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The WRKY transcription factor family plays important regulatory roles in multiple biological processes in higher plants. They have been identified and functionally characterized in a number of plant species, but very little is known in Neolamarckia cadamba, a 'miracle tree' for its fast growth and potential medicinal resource in Southeast Asia. In this study, a total of 85 WRKY genes were identified in the genome of N. cadamba. They were divided into three groups according to their phylogenetic features, with the support of the characteristics of gene structures and conserved motifs of protein. The NcWRKY genes were unevenly distributed on 22 chromosomes, and there were two pairs of segmentally duplicated events. In addition, a number of putative cis-elements were identified in the promoter regions, of which hormone- and stress-related elements were shared in many NcWRKYs. The transcript levels of NcWRKY were analyzed using the RNA-seq data, revealing distinct expression patterns in various tissues and at different stages of vascular development. Furthermore, 16 and 12 NcWRKY genes were confirmed to respond to various hormone treatments and two different abiotic stress treatments, respectively. Moreover, the content of cadambine, the active metabolite used for the various pharmacological activities found in N. cadamba, significantly increased after Methyl jasmonate treatment. In addition, expression of NcWRKY64/74 was obviously upregulated, suggesting that they may have a potential function of regulating the biosynthesis of cadambine in response to MeJA. Taken together, this study provides clues into the regulatory roles of the WRKY gene family in N. cadamba. [ABSTRACT FROM AUTHOR]

In this paper, a highly sensitive fiber Bragg grating (FBG) interrogation system based on a dual-loop optoelectronic oscillator (OEO) with the enhanced Vernier effect has been proposed and experimentally demonstrated. Light reflected from the FBG sensor is used as the optical source of the OEO. By introducing dispersion in the OEO loop, the sensor information encoded in the FBG wavelength can be interrogated by detecting the frequency of microwave signal generated by the OEO loop. The dispersive media in OEO has two paths, one path is formed with a roll of dispersion compensation fiber (DCF), and the other path is formed with a roll of single-mode fiber (SMF). By designing the length of two paths with slightly difference, the Vernier effect is generated in the OEO. Since the dispersion of the two paths is opposite, an enhanced Vernier effect can be realized, which can significantly enhance the sensitivity. The experimental results prove the possibility of applying the concept of enhanced Vernier effect to the OEO for temperature sensing. The sensitivity is about 0.926 kHz/°C and 0.0912 kHz/°C for a single-loop OEO with DCF and SMF, respectively. By employing the enhanced Vernier effect, the sensitivity can be improved to 141.13 kHz/°C, which is estimated about 152.4 and 1547.5 times higher than that of the two single loops, respectively. Furthermore, sensitivity can be further improved by using a dispersive link with larger dispersion. [ABSTRACT FROM AUTHOR]

Er‐activated fiber lasers are critical for many significant applications, including fiber communication, gas sensing, lidar and military. Although the design of suitable fiber materials has improved the performance of Er‐activated fiber lasers, extension of their operation wavebands still remains a significant challenge. Here, a compact all‐fiber laser is proposed and demonstrated, which can support lasing beyond 1630 nm, based on an Er‐activated hybridized glass fiber. The collaborative theoretical analysis and experimental characterization indicate that various distinct structure units can form in the hybridized fiber. This leads to the notable inhomogeneous spectral broadening. By using this hybridized fiber, a tunable fiber laser device is constructed and the wavelength can be rationally tuned in the range from 1609 to 1631 nm by mechanically stretching the fiber Bragg gratings (FBGs) manufactured by the point‐by‐point femtosecond laser inscription. Furthermore, a new fiber sensor system based on this seldom exploration waveband is built and efficient ethylene detection is demonstrated. The results highlight that rational hybridization mediated short‐ and medium‐structure modification strategy, demonstrated here in Er‐activated fiber laser, can be extended to other rare‐earth glass fiber systems for the exploration of fiber devices at new wavebands. [ABSTRACT FROM AUTHOR]

