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Abstract Spodoptera frugiperda is a highly polyphagous pest worldwide with a wide host range that causes serious losses to many economically important crops. Recently, insect-microbe associations have become a hot spot in current entomology research, and the midgut microbiome of S. frugiperda has been investigated, while the effects of cruciferous vegetables remain unknown. In this study, the growth of S. frugiperda larvae fed on an artificial diet, Brassica campestris and Brassica oleracea for 7 days was analyzed. Besides, the microbial community and functional prediction analyses of the larval midguts of S. frugiperda fed with different diets were performed by high-throughput sequencing. Our results showed that B. oleracea inhibited the growth of S. frugiperda larvae. The larval midgut microbial community composition and structure were significantly affected by different diets. Linear discriminant analysis effect size (LEfSe) suggested 20 bacterial genera and 2 fungal genera contributed to different gut microbial community structures. The functional classification of the midgut microbiome analyzed by PICRUSt and FUNGuild showed that the most COG function categories of midgut bacterial function were changed by B. oleracea, while the guilds of fungal function were altered by B. campestris significantly. These results showed that the diversity and structure of the S. frugiperda midgut microbial community were affected by cruciferous vegetable feeding. Our study provided a preliminary understanding of the role of midgut microbes in S. frugiperda larvae in response to cruciferous vegetables.

Erbium doped integrated waveguide amplifier and laser prevail in power consumption, footprint, stability and scalability over the counterparts in bulk materials, underpinning the lightwave communication and large-scale sensing. Subject to the highly confined mode in the micro-to-nanoscale and moderate propagation loss, gain and power scaling in such integrated devices prove to be more challenging compared to their bulk counterparts. In this work, a thin cladding layer of tantalum pentoxide (Ta2O5) is employed in the erbium doped lithium niobate (LN) waveguide amplifier fabricated on the thin film lithium niobate on insulator (LNOI) wafer by the photolithography assisted chemo-mechanical etching (PLACE) technique. Above 20 dB small signal internal net gain is achieved at the signal wavelength around 1532 nm in the 10 cm long LNOI amplifier pumped by the diode laser at ∼980 nm. Experimental characterizations reveal the advantage of Ta2O5 cladding in higher optical gain compared with the air-clad amplifier, which is further explained by the theoretical modeling of the LNOI amplifier including the guided mode structures and the steady-state response of erbium ions.

Thin film lithium niobate (TFLN) has become a promising material platform for large scale photonic integrated circuits (PICs). As an indispensable component in PICs, on-chip electrically tunable narrow-linewidth lasers have attracted widespread attention in recent years due to their significant applications in high-speed optical communication, coherent detection, precision metrology, laser cooling, coherent transmission systems, light detection and ranging (LiDAR). However, research on electrically driven, high-power, and narrow-linewidth laser sources on TFLN platforms is still in its infancy. This review summarizes the recent progress on the narrow-linewidth compact laser sources boosted by hybrid TFLN/III-V semiconductor integration techniques, which will offer an alternative solution for on-chip high performance lasers for the future TFLN PIC industry and cutting-edge sciences. The review begins with a brief introduction of the current status of compact external cavity semiconductor lasers (ECSLs) and recently developed TFLN photonics. The following section presents various ECSLs based on TFLN photonic chips with different photonic structures to construct external cavity for on-chip optical feedback. Some conclusions and future perspectives are provided. [ABSTRACT FROM AUTHOR]

Subwavelength gratings play a fundamental and pivotal role in numerous science and applications for wave manipulation, exhibiting distinctive features such as filtering, phase manipulation, and anti‐reflection. However, conventional fabrication methods for ultrasmall periodic structures are constrained by the fundamental optical diffraction limit, making it challenging to produce subwavelength gratings for optics. Here, a novel technique is demonstrated to build a reconfigurable subwavelength photorefractive grating (SPG) in a thin‐film lithium niobate on the platform of an optical microcavity. Such SPGs are optically induced through the photorefractive effect and the subwavelength features originate from the spatial phase modulations of the pump's standing wave. The resulting SPGs lead to the mode splitting of two counter‐propagating modes inside the microcavity, exhibiting an Electromagnetically Induced Transparency (EIT)‐like transmission spectrum. Moreover, the unique subwavelength characteristic of SPGs enables first‐order quasi‐phase‐matching for backward second‐harmonic generation, a long‐standing problem in nonlinear optics. Also, free‐space‐to‐chip vertical nonlinear frequency conversion can be achieved in a similar manner. These results provide a flexible approach toward fabricating subwavelength gratings, which holds significant potential in various applications such as nonlinear frequency conversion, optical communication, sensing, and quantum technologies. [ABSTRACT FROM AUTHOR]

