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The Er3+/Yb3+ co-doped Y2Ti2O7 nanocrystals were synthesized by the sol-gel method. X-ray diffraction, transmission electronic microscopy, and photoluminescence spectra were measured to verify the Y2Ti2O7 nanocrystalline produced in the sample annealed at 800 °C. The anomalous slopes of the fitted line in the log-log plots for upconversion emissions and the pump-saturation effect of near-infrared emission were observed in the nanocrystalline samples. A theoretical model of practical Er3+/Yb3+ co-doped system based on the rate equations were put forward and explained the experimental phenomena well. [ABSTRACT FROM AUTHOR]

When two coherent green beams offset from each other by a small angle are coupled in bacteriorhodopsin film, the diffraction intensity rises from zero to a maximum, and then decreases along with the writing time. Based on the change of the diffraction intensity with the writing time, we proposed and demonstrated a time-dependent all-optical exclusive not or (XNOR) operation and a time-dependent all-optical logical inverter (NOT) operation. Based on the relation between the self-diffraction intensity and the polarization states of the input beams, the time-dependent all-optical XNOR logic gate was achieved, and based on the relation between the polarization states of the diffraction beams and that of the recording beams, the time-dependent all-optical NOT logic gate was obtained. [ABSTRACT FROM AUTHOR]

The refractive index of blood is a key biophysical parameter, which can reflect the physiological state. We measured the refractive index of whole blood and other components, such as serum, plasma, and hemoglobin, based on internal reflection by using a homemade apparatus in the spectral range of 400 to 750 nm. In addition to the hemoglobin solution, which has a Soret band about 420 nm and two Q-bands between 500 and 600 nm, the measurements of other samples are the normal dispersion curve. The results are approximated by the Cauchy equation and Sellmeier equation, and the correlation coefficients are more than 0.997. [ABSTRACT FROM AUTHOR]

We propose a phase imaging method that combines the Fourier ptychography and compressive sensing theories using single-pixel detection in the spatial spectrum plane. Specifically, the spatial Fourier spectrum is shifted based on the Fourier ptychography theory, and the compressive sensing theory is applied to reduce the amount of acquired data. Further, an algorithm has been developed to reconstruct the phase images and an asymmetric mask introduced to eliminate ghost interference. The feasibility of the proposed method was verified through simulation and evaluated in terms of the compressive sensing theory realized. The results show that a two-dimensional image can be restored at a low sampling rate of 5% using the proposed method. [ABSTRACT FROM AUTHOR]

Aim: This study aimed to investigate the key transcription factors (TFs), long noncoding RNAs (lncRNAs), and microRNAs (miRNAs) associated with hepatocellular carcinoma (HCC).Materials and Methods: The datasets GSE31383 and GSE54238 were downloaded from Gene Expression Omnibus data repository. GSE31383 was used to screen differentially expressed miRNAs, and GSE54238 was used to screen differentially expressed messenger RNAs (mRNAs) and lncRNAs. ChipBase was used to identify TF-miRNA pairs. StarBase was selected to identify miRNA-mRNA and lncRNA-miRNA interactions. Kyoto Encyclopedia of Genes and Genomes pathway analysis was also conducted using Database for Annotation, Visualization, and Integrated Discovery tool.Results: A total of 2065 mRNAs, 1050 lncRNAs, and 26 miRNAs were identified to be divergently expressed in HCC compared with normal tissues. There were 338 miRNA-mRNA and 65 lncRNA-miRNA pairs with reverse expression trend. Besides 249 TF-miRNA relationships including differentially expressed miRNA were isolated. Among them, 11 TF-miRNA had the same expression trend. Furthermore, lncRNA-miRNA-mRNA and TF-miRNA-mRNA regulatory networks were constructed. hsa-miR-497, hsa-miR-195, and hsa-miR-424 were identified as hub nodes in these two networks. Hub TFs, such as TATA box binding protein-associated factor 1 (TAF1) and hepatocyte nuclear factor 4, alpha (HNF4α), and lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) were also screened out in the network.Conclusions: Our findings highlight the regulatory networks among TFs, lncRNAs, miRNAs, and mRNAs in HCC. Several key molecules, such as hsa-miR-195, lncRNA MALAT1 and TFs TAF1 and HNF4α, may contribute to the progression of HCC. [ABSTRACT FROM AUTHOR]

