Silicon photonics is an enabling technology that provides integrated photonic devices and systems with low-cost mass manufacturing capability. It has attracted increasing attention in both academia and industry in recent years, not only for its applications in communications, but also in sensing. One important issue of silicon photonics that comes with its high integration density is an interface between its high-performance integrated waveguide devices and optical fibers or free-space optics. Surface grating coupler is a preferred candidate that provides flexibility for circuit design and reduces effort for both fabrication and alignment. In the past decades, considerable research efforts have been made on in-plane grating couplers to address their insufficiency in coupling efficiency, wavelength sensitivity and polarization sensitivity compared with out-of-plane edge-coupling. Apart from improved performances, new functionalities are also on the horizon for grating couplers. In this paper, we review the current research progresses made on grating couplers, starting from their fundamental theories and concepts. Then, we conclude various methods to improve their performance, including coupling efficiency, polarization and wavelength sensitivity. Finally, we discuss some emerging research topics on grating couplers, as well as practical issues such as testing, packaging and promising applications.

Abstract. To analyze the factors influencing online shopping intention for fresh agricultural products, this paper constructs a research model based on UTAUT2. Data obtained from questionnaires are processed using structural equation model. The results show that performance expectancy, effort expectancy, hedonic motivation, facilitating conditions have positive impacts on the online shopping intention for fresh agricultural products, gender has a significant influence on the measuring model, while neither experience nor personal innovativeness has influence on the measuring model.

The beam-steering device is a critical component in LiDAR systems for 3D imaging. Solid-state beam-steering devices attract the most attention for their advantages of robustness, fast beam-steering speed, and stability. However, solid-state beam-steering devices, such as optical phased arrays (OPAs), are challenging to realize 2D scanning ability. Here we employed a virtually imaged phased array (VIPA) in the LiDAR system to realize all solid-state two-dimensional (2D) beam-steering based on dispersion only. A frequency swept laser source is used for performing optical frequency-modulated continuous-wave (FMCW) ranging and 2D beam steering simultaneously. The 2D disperser is compact and can be easily implemented owing to its simple structure. The mechanism of continuous scanning and ranging is beneficial for obtaining high lateral resolution, and a lateral resolution of 0.06° is achieved. 3D maps of the object at a distance of 2 m are obtained with cm-level ranging precision. The frame rate of the proposed LiDAR system only depends on the wavelength-tuning speed of the swept laser source, with the potential to realize ultrafast solid-state LiDAR systems.

ObjectiveTo investigate the effects of combined medication of nifedipine and magnesium sulfate on the blood pressure, pregnancy-associated plasma protein A (PAPP-A), vascular endothelial growth factor (VEGF), nitric oxide (NO), homocysteine (Hcy) and von Willebrand factor (vWF) in gestational hypertension patients.MethodsA total of 220 gestational hypertension patients were enrolled as the subjects, and divided into two groups randomly, i.e. the observation group and the control group. In observation group, patients took combined medication of nifedipine and magnesium sulfate, while those in the control group only took magnesium sulfate for treatment. Clinical efficacy, and the changes in blood pressure, PAPP-A, VEGF, NO, Hcy and vWF before and after treatment were compared between two groups.ResultsIn the observation group and the control group, total effectiveness rates were 92.7% and 70.9%, respectively (p < 0.05). After treatment, we found significant decreases in PAPP-A, VEGF, NO, Hcy and vWF in patients of two groups, with more significant decreases in the observation group (p < 0.05). Incidence rates of the adverse reactions in two groups were 5.5% and 6.4%, respectively, without any statistically significant differences (p > 0.05). In the observation group, patients had fewer complications (p < 0.05).ConclusionCombined medication of magnesium sulfate and nifedipine can decrease the levels of PAPP-A, VEGF, NO, Hcy and vWF in serum as well as the blood pressure of patients with gestational hypertension, with a reduction in incidence rate of complications and improvement in efficacy.