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A novel, simple, and inexpensive flexible surface-enhanced Raman-scattering (SERS) platform based on common laboratory filter paper modified with

Simple and traditional hydrothermal fabrication of a novel balsam pear-shaped CuO with high SERS enhancement is presented. XRD (X-ray diffraction), SEM (scanning electronic microscopy), TEM (transmission electron microscope), HRTEM (high-resolution transmission electron microscope), UV-Vis, and Raman are adopted to ensure that this balsam pear-shaped CuO with dense nanoparticle protuberance is successfully prepared. The LOD of this CuO SERS substrate is 4.79 μg L−1 with R6G as molecular probe. By using DFT (density functional theory) calculation and FDTD (finite difference time domainmethod) simulation, both EM (electromagnetic enhancement) and CM (chemical enhancement) mechanisms are investigated, and the results show that these two-enhancement mechanisms can coexist in this balsam pear-shaped CuO. Finally, the prepared substrate has been applied for the determination of trace levels of paraquat in solution , and results show that its LOD for paraquat is 275 μg L−1 (optimum Raman band: 1646 cm−1 Raman shift), which is better than the government standard in China. A dexterous and facile way for fabrication of CuO SERS-active substrates with low cost and high performance, quite promising in detection of chemically hazardous substances and pesticide residue is provided.

As a new class of two-dimensional material, MXene not only has the unique planar structure, electronic and optical properties, but also has a large surface area and hydrophilicity, which make them to build as potential SERS substrates with good sensitivity and stability. In this work, we reported a modified method by adjusting the ratio of HCl to LiF and reducing sonicate time to form large-sized monolayer Ti3C2Tx nanosheets. SERS performance of Ti3C2Tx was demonstrated by detecting dye molecules such as CV, R6G and MG. A remarkable enhanced effect was obtained, and Raman signals up to 10−8 M could be detected. Furthermore, the relationship between SERS effects and illumination laser wavelengths of different probe molecules has been studied, the results showed the selectivity between dye molecules and the excitation wavelengths. Besides, the uniformity and stability of the substrates have been proved by mapping experiments in a large area (80 × 80 μm2). The results demonstrated that Ti3C2Tx nanosheets can be built as lager-sized, uniform and stable sensor for ultra-sensitive detection of organic dye pollutant molecules.

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Single-base mutations of Factor V Leiden G1691A and Prothrombin gene G20210A are the main genetic risk factors for inherited thrombotic tendency. The establishment for rapid and efficient detection method is of great significance to the prevention of venous thrombosis. In this work, a multiplexed, highly sensitive and regenerable surface plasmon resonance imaging (SPRi) sensor is described to identify and detect the two pathogenic genes by fixing probes in one-step. The probes are fixed by ployA, which is a simpler, faster and lower cost modification method compared with traditional thiol (-SH). PolyA-DNA-AuNPs is used to amplify the signal to improve sensitivity. The detection limit of the sensor is 8 pM, and it has a wide dynamic range between 8 pM and 100 nM and a good linear relationship between 8 pM to 50 pM. The equilibrium dissociation constant (KD) of 3.0 (± 0.3) pM indicates a high binding capacity. Based on the advantages of high-throughput detection, the SPRi chip can simultaneously identify and detect two genes related to thrombotic Diseases. In addition, more than 90% signal intensity can still be obtained on the surface of the chip after being regenerated of 25 times, indicating that this SPRi sensor has good stability and reproducibility. The established SPRi sensor has the advantages of high-throughput, high-sensitivity, label-free and no need for amplification, which is expected to become an effective technical means for real-time online detection of gene point mutations, and can be extended to detect and quantify a wider range of DNA mutation diseases.

Pesticide detection is of tremendous importance in agriculture, and Raman spectroscopy/Surface-Enhanced Raman Scattering (SERS) has proven extremely effective as a stand-alone method to detect pesticide residues. Machine learning may be able to automate such detection, but conventional algorithms require a complete database of Raman spectra, which is not feasible. To bypass this problem, the present study describes a transfer learning method that improves the algorithm's accuracy and speed to extract features and classify Raman spectra. The transfer learning model described here was developed through the following steps: (1) the classification model was pre-trained using an open-source Raman spectroscopy database; (2) the feature extraction layer was saved after training; and (3) the training model for the Raman spectroscopy database was re-established while using self-tested pesticides and keeping the feature extraction layer unchanged. Three models were evaluated with or without transfer learning: CNN-1D, Resnet-1D, and Inception-1D, and they have improved the accuracy of spectrum classification by 6%, 2%, and 3%, with reduced training time and increased curve smoothness. These results suggest that transfer learning can improve the feature extraction capability and therefore accuracy of Raman spectroscopy models, expanding the range of Raman-based applications where transfer learning model can be used to identify the spectra of different substances.