We report the design, characterization, and experimental demonstration of a broadband nearperfect absorber in the visible regime based on strong interference in ultrathin molybdenum disulfide films obtained by the spin-coating method. The absorber is polarization-insensitive, and the absorption peak maintains a high value for large angles of incidence, which provides more efficient absorption for nonpolarized or oblique incident beams. The experimental results show that the absorption can reach more than 87% between 400 nm and 640 nm, which is in reasonable agreement with the simulated results. This work may offer a further step in the development of solar absorption-based nano-optoelectronic devices. [ABSTRACT FROM AUTHOR]

Manipulating electromagnetic waves with artificial nanostructures has garnered great interest for their properties and potential applications. However, existing devices performing various desired operations at different wavelengths usually require cascading with different geometry patterns, which does not offer satisfactory simplicity. Here, we theoretically and experimentally demonstrate that an ultrathin, multifunctional metasurface, consisting of an array of nanorods, can perform various functions at different wavelengths. Simulated and experimental results indicate that nearly perfect absorption, linear-to-circular conversion, and linear cross-polarization conversion can be integrated into one multifunctional metasurface. Furthermore, the multifunctional metasurface can maintain very high performance across a large range of incident angles. The proposed configuration is extremely compact and easy to fabricate; these qualities should support the development of practical applications. [ABSTRACT FROM AUTHOR]

We investigated the effect of thiazone, a widely used penetration enhancer, on in vitro porcine skin and muscle tissue by single-integrating sphere technique during optical clearing (OC) treatment. The results showed that thiazone induced an increase on the total transmittance of skin which led to a reduction in that of muscle in the spectral range from 400 to 800 nm. Small particles crystalized out from the thiazone-treated muscle were observed by microscopy imaging. With the help of x-ray diffraction measurement, we ascertained that the crystal was a single-crystal of thiazone, which mainly induced an increase of the scattering. Contrast transmittance measurements carried on the mixture of water, thizaone–propylene glycol solution showed that the free water in muscle could be the main reason for the thiazone crystallization. Therefore, during OC treatment of thiazone, the remarkable effect on skin and the noticeable inhibition effect on subcutaneous muscle tissue after penetrating into the skin should be considered. The experimental results provide such a reference for the choice of penetration enhancer. [ABSTRACT FROM AUTHOR]

We propose a simple and cost-effect method, current-stimulus dielectric breakdown, to manipulate the 3D shapes of the nanochannels in 20-nm-thick SiNx membranes. Besides the precise control of nanopore size, the cone orientation can be determined by the pulse polarity. The cone angle of nanopores can be systematically tuned by simply changing the stimulus pulse waveform, allowing the gradual shape control from conical to obconical. After they are formed, the cone angle of these nanopores can be further tuned in a certain range by adjusting the widening pulse. Such size and 3D shape controllable abiotic nanopores can construct a constriction in the nanochannel and hence produce a sub-nm "sensing zone" to suit any desired bio-sensing or precise DNA sequencing. Using these conical nanopores, 20-nt ssDNA composed of homopolymers (poly(dA)20, poly(dC)20, and poly(dT)20) can be clearly differentiated by their ionic current signals. [ABSTRACT FROM AUTHOR]

In this paper we calculate the radiation forces and moving trajectories of Mie particles induced by 1D Airy beams using the plane wave spectrum method and arbitrary beam theory. Numerical results show that both the transverse and the longitudinal radiation forces are deeply dependent on the relative refractive index, radii and positions of the scattering particles illuminated by the Airy beam. Due to the radiation forces, Mie particles with different radii and initial positions can be dragged into the nearest main intensity lobes, and move along parabolic trajectories in the direction of the Poynting vector. At the ends of these trajectories, in the presence of Brownian force, the trapped scattering particles show irregular Brownian movement near their equilibrium positions. This characteristic property of Airy beams enables optical sorting to be used more easily in the colloidal and biological sciences. [ABSTRACT FROM AUTHOR]