Integrated Raman microlasers, particularly discrete multi‐color lasers which are crucial for extending the emission wavelength range of chip‐scale laser sources to much shorter wavelengths, are highly in demand for various spectroscopy, microscopy analysis, and biological detection applications. However, integrated multi‐color Raman microlasers have yet to be demonstrated because of the requirement of high‐Q microresonators possessing large χ(2) nonlinearity, strong Raman phonon branches, and the challenge in the cavity‐enhanced multi‐photon hyper‐Raman scattering parametric process. In this work, integrated multi‐color Raman lasers have been demonstrated for the first time at weak pump levels, via the excitation of high‐Q (> 6 × 106) phase‐matched modes in single thin‐film lithium niobate (TFLN) microresonators by dispersion engineering. Raman lasing is observed at 1712 nm for a 1547‐nm pump threshold power of only 620 µW, representing the state of the art in the TFLN platform. Furthermore, multi‐color Raman lasers are realized at discrete wavelengths of 1712, 813, 533, and 406 nm with pump levels as low as 1.60 mW, which is more than two orders of magnitude lower than the current records (i.e., 200 mW) in bulk resonators, allowed by the fulfillment of the requisite conditions consisting of broadband natural phase match, multiple‐resonance, and high‐Q factors. [ABSTRACT FROM AUTHOR]

Raman microlasers form on-chip versatile light sources by optical pumping, enabling numerical applications ranging from telecommunications to biological detection. Stimulated Raman scattering (SRS) lasing has been demonstrated in optical microresonators, leveraging high Q factors and small mode volume to generate downconverted photons based on the interaction of light with the Stokes vibrational mode. Unlike redshifted SRS, stimulated anti-Stokes Raman scattering (SARS) further involves the interplay between the pump photon and the SRS photon to generate an upconverted photon, depending on a highly efficient SRS signal as an essential prerequisite. Therefore, achieving SARS in microresonators is challenging due to the low lasing efficiencies of integrated Raman lasers caused by intrinsically low Raman gain. In this work, high-Q whispering gallery microresonators were fabricated by femtosecond laser photolithography assisted chemo-mechanical etching on thin-film lithium niobate (TFLN), which is a strong Raman-gain photonic platform. The high Q factor reached 4.42 × 106, which dramatically increased the circulating light intensity within a small volume. And a strong Stokes vibrational frequency of 264 cm−1 of lithium niobate was selectively excited, leading to a highly efficient SRS lasing signal with a conversion efficiency of 40.6%. And the threshold for SRS was only 0.33 mW, which is about half the best record previously reported on a TFLN platform. The combination of high Q factors, a small cavity size of 120 μm, and the excitation of a strong Raman mode allowed the formation of SARS lasing with only a 0.46 mW pump threshold. [ABSTRACT FROM AUTHOR]

This article analyzes the research progress of pulsed light emitting diode (LED) light sources and aims to produce different wavelength pulse LED light source light panels, and to measure the variation of photosynthetic photon flux density (PPFD) at 25 cm below the lamp panel with the change of wavelength, frequency, and duty cycle of the light source. Under the condition of fixed light source duty cycle, the variation of photosynthetic rate with frequency was studied, and it was found that under different wavelengths, the plant photosynthetic rate had its respective optimized frequency; under the condition of fixed light source frequency, the variation of photosynthetic rate with duty cycle was studied, and it was found that under different duty cycles, the plant photosynthetic rate had its respective optimized duty cycle. Because its PPFD cannot be kept constant with the change of duty cycle and frequency under the condition of fixed frequency or duty cycle, the concept of photocarbon capa- bility is proposed with photocarbon capability=photosynthetic rate PPFD-1 =Pn PPFD-1, its biological significance is how many carbon dioxide molecules can be stimulated by a photon energy to photosynthesis. Under the condition of fixed light source duty cycle, the variation of photocarbon capacity with frequency change was studied. Each type of light source has a corresponding optimized frequency, corresponding to the maximum photosynthetic rate under this type of light source; each type of light source has a corresponding optimized frequency, corresponding to obtaining the maximum PPFD under this type of light source; each type of light source has a corresponding optimized frequency, which corresponds to the maximum photocarbon capacity under this type of light source. This article proposes a method to measure the corresponding relationship between plant lighting parameters and carbon reduction by proposing light carbon capacity. It is hoped that in the future, optical design can achieve the most economical carbon reduction by optimizing this parameter to obtain the optimal lighting conditions. [ABSTRACT FROM AUTHOR]

A new on‐chip diagnostic tool is developed, allowing for real‐time full characterization of waveguided ultrashort optical pulses. This technique, called transverse frequency‐resolved optical gating (T‐FROG), relies on second harmonic generation (SHG) in a transverse (surface emitting) geometry. The T‐FROG is implemented on a thin‐film lithium niobate (LN) platform, demonstrating its versatility and consistency in accurately characterizing waveguided femtosecond pulