Polarization-separated feedback spectral beam combining source.

A novel, to the best of our knowledge, structure for spectral beam combining (SBC) is proposed, utilizing a polarization-separated feedback (PSF). A polarization separation element is introduced to separate the laser beam into a TE-polarized light and a TM-polarized light. The lower-power light is selected as the external feedback to adjust the resonant wavelength, while the other light is combined spectrally. Compared to the conventional SBC source with a similar feedback, the power and efficiency of the PSFSBC are improved by approximately 20%. Additionally, the beam quality in the non-SBC direction is optimized by 10%, and the power on the output coupler is reduced to nearly one-third. This provides an effective method for achieving an optimized SBC performance.

Tunable ultra-narrow linewidth diode laser for multiple metastable rare gas pumping.

We present what we believe to be a novel external cavity feedback structure based on a double-layer laser diode array with volume Bragg grating (VBG). Diode laser collimation and external cavity feedback result in a high-power and ultra-narrow linewidth diode laser pumping source with a central wavelength of 811.292 nm, spectral linewidth of 0.052 nm, and output power exceeding 100 W, with external cavity feedback and electro-optical conversion efficiencies exceeding 90% and 46%, respectively. The temperature of VBG is controlled to tune the central wavelength from 811.292 nm to 811.613 nm, covering the Kr* and Ar* absorption spectra. We believe this is the first report of an ultra-narrow linewidth diode laser that can pump two metastable rare gases.

A 1-µm-Band Injection-Locked Semiconductor Laser with a High Side-Mode Suppression Ratio and Narrow Linewidth.

We demonstrate a narrow-linewidth, high side-mode suppression ratio (SMSR) semiconductor laser based on the external optical feedback injection locking technology of a femtosecond-apodized (Fs-apodized) fiber Bragg grating (FBG). A single frequency output is achieved by coupling and integrating a wide-gain quantum dot (QD) gain chip with a Fs-apodized FBG in a 1-µm band. We propose this low-cost and high-integration scheme for the preparation of a series of single-frequency seed sources in this wavelength range by characterizing the performance of 1030 nm and 1080 nm lasers. The lasers have a maximum SMSR of 66.3 dB and maximum output power of 134.6 mW. Additionally, the lasers have minimum Lorentzian linewidths that are measured to be 260.5 kHz; however, a minimum integral linewidth less than 180.4 kHz is observed by testing and analyzing the power spectra of the frequency noise values of the lasers.

Spectral beam combining of diode lasers extended into the non-SBC direction.

An extended spectral beam combining (SBC) configuration that folds the optical path of the combining laser into the non-SBC direction and doubly narrows the SBC spectrum by introducing a right angular prism is proposed. Similar combined power and beam quality but half of the spectral width and a smaller size are demonstrated by comparing the standard SBC with the proposed SBC of the same 800nm laser bar. It provides an effective way to miniaturize the SBC size, improve the SBC stability and compress the SBC spectrum simultaneously. As far as we know, this study is also the first to report on folding the SBC optical path to the non-SBC direction, which provides a new idea for the SBC source.

Optimal Design and Analysis of 4.7 µm Hybrid Deep Dielectric High Efficiency Transmission Gratings.

There is currently no transmission grating with good diffraction efficiency in the 4.7 µm band. Metal gratings at this wavelength are all reflective gratings which has a diffraction efficiency of lower than 90% and lower laser damage threshold. In this paper, we bring up a design of a multi-layer transmission grating with both high diffraction efficiency and wide working wavelength band. We have proved that the transmission grating made of composite materials has an average diffraction effectiveness of more than 96% throughout the whole spectral range of 200 nm. Meanwhile, the theoretically computed transmission grating has a highest first-order diffraction efficiency of more than 99.77% at 4746 nm. This multilayer dielectric film transmission grating's optimized design may further boost spectral beam combining power, providing a practical technique for increasing SBC power and brightness.

Dense spectral beam combining of quantum cascade lasers by multiplexing a pair of blazed gratings.

A method of compressing spectral bandwidth in spectral beam combining (SBC) of quantum cascade lasers (QCLs) by multiplexing a pair of blazed gratings arranged in a V-shaped configuration is proposed. The spectral interval can be compressed by increasing the number of diffractions via the round-trip propagation between gratings. Experimental results show that the SBC spectral interval of three diffractions is narrowed to 1/3 that of a single diffraction. The SBC power can be further improved within a given spectrum range by increasing the number of QCLs, which provides a feasible scheme to scale the SBC power and the brightness of QCLs.

Novel scheme for non-invasive gut bioinformation acquisition with a magnetically controlled sampling capsule endoscope.