The complex refractive index dispersion (CRID), which contains the information on the refractive index dispersion and extinction coefficient spectra, is an important optical parameter of biotissue. However, it is hard to perform the CRID measurement on biotissues due to their high scattering property. Continuous CRID measurement based on internal reflection (CCRIDM-IR) is introduced. By using a lab-made apparatus, internal reflectance spectra of biotissue samples at multiple incident angles were detected, from which the continuous CRIDs were calculated based on the Fresnel formula. Results showed that in 400- to 750-nm range, hemoglobin solution has complicated dispersion and extinction coefficient spectra, while other biotissues have normal dispersion properties, and their extinction coefficients do not vary much with different wavelengths. The normal dispersion can be accurately described by several coefficients of dispersion equations (Cauchy equation, Cornu equation, and Conrady equation). To our knowledge, this is the first time that the continuous CRID of scattering biotissue over a continuous spectral region is measured, and we hereby have proven that CCRIDM-IR is a good method for continuous CRID research of biotissue. [ABSTRACT FROM AUTHOR]

Traditionally, continuous refractive index dispersion (CRID) measurement of materials with scattering is hard to realize. In this paper, CRID measurement based on the derivative total reflection method (CRIDM-DTRM) is proposed to measure the CRID of both absorption and scattering materials. It effectively determined the CRID of K9 glass, concentrated milk, and 0.5% methyl red solution in the 400-750 nm range with the spectral resolution of about 0.259 nm. For the first time, CRID of a scattering material is measured. CRIDM-DTRM is a useful technique in the field of RID measurement, especially for biotissues and anomalous dispersion materials. [ABSTRACT FROM AUTHOR]

The refractive-index profile (RIP) of optical fibers is of fundamental significance in determining critical fiber properties. Here, we present the application of a two-dimensional (2-D) scanning focused refractive-index microscopy (SFRIM) to accurately obtain the 2-D RIP of a graded-index optical fiber. Some modifications are made to SFRIM for better 2-D measurement. Quantitative RIP of the fiber is obtained with derivative total reflection method. The refractive-index accuracy is 0.002. The measured result is in good agreement with theoretical expectation. This method is straightforward, simple, repeatable, and free from signal distortion. This technique is suitable for symmetric and asymmetric optical fibers. The results indicate that this technique can be applied to obtain the RIPs of a wide range of materials and has broad application prospect in many fields. [ABSTRACT FROM AUTHOR]

We present the underlying theory, the design specifications, and the experimental demonstration of the broadband diodelike asymmetric transmission of linearly polarized light in the near-infrared regime. This result is achieved through the use of a two-layer hybrid metamaterial, composed of an L-shaped metallic particle and a double nano antenna. The experimental results are shown to agree well with the theoretical predictions and the simulated transmission spectra. The realization of the diodelike asymmetric transmission can be attributed to the combination of two independently functioning metallic structures, which are shown to perform their respective function even when shifted away from perfect alignment. This work offers a further step in developing broadband diodelike asymmetric transmission for use in electromagnetic devices. [ABSTRACT FROM AUTHOR]

We report the dynamic refractive index (RI) change of tissue under a stepped compression load using a custom-built pressure apparatus. Angle-dependent reflectance profiles of biotissue samples are recorded, and the RI values are resolved using the derivative total reflection method. These results are relevant for understanding the mechanism of mechanical optical clearing, for investigating tissue dynamics under mechanical stimuli, and for other biomedical applications. [ABSTRACT FROM AUTHOR]

Light distribution in the biological tissue phantom intralipid suspension with different interface roughness was measured for quantitative understanding of surface roughness effect. The results show that the surface roughness strongly affects light distribution inside the approximately semi-infinite biological tissue phantom. The phantom surface possesses a certain degree roughness and the effect of the surface roughness on measurement results of light distribution in tissue is substantial, so the measurement of light distribution in biological tissue needs to take surface roughness into account. [ABSTRACT FROM AUTHOR]