The CMOS single photon avalanche photodiode (SPAD) image sensor, as the third-generation solid-state imaging device, features single photon response capability, picosecond magnitude time resolution and micron-scale spatial resolution. The device is currently the mainstream ideal device for single-photon, picosecond time-resolved transient imaging, and is gradually applied to time-resolved spectral measurement, 3D ranging and imaging, fluorescence lifetime imaging, quantum imaging sensing and such low light or even single photon ultrafast imaging. In this paper, we introduce the research progress of the CMOS SPAD image sensor, and the challenges and solutions of the device are analyzed. In the past years, the mainstream CMOS SPAD image sensor features front-illuminated SPAD and the planar-structure pixel. However, for the planar-structure pixel, in order to make the SPAD with higher fill factor, reducing the duty cycle of the readout electronics within the pixel is the usual method, which to some extent sacrifices the function of reading electronics. In addition, the lower process node was used to improve the integration of electronics, but the high dark count rate was easily caused; The integration of micro-lens array in pixels was also used, but limits the flexibility of pixel size and increases the costs. Compared with planar-structure pixel, the pixel scheme of the three dimensional (3D) stacked structure, integrates the SPAD device and the readout electronics in the pixel correspondingly on the vertically coupled two wafers, which eliminates the problem of duty cycle of the readout electronics within the pixel and would be the development direction in the future.

Zn-doped In0.53Ga0.47As (100) β2 (2 × 4) photocathode surface is an important process for forming the performance of the negative electron affinity (NEA) photocathode. In this paper, the first-principles calculation is used based on the density functional theory (DFT) within scope of the generalized gradient approximation (GGA). The electronic and optical properties of zinc interstitial doped on five sites of In0.53Ga0.47As (100) β2 (2 × 4) photocathode surface are chosen and investigated. The band structure, density of state, dielectric function and absorption coefficient of zinc interstitial doping on In0.53Ga0.47As (100) β2 (2 × 4) photocathode surface are calculated. Results show that the zinc interstitial doping on In0.53Ga0.47As (100) β2 (2 × 4) photocathode surface makes energy band bend and some new energy bands are generated. The band gaps of zinc interstitial doping on In0.53Ga0.47As (100) β2 (2 × 4) surface are all becoming narrow. And it is beneficial for the formation of the NEA photocathode when zinc atom is interstitial doping at 1 position of In0.53Ga0.47As (100) β2 (2 × 4) photocathode surface, which researches dielectric constant and absorption coefficient. The theoretical calculations and analysis provide a guide for designing the near-infrared material.

The emergence of antibiotic-resistant bacterial strains has caused bacterial infections to become a more serious worldwide health problem. The development of multi-functional platform that can quickly and sensitively detect bacteria and effectively inhibit or kill bacterial is important and urgent. Herein, a novel versatile MXene-Au nanocomposite was successfully synthesized by self-assembly method for rapid detection of bacteria and photothermal sterilization. The typical gram-negative Escherichia coli (E. coli) and the gram-positive Bacillus subtilis (B. subtilis) were used as models to perform label-free, rapid and sensitive detection of bacteria based on SERS method. The antibacterial performance of the material was proved by the colony counting method, and the survival rates of E. coli and B. subtilis were as low as 8.05% and 0.06%, respectively. The Ti3C2Tx-Au nanoparticles (NPs) irradiated with 808 nm light showed significant antibacterial effect within only 6 min, and the germicidal rates for E. coli and B. subtilis were 99.25% and 100%, respectively. The photothermal conversion efficiency reached as high as 43.40%. Accordingly, this multi-functional nanocomposite material can not only detect bacteria sensitively, but also has antibacterial and photothermal sterilization effects, which provides a greatly promising countermeasure for clinical treatment of diseases caused by multi-drug resistant bacteria.

Holographic reconstruction is affected by the phase-conjugate wave arising from the symmetry of the complex field. Compressive sensing (CS) has been used in in-line digital holography (DH) to eliminate noise, especially the interference from twin images. Herein, CS with total variation regularization combining autofocusing is presented. It provides an autofocusing function from a single-exposure hologram and obtains reconstructed objects without twin image noise. A series of images at a fixed interval within a reconstruction distance are processed using a two-step iterative shrinkage/thresholding algorithm in CS. It can calculate the focus distance in a larger range around the focal plane using twin-image-free reconstruction, so it can achieve a higher focusing accuracy than traditional focusing methods, including the Laplace operator, absolute gradient operator, and Tamura coefficient. The proposed method is a simple combination of algorithms and a powerful extension that can effectively improve simulated and experimental image quality and handle difficult datasets, which existing algorithms cannot.

A mode-locked all-fiber laser based on the nonlinear multimode interference (NL-MMI) effect of the graded-index multimode fiber (GIMF) is proposed and demonstrated. The saturable absorber (SA) used in the laser consists of a step-index multimode fiber (SIMF) connected by a GIMF. Compared with the theoretically proposed SMF–GIMF–SMF structure, the introduction of the SIMF eliminates the restriction on the length of the GIMF and provides a more flexible method of making an SA based on the NL-MMI. Through bending the device to a certain state, the modulation depth of the SA was measured to be 3.16%. The mode-locked laser output pulses have the pulsewidth of ∼446 fs, the bandwidth of 4.48 nm, and the fundamental repetition rate of 11.73 MHz. This versatility and simplicity of the SA device combined with the possibility of scaling the pulse energy in the large-mode-area double-clad fiber laser make it highly attractive in ultrafast photonics.