OBJECTIVE: Intestinal flora and metabolites are associated with multiple systemic diseases. Current approaches for acquiring information regarding microbiota/metabolites have limitations. We aimed to develop a precise magnetically controlled sampling capsule endoscope (MSCE) for the convenient, non-invasive and accurate acquisition of digestive bioinformation for disease diagnosis and evaluation. DESIGN: The MSCE and surgery were both used for sampling both jejunal and ileal GI content in the control and antibiotic-induced diarrhoea groups. The GI content was then used for microbiome profiling and metabolomics profiling. RESULTS: Compared with surgery, our data showed that the MSCE precisely acquired data regarding the intestinal flora and metabolites, which was effectively differentiated in different intestinal regions and disease models. Using MSCE, we detected a dramatic decrease in the abundance of Bacteroidetes, Patescibacteria and Actinobacteria and hippuric acid levels, as well as an increase in the abundance of Escherichia-Shigella and the 2-pyrrolidinone levels were detected in the antibiotic-induced diarrhoea model by MSCE. MSCE-mediated sampling revealed specific gut microbiota/metabolites including Enterococcus, Lachnospiraceae, acetyl-L-carnitine and succinic acid, which are related to metabolic diseases, cancers and nervous system disorders. Additionally, the MSCE exhibited good sealing characteristics with no contamination after sampling. CONCLUSIONS: We present a newly developed MSCE that can non-invasively and accurately acquire intestinal bioinformation via direct visualization under magnetic control, which may further aid in disease prevention, diagnosis, prognosis and treatment.

Application of stabilized sludge to extensive green roofs in Shanghai: Feasibility and nitrogen leaching control.

Extensive green roofs, in which commercial compost is usually used as organic component, have great potential to mitigate some environmental problems caused by urbanization, but carry risks of nutrients leaching into downstream aquatic. Stabilized sludge (SS) from wastewater treatment plants could be potentially used as nutrient component for green roof, but the effects on effluent quality are uncertain. To investigate the problem, a pilot experiment was conducted under field conditions, the effluent quality of green roof using SS was compared with green roofs using peat soil and controlled release fertilizer. In the field experiment, the nutrient concentrations in effluent of the green roof using SS (TN, NO3--N, NH4+-N and TP were 3.27 mg/L, 1.75 mg/L, 1.14 mg/L and 0.34 mg/L, respectively) were not significantly different from the green roofs using peat soil and controlled release fertilizer, and the chemical oxygen demand level (92 mg/L) was lower than the roofs using compost or commercial substrate. To reduce the environmental risks caused by the application of SS to green roofs, a laboratory test was carried out to analyze the effects of biochar and dual-substrate structure on nitrogen leaching. The results showed that both biochar and dual-substrate reduced nitrogen leaching, and nitrogen leaching from green roofs using SS was a combined effect of organic nitrogen mineralization during dry period and biological processes during wet period. A high temperature and low humidity environment which is common in green roofs reduced nitrate accumulation during dry period, and nitrate was transformed to other substances in gaseous form by denitrification, which tended to occur in long duration, low intensity rainfall events. The results suggest that the application of stabilized sludge to green roofs is feasible in area where average rain intensity is not high, preferably combined with amendment of biochar and a dual-substrate structure.

Optically Pumped Monolayer MoSe2 Excitonic Lasers from Whispering Gallery Mode Microcavities.

Developing integrable, nanoscale, and low-energy-consumption lasers is a crucial step toward on-chip optical communications and computing technologies. The strong exciton-photon interaction that emerged in monolayer transition metal dichalcogenides (TMDs) holds promise for engineering and integration. Herein, we prepare the MoSe2/microsphere cavities excitonic lasers by placing SiO2 microspheres on top of a monolayer MoSe2 film. By virtue of continuous-wave exciting MoSe2/microsphere whispering gallery mode (WGM) cavities, we realize multiple excitonic WGM lasing in the emission wavelength range of ∼750-875 nm at room temperature with tunable properties of free spectral range (FSR) and full width at half-maximum (fwhm) by varying the microsphere size. Theoretical calculations based on the finite element method (FEM) using COMSOL software were utilized to identify lasing modes and reveal the corresponding electric field distribution. These findings help to deepen fundamental understanding of excitonic WGM lasing and provide a promising research platform for integrable, scalable, and low-cost laser devices.

[Control Measure Effects on the Effluent Quality from Extensive Green Roofs Based on Stabilized Sludge Recycling].

