical node were introduced in the analytical model since this factor should be
considered in the procedure of resource reserved for optical network.
Then the final numerical result show that the receiver configuration in optical nodes can distinctly improve the
blocking performance for optical network when the number of wavelengths per link is augmented with offered light load,
when the receiver number is 3/4 of the number of wavelengths multiplexed per link, The blocking probability of
light-path calls reach the minimum. it is difficult to enhance blocking performance of light-path calls even though the
more optoelectronic receivers are added.
ZnS/CdS were deposited by chemical vapor deposition (CVD) technique on porous silicon substrates formed by electrochemical anodization of n-type (100) silicon wafer. The optical properties of ZnS/CdS porous silicon composite materials are studied. The results showed that new luminescence characteristics such as strong and stable visible-light emissions with different colors were observed from the ZnS/CdS-PS nanocomposite materials at room temperature.
Photoluminescence of Ar+ implanted porous silicon and porous structure of Ar+-implanted silicon (porous silicon by
preanodization ion implantation) at energy of middle-energy (30keV) are investigated to gain insight into the
photoluminescence properties and photoluminescence mechanism. The results show that the photoluminescence intensity
of Ar+ implanted porous silicon was reduced, which was attributed to the removal of surface oxygen and creation of
defects that act as nonradiative recombination; And whether samples were prepared by p-type or n-type silicon wafers,
the photoluminescence intensity of porous structure of Ar+-implanted silicon was enhanced that we attribute these to the
enhanced formation of porous silicon microstructure induced by ion implantation and oxygen-related defects were
increased.
We report on the design of porous silicon based polarization band-pass filters, which is not only have excellent optical properties with p-polarization transmittance and s-polarization reflectance in the NIR field, but also can be used for excellent biosensor and gas sensing applications.
Diffuse processes on the p-type single crystal silicon produced the p-n junction. Porous silicon was
prepared by using oxidation etching on the surface of the single crystal with p-n junction. A quantum-sized thin
film of TiO2 was deposited by reactive magnetron sputtering on the p-n junction. The results obtained by the
surface photovoltage spectroscope (SPS) showed that the photovoltage of TiO2/n-Si/p-Si and n-PS/p-PS/Si increase
than the photovoltage of n-Si/p-Si. In 300~600 °C, the photovoltage of TiO2/n-Si/p-Si was enhancing with the rise
of temperature, but the photovoltage of TiO2/n-Si/p-Si was reducing with the rise of temperature in 600~800 °C.
The effects of different ion-implantation in single crystal silicon and porous silicon on the photovoltaic
characteristics are studied, the photovoltage of argon implanted samples and nitrogen implanted samples was
increased a lot beyond the photovoltage of non-implanted samples.
It was found that the porosity of porous silicon has a maximum value under certain illumination intensity in our experiment. According to the experimental result, the grating was fabricated from porous silicon by controlling illumination intensity. As the refractive index of porous silicon decreases with an increase of the porosity, so the index distributing of porous silicon can be controlled by illumination intensity. A holographic process allows obtaining a mask of light on top layer during fabricating the multilayer porous silicon optical waveguides. The interference of two coherent Ar+ laser beams produces at the sample surface bright parallel lines. The porosity is modulated in the plane. The effective deep of modulation is directly related to the penetration of the illuminating beam. We have developed an experimental setup that allows guide light at 1064nm incidents vertically into the grating in porous silicon optical waveguides. The diffractive efficiency of the first order diffraction light in TE and TM polarization are measured in our experiment respectively.
Thin Sn films in the thickness range 0.3-2nm are deposited by
r.f.-sputtering on porous silicon (PS) anodized
on p-type silicon. Microstructural features of the samples before and after r.f.-tin-sputtered are investigated with scanning
electron microscopy (SEM). The photoluminescence (PL) studies showed that a broad luminescence peak of PS near the
621nm region gets a reduction in intensity, and a new peak at 441nm was produced at first and then disappeared. The
FTIR spectra on the PS/Sn structure revealed no major change of the native PS peaks.
Under the high energy irradiation, the charges (even little) of molecules of polymer can cause the physical and chemical
characteristics evident changes of polymer. The physics and chemical mechanisms which are responsible for radiation induced loss
was analyzed. The radiation damage of polymethylmethacrylate (PMMA), Polystyrene PS and polycarbonate (PC) optical fiber
under γ-ray irradiation was researched experimentally. The visible light transmission of the POF under different irradiation dose
was measured. The results indicated that the radiation damage of three kinds of POF was wavelength-dependent. Under lower dose
below 1KGy, the transmission rate decreased identical in the whole visible light range. When the irradiation dose exceeded 5KGy, the
transmission rate reduced obviously, and the recovery indicated that the visible light transmission rate of the POF in the range of
400nm to 500nm comparing with 600nm to 800nm, decreased seriously under the irradiation dose exceeded 5kGy. The transmission
rate of both PMMA and PC have an evident peak value at the range 550nm-650m, and that of PS has a wide band at the range
500-700nm. We also measured the recovery of three kinds of POF under different irradiation dose by measuring several times the POF
after stopping irradiating.
This paper presents an optimal design of the waveguide separation and the orientation angle of the slabs for the arrayed waveguide gratings (AWGs) with low-crosstalk and low-loss. To demonstrate the effectiveness of the proposed method, a 16×16 AWG using silica-based sol-gel material is designed as an example to meet our prescribed specifications. The performance of the designed AWG is perfectly verified by simulation usingbeam propagation method (BPM). And the methodology of determining the optimal waveguide separation and the orientation angle of the slabs is simple and useful to obtain a low-crosstalk and low-loss AWG.
The oxidised porous silicon layer with high porosity is obtained by anodization process followed by fully oxidation step. The planar optical waveguides is fabricated by penetrating polymer polymethylmetacrylate (PMMA-DR1) into the oxidised porous silicon film. The core layer of waveguide is formed by impregnating polymer into pores of oxidised porous silicon using method of immersion sample into PMMA-DR1/toluene solution under ultrasonic agitation in our experiment. The thickness of core of planar waveguides is controlled within 4μm by choice suitable immersion time. The waveguides consist of a higher index core oxidized oxidised porous silicon /PMMA-DR1 layer and a lower index buffer oxidised porous silicon layer separating the core from a high index silicon substrate. Optical parameters of waveguides are characterized by the dark mode spectroscopy method. Both refractive index and thickness of oxidised porous silicon /PMMA-DR1 film are obtained simultaneously and with good accuracy by measuring the coupling angles at the prism at a wavelength of 633 nm.
The criterions for determining the minimum number of arrayed waveguides are presented using the design theory of arrayed waveguide gratings (AWGs) and Fraunhofer diffraction principle for the optimal design of AWGs. In addition, some parameters such as the cross section of waveguides and the waveguide separation between adjacent waveguides are chosen to optimize the AWG structure to satisfy the performance specifications and to match the fabrication conditions in our laboratory. As an example to demonstrate the effectiveness of the proposed method, the simulated results of the designed 16 16 AWGs with silica-based sol-gel material were provided using the beam propagation method (BPM). And the effectiveness of optimal parameters, especially to the selection of the minimum number of arrayed waveguides on the performance of the AWG, has been perfectly verified by comparing the transmission spectra of the designed AWGs. The design methodology can serve as a simple and useful tool for the optimal design of AWG multiplexers/demultiplexers.
We fabricate the porous silicon/ PMMA/DR1 composite films by spin-coating methods in our work. The influence of the rotation speed of spin-coating and solution concentration on inserting of PMMA/DR1 in the porous silicon pores were studied. Micro-Raman spectrometry technique was used to examine the pores filling with PMMA/DR1. The linear and nonlinear refractive index of porous silicon and PMMA/DR1 composite films were studied by Optical reflectivity measurements and Z-scan technique respectively. The luminescence characteristics and stability emission of PMMA/DR1 impregnated samples were also studied in this paper.
The oxidised porous silicon buried channel waveguides were fabricated by selectively anodized with a PMMA film mask and controlling the electric current density intensities and anodisation time during anodisation process is reported in this paper. The propagaion loss of this oxidised porous silicon buried channel waveguides was measured to be 9.2dB/cm.
The oxidised porous silicon channel waveguides were fabricated by controlling the illumination intensities and anodisation time during anodisation process is reported in this paper. By the technique combined the optimisation end-fire coupling and cut-back methods, the relatively exact results of measured propagation loss, endface' s scattering loss and the mode mismatching loss of oxidised porous silicon channel waveguides were 12.5.2dB/cm, 4.6dB and 3.1dB respectively.
A simpler method for the fabrication of multilayer porous silicon optical waveguides is studied in this paper. It is based on the dependence of porosity on illumination intensity during anodisation process. The influence of illumination intensity on porosity during preparing porous silicon was studied. The experimental results show that the porosity of porous silicon has a maximum value under certain illumination intensity. Porous silicon channel waveguides were obtained by controlling the illumination intensities and the anodisation time in anodisation time in anodisation process.
We study the influence of photo-bleaching process on third order optical nonlinearities of PMMA/DR1 polymer at 1064 nm by Z-scan technique. The measured results show the coefficient of two-photon absorption decreases and the nonlinear refractive index has not obviously change after photo-induced ultraviolet bleaching.
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