Digital holographic imaging is able to reconstruct phase and three-dimensional (3D) information of an object from a one-shot two-dimensional (2D) lensless hologram. A dense encoder–decoder network, called Dense-U-net, is proposed to realize the reconstruction of a 3D particle field. The radii and 3D coordinates of the particles are encoded into a 2D grayscale image as the ground truth. The 2D hologram was served as the input of the network. A Dense_Block is designed and added to the encoder and decoder of the traditional U-net model. Each layer takes the inputs from all previous layers and passes its own feature map to all subsequent layers. Thus, as the diffraction is distributed throughout the entire hologram, both the features with high signal-to-noise ratio at the center of the particle and the diffraction features with low signal-to-noise ratio around the particle can be learned, thereby facilitating the full characterization of the particles. Using the specially designed dense connection module, network training can be accomplished with fewer parameters and faster speeds.

The research of surface enhanced Raman scattering (SERS) based on semiconductor substrate expends the application field of SERS technology. However, the relatively low enhancement sensitivity of semiconductor materials is still a problem to be solved urgently. Herein, high-performance enhancement of Raman scattering is achieved through hierarchical CuS microflowers. Simultaneously based on electromagnetic near-filed effect and charge transfer effect between the reporter molecule and CuS material system, the enhancement factor can reach 105 and the detection limitation is as low as 10−8 M for MG and 10−7 M for CV and R6G molecules. The enhancement sensitivity is proved to be related to the number and spacing of petals of the CuS flowers, and illumination of the incident wavelength. A finite integration method is conducted to estimate the electromagnetic field around the CuS microflower system. The ground-state properties of the system are calculated by DFT method. The energy level schematic diagram of the probe molecules on CuS system is employed to investigate the charge transfer process between the reporter molecule and CuS microflower system. Due to the unique properties of semiconductors, such as surface functionalization, stable material properties and degradability, CuS microflower can be served as a high-performance SERS platform to expend the application field of SERS, and is a valuable tool for the research of semiconductor surfaces.

Using TiO2 on slides to facilitate photo-catalysis of silver nano-particles (AgNPs) is a simple and versatile way of making silver based solid SERS substrates. However, due to the difficulty of getting optimal surface AgNPs structure, it is difficult to reach optimal enhancement factor or measurement uniformity with this method. In this research, production conditions and setups, ranging from dip-coating to photo-catalysis are investigated. Spectral analysis show that some conditions, such as time of calcination and the purity of UV light used in photo-catalysis, affect the resulting SERS substrates more significantly. The overall performance of substrates made using this method is increased; sensitivity is increased so that the limit of detection for Rhodamin 6G (R6G) is as low as 10−8 M, and the signature peak of R6G at 1650 cm−1 measured from different spots on substrates has a standard deviation of less than 20%.

The Raman spectra of human blood serum can be used to identify cancer or other diseases; however, obtaining a reliable surface enhanced Raman scattering (SERS) signal of human blood serum is difficult. Two primary factors that affect SERS measurement of serum are photodegradation and sample composition, which are investigated in this research. In the end, this research proposes a promising set of measurement conditions that can both acquire reliable serum Raman signals and avoid photodegradation.

A stable substrate is extraordinarily important for the trace detection of Surface Enhanced Raman Scattering technique. We have designed in this paper a simple seed growth method to prepare Ag@ZrO

The artificial intelligence technology has achieved great progress recently and has potential in the applications of military, intelligent industry, transportation and logistics, intelligent security check, national security, biomedicine, intelligent agriculture, intelligent services, and so on. Human-like sensor and algorithm are two pillars of artificial intelligence technology, corresponding to the ‘senses’ and ‘brains’ of intelligent machines, respectively. Based on traditional sensor technology, the artificial intelligence human-like sensor combines the novel complementary metal oxide semiconductor (CMOS), micro-electro-mechanical systems (MEMS), nanotechnology, big data and cloud computing, Internet technology, and so on, leading to the great improvement of the sensors performance. In this paper, the artificial intelligence human perception is divided into five categories: vision, hearing, smell, taste, and touch, and corresponding research progress and application of the sensors were introduced.

Recently, more and more attention has been given to a semiconductor oxide-based surface-enhanced Raman spectroscopy substrate for its great stability and biocompatibility. However, its poor SERS sensitivity limits the applications of semiconductor oxide SERS substrates. In this paper, we provide a facile reduction method to modulate oxygen vacancy concentrations in oxide SERS substrates. Using MoO

Surface-enhanced Raman spectroscopy (SERS) has the potential to detect pesticide residues in agricultural products. However, some systemic pesticides, such as chlorpyrifos, can enter the plant tissue, and not just stay on the surface. Consequently, many SERS studies halted at practical application because of its complexity. In this work, SERS technology was used to detect chlorpyrifos residues in tea products at the semiquantitative level. A simple pretreatment method effectively avoided interference of other fluorescent substances, and all major peaks could be distinguished on the basis of a novel substrate. A principal component analysis algorithm was applied to form a regression model, and a nanogram detection limit was obtained. Furthermore, chlorpyrifos residues in the same tea products were also measured by gas chromatography–mass spectrometry, and the results show a small range of errors. From the comparative study of the two detection methods, the results suggest the great promise of SERS technology for rapid inspection of agricultural products.

