查看更多>>摘要：Biologists have long been interested in the submicroscopic structures of cells and interactions between organelles. However, due to resolution limitations, investigating cell biology using fluorescence microscopy remains a challenge. In recent decades, super-resolution microscopy has been developed as an essential solution. Recently, a new microscopic technique called expansion microscopy has been developed, which circumvents this resolution limit by increasing the size of the biological sample, thus allowing for super resolution of the enlarged structure. In this study, we combined expansion microscopy with fluorescence emission difference microscopy (ExFED) and achieved a spatial resolution of approximately 40 nm in mammalian cells. Delicate subcellular and sub-organelle structures were investigated, and potential contacts were detected. The results indicated that ExFED is a simple and powerful super-resolution method for studying biological specimens.
查看更多>>摘要：We simulate space-time (ST) light sheet generation by combining multiple frequency comb lines, each carrying multiple Laguerre-Gaussian modes. Due to the correlation relationship between the spatial and temporal domain, the resulting ST light sheet has (a) a controllable group velocity and (b) reduced diffraction. We investigate the deviation of the group velocity from the designed value while varying the propagation distance and number of modes. The simulation results show that (i) the range of the propagation distance that the group velocity v(g) remains near the target value tends to decrease when v(g) deviates from the speed of light, (ii) when the maximum mode number increases, the simulated group velocity tends to be closer to the target value. In addition, we also characterize the reduced diffraction by the ratio of propagation distance over which the axial intensity is reduced by half (D-0.5I) with and without the spatial and temporal spectral correlation. Our results show that the ratio of the D-0.5I tends to (i) increase when the number of frequency lines increases, (ii) increase when the number of modes increases, and (iii) decrease when the target group velocity v(g) approaches the speed of light.
Dat, Le TriLuong, Sang H.Pham, Vinh N. T.Vy, Nguyen Duy...
6页
查看更多>>摘要：Controlling of graphene layer by optical force is an emerging topic in recent electronic and bio-inspired technologies. In this work, we theoretically investigated the radiation pressure (RP) force exerting on a graphene layer inserted inside an optical microcavity using the Maxwell's stress tensor. In the resonant cavity where the cavity length matches the optical half-wavelength (lambda/2) the stored field could be greatly enhanced and a strong RP force is observed. This RP force could be effectively tuned by changing the optical wavelength, the thickness of the cavity mirrors, and the position of the graphene in the cavity. Moreover, the graphene also alters field distribution inside the OMC and the RP on the cavity mirrors. The optical rigidity results from the change of RP with the graphene displacement has been shown to strongly dependent on the system parameters and reaches a value of ~ 30 pN/lambda. These results could open a way to control the spatial and temporal behavior of a graphene layer inserted inside the cavity toward the graphene optomechanics.
查看更多>>摘要：A novel optical fiber surface plasmon resonance (SPR) sensor based on the copper-coated hollow fiber structure was proposed. The simple chemical liquid phase deposition method was developed to coat the thin copper film on the inner surface of the hollow fiber to fabricate the proposed sensor. The performance of the hollow fiber SPR sensors with different copper film thickness were investigated experimentally by measuring the transmission spectra of the sensors filled by sensed liquid media with different refractive indices. Theoretical analysis based on the ray transmission model was also carried out for comparison. The experimental and theoretical results agree well with each other. The factors which affect the sensor performance are discussed. The sensor achieves a maximum sensitivity of 7111 nm/RIU, which is relatively high in the copper film based optical fiber SPR sensors and comparable to the silver-coated hollow fiber sensors. Moreover, the fabrication process of the proposed sensor is much simpler than other copper based optical fiber SPR sensors, which make it more practical. The copper film deposition method presented in this paper is also applicable to the fabrication of some microstructured optical fiber or photonic crystal fiber based sensors with copper film.
查看更多>>摘要：The extended nonlinear Schrodinger equation which can be used to describe the propagation of the femtosecond soliton pulse has been investigated. A type of quartic and dipole soliton solutions is constructed based on the extended nonlinear Schrodinger equation with varying third-order and fourth-order dispersions, self-steepening and Raman effects. Parameter modulation of self-similar dipole soliton in some non-uniform management systems is also discussed in detail. The results show that with different forms of four-order dispersion and nonlinear coefficients, it exhibits different propagation dynamics. Modulation of the certain parameters, the amplitude and the trajectory of self-similar dipole soliton can be manipulated.