Azo dye ethyl red (ER) doped methyl methacrylate polymer (PMMA) films were prepared by the sol-gel process and the spin coating method. The samples were 3% ER by weight and 33 μm thick. The absorption spectra of the samples, illuminated by He-Cd laser (441.6 nm, CW) and YAG laser (532 nm, CW) were measured and the change of nonlinear refractive index distribution curve of the ER-doped PMMA thin film induced by 532 nm laser was simulated using the Kramers-Kronig relation. Additionally, the transmission intensity mutual modulations of the two beams were studied. Our results suggest that ethyl red (ER) has potential applications in all-optical devices. [ABSTRACT FROM AUTHOR]

In this work, a model for analyzing the gain characteristics of heavily Er3+/Yb3+ co-doped compact fiber amplifier is presented. Four-level rate equations and finite-difference beam propagation method are applied to simulate the optical field evolution along the active fiber. Based on this model, the influences of ion concentration, fiber length and pump power on the gain characteristics of Er3+/Yb3+ co-doped phosphate glass fiber amplifiers are theoretically investigated. Numerical results show that for a fiber length of 3.6 cm the internal gain can reach 27.2 dB with NEr = 2.6 × 1026 ions/m3 and NYb = 1.2 × 1027 ions/m3 when pumped with 224 mW at 980 nm. The gain per centimeter is 7.56 dB/cm. The results can provide useful information to optimize the gain performance of these compact fiber amplifiers. [ABSTRACT FROM AUTHOR]

The reduced scattering and absorption coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region respectively were determined by a spatially resolved steady-state diffuse reflection technique. The anisotropy factors of the nylon film with different surface roughness for the smooth and rough surface of the incident region, respectively, were determined by a goniophotometric measurement technique. The scattering coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region, respectively, were determined for the determination of the reduced scattering and the corresponding anisotropy coefficients of the nylon bar with different surface roughness for the smooth and rough surface of the incident region, respectively. Comparing the determined optical parameters of the nylon bar with different surface roughness for the smooth surface of the incident region with that for the rough surface of the incident region, the results indicate surface roughness can significantly affect the determination of the tissue optical parameters and the effect of the surface roughness of the incident region on the determination of tissue optical parameters is predominant. [ABSTRACT FROM AUTHOR]

A theoretical model of longitudinally laser diode (LD) pumped erbirum—ytterbium-codoped phosphate glass microchip laser that includes the influence of cooperative upconversion and cumulative upconversion effects has been developed. The analytic solution with an approximation of top-hat pump and laser profile is derived to show the influence of the both upconversions on the threshold and slope efficiency. When the Guassian profiles of both pump and oscillating lasers are considered, rigorous numerical calculations have been made to study the influence of cooperative upconversion and cumulative upconversion effects. The results of calculations are in good agreement with our experimental data. The influence of the round-trip dissipative optical loss, the waist of pump beam and the transmission on laser optimization is also discussed when considering the upconversion effects. [ABSTRACT FROM AUTHOR]

When the parameters of a bacteriorhodopsin (bR) film are fixed, the quality of the output image of an optical novelty filter depends on the velocity and the size of the image of the object on the bR film. The contrast of the output image changes with the velocity and the size. When the velocity is small, it tends to saturation. The detectable minimum velocity increases with increasing size of the input image and increasing lifetime of the M state and it tends to a fixed value when the lifetime of the M state is longer than 25  s. We discuss the relation between the velocity and the gradient I g and the contrast I c . The optimizing ranges of the velocity are given for different sizes. We also discuss the relation between the size and the gradient I g and contrast I c . We make a suggestion about which kind of bR film is suitable for use in the novelty filter. [ABSTRACT FROM AUTHOR]

Formulas for light propagation in biotissue with cylindrical boundaries are deduced. A model simulating light propagation in one-layered biotissue with a cylindrical boundary is established. Simulation results of the density distribution of absorbed photons are shown when a circularly flat beam is incident on the biotissue. The model can easily be extended to multilayered tissues with cylindrical boundary. [ABSTRACT FROM AUTHOR]