In this work, surface-enhanced Raman scattering (SERS) spectrum was used to build a rapid analytical method for pesticide residues in fruits. QuEChERS (quick, easy, cheap, effective, rugged and safe) method was modified by multi-walled carbon nanotubes as clean-up sorbents. Overall recoveries of selected pesticide phosmet ranged from 77 to 97% in apples at three spiking levels (0.5, 1 and 2 mg kg−1). The relative standard deviations were between 6.6 and 14%. The limit of detection for phosmet was 0.1 mg kg−1 in standard solution and 0.5 mg kg−1 in apples, which was below the maximum residue limits in fruits of USA, EU and China. The intensity of phosmet characteristic peak existed good linear relationship with the logarithm of concentration between 0.5 and 5 mg kg−1, with the calibration curve coefficients (R2) of 0.9994, which indicated quantitative potential for pesticide residue detection. The method was extended to other pesticides, and the obtained SERS results could be used to establish a spectra database. All the experiments were performed with a portable Raman instrument. Combining pretreatment method with spectra database, a sensitive, rapid and convenient method could be built for pesticide residues detection in fruits.

This paper introduces the major Chinese research groups in the fields of biomedicine, food safety, environmental testing, material research, archaeological and cultural relics, gem identification, forensic science, and other research areas of Raman spectroscopy and combined methods spanning the two decades from 1997 to 2017. Briefly summarized are the research directions and contents of the major Chinese Raman spectroscopy research groups, giving researchers engaged in Raman spectroscopy research a more comprehensive understanding of the state of Chinese Raman spectroscopy research and future development trends to further develop Raman spectroscopy and its applications.

A surface enhanced Raman scattering (SERS) method is described for the determination of vanillin, methyl vanillin and ethyl vanillin at trace levels. Flower-like silver nanoparticles on a silicon wafer are used as the SERS substrate, and the analytes can be specifically and non-destructively recognized by their specific Raman bands. The molecules can be recognized rapidly by identifying the characteristic bands. The SERS spectra of vanillin (C8H8O3) were used as mid-contrast, and specific bands of methyl vanillin and ethyl vanillin (C9H10O3) were acquired at 775 cm−1, 1350 cm−1 and 1282 cm−1, 1382 cm−1, respectively. In addition, by using an improved principal component analysis (PCA) algorithm, the organic molecule can be quantitatively determined. Dissolved in water, vanillin, methyl vanillin and ethyl vanillin still can be detected at a concentration of 10−8 M, at which their characteristic Raman peaks are still visible. The method was successfully applied to the determination of vanillin in milk powder products.

Prescription drug abuse can lead to serious medical negligence, so there is an urgent need to address its screening problem. Gliclazide is widely used as an antihypertensive drug for lowering blood sugar, but its excessive intake can cause serious harm to human body. Here we take gliclazide as an example to provide a method to realize the screening of drug abuse. Flower-like silver nanoparticles were prepared as surface enhanced Raman scattering (SERS) substrate, which can quantitatively and accurately detect the concentration of gliclazide. To understanding the enhanced activity of flower-like silver substrates, the Finite-Difference Time-Domain (FDTD) simulation model was established, and the simulation results showed that flower-like silver had high SERS substrate activity as well as enhanced hot spots at the rough particle surface and the adjacent particles. The experimental results indicated that the flower-shaped silver had an excellent Raman enhancement effect using R6G as detection molecules. When the gliclazide solutions with different concentration gradients were tested, the molecular vibrational modes were also obtained using Gaussian calculations. The rapid and accurate detection of gliclazide concentration was processed by Principal Component Analysis, which were consistent with the experiment, suggesting the importance of the combination of experiment and calculation. Finally, SERS substrate test was performed on the daily medication gliclazide tablets (II), which proved that the flower-like silver still has great Raman enhancement effect on the detection of actual samples.

Raman spectroscopy is a molecular vibrational spectroscopic technique has developed rapidly in recent years, especially in rapid field detection. In this paper, we discuss the Raman spectral pretreatment method and classification algorithm by using nearly 300 pigments spectral data as an example. Here, more than 5 kinds of classification algorithms such as SVM, KNN, ANN and et al are used to sovle the problem of pigments visualization, classification and identification via Raman spectral, and the results show that most of the algorithms fit well, with an accuracy of 90%. Moreover, SNR (Signal to noise ratio) is introduced to evaluate the stability of our algorithm. When the SNR is low, the accuracy of the algorithm decreases sharply. When the SNR was 1, the accuracy rate reached the highest value of 39.46%. In order to slove this problem, the flattopwin, hanning, blackman algorithm was introduced to denoise the signal with low SNR, even when SNR = 1, the signal is 80% accurate. It is proved that in the extreme case of this application, the algorithm still maintains good accuracy, and our research pave the way to use interlligent algorithms to solve the problems in the fields of Raman spectral detection.