Ultrafast fiber lasers offer a unique opportunity to implement optically a Poincaré mapping in the phase space of a variety of complex dissipative dynamical systems operating far from the equilibrium. Understanding of such complex optical dynamical systems revealing, for instance, ultrafast dynamics of the dissipative solitons (DSs) and more complex regimes is important for advancing specification and performance of the mode‐locked lasers used in a vast number of applications ranging from spectroscopy and medicine to metrology and telecom. Here, using the mode‐locked fiber laser as a test‐bed, the Shilnikov‐type ultrafast dynamics taking the form of randomly switching between noise‐like pulsing and quasi‐continuous‐wave regimes is experimentally demonstrated. The transient coherence recovery is revealed, during which the noise‐like pulse (NLP) is transformed into a coherent DS state and then returned to an incoherent NLP state. The demonstrated alternation of mode synchronization and desynchronization is both of practical importance for developing new types of partially mode‐locked lasers and of the fundamental interest for the nonlinear science in the context of revealing routes to the turbulence in distributed nonlinear systems. [ABSTRACT FROM AUTHOR]

We demonstrate a proposed fiber optic sensor based on detecting the envelope of a Vernier microwave frequency comb (VMFC). A mode-locked fiber laser was employed as a microwave frequency comb source. A fiber ring, functioning as a sensor head as well as a microwave photonic filter, tailored the amplitude of each harmonic of the microwave frequency comb. By carefully designing the fiber ring length and the frequency separation of the microwave frequency comb, the Vernier effect is generated on the photodiode recovered microwave frequency comb after the laser pulses pass through the fiber ring. The sensing information can be deduced by tracking the envelope of the VMFC. The experimental results of a temperature sensing test show that the frequency shifts of the envelope peak have a good linear relationship with temperature variation. Furthermore, the sensitivity of the proposed sensor system is controllable. [ABSTRACT FROM AUTHOR]

An $8\times \,\,16$ wavelength selective switch (WSS) with full contentionless switching is proposed and experimentally demonstrated. Utilizing two chips of liquid crystal on silicon, the optical wavelengths can be switched, attenuated, or blocked among 8 input ports and 16 output ports. The maximum insertion loss is less than 14 dB; the bandwidth tuning range is from 50 to 5000 GHz. The attenuation range is from 0 to 15 dB, and the optical blocking value is greater than 27 dB. Compared with the previous reports, the $8\times16$ WSS proposed in this letter is a truly contentionless WSS device with the highest number of input and output ports. [ABSTRACT FROM AUTHOR]

Botanical insecticides are considered an environmentally friendly approach to insect control because they are easily biodegraded and cause less environmental pollution compared to traditional chemical pesticides. In this study, we reported the insecticidal activities of the ingredients from Taiwania flousiana Gaussen ( T. flousiana ). Five compounds, namely helioxanthin (C1), taiwanin E (C2), taiwanin H (C3), 7,4'-dimethylamentoflavone (C4), and 7,7″-di- O -methylamentoflavone (C5), were isolated and tested against the second, third, and fourth instar larvae of Aedes aegypti . Our results indicated that all five compounds showed insecticidal activities, and helioxanthin, which is an aryltetralin lignan lactone, was the most effective with LC 50 values of 0.60, 2.82, and 3.12 mg/L, respectively, 48 h after application, with its activity against the second instar larvae similar to that of pyrethrin and better than that of rotenone. Further studies found that helioxanthin accumulated in the gastric cecum and the midgut and caused swelling of mitochondria with shallow matrices and fewer or disappeared crista. Additionally, our molecular mechanisms studies indicated that the significantly differentially expressed genes (DEGs) were mainly associated with mitochondria and the cuticle, among which the voltage-dependent anion-selective channel (VDAC) gene was the most down-regulated by helioxanthin, and VDAC is the potential target of helioxanthin by binding to specific amino acid residues (His 122 and Glu 147) via hydrogen bonds. We conclude that aryltetralin lignan lactone is a potential class of novel insecticides by targeting VDAC.

