Non-contact fluorescent detection of pesticide residues based on segment prediction using PLS and a curve fitting algorithm.

Fluorescence spectral analysis is an important method to detect the pesticide residues, which is vital for food safety issues. It has been demonstrated that the traditional curve fitting (CF) method can predict the concentration of pesticide with a high accuracy. However, low absorption of the samples at low concentration of pesticide is required; moreover, the pre-process of fruit juice is time-consuming and destructive to the samples. To overcome these disadvantages while maintaining the high accuracy in the high concentration range, the segment detection method is proposed in this paper. Two models were employed to predict the concentration according to the fluorescence intensity. The partial least squares (PLS) model was used to predict the concentration of the samples when the fluorescence intensity at 356 nm was smaller than 1, while the CF method was used to predict the concentration of samples when the fluorescence intensity at 356 nm was larger than 1 in our system. In total, 101 samples with concentration ranging from 0 to 0.0714 mg/mL were used to validate this method. The results indicated that the PLS method exhibited a high sensitivity in the low concentration range, while the CF method exhibited high accuracy in the high concentration range.

Tunable compact nanosensor based on Fano resonance in a plasmonic waveguide system.

An ultracompact plasmonic refractive index sensor based on Fano resonance is proposed. The sensor comprises a metal-insulator-metal waveguide with a stub and a side-coupled split-ring resonator. The effect of structural parameters on Fano resonance and the refractive index sensitivity of the system are analyzed in detail by investigating the transmission spectrum. Simulation results show that Fano resonance has different dependences on the parameters of the sensor structure. The reason is further discussed based on the field pattern. The peak wavelength and lineshape can be easily tuned by changing the key parameters. Furthermore, dual Fano resonance effects with different frequency intervals are obtained, which are mainly induced by the symmetry breaking of the structure. The proposed sensor yields sensitivity higher than 1.4×103 nm/RIU and a figure of merit of 1.2×105. The sensitivity and figure of merit can be further improved by optimizing the geometry parameters.

Single-lens Fourier-transform-based optical color image encryption using dual two-dimensional chaotic maps and the Fresnel transform.

We propose an optical color image encryption system based on the single-lens Fourier transform, the Fresnel transform, and the chaotic random phase masks (CRPMs). The proposed encryption system contains only one optical lens, which makes it more efficient and concise to implement. The introduction of the Fresnel transform makes the first phase mask of the proposed system also act as the main secret key when the input image is a non-negative amplitude-only map. The two CRPMs generated by dual two-dimensional chaotic maps can provide more security to the proposed system. In the proposed system, the key management is more convenient and the transmission volume is reduced greatly. In addition, the secret keys can be updated conveniently in each encryption process to invalidate the chosen plaintext attack and the known plaintext attack. Numerical simulation results have demonstrated the feasibility and security of the proposed encryption system.

Enhancing the sensitivity of fiber Mach-Zehnder interferometers using slow and fast light.

We demonstrate theoretically and experimentally that the sensitivity of a fiber Mach-Zehnder (M-Z) interferometer can be enhanced by coupling fiber ring resonators with it. The experimental results agree well with theoretical predications that combining slow light with fast light will further increase the sensitivity of a fiber M-Z interferometer.

Simultaneous observation of superluminal and slow light propagation in a nested fiber ring resonator.

We observe both superluminal and slow light propagation simultaneously in a nested fiber ring resonator. The two outputs of the resonator exhibit different absorption characteristics that produce opposite dispersion performance. The transmission spectra of two outputs are demonstrated experimentally for a variety of coupler settings. In particular, the group delays of the resonator for various values of the coupling coefficients are demonstrated theoretically and experimentally. We also discuss potential applications of the resonator.

A high spectral sensitivity interferometer based on the dispersive property of the semiconductor GaAs.

We develop an interferometer which has high spectral sensitivity based on the dispersive property of the semiconductor GaAs in the near-infrared region. Our experiment demonstrates that the spectral sensitivity could be greatly enhanced by adding a slow light medium into the interferometer and is proportional to the group index of the material. Subsequently the factors which influence the spectral sensitivity of the interferometer are analyzed. Moreover, we provide potential applications of such interferometers using the dispersive property of semiconductor in whole infrared region.

Nearly preprocessing-free method for skeletonization of gray-scale electronic speckle pattern interferometry fringe patterns via partial differential equations.

We describe a novel method for skeletonization of gray-scale electronic speckle pattern interferometry (ESPI) fringe patterns. Our method is based on the gradient vector field (GVF). We propose a new partial differential equation model for calculating the GVF of ESPI fringe patterns. Further, we propose rules used to measure the possibility of each pixel on the skeleton based on the topological analysis of the GVF. The final skeletons are traced, which mimics the behavior of edge detection based on these rules. The proposed method works directly on the gray-scale images.