Recent years, two-dimensional transition metal carbonitrides, MXene, have emerged as SERS substrates due to their unique optical and electrical properties. In order to combine the advantages of metal nanoparticles and MXene for SERS substrates, this paper prepared an MXene (Ti3C2Tx) -Ag nanoparticles (NPs) hybrid biosensor through in-situ electrostatic self-assembly method, in which the citrate-coated Ag NPs are loaded on the negatively surface of Ti3C2Tx flakes through positively charged PDDA polymer. The characterizations show that a large number of Ag NPs uniformly adsorb on both side of Ti3C2Tx nanosheets. The prepared platform exhibits excellent SERS performance, long-term stability and good uniformity by detecting 4-MBA molecules. The electromagnetic field distribution was simulated to theoretically show the Raman enhancement mechanism of this platform. In order to explore the possible application of the sensor in clinical diagnosis and monitoring of biological environment, the platform was used for biomolecule detection. The detection limit of adenine molecules can be as low as 10−8 M. For dopamine molecules with concentration ranging from 5 × 10-6 M to 5 × 10−8 M, the SERS results show a linear relationship between peak intensity and concentration of dopamine molecules. The biosensor was applied for serum detection. The results suggest that MXene-PDDA-Ag NPs hybrid platform could be used as a sensitive and uniform biosensor for label-free quantitative detection of bio-molecular based on SERS method, which could be applied in the field of biotechnology.

A nonlinear interferometer can be constructed by replacing the beam splitter in the Mach-Zehnder interferometer with four-wave mixing (FWM) process. Meanwhile, the conventional surface plasmon resonance (SPR) sensors can be extensively used to infer the information of refractive index of the sample to be measured via either angle demodulation technique or intensity demodulation technique. Combined with a single FWM process, a quantum SPR sensor has been realized, whose noise floor is reduced below standard quantum limit with sensitivity unobtainable with classical SPR sensor. Therefore, in this work we have theoretically proposed a nonlinear interferometric SPR sensor, in which a conventional SPR sensor is placed inside nonlinear interferometer, which is called as I-type nonlinear interferometric SPR sensor. We demonstrate that near resonance angle I-type nonlinear interferometric SPR sensor has the following advantages: its degree of intensity-difference squeezing, estimation precision ratio, and signal-noise-ratio are improved by the factors of 4.6 dB, 2.3 dB, and 4.6 dB respectively than that obtained with a quantum SPR sensor based on a single FWM process. In addition, the theoretical principle of this work can also be expanded to other types of sensing, such as bending, pressure, and temperature sensors based on a nonlinear interferometer.

The detection of glutathione (GSH) in human serum is significant for the clinical diagnosis of various diseases, such as Alzheimer's disease and cancer. A sensitive surface enhanced Raman scattering (SERS) sensor is proposed to detect low-concentration biomolecule GSH. The sensor is built based on a dense monolayer film of self-assembly Au Nano cubes. The film has an excellent enhancement effect on the probe molecule DTNB. After the GSH molecule is continuously added, the disulfide bond in DTNB breaks into TNB molecule. In a neutral or alkaline environment, TNB will be hydrolyzed into anions, and bind to the surface of the positively charged Au NCs film through electrostatic interaction, thereby enhancing the Raman spectroscopy of TNB. As a result, the proposed sensor can detect low concentrations GSH. The detection limit is 50 nM, and the relative spectral intensity of TNB characteristic peak existed good linear relationship with the concentration of GSH between 50 and 750 nM. The SERS substrate used in the sensor is easy to prepare, with high uniformity and reproducibility, the sample does not require complicated pre-processing and preparation. The SERS sensor provides a novel strategy for sensitive and quantitative detection of the trace analytes and has potential for clinical applications.

Pathogenic bio-aerosols are a threat to public health today, and thus quick detection and identification is of paramount importance. In this study, Raman spectroscopy was used to test 14 types of pollens, one type of fungus and two types of bacteria that are commonly found in bio-aerosols. For bacteria and fungus, surface enhanced Raman spectroscopy (SERS) was used due to their relatively weak signals. Data analysis was performed on the Raman measurement results; principal component analysis was used to reduce the dimension of the data, and support vector machine was used to establish a model for sample identification. The model was able to identify data in the validation set with high (97.3%) accuracy.

We present a compact and novel “T” structure optical fiber refractive index sensor proposal based on surface plasmon resonance. “T” structure sensing head consists of a single mode fiber (SMF) with a plasmonic facet and a cladding partly removed single mode fiber (CPR-SMF) with a gap. The gold film is deposited on the end of SMF instead of the side of the CPR-SMF. The simulation results show that the SPR based on the “T” structure can be excited effectively. The SPR transmission spectrum shifts towards longer wavelength with the sensing sample refractive index increasing largely. When we divide the refractive index range of the sensing sample to two parts, the linear relationships between the SPR wavelength and the refractive index can be used. The resolutions can be highly up to 7.115×10 −6 RIU and 3.525×10 −6 RIU for the refractive index ranges of 1.3333–1.36 and 1.37–1.4, respectively. The proposed “T” structure sensor works well for achieving the refractive index measurement with high sensitivity and wide range for samples with a tiny amount.