Flexible engineering of the complex shapes of the surface nanoscale axial photonics (SNAP) bottle microresonators (SBMs) is challenging for future nanophotonic technology applications. Here, we experimentally propose a powerful approach for the one-step fabrication of SBMs with simultaneous negative and positive radius variations, exhibiting a distinctive "bump-well-bump" profile. It is executed by utilizing two focused and symmetrical CO 2 laser beams exposed on the fiber surface for only several hundred milliseconds. The spectral characteristics of different eigenmodes are analyzed, providing deep insights into the complex physical processes during the CO 2 laser exposure. The shapes of the SBMs can be flexibly adjusted by the exposure time, laser power, and applied pre-strains. As a proof of this technique, the developed approach enables the efficient production of a bat SBM, ensuring a uniform field amplitude of the bat mode over the length exceeding 120 µm with 7% deviation. Our proposed technique provides a powerful technique for the efficient fabrication of SBMs with predetermined shapes, laying the groundwork for its applications on microscale optical signal processing, quantum computing, and so on.

A stable single wavelength random fiber laser (RFL) with a partial-reflection random fiber grating (PR-RFG) for high temperature sensing is proposed and demonstrated for the first time, to the best of our knowledge. The PR-RFG is fabricated with the help of a femtosecond laser, with its highest reflection peak significantly higher than all other reflection peaks, which can ensure the stability of this filter-free RFL. Theoretical calculations also show that such a PR-RFG should be designed with reflectivity in the range of ∼30 % -90 % to obtain one reflection peak significantly higher than other peaks. The threshold of this laser is only 6.4 mW. In addition, the RFL realizes temperature sensing in the range from 25°C to 500°C and has an optical signal-to-noise ratio of up to 70 dB.

Fiber Bragg grating (FBG) usually can be seen as a stack of Fabry-Perot (FP) cavities, which result in strong Bragg resonance through multi-cavity FP interference. In this Letter, we report surprising and interesting dual interference effects in a line-by-line (LBL) inscribed FBG with a femtosecond laser. Besides the well-known FP effect, the equivalent Mach-Zehnder interference (MZI) effect caused by mode interference can also be observed in the LBL FBG simultaneously. The experimental results of the comparison between the LBL FBGs and the point-by-point inscribed FBGs show that the dual interference effects are merely observed in the LBL FBGs. Meanwhile, the achieved MZI exhibits a strong polarization dependence. Sharing the merits of the FBG and MZI simultaneously, the achieved optical fiber device may find potential applications in optical fiber communication, fiber lasers, and multi-parameter sensor systems.

In this article, we propose and experimentally demonstrate a fiber Bragg grating (FBG) sensor interrogation technique based on an optoelectronic oscillator (OEO). The main components of the OEO loop in this proposed scheme contains an electro-optic modulator (EOM), a section of dispersive element, an electric filter, and a photodiode (PD). The reflection signal of the FBG sensor is functioning as the optical source of the OEO. The oscillating frequency of the OEO is determined by the overall time delay of the OEO loop. Due to the dispersive element in the loop, time delay of the OEO loop is a function of the OEO optical source wavelength. As a result, the wavelength change of the FBG can be converted into the oscillating frequency shift of the OEO. A proof-of-concept FBG based axial strain sensing experiment is carried out. The experimental results show that the frequency of the OEO generated microwave signals have a good linear relationship with the axial strain applied to the FBG. The sensitivity is about 58 Hz/με when using dispersion compensation fiber (DCF) with dispersion of -120 ps/(nm*km) as the dispersive medium and tracking the microwave signal with frequency near 2056.4 MHz, which is consistent with the theoretical calculation. The proposed method can also be applied to interrogate optical sensors based on detecting the wavelength change of the optical signals.

We report a stable and low-threshold Er-doped random fiber laser (RFL) based on a femtosecond-laser-inscribed random-distributed-grating array (RDGA) as the random feedback. The RDGA had a reflectivity of 93.5%, and its properties were numerically analyzed based on the transfer matrix method. The threshold of the laser was significantly reduced to 5.7 mW, and the linewidth was ~0.4 pm near the threshold as the Anderson localization effect existing in the RDGA significantly improved the laser quality factor (4 × 10 6 ). In addition, we propose a method to select RFL lasing modes by stretching a fiber grating filter used in the cavity with different axial strains. The center wavelength hardly drifted and the maximum jitter value of the peak power was less than 0.12 dB over 1 hour for the selected three lasing modes, which indicated that our laser operation was quite stable.