查看更多>>摘要：We show the active role that the transition metal dichalcogenide MoS2 plays in enhancing the sensing performance of optical fiber sensors based on surface plasmon resonance (SPR). This is proved experimentally suggesting that the optical fiber SPR sensor with the MoS2 has an about 24 percent increase in the bulk refractive index sensitivity compared to the one without the MoS2. Also, we investigate the surface sensing performance of the sensor using self-assembly monolayers of polyelectrolytes with well-defined thickness and refractive index.
查看更多>>摘要：In order to enhance the OAM mode purity and quality, we propose a graded-index ring-core photonic crystal fiber (GRC-PCF) and its general design strategy by the finite element method (FEM). In addition, the numerical results turn out that the GRC-PCF is better than conventional step-index ring-core-photonic crystal fiber (SRCPCF) in terms of mode purity and mode quality, when the two fibers support the same numbers of OAM modes at 1.55 mu m, respectively. After optimizing structural parameters, a GRC-PCF that can support 14 OAM modes without phase distortion and high-radial modes in C+L bands is designed. Particularly, the mode purity and mode quality of all the OAM modes are higher than 97.05% and 98.42%, respectively. The confinement losses are maintained at the order of 10(-11) and flat dispersion. The proposed fiber can be used in the MDM system and realize the stable transmission of the OAM modes.
查看更多>>摘要：Yb-Er co-doped CaF2 crystals with different Yb3+ ions concentrations are successfully grown by the temperature gradient technique (TGT) method. Up-conversion (UC) luminescence characteristics and optical temperature sensing behavior of all samples are thoroughly investigated in this work. Under the excitation of a 980 nm laser-diode, the up-conversion luminescence intensity firstly increases and then decreases. By adjusting the content of Yb3+ ions, multi-color visible light emissions of red, yellow and green could be easily obtained. The fluorescence intensity ratio from two thermally coupled 2H11/2 and 4S3/2 levels technology is used to evaluate the temperature sensing performance of Yb-Er co-doped CaF2 crystals. The concentration of Yb3+ ions shows a significant influence on the temperature sensing performance. The sensitivity reaches the maximum value of 2.24 x 10-3 K-1 at 548 K with a 5 at.% doping concentration of Yb3+ ions. The experiment also confirms that Yb-Er co-doped CaF2 crystal exhibit high stability as optical temperature sensors. In general, it is proved that Yb-Er co-doped CaF2 single crystals are a kind of promising materials used in the optical temperature sensor.
查看更多>>摘要：Interferometric particle imaging is generally interpreted in the framework of Fresnel conditions. We develop here a new formalism based on Luneburg's kernel. It enables to predict the interferometric images of droplets or rough particles when Fresnel conditions are not respected. It is compared to previous experimental results, and then used to understand possible sources of noise when analyzing interferometric particle images.
查看更多>>摘要：The fluorescence distribution of the emulsified oil spills (water-in-oil and oil-in-water) on the sea surface based on laser-induced fluorescence (LIF) is profoundly researched. First, the fluorescent radiative transmission model of the emulsified oil spills is established based on the MIE scattering theory and the Monte Carlo method. And then, the correctness of the fluorescent radiative transmission model is verified by the experimental and simulated fluorescence signal data. Second, the positional distributions and directional distributions of the fluorescence emitted from the emulsified oil spills to sea level under different detection parameters are discussed based on this model, respectively. Finally, the effective receiving area of the emulsified oil spills under certain LIF detection conditions is also analyzed. The results demonstrate that the fluorescence positional distribution for two types of the emulsified oil spills varies extremely. When the laser is vertically incident on the sea surface to the emulsified oil spills, the fluorescence emitted from the sea surface assumes Gaussian distribution. Simultaneously, the fluorescence signal in all directions enhances first and then stabilizes with the increase of the detection area. Further when the detection area reaches a certain value, the strongest fluorescence signal can be received in the vertical sea surface. In addition, the effective detection area of oil-in-water is significantly sharper than that of water-in-oil, and light emulsified oil spill is larger than that of heavy emulsified oil spill.
NSTL
Elsevier