Substrate type is an important factor affecting the quality of water deriving from rainfall onto extensively green roofed areas. Here, stabilized sludge was used as the main nutrient component of the substrate combined with biochar and a dual-substrate structure. Five green roof pilot facilities were constructed, and the effect of control measures on effluent quality was analyzed. The results showed that the stabilized sludge dosage was 3%, and the annual average mass concentrations of total nitrogen (TN) and nitrate nitrogen (NO3--N) were 3.27 mg·L-1 and 1.61 mg·L-1. The use of stabilized sludge as a nutrient component under real rainfall and temperature conditions in Shanghai did not cause significant leaching of TN and NO3--N. In order to further improve the quality of the effluent, biochar was used as an amendment measure. As a result, the concentrations of TN and NO3--N in the effluent were decreased to 2.16 mg·L-1 and 1.38 mg·L-1, respectively. Using an adsorption layer of pumice can alleviate the leaching of total phosphorus (TP) and chemical oxygen demand (COD). For the total nitrogen budget of each pilot facility, the retained TN was about 55% of the original TN after one year of operation. Thus, stabilized sludge could be used as a nutrient substrate to meet the long-term requirements of plants. In the substrate with biochar, the retained TN in the substrate and the NO3--N concentration in the effluent was decreased, which was related to the mineralization of organics during dry periods and the enhancement of denitrification during rainfall periods. Stabilized sludge was not a polluting source of N but was a source of P. Using biochar and a dual-substrate structure can effectively reduce the TN and COD load of the tested green roof facilities.

A new structure of permeable pavement for mitigating urban heat island.

The urban heat island (UHI) effect has been a great threat to human habitation, and how to mitigate this problem has been a global concern over decades. This paper addresses the cooling effect of a novel permeable pavement called evaporation-enhancing permeable pavement, which has capillary columns in aggregate and a liner at the bottom. To explore the efficiency of mitigating the UHI, bench-scale permeable pavement units with capillary columns were developed and compared with conventional permeable pavement. Criteria of capillary capacities of the column, evaporation rates, and surface temperature of the pavements were monitored under simulated rainfall and Shanghai local weather conditions. Results show the capillary column was important in increasing evaporation by lifting water from the bottom to the surface, and the evaporation-enhancing permeable pavement was cooler than a conventional permeable pavement by as much as 9.4°C during the experimental period. Moreover, the cooling effect of the former pavement could persist more than seven days under the condition of no further rainfall. Statistical analysis result reveals that evaporation-enhancing permeable pavement can mitigate the UHI effect significantly more than a conventional permeable pavement.

[Characteristics of Phthalic Acid Esters Pollution in Urban Surface Runoff in Shanghai, China].

Phthalic acid esters (PAEs) are still widely applied in China, and their pollution characteristics in urban surface runoff are important to receiving water protection. To evaluate the pollution characteristics of PAEs in urban runoff, six priority PAEs in road and roof runoff were monitored in nine storm events from June to September 2017 in Shanghai, China, and related rainwater samples were collected simultaneously. The average ∑6PAEs in urban road and roof runoff were 170.64 µg·L-1 and 40.92 µg·L-1, respectively, much higher than the values reported in Europe and Australia. Di-2-ethylhexyl phthalate (DEHP) was the dominating pollutant in both road and roof runoff. Significance analyses indicated there was no significant difference for low molecular weight(LMW)PAEs concentrations between road and roof runoff, whereas high molecular weight (HMW) PAEs concentrations in road runoff were significantly higher than those in roof runoff and rainwater (P<0.01), which implied that traffic was an important factor contributing to PAEs pollution in urban runoff. The pollutograph of PAEs, total suspended solids (TSS), and chemical oxygen demand (COD) concentrations vs rainfall duration for road runoff showed the same trend, and the first flush effect of PAEs was generally apparent. The influencing factors of PAEs in urban runoff were investigated. EMCs of PAEs in roof runoff were negatively correlated with rainfall intensity and positively correlated with TSS. EMCs of PAEs in road runoff were negatively correlated with rainfall volume and intensity and positively correlated with antecedent dry period, TSS, and COD. PAEs in surface runoff were significantly correlated with particulate matter. According to the criteria of the National Standard of Surface Water Quality of China, DEHP and DBP have limiting values of 8 µg·L-1 and 3 µg·L-1, respectively. The ratios of DEHP concentrations in road and roof runoff to the limiting values are 32 and 7, respectively. DBP concentrations were higher than the limiting value in most rainfall events for road runoff but lower than those for roof runoff. Without reasonable management measures, urban runoff could contaminate receiving water, especially drinking water sources.

CW 50W/M2 = 10.9 diode laser source by spectral beam combining based on a transmission grating.

An external cavity structure based on the -1st transmission grating is introduced to spectral beam combining a 970 nm diode laser bar. A CW output power of 50.8 W, an electro-optical conversion efficiency of 45%, a spectral beam combining efficiency of 90.2% and a holistic M(2) value of 10.9 are achieved. This shows a way for a diode laser source with several KW power and diffraction-limited beam quality at the same time.