Pump-probe-alternating photothermal interferometry for two-component gas sensing.

We demonstrate a high-sensitivity acetylene/methane gas sensor based on hollow-core fiber photothermal interferometry (PTI) with a pump-probe-alternating technique. This technique utilizes two distributed-feedback lasers as pump and probe beams alternatively for two gas components to facilitate photothermal phase modulation and detection through time-division multiplexing. With a 2.

Soliton rain in all-polarization-maintaining mode locked fiber laser.

For the first time the phenomenon of soliton rain is observed in a mode-locked fiber laser with all-polarization-maintaining (all-PM) architecture. The laser is mode-locked using a semiconductor saturable absorber mirror (SESAM) and operates in the all-normal dispersion (ANDi) regime. The operation state of the laser can be switched from dissipative soliton to soliton rain by simply raising the pump power, without any manipulation of the intracavity polarization state given that all components of the resonator are made of PM fibers.

Ultrahigh-resolution and ultra-simple fiber-optic sensor with resonant Sagnac interferometer.

The resonant fiber-optic sensor (RFOS) is well known for its high sensing resolution but usually suffers from high cost and system complexity. In this Letter, we propose an ultra-simple white-light-driven RFOS with a resonant Sagnac interferometer. By superimposing the output of multiple equivalent Sagnac interferometers, the strain signal is amplified during the resonance.

Parameter optimization of hollow-core optical fiber phase modulators.

We studied the effect of varying gas concentration, buffer gas, length, and type of fibers on the performance of optical fiber photothermal phase modulators based on CH-filled hollow-core fibers. For the same control power level, the phase modulator with Ar as the buffer gas achieves the largest phase modulation. For a fixed length of hollow-core fiber, there exists an optimal CH concentration that achieves the largest phase modulation.

Amplified Photothermal Phase Modulation for Carbon Dioxide Detection by Operating a Dual-Mode Interferometer at Destructive Interference.

Photothermal interferometry is a highly sensitive spectroscopic technique for trace gas detection. However, the performance of the state-of-the-art laser spectroscopic sensors is still insufficient for some high-precision applications. Here, we demonstrate optical phase-modulation amplification by operating a dual-mode optical fiber interferometer at destructive interference for ultrasensitive carbon dioxide detection.

Frequency-Division-Multiplexed Multicomponent Gas Sensing with Photothermal Spectroscopy and a Single NIR/MIR Fiber-Optic Gas Cell.

We report a multicomponent gas sensor based on hollow-core fiber (HCF) photothermal spectroscopy with frequency-division multiplexing (FDM). A single antiresonant HCF (AR-HCF) is used as the gas cell, which supports broadband transmission from near-infrared (NIR) to mid-infrared (MIR), covering the absorption lines of water vapor (HO) at 1.39 μm, carbon dioxide (CO) at 2.

Dual-comb photothermal spectroscopy.

Dual-comb spectroscopy (DCS) has revolutionized optical spectroscopy by providing broadband spectral measurements with unprecedented resolution and fast response. Photothermal spectroscopy (PTS) with a pump-probe configuration offers a highly sensitive gas sensing method, which is normally performed using a single-wavelength pump laser. The merging of PTS with DCS may enable a spectroscopic method by taking advantage of both technologies, which has never been studied yet.

Ethane detection with mid-infrared hollow-core fiber photothermal spectroscopy.

We report a compact mid-infrared (MIR) photothermal spectroscopic ethane (CH) sensor with a hollow-core negative-curvature-fiber (HC-NCF) gas cell. The HC-NCF supports low-loss transmission of an MIR pump (3.348 µm) and a near-infrared (NIR) probe (1.

Oxygen Gas Sensing with Photothermal Spectroscopy in a Hollow-Core Negative Curvature Fiber.

We demonstrate a compact all-fiber oxygen sensor using photothermal interferometry with a short length (4.3 cm) of hollow-core negative curvature fibers. The hollow-core fiber has double transmission windows covering both visible and near-infrared wavelength regions.

Geomagnetic field absence reduces adult body weight of a migratory insect by disrupting feeding behavior and appetite regulation.

The geomagnetic field (GMF) is well documented for its essential role as a cue used in animal orientation or navigation. Recent evidence indicates that the absence of GMF (mimicked by the near-zero magnetic field, NZMF) can trigger stress-like responses such as reduced body weight, as we have previously shown in the brown planthopper, Nilaparvata lugens. In this study, we found that consistent with the significantly decreased body weight of newly emerged female (-14.

Molecular Evidence for the Fitness of Cotton Aphid, in Response to Elevated CO From the Perspective of Feeding Behavior Analysis.

Rising atmospheric carbon dioxide (CO) concentration is likely to influence insect-plant interactions. Aphid, as a typical phloem-feeding herbivorous insect, has shown consistently more positive responses in fitness to elevated CO concentrations than those seen in leaf-chewing insects. But, little is known about the mechanism of this performance.

Experimental demonstration of a few-mode Raman amplifier with a flat gain covering 1530-1605 nm.

We design and experimentally demonstrate a few-mode Raman amplifier over the C+L band with a flat on-off gain of ∼4  dB, for the first time, to the best of our knowledge. A state-of-the-art gain bandwidth of 75 nm (1530-1605 nm) is achieved. The wavelength-dependent gain for both LP and LP modes is about 0.

Mode-interference-induced oscillation in propagation speed of fiber fuse in few-mode fibers.

We investigated the fiber fuse propagation speed in different kinds of few-mode fibers (FMFs) by combining heterodyne detection and time-frequency analysis. The periodic speed oscillation due to mode interference was observed, and we confirm that the characteristic length L (defined as the optical discharge propagation distance within a period of speed oscillation) is independent of the launched power, which is different from that observed in single-mode fibers. Moreover, we believe that the optical field modulation with enough intensity led to the variation of the optical discharge center position.

Host-selection behavior and physiological mechanisms of the cotton aphid, Aphis gossypii, in response to rising atmospheric carbon dioxide levels.

Rising atmospheric carbon dioxide (CO) levels can markedly affect the growth, development, reproduction and behavior of herbivorous insects, mainly by changing the primary and secondary metabolites of their host plants. However, little is known about the host-selection behavior and the respective intrinsic mechanism of sap-sucking insects in response to elevated CO. In this experiment, the host-selection behavior, as well as the physiological mechanism based on the analysis of growth, development and energy substances, and the expression of the olfactory-related genes of the cotton aphid, Aphis gossypii, were studied under ambient (407.

Orientation-insensitive azimuthally asymmetric mode rotator using chirally-coupled-core fiber.

We propose orientation-insensitive azimuthally asymmetric mode rotators (OI-AAMR) using chirally-coupled-core fiber. The proposed mode rotator can convert azimuthally asymmetric mode to the orthogonal degenerate mode without the requirement for angle alignment. An LP mode rotator with a rotation efficiency and an extinction ratio as high as 97% and 17 dB over C-band respectively, has been successfully demonstrated for any incident lobe orientation for the first time to the best of our knowledge.

Impacts of elevated CO on exogenous Bacillus thuringiensis toxins and transgene expression in transgenic rice under different levels of nitrogen.

Recent studies have highlighted great challenges of transgene silencing for transgenic plants facing climate change. In order to understand the impacts of elevated CO on exogenous Bacillus thuringiensis (Bt) toxins and transgene expression in transgenic rice under different levels of N-fertilizer supply, we investigated the biomass, exogenous Bt toxins, Bt-transgene expression and methylation status in Bt rice exposed to two levels of CO concentrations and nitrogen (N) supply (1/8, 1/4, 1/2, 1 and 2 N). It is elucidated that the increased levels of global atmospheric CO concentration will trigger up-regulation of Bt toxin expression in transgenic rice, especially with appropriate increase of N fertilizer supply, while, to some extent, the exogenous Bt-transgene expression is reduced at sub-N levels (1/4 and 1/2N), even though the total protein of plant tissues is reduced and the plant growth is restricted.

Circular-core single-mode polymer waveguide for high-density and high-speed optical interconnects application at 1550 nm.

We demonstrate circular-core 1550 nm single-mode polymer waveguides with a graded-index profile fabricated by commercially available UV-curable epoxies using so-called mosquito method. The relative index difference ∆n of the waveguides was designed to be 0.46% in order to guarantee both single-mode operation and good compatibility with standard single-mode fiber.

Observation of fiber fuse propagation speed with high temporal resolution using heterodyne detection and time-frequency analysis.

We demonstrate real-time observation of fiber fuse propagation speed with high temporal resolution of 2.4 μs by combining heterodyne detection and time-frequency analysis. The periodic oscillation of fiber fuse propagation speed over a power range from 2.

Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry.

We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability.

Rice stripe virus counters reduced fecundity in its insect vector by modifying insect physiology, primary endosymbionts and feeding behavior.

Virus-vector relationships can be complex and diverse as a result of long-term coevolution. Understanding these interactions is crucial for disease and vector management. Rice stripe virus (RSV) is known to be transovarially transmitted within its vector, Laodelphax striatellus, and causes serious rice stripe disease.

Bio-effects of near-zero magnetic fields on the growth, development and reproduction of small brown planthopper, Laodelphax striatellus and brown planthopper, Nilaparvata lugens.

Magnetic fields markedly affect the growth and development of many species of organisms potentially due to cryptochrome and endogenous presence of magnetic materials. Sensitivity to magnetic fields can also be involved in geomagnetic orientation by some long-distance migratory insects. In this study, near-zero magnetic fields (NZMF) in relation to normal geomagnetic fields (GMF) were setup using the Hypomagnetic Field Space System (HMFs) to investigate the effects of magnetic fields on the growth, development and reproduction of two species of migratory planthopper, the small brown planthopper (abbr.