Hui Lv

Design of all-normal dispersion photonic crystal fiber for high coherent broadband supercontinuum generation in the telecommunication window

An all-normal dispersion photonic crystal fiber with nearly zero flattened dispersion at 1550 nm is designed for generating high coherent broadband supercontinuum. It is found that an all normal dispersion photonic crystal fiber with nearly zero flattened dispersion at 1550 nm can be obtained by appropriately designing geometrical parameters and optimizing the index of the first ring of air-holes with filling different index liquid of the photonic crystal fiber. The results show that the optimized design photonic crystal fiber for pumping at 1550 nm is suitable for flat broadband and high coherent supercontinuum generation with only 4 kW input peak power in a 40 cm long of the photonic crystal fiber. It is also found the weaker the dispersion effect is, the more advantage to the high coherent broadband supercontinuum generation due to the self-phase modulation.

Salient object detection with fixation priori

There are two main areas in saliency detection: fixation prediction and salient object detection. Researchers always use bottom-up low-level features and straightforward rules for salient object detection. However these rules are unreliable in common scenes. As a result, most salient object detection technologies can gain a fine performance in limited situation. While in a more complex scene (such as PASCAL-S dataset), they may miss the really wanted salient objects. Fixation prediction is a technology of predicting the regions which can attract humans attention. Most fixation prediction technologies are based on the discoveries of neuroscience and cognitive psychology. Their rules for fixation prediction more accord with humans sensory mechanism. Thus, fixation map can provide a more reliable salient priori. Based on above reasons, we propose a novel salient object detection method with fixation priori. We refine fixation map to gain a reliable priori, and conduct salient object detection based on the priori. We perform experiment on two datasets, and find that our method outperforms the comparative state-of-art salient object detection technologies.

A novel application for concentrator photovoltaic in the field of agriculture photovoltaics

Agriculture photovoltaics is a trend setting area which has already led to a new industrial revolution. Shortage of land in some countries and desertification of land where regular solar panels are deployed are some of the major problems in the photovoltaic industry. Concentrator photovoltaics experienced a decline in applicability after the cost erosion of regular solar panels at the end of the last decade. We demonstrate a novel and unique application for concentrator photovoltaics tackling at a same time the issue of conventional photovoltaics preventing the land being used for agricultural purpose where ever solar panels are installed. We leverage the principle of diffractive and interference technology to split the sun light into transmitted wavelengths necessary for plant growth and reflected wavelengths useful for solar energy generation. The technology has been successfully implemented in field trials and sophisticated scientific studies have been undertaken to evaluate the suitability of this tec...

Theoretical investigation on the effect of ASE noise for amplified fiber loop ring-down gas sensing

The effect of spontaneous emission (ASE) noise produced by the erbium-doped fiber amplifier (EDFA) on the performance of amplified fiber loop ring-down gas sensing systems is theoretically investigated. The results show that the EDFA placed after the gas cell with a smaller ASE noise can improve the measurement accuracy. The more narrower the noise equivalent optical bandwidth of the optical band pass filter following the EDFA is, the up shift of baseline of ring-down signal can be more effectively suppressed and thus improving the measurement accuracy. It is also found the longer ring-down time can be obtained by reducing the input power due to the smaller gain fluctuations of the EDFA.

Continuous-Wave Fiber Cavity Ringdown Pressure Sensing Based on Frequency-Shifted Interferometry

We present a continuous-wave fiber cavity ringdown (FCRD) pressure-sensing method based on frequency-shifted interferometry (FSI). Compared with traditional CRD or FCRD techniques, this FSI-FCRD scheme deduces pressure by measuring the decay rate of continuous light exiting the fiber ringdown cavity (RDC) in the spatial domain (i.e., the CRD distance), without the requirement for optical pulsation and fast electronics. By using a section of fiber with the buffer layer stripped in the fiber RDC as the sensor head, pressures were measured within the range from 0 to 10.4 MPa. The sensitivity of 0.02356/(km∙MPa) was obtained with a measurement error of 0.1%, and the corresponding pressure resolution was 0.05 MPa. It was found that the measurement sensitivity can be improved by enlarging the interaction length of the sensor head. The results show the proposed sensor has the advantages of simple structure, low cost, high sensitivity, and high stability in pressure detection.

Facial-hydroxylated pure-phase BiFeO 3 with controllable micro-morphology: performance as a highly efficient visible light photocatalyst

The pure-phase BiFeO3 crystals with distinguished micro-morphologies were successfully prepared by a novel coprecipitation-hydrothermal collaborative synthesis method. Hydroxylation technique was innovatively employed to hydroxylate BiFeO3 samples. XPS and PL spectra proved that hydroxylation treatment indeed introduced more ·OH radicals on the surfaces of the BiFeO3 samples. Sample E (hydroxylated BiFeO3 ultra-thin slices) showed the highest photocatalytic activity. Hydroxylated BiFeO3 prepared in this work also showed high activities in water photo-oxidation reactions for producing oxygen gas. All hydroxylated samples showed notably enhanced photocatalytic activities due to the large specific surface areas, strong visible light responses, diminished recombination rates of the photo-excited carriers and excess ·OH radicals introduced by surface hydroxylation. All BiFeO3 samples showed good photochemical stabilities for reusage. This work provides valuable contributions in the future preparations and applications for BiFeO3 photocatalysts.

Ag modified Fe-doping TiO 2 nanoparticles and nanowires with enhanced photocatalytic activities for hydrogen production and volatile organic pollutant degradation

The Ag modified Fe-doping TiO2 nanoparticles and nanowires (Ag@Fe–TiO2 NPs and NWs) were prepared by convenient modified sol–gel and one-pot solvothermal method, respectively. The high photocatalytic activities of the Ag@Fe–TiO2 photocatalysts for H2 production and formaldehyde degradation were ascribed to the extended light-responsive range, accelerated migration, increased specific surface area and suppressed recombination of photogenerated carriers. All Ag@Fe–TiO2 samples showed good photochemical stabilities for reusage. The mechanisms for the significantly enhanced photocatalytic activities of the Ag@Fe–TiO2 NPs and NWs were proposed. Our research provides valuable contributions in the future preparations and applications for TiO2 based photocatalysts.