We demonstrated the subangstrom precise correction of surface nanoscale axial photonics (SNAP) micro-resonators by the femtosecond (fs) laser postprocessing technique for the first time. The internal stress can be induced by fs laser inscriptions in the fiber, causing nanoscale effective radius variation (ERV). However, the obtained ultraprecise fabrication usually undergoes multiple tries. Here, we propose a novel postprocessing technique based on the fs laser that significantly reduces the ERV errors and improves the fabrication precision without iterative corrections. The postexposure process is achieved at the original exposure locations using lower pulse energy than that in the initial fabrication process. The results show that the ERV is nearly proportional to the pulse energy of the postexposure process. The slope of the ERV versus the pulse energy is 0.07 Å/nJ. The maximum of the postprocessed ERV can reach 8.0 Å. The repeatability was experimentally verified by accomplishing the correction on three SNAP microresonators with the precision of 0.75 Å. The developed fabrication technique with fs laser enables SNAP microresonators with new breakthrough applications for optomechanics and filters.

For the first time, to the best of our knowledge, we observed the pulsating dissipative solitons in a mode-locked fiber laser at normal dispersion using the dispersive-Fourier transformation technology. The artificial saturable absorbers, as well as the birefringent filter formed by the nonlinear polarization rotation, make the polarization controller an effective component to adjust the laser state from stationary to pulsating. The pulsating dissipative solitons are accompanied with the spectrum breathing and oscillating structures due to the nonlinear pulse propagation. Our results can enhance the understanding of the pulsating solitons in the dissipative systems.

A temperature sensor employing the Vernier effect generated from a cascaded fiber rings based microwave photonic filter (MPF) is proposed and experimentally demonstrated. The structure of the fiber ring is used as a sensing element as well as the sampling and delaying component of the MPF in our proposed sensing scheme. The sensing characteristics of both single ring and cascaded fiber rings based sensors have been studied and compared. By employing two cascaded fiber rings of slightly different length, the Vernier effect can be generated in the frequency response of the MPF. The sensing interrogation of the cascaded fiber rings based sensor is conducted by detecting the frequency shift of the upper envelope of the measured frequency response curve. The experimental results show that the sensitivity of the cascaded fiber rings based sensor can be improved about 30 times compared with the single fiber ring based temperature sensor.

A novel passively mode-locked all-fiber laser using a chiral fiber grating as a polarization-selective element is demonstrated for the first time, to the best of our knowledge. The chiral fiber grating serves as a key component to form an artificial saturable absorber to realize mode locking through nonlinear polarization rotation in the cavity. The laser generates stable short pulses with energy of 0.34 nJ, a fundamental repetition rate of 3.27 MHz, and an FWHM bandwidth of 28 nm. We also show that harmonic mode-locked pulse trains of different orders can be obtained by increasing the pump power.

In this paper, a novel approach to implement switchable and tunable microwave frequency multiplication has been proposed and experimentally demonstrated. High order harmonics of microwave signal with external modulation technique can be selected by using a novel switchable dual-passband microwave photonic filter (MPF) based on a modified fiber Mach-Zehnder interferometer (FMZI) and a dispersive medium. By adjusting the polarization controllers in the modified FMZI, the passbands of the MPF can switch between lower frequency, higher frequency or dual-passband states, and by changing the length of the variable optical delay line (VODL) in the modified FMZI, the central frequencies of these passbands can also be tuned. Therefore, tunable and switchable microwave signal frequency multiplication can be achieved. The experimental results show that by modulating a driving signal with frequency of 2.5 GHz, a signal with frequency of 7.5 GHz, which is three times of the driving frequency, the other one with the frequency of 15 GHz, which is six times of the driving frequency can be generated and freely switchable between two frequencies and dual frequency states by simply adjusting the polarization controllers in the modified FMZI.