Portable near-infrared diffusive light imager for breast cancer detection

We present a frequency-domain near-infrared optical tomography system designed for breast cancer detection, in conjunction, with conventional ultrasound. It features fast optical switching, threewavelength excitations, and avalanche photodiode as detectors. Laser diodes at 660, 780, and 830 nm are used as light sources and their outputs are distributed sequentially to one of nine source fibers. An equivalent 130-dB isolation between electrical signals from different source channels is achieved with the optical switches of very low crosstalk. Ten detection channels, each of which includes a silicon avalanche photodiode, detect diffusive photon density waves simultaneously. The dynamic range of an avalanche photodiode is about 20 to 30 dB higher than that of a photomultiplier tube, thus eliminating the need for multistep system gain control. The entire system is compact in size (<0.051 m3) and fast in data acquisition (less than 2 sec for a complete scan). Calibration and the clinical experiment results are presented in the paper.Electrical and Computer Engineerin

Ultrafast control of vortex microlasers

The development of classical and quantum information-processing technology calls for on-chip integrated sources of structured light. Although integrated vortex microlasers have been previously demonstrated, they remain static and possess relatively high lasing thresholds, making them unsuitable for high-speed optical communication and computing. We introduce perovskite-based vortex microlasers and demonstrate their application to ultrafast all-optical switching at room temperature. By exploiting both mode symmetry and far-field properties, we reveal that the vortex beam lasing can be switched to linearly polarized beam lasing, or vice versa, with switching times of 1 to 1.5 picoseconds and energy consumption that is orders of magnitude lower than in previously demonstrated all-optical switching. Our results provide an approach that breaks the long-standing trade-off between low energy consumption and high-speed nanophotonics, introducing vortex microlasers that are switchable at terahertz frequencies.This research was supported by the National Key Research and Development Program of China (grant no. SQ2018YFB220027), the Shenzhen Fundamental Research Fund (grant no. JCYJ20180507184613841), the Australian Research Council (grant no. DP200101168), and the National Science Foundation (grant no. PHY-1847240). The authors also acknowledge support from the Shenzhen Engineering Laboratory on Organic-Inorganic Perovskite Device

Trichoderma-amended biofertilizer stimulates soil resident Aspergillus population for joint plant growth promotion

Application of plant growth-promoting microbes (PGPMs) can contribute to sustainable agricultural ecosystems. From a three-year field experiment, we already found that the addition of Trichoderma bio-organic fertilizer (BF) significantly improved crop growth and yield compared to the application of organic fertilizer (OF). Here, we tracked the responses of soil bacterial and fungal communities to these treatments to find the key soil microbial taxa that contribute to the crop yield enhancement. We also examined if bacterial and fungal suspensions from resulting soils could improve plant growth upon inoculation into sterilized soil. Lastly, we isolated a number of fungal strains related to populations affected by treatments to examine their role in plant growth promotion. Results showed that consecutive application of BF impacted soil fungal communities, and the biological nature of plant growth promotion was confirmed via pot experiments using γ-sterilized versus none-sterilized soils collected from the field. Soil slurry experiments suggested that fungal, but not bacterial communities, played an important role in plant growth promotion, consistent with the results of our field experimental data. Fungal community analysis of both field and slurry experimental soils revealed increases in specific resident Aspergillus spp. Interestingly, Aspergillus tamarii showed no plant growth promotion by itself, but strongly increased the growth promotion activity of the Trichoderma amendment strain upon their co-inoculation. The effectiveness of the fungal amendment appears to stem not only from its own action, but also from synergetic interactions with resident fungal populations activated upon biofertilizer application

Random scattering of images and visibility enhancement via stochastic resonance

We investigate numerically the random scattering of two-dimensional (2-D) images and the visibility enhancement via stochastic resonance both in intensity and momentum spaces. The multiple scattering destroys the direct transmission of photons, but some ballistic photons carrying the image information still penetrate the scattering media. The underlying ballistic image signals exhibit an instability and are enhanced at the expense of scattering noise under self-focusing nonlinearity, which is described as a stochastic resonance. It is found that the higher ratio of ballistic signals to scattering noise triggers a stronger instability. The effect of visibility enhancement in different scattering conditions is discussed, and the 2-D quasiparticle motion model is designed to analyze the nonlinear dynamic evolution. Our results provide potential guidance for noisy image detection. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)

