Vacuum ultraviolet (VUV) light sensing shows great potential applications in the space science, materials, biophysics, and plasma physics. In this work, an all-optical detection method is proposed for VUV sensing by constructing an optical fiber-end Fabry-Pérot interferometer based on a single aluminum nitride (AlN) microwire. Compared with the traditional electrical devices, this all-optical detection method overcomes the difficulties like the fast response and electromagnetic interference immunity in detecting VUV bands at the present stage, and improves the response speed. The proposed device shows the excellent performance of VUV detection, with the static sensitivity of 1.03 nm/(W·cm⁻²), response rise time of down to 10 µs, and decay time of 0.64 ms. Beneficial from the excellent radiation resistance of AlN microwires and UV resistance of silica fibers, the proposed device is expected to have the good stability and potential applications in the fields of the solar physics and space exploration.

Herein, an innovative glyphosate imprinted poly(hydroxyethyl methacrylate-N-methacroyl-(L)-phenylalanine methyl ester nanoparticles (MIP@NPs) based plasmonic nanosensor featured with high sensitivity and selectivity was constructed by using the molecular imprinting technique and used for real-time glyphosate detection. The characterization of nanoparticles was performed by the nano Zetasizer and scanning electron microscopy (SEM), while nanosensors were characterized by the Fourier transform infrared-attenuated total reflection (FTIR-ATR) and contact angle measurement. Control experiments were conducted to evaluate the imprinting efficiency on the signal response using a non-imprinted surface plasmon resonance (NIP SPR) nanosensor prepared without adding glyphosate pesticide into the polymerization mixture. The MIP@NPs integrated molecularly imprinted surface plasmon resonance (MIP SPR) nanosensor having synthetic molecular recognition elements yielded a novel biosensing platform for label-free detection and real-time monitoring of glyphosate pesticide. The MIP SPR nanosensor detected the target glyphosate molecule 4.950 times more selectively than the competitor molecule malathion while 3.918 times more selectively than the competitor molecule malaoxon. In addition, the imprinting efficiency factor was found to be 6.76, indicating that the molecular imprinting process was successful. In addition, the imprinting factor was found to be 6.76. Kinetic studies and adsorption characteristics of glycosate adsorption were carried out to assess adsorption dynamics. The linear concentration range for glyphosate detection was 0.001 ppm–10.000 ppm of pesticide, and the detection limit was found to be 0.120 ppb. Studies on the repeatability of the MIP SPR nanosensor revealed that even after five cycles, the signal response for glyphosate detection did not change significantly with relative standard deviation, RSD<1.5 value. The artificial urine selected as the real sample was spiked with glyphosate at a final concentration of 10.000 ppm to evaluate the matrix effect, and the glyphosate amount was reported.

In this paper, a graphene oxide (GO) composite film-coated humidity sensor is proposed based on the hollow core fiber (HCF). A segment of the HCF is spliced between two segments of the single-mode fiber (SMF). The relative humidity (RH) sensing characteristics of the sensor are experimentally investigated by observing the intensity shift of resonant dips in the transmission spectrum, which shows the GO composite film-coated HCF has the good stability in the measurement of humidity. The maximum humidity sensitivity of 0.12 dB/%RH is obtained in the RH range of 30%–78%. The proposed sensor has the advantages of the simple structure, easy fabrication, good stability, and high performance, which can be applied to marine climate detection, tunnel air humidity detection, agricultural testing, and other fields.

This study presents the two-dimensional (2D) image of a subsurface structure reconstructed using an imaging method based on the photothermal effect. The photothermal imaging method is based on the deflection method using two lasers: pump and probe lasers. A continuous scanning technique is proposed for 2D (x- and y-directions) surface scanning. The continuous scanning method is compared with the conventional point-by-point scanning technique, and a low-pass fast Fourier transform filter and a Marr-Hildreth detector are found to produce significant results. The photothermal imaging method with continuous 2D surface scanning is performed on three copper-resin double-layer samples with different subsurface structures. The subsurface structures of the copper-resin double-layer samples comprise a square block of 5×5 mm² area and blocks shaped as the alphabet letters “T” and “F”. The letters are 3 mm wide and 10×13 mm² in area. All three shapes are 1 mm thick and located at a depth of 0.5 mm from the surface of the copper block. The reconstructed photothermal images show an absolute error within 0.122 mm compared with the actual subsurface structure, equivalent to a 2.3% relative error.

A novel optical fiber hydrogen sensor based on the π-phase-shifted grating and partial coated Pd/Hf composite film is proposed and experimentally demonstrated in this paper. The hydrogen sensitive Pd/Hf film with the length of 4 mm is successfully deposited in the π-phase-shifted grating region by the magnetron sputtering process and rotating fixture technology. Since the hydrogen sensitivity between the notch and flank wavelengths of the π-phase-shifted grating is different due to the partial coating only on the π-phase-shifted grating region, the relative shift between the notch and flank wavelengths is employed to characterize the hydrogen concentration in this paper. The hydrogen calibration results show that the sensor shows the good response and repeatability. At the temperature of 20 °C and the hydrogen concentration of 2%, the wavelength distance shifts of 200 nm and 500 nm Pd/Hf coatings are 12.6 pm and 33.5 pm, respectively.

Since photo-induced polymerization of the ultra-violet (UV)-curing adhesive from a fluid state to a solid state is an exothermic process, the UV curing exothermic behavior can be regarded as a potential evaluation methodology to analyze UV-curing kinetics. Herein, a fiber Bragg grating (FBG)-based UV curing exothermic behavior monitoring is proposed to evaluate the UV-curing dynamic process and analyze a series of thermal and mechanical properties changes during curing. The exothermic behavior of the UV curing adhesive during curing and the feasibility of FBG-based curing kinetic analysis scheme are verified experimentally, full cycle cure monitoring of the UV curing adhesive can be realized by this FBG-based curing kinetic analysis scheme, and the UV-curing kinetics of four different types of the UV curing adhesive are corresponding to different exothermic behaviors. Compared with curing process evaluation based on refractive index variation, this FBG-based exothermic behavior monitoring has the ability to extract more details of the curing process, and some curing stages with negligible refractive index changes also can be distinguished. By using this proposed scheme, the UV-curing dynamic process and multiple characteristic parameters, such as curing time, time constant, transient temperature rise, and residual stress, can be evaluated, which may contribute to evaluating and analyzing UV-curing kinetics more comprehensively.