A simple multipoint volatile organic compounds (VOC) measurement by zeolite thin film-coated Fresnel reflection-based fiber sensor with an Array-Waveguide Grating (AWG) is proposed and demonstrated. The sensor comprise a polycrystalline silicalite thin film grown up on the cleaved end face of single-mode fiber. The chemical vapors concentration is measured by monitoring the reflection intensity, which is a function of the molecular adsorption in the crystalline micro-porous structure. Multipoint measurement is achieved by an AWG with 16 channels. Four of the 16 channels has been connected to the sensing channels as representative. The proposed VOC sensor performed with the sensitivity from 0.015 to 3.9 × 10 −3 dB/ppm in the concentration range from 0 to 550 ppm.

This paper concerns the problem of platform vibration induced band-to-band misregistration with acousto-optic imaging spectrometer in spaceborne application. Registrating images of different bands formed at different time or different position is difficult, especially for hyperspectral images form acousto-optic tunable filter (AOTF) imaging spectrometer. In this study, a motion detection method is presented using the polychromatic undiffracted beam of AOTF. The factors affecting motion detect accuracy are analyzed theoretically, and calculations show that optical distortion is an easily overlooked factor to achieve accurate band-to-band registration. Hence, a reflective dual-path optical system has been proposed for the first time, with reduction of distortion and chromatic aberration, indicating the potential of higher registration accuracy. Consequently, a spectra restoration experiment using additional motion detect channel is presented for the first time, which shows the accurate spectral image registration capability of this technique.

An all fiber real-time laser wavelength measurement method based on Faraday rotation effect is proposed and demonstrated, for correcting the nonlinear tuning of wavelength sweep lasers. The wavelength measurement setup is mainly composed of a specially designed fiber magneto-optic device and a wavelength sensitive filter. When the linearly polarized lights with different wavelengths pass through the magneto-optic crystal, their polarization planes will be rotated at different angles. By taking use of the dispersion effect, the light wavelength can be measured by detecting the rotated angles. In our experiments, the wavelength resolution can reach 2.1 pm with a measurement range from 1520 to 1570 nm. Besides monitoring the wavelength tuning, it should be also useful in laser wavelength calibration and optical fiber sensing.

A novel, simple, and inexpensive flexible surface-enhanced Raman-scattering (SERS) platform based on common laboratory filter paper modified with T i 3 C 2 T x flakes was reported. T i 3 C 2 T x synthesized from a T i 3 A l C 2 phase with a mixture of HCl and LiF and T i 3 C 2 T x nanosheets were characterized by the TEM, XRD, UV–Vis spectrum, and Raman spectrum. Paper-based substrate has been proven to sample on rough and irregular surfaces. Thus, T i 3 C 2 T x was further manufactured as paper substrate by the immersion method to transfer nanosheets to filter paper. SERS activity of prepared substrate was demonstrated using R6G by the same filter paper modified with and without T i 3 C 2 T x , and various concentrations of R6G were tested to prove the sensitivity of the substrates. Further detection of CV and MG certified the universality of paper substrate based on T i 3 C 2 T x nanosheets for detection of organic pollutants. The uniformity and stability were proved by CV and R6G molecules. This SERS platform combines the advantages of 2D material and flexible paper scaffolds, resulting in a highly sensitive, cost-efficient, and easy-to-manufacture large-scale flexible substrate and is expected to be used in practice.

A stable substrate is extraordinarily important for the trace detection of Surface Enhanced Raman Scattering technique. We have designed in this paper a simple seed growth method to prepare Ag@ZrO2 core-shell nanoparticles as well as regulate the core-shell ratio by adjusted concentration of zirconium propoxides added. The shell thickness effect and spacing on SERS activities have been simulated in different finite time domains, which goes perfectly with those previous experiment results. With Ag@ZrO2 core-shell nanoparticles adopted as the SERS substrate and R6G as molecular probe, the detection range could reach as great as 10-8 M. The regression model, obtained through principal component analysis, is adopted for some rapid and precise detection; and the determination coefficient (R2) is going up to 0.9743, proving that the SERS substrate we have prepared has extremely high detection accuracy. To explore the stability of core-shell nanoparticles, we have taken both two different cases of strong acid solution as well as strong alkali solution for the core-shell nanoparticle etching, and this is how a SERS test could be carried out. These experimental results have indicated that the outer zirconia layer could keep the silver surface from oxidation and its stability is ensured, quite crucial for the applied SERS.

The present study aims to diagnose malignant pleural effusion (MPE) based on the identification of distinctive Raman spectra bands. The tests on 83 pleural effusion (PE) samples including 32 benign PE (BPE) and 51 MPE were performed based on rapid and label-free surface-enhanced Raman spectroscopy (SERS). The TiO2 photo-catalyzed Ag NPs were used as SERS substrate. And the SERS spectra of BPE and MPE were compared and diagnosed through orthogonal partial least squares discriminant analysis (OPLS-DA). The diagnosis results showed that the sensitivity and specificity can reach 92.2% and 93.8%, respectively, based on leave-one-out cross validation. And the area under curve values of MPE was 0.985. This study demonstrated an accurate way of combining Raman spectra of PE with OPLS-DA to identify MPE and BPE.