The absorption spectra of trans and cis isomers of mercury dithizonate in a doped poly(methyl methacrylate) film are measured, and the optical properties of the two isomers are analysed. The properties indicate that different isomers of mercury dithizonate can convert into each other when irradiated by light of appropriate wavelength. With the Z -scan method, the nonlinear optical properties of mercury dithizonate are investigated, and experimental data on the nonlinear refractive index and the change in refractive index are obtained. The changes in refractive index as a function of wavelength are obtained by the Kramers-Kronig transformation. [ABSTRACT FROM AUTHOR]

The total time-resolved diffusion reflectance from a semi-infinite turbid media was investigated, which based on the diffusion approximation with zero boundary conduction ZBC and extrapolated-boundary conduction EBC, and the total time resolved reflectance from the diffusion theory were compared with that of Monte Carlo simulations. The corresponding diffusion equations were fitted to Monte Carlo simulations data to determine optical parameters. The effects of different boundary conditions on the accuracy of the deducing optical parameters were analyzed. It is shown that the errors in the reduced scattering coefficients derived with ZBE is much larger than that with EBC, while the absorption coefficients can be always extracted from given data with high accuracy whether with ZBC or EBC. [ABSTRACT FROM AUTHOR]

Non-homogenous material such as solid composite materials examination using refractive index-sensing remains a challenge for researchers. A derivative total reflection method for simultaneous measurement of the refractive indices of various components of a non-homogeneous solid was developed. Only a measurement of the reflectance from the surface of composite sample is necessary. In our experiments, simulation samples, porcine tissue, and Rosso Levanto marble samples were measured to verify proposed method. [ABSTRACT FROM AUTHOR]

Scatterings and transport in Weyl semimetals have caught growing attention in condensed matter physics, with observables including chiral zero modes and the associated magnetoresistance and chiral magnetic effects. Measurement of electrical conductance is usually performed in these studies, which, however, cannot resolve the momentum of electrons, preventing direct observation of the phase singularities in scattering matrix associated with Weyl point. Here we experimentally demonstrate a helical phase distribution in the angle (momentum) resolved scattering matrix of electromagnetic waves in a photonic Weyl metamaterial. It further leads to spiraling Fermi arcs in an air gap sandwiched between a Weyl metamaterial and a metal plate. Benefiting from the alignment-free feature of angular vortical reflection, our findings establish a new platform in manipulating optical angular momenta with photonic Weyl systems. [ABSTRACT FROM AUTHOR]

We present an improved Kretschmann configuration with nonlinear dielectric as substrate, in which long-range surface plasmon polaritons (SPPs) may appear, the modes and propagation lengths are tunable. We numerically simulated the solutions of SPP modes and their propagations. The results show that the SPP propagation length can range from tens of micrometers to tens of centimeters or even longer. The configuration proposed in this letter makes a breakthrough of the intrinsic restriction in conventional Kretschmann configuration and there exist the continuous steady SPP modes also in the range of k0[variant_greek_epsilon]31/2>β>k0[variant_greek_epsilon]11/2. It allows for optimization of SPP properties and makes SPP application more flexible in practices. [ABSTRACT FROM AUTHOR]

Compact high power broadband superfluorescent fiber source has been demonstrated using an ultrashort Er3+-Yb3+-codoped phosphate glass fiber. The fiber is 10.4-cm-long and at 1.68 W pump power, an output power of 16.85 mW, a mean wavelength of 1540.9 nm, a bandwidth of 18.4 nm, and a slope efficiency of 18.6% have been obtained. The dependence of output power, mean wavelength, and bandwidth stability on pump power and fiber length are also studied, and there is an excellent agreement between the theoretical results and experimental data. [ABSTRACT FROM AUTHOR]

We present the design and analysis of a polarization-insensitive and wide-angle broadband nearly perfect absorber by planar metamaterial in the visible regime. The bandwidth of absorption spectrum can be effectively expanded by combining multiple resonant elements. The forming mechanisms of the broadband metamaterial perfect absorber (MPA) are also demonstrated by the hybridization of the plasmonic system. The resonance of the broadband MPA can be dynamically tuned by varying the intensity of the incident beam. This kind of all-optically tunable perfect absorber will help to overcome some of the limitations of customary designs developed so far. [ABSTRACT FROM AUTHOR]