We propose a hyperbolic metamaterial-based surface plasmon resonance (HMM-SPR) sensor by composing a few pairs of alternating silver (Ag) and zinc oxide (ZnO) layers. Aiming to achieve the best design for the sensor, the dependence of the sensitivity on the incidence angle, the thickness of the alternating layer and the metal filling fraction are explored comprehensively. We find that the proposed HMM-SPR sensor achieves an average sensitivity of 34,800 nm per refractive index unit (RIU) and a figure of merit (FOM) of 470.7 RIU⁻¹ in the refractive index ranging from 1.33 to 1.34. Both the sensitivity (S) and the FOM show great enhancement when compared to the conventional silver-based SPR sensor (Ag-SPR). The underlying physical reason for the higher performance is analyzed by numerical simulation using the finite element method. The higher sensitivity could be attributed to the enhanced electric field amplitude and the increased penetration depth, which respectively increase the interaction strength and the sensing volume. The proposed HMM-SPR sensor with greatly improved sensitivity and an improved figure of merit is expected to find application in biochemical sensing due to the higher resolution.

In digital holographic microscopy (DHM), the use of microscope objective always introduces a phase aberration and thus affects the retrieved phase. To address this problem, we present a simple phase aberration compensation method in DHM based on geometrical transformations. After doing the geometrical transformations (including reflection, rotation of 180 ° , and transpose) for the unwrapping phase (+1 order) of the original hologram, we could get a transformation phase. By subtracting the transformation phase from the unwrapped phase (+1 order) of the original hologram, the parabolic phase aberration is compensated. The fully automatic and effective performance makes the proposal available for single-shot quantitative phase imaging without complex numerical fitting procedures or prior knowledge of the specimen and system. A series of simulations and the experiment results of the micro-lens array, phase plate and cells demonstrate the feasibility and effectiveness of the proposed method.

We present a single-shot wavelength-multiplexing technique for off-axis digital holography based on a spectral filter. Only a spectral filter is inserted between beam splitter and mirror in reflection off-axis digital holography (RODH). The spectral filter can transmit a well-defined wavelength band of light, while reject other unwanted radiation. By adjusting the filter and mirror separately, the propagation orientation of different reference beams of two wavelengths can be separated, and thus two off- axis holograms with different fringe directions are simultaneously captured by a monochrome camera. The wavefront interference analysis of using a spectral filter is discussed in detail. Our scheme is available for real-time wavelength-multiplexing but requires fewer optical elements and system modifications. Numerical simulation and experiment results of different types of spectral filters demonstrate the validity of proposed method.

We demonstrate the existence of two types of dark gap solitary waves—the dark gap solitons and the dark gap soliton clusters—in Bose–Einstein condensates trapped in a bichromatic optical superlattice with cubic–quintic nonlinearities. The background of these dark soliton families is different from the one in a common monochromatic linear lattice; namely, the background in our model is composed of two types of Gaussian-like pulses, whereas in the monochromatic linear lattice, it is composed of only one type of Gaussian-like pulses. Such a special background of dark soliton families is convenient for the manipulation of solitons by the parameters of bichromatic and chemical potentials. The dark soliton families in the first, second, and third bandgap in our model are studied. Their stability is assessed by the linear-stability analysis, and stable as well as unstable propagation of these gap solitons are displayed. The profiles, stability, and perturbed evolution of both types of dark soliton families are distinctly presented in this work.

Existing methods to eliminate the laser speckle noise in quantitative phase imaging always suffer from the loss of detailed phase information and the resolution reduction in the reproduced image. To overcome these problems, this paper proposes a speckle noise suppression method based on empirical mode decomposition. Our proposed method requires only one image without additional equipment and avoids the complicated process of searching the optimal processing parameters. In this method, we use empirical mode decomposition to highlight the high frequency information of the interference image and use the Canny operator to perform edge detection, so the diffusion denoising process is guided by high-precision detection results to achieve better results. To validate the performance of our proposed method, the phase maps processed by our proposed method are compared with the phase maps processed by the improved anisotropic diffusion equation method with edge detection, the mean filter method and the median filter method. The experimental results show that the method proposed in this paper not only has a better denoising effect but also preserves more details and achieves higher phase reconstruction accuracy.

Based on the refraction characteristic of uniform and transparent liquid, the measurement error of the liquid refractive index using the internal standard method is analyzed, and an improved laser speckle method is proposed. This method designs a double-cell structure composed of two identical rectangular parallelepiped glass cells with one cell containing the liquid to be measured and the other one being empty. This double-cell structure is placed in the built optical system based on laser speckle, and then the refractive indices of sodium chloride solution and sucrose solution with various concentrations are measured by the improved method. Compared with the measurement values of the Abbe refractometer and the internal standard method, the results show that the improved method can significantly reduce the measurement error and improve the measurement accuracy.