Pesticide residues pose a great threat to human health, and it is an urgent matter to realize fast and accurate detection of pesticide. SERS (Surface Enhanced Raman Scattering), as a nondestructive detection technology, performs a prominent role in fast detection field due to the strong surface plasmon resonance from short range effect between analyte and nanoparticle. Therefore, in order to solve the incompatibility between organochlorine pesticides molecules and noble metal nanoparticles, this paper proposed a concept of "bridge" substances acting as an interconnect function role to achieve a binding model (object-binder-metal (OBM)) and developed a droplet concentration method to enhance Raman signals. Both combination mode of pesticide molecules to bridge molecules and energy transfer of SERS experiment may relate to the compound ring according to the changes of peaks based on surface plasmon resonance. The selectivity and stability of different bridge substances interacting with pesticides molecules were illumined via binding energy of these two substances obtained by DFT calculations. A droplet can capture nanoparticles and analytes, which is conducive to SERS performance. Chloride ions in the solution contribute to rearrangement of nanoparticles and can validly promote surface activation of Ag nanoparticles to improve energy transfer efficiency of plasma resonance, resulting in superior SERS effect.

Temperature characteristics of Sensitivity-enhanced Fabry-Perot filled with PDMS temperature sensor based on Vernier effect consisting of two Fabry–Perot interferometers (FPI), one of the FPI’s cavity is internally filled with PDMS, are observed experimentally. Results show that temperature sensitivity of the Sensitivity-enhanced Fabry-Perot sensors is 1.808 nm/°C. It is Vernier effect lead to a double improvement of the temperature sensitivity compared with the sensor with single FPI, of which the cavity is internally populated with PDMS but no Vernier effect. Moreover, the improvement can be enlarged by optimizing the free spectra range of these two FPIs.

A novel mode-locking method based on the nonlinear multimode interference in the stretched graded-index multimode optical fiber (GIMF) is proposed in this Letter. The simple device geometry, where the light is coupled in and out of the stretched GIMF via single-mode fibers, is demonstrated to exhibit the temporal intensity discrimination required for mode locking. The nonlinear saturable absorber (SA) characteristics of the device are controllable by simply adjusting the strength of the stretching applied. The modulation depth of the device, which consists of ∼23.5 cm GIMF, is tuned from 10.37% to 22.27%. Such a simple SA enables the wavelength-switchable mode-locking operation in a ring Er-doped fiber laser, and ultrafast pulses with a pulse width of 506 fs at 1572.5 nm and 416 fs at 1591.4 nm were generated. The versatility and simplicity of the SA device, together with the possibility of scaling the pulse energy, make it highly attractive in ultrafast photonics.

An Er-doped mode-locked fiber laser with a saturable absorber based on single mode - graded index multimode - single mode fiber (SMF-GIMF-SMF) with inner micro-cavity is demonstrated. The modulation depth of the saturable absorber was measured to be 1.9% when the SMF-GIMF-SMF structure is bent to a certain state. Such a simple saturable absorber enables the mode-locking operation in a ring Er-doped fiber laser and ultrafast pulses with pulse energy of 0.026 nJ and pulse width of 528 fs at the fundamental repetition rate of 14.34 MHz can be generated. In addition, the harmonic mode-locking operation can also be achieved.

The platform vibration will cause spectral images blurring when using computed tomographic imaging spectrometer (CTIS) on unstable platform, especially in space-borne or ship-based application. As a result, a phenomenon of blur-induced spectral distortion occurs, which greatly affects the accuracy of classification of target. However, without easy accessibility of the knowledge of image motion kernel, it is difficult to restore the degraded images accurately. With the desire to solve the motion function, this paper has made a breakthrough by proposing a motion detection method using short exposure images from zeroth order beam light of 2D-grating. Contributed by the accurate motion kernel, blurred spectral images could be reliably restored as well as the improvement of spectra accuracy. Laboratory experiment result shows the robust spectra restoration capability of this technique.

Raman spectroscopy is a novel method of food analysis and inspection. It is highly accurate, quick, and noninvasive. The investigation and monitoring of food processing is important because most of the foods humans eat today are processed in various ways. In this article, the use of Raman spectroscopy in food processes, such as fermentation, cooking, processed food manufacturing, and so on, are explored. The characteristics and difficulties of the Raman inspection of these processes are also discussed. According to the various research reports, Raman spectroscopy is a very powerful tool for monitoring these food processes in lab environments and is likely to see usage in situ in the future.

A curvature sensor based on two cascading abrupt-tapers modal interferometer in a single mode fiber (SMF) is proposed and experimentally demonstrated in this paper. The device consists of two cascading abrupt-tapers with different sizes, manufactured by CO2 laser in a standard SMF. The cladding modes will be excited in the first abrupt-taper section, partly coupled with the core mode. After propagation of these coupled modes, they will recombine at the second abrupt-taper section. The experimental results show that the optimum visibility of interference fringe can be got only when the two abrupt-tapers are at different sizes. If we bend the proposed modal interference, part of the cladding modes will be leaked out, making the interference pattern having a shift. Thus it can be used to measure curvature. The experimental results show that the shift of the dip wavelength is almost linearly proportional to the change of curvature, and the curvature sensitivities are −13.176 nm/m−1 in the measurement ranges of 4.8 m−1 to 6.38 m−1. As the curvature continues to increase, ranging from 6.38 m−1 to 7.98 m−1, the sensitivity is doubled to −25.946 nm/m−1. Moreover, this curvature sensor can be seen low sensitive to either the external refractive index or the temperature when employing in a relatively stable environment. The proposed curvature sensor is simple-fabricated and inexpensive, which is very suitable for curvature measurement in practical applications.