High-efficiency Terahertz-wave generation in silicon membrane waveguides

Terahertz (THz) wave generation via four-wave mixing (FWM) in silicon membrane waveguides is investigated with mid-infrared pump. The silicon membrane waveguides with width of 12 μm and heights varied from 14 μm to 17 μm, which can confine the THz-wave ranging from 7.5 THz to 10 THz due to the large refractive index contrast of the waveguide core and cladding, are designed to realize the collinear phase matching for THz-wave generation via FWM. Compared with the conventional parametric amplification or wavelength conversion based on FWM in silicon waveguides, which needs a pump wavelength located in the anomalous group-velocity dispersion (GVD) regime to realize broad phase matching, the pump wavelength located in the normal GVD regime is required to realize phase matching because of the large signal-pump frequency detuning. Phase matching for a tunable THz-wave ranging from 8.57 THz to 10 THz can be realized by tuning the pump wavelength from 4.2 μm to 4.4 μm in the silicon waveguide with rib height of 15 μm. Whilst, the phase matching bandwidth of THz-wave ranging from 7.7 THz to 10 THz can be achieved by tailoring the waveguide height from 14 μm to 17 μm when the pump wavelength is 4.3μm. Moreover, the conversion efficiency of the THz-wave generation is studied with different pump wavelengths and waveguide heights, the maximum conversion efficiency of 1.25 % at 9.2 THz can be obtained in a 6-mm long silicon waveguide when the pump wavelength is 4.3 μm and the waveguide height is 15 μm

Impact of sustained low oil prices on China's oil & gas industry system and coping strategies

The global sustained low oil prices have a significant impact on China's oil and gas industry system and the national energy security. This paper aims to find solutions in order to guarantee the smooth development of China's oil and gas industry system and its survival in such a severe environment. First, the origins of sustained low oil prices were analyzed. Then, based on those published data from IEA, government and some other authorities, this study focused on the development status, energy policies and the future developing trend of those main oil & gas producing countries. Investigations show that the low-price running is primarily contributed to the so-called oil and gas policies in the USA. It is predicted that national petroleum consumption will reach up to 6.0 × 108 t (oil) & 3300 × 108 m3 (gas) in 2020 and 6.8 × 108 t (oil) & 5200 × 108 m3 (gas) in 2030. For reducing the dependence on foreign oil and gas, the investment in the upstream of oil and gas industry should be maintained and scientific research should be intensified to ensure the smooth operation of the oil and gas production system. Considering China's national energy security strategy, the following suggestions were proposed herein. First, ensure that in China the yearly oil output reaches 2 × 108 t, while natural gas yield will be expected to be up to 2700 × 108 m3 in 2030, both of which should become the “bottom line” in the long term. Second, focus on the planning of upstream business with insistence on risk exploration investment, scientific and technological innovation and pilot area construction especially for low-permeability tight oil & gas, shale oil & gas reservoir development techniques. Third, encourage the in-depth reform and further growth especially in the three major state-owned oil & gas companies under adverse situations, and create more companies competent to offer overseas technical services by taking the opportunity of the “One Belt and One Road” policy. Finally, promote the new energy business and find solutions to turning those oil companies to integrated energy companies

Enhancement of quantum-enhanced LADAR receiver in nonideal phase-sensitive amplification

The phase-sensitive amplification (PSA) with an injected squeezed vacuum field is theoretically investigated in quantum-enhanced laser detection and ranging (LADAR) receiver. The theoretical model of the amplified process is derived to investigate the quantum fluctuations in detail. A new method of mitigating the unflat gain of nonideal PSA is proposed by adjusting the squeezed angle of the squeezed vacuum field. The simulation results indicate that signal-noise ratio (SNR) of system can be efficiently improved and close to the ideal case by this method. This research will provide an important potential in the applications of quantum-enhanced LADAR receiver

Multi-channel terahertz wavelength division demultiplexer with defects-coupled photonic crystal waveguide

Terahertz (THz) wavelength division demultiplexer based on a compact defects-coupled photonic crystal waveguide is proposed and demonstrated numerically. This device consists of an input waveguide that perpendicularly coupled with a series of defects cavities, each of which captures the resonance frequency from the input waveguide. Coupled-mode theory and finite element method are used to analyze the transmission properties of the structure. It is found that the transmission wavelength centered around 1THz can be adjusted by changing the geometrical parameters of defects cavities, which equals to THz waves generated by optical methods such as difference frequency generation and optical rectification. Applications in this frequency range are urgently needed. Furthermore, the highest transmission efficiency of 0.94 can be achieved when a perfect wavelength-selective mirror is set in the output waveguide