A compact chemical vapor sensor based on a fiber loop mirror (FLM) inserted with a high-birefringent photonic crystal fiber (HiBi-PCF) is proposed and experimentally demonstrated. Because the resonant dips of the HiBi-PCF FLM are sensitive to the phase difference between two counter-propagating waves in the FLM, a highly sensitive chemical vapor can be achieved by measuring the resonant dip shifts when chemical vapor diffuses into the air holes of the HiBi-PCF. Experimental results show a high sensitivity of 15.5 pm/ppm for ethanol is obtained when a 5.1 cm long HiBi-PCF is used in the FLM. Three different mechanisms for the high sensitivity of the proposed sensor are discussed. A liquefaction model with a full-vector finite element method is proposed and is regarded as the main contribution.

The orientation of talents cultivation for local colleges is to train engineering application-oriented talents, so the exploration and practice on teaching reform of theory curriculum was carried out. We restructured the knowledge units basing on numerical solution problems, and chose the software to build algorithm models for improving the analytical and designed ability. Relying on micro video lessons platform, the teacher-student interaction was expanded from class to outside. Also, we programmed new experimental homework, which was suited for process evaluation. The new teaching mode has achieved good effect, and the students' application ability was significantly improved.

A rapid method for identification of plastics based on Raman spectroscopy with the combination of support vector machine (SVM) is presented in this paper. Plastics studied consist of polyethylene, polyethylene terephthalate, polymethyl methacrylate, polyacetal, polypropylene, polystyrene and polyvinyl chloride. With spectral preprocessing and principal component analysis (PCA), support vector machine model for identification of plastics was established. The results show that the presented method can identify the plastics rapidly with accuracy of 100%. Indicating that support vector machine used to rapid identification of plastics performs well based on Raman spectroscopy.

It is well known that broadband antireflective characteristics are frequently realized by using subwavelength tapered micro- or nanostructures. In this paper, we propose that the triangular grating in the resonance domain with period larger than the incident wavelength can also possesses broadband and wide angle antireflective performance and polarization selection. The diffraction pattern for the external reflection grating and the internal reflection one is demonstrated by the rigorous vector diffraction theory. It is found that the total transmittivity with TE polarized illumination is clearly less than that for TM polarization. The aspect ratio of grating is a significant parameter to broadband antireflection performance. For the external reflection grating, the broadband antireflection function can be achieved with the aspect ratio larger than 1.5 for both polarization modes in the resonant domain. For the internal reflection grating, the narrow band antireflection properties are demonstrated for TE polarization with higher aspect ratio. And the broadband antireflection characteristics can be revealed at the aspect ratio higher than 4.0 in the resonance domain for TM polarization. Besides, in order to determine intuitively diffraction pattern and antireflection performance, the electric field distribution was calculated for both types of triangular profile in the resonant domain, and the aspect ratio of the grating is crucial to the total transmittance.

Gauss simulation is often used to help design new LEDs according to photometric and colorimetric performance requirements. This research investigates an improved Gauss simulation model for simulating YAG-PC LEDs. Three types of PC-LEDs are investigated at commonly used CCT ranges. This research shows that desirable photometric and colorimetric qualities can be achieved. For warm white, pure white and cold white CCT ranges, CRI of 72.1, 79.8 and 84.5 can be achieved, respectively. LEDs with optimal color rendering qualities are designed; packaging and measurement of said LEDs shows that the simulation model is successful.

In this study, a fiber in-line air-gap Fabry–Perot interferometer (FPI) is fabricated by HF acid etching. For a low-cost and higher precise measurement, a demodulation system based on frequency modulated continuous wave (FMCW) technique is build up and demonstrated in this air-gap FPI. In temperature measurements, the temperature sensitivity is about 1.75 rad/°C by phase shift detection. We also test the long term performance of the system and the RMS error is about 0.04 rad, which corresponds to the temperature resolution of ~0.02 °C. It is much higher than the measurement resolution by using the traditional wavelength shift detection method. Our experiments show that the FMCW can provide a low-cost, high resolution and high speed interrogation solution to the fiber FPIs.

In this study, a high birefringence (Hi-Bi) polarization maintaining fiber (PMF) is used as the sensing element for static axis strain and dynamic vibration measurements. This multifunctional fiber sensor adopts the Sagnac loop structure, where the Hi-Bi PMF is incorporated in the fiber loop. The static axis strain measurement is realized by interrogating the broadband transmission spectra and the strain sensitivity of 1.09 pm/µs is achieved. Furthermore, the Sagnac fiber loop is applied in dynamic acoustic vibration measurements. The experimental results show that it can detect the acoustic vibrations over the frequency range of 30 Hz to 22 kHz, and shows signal to noise ratios (SNRs) over 40 dB from 800 Hz to 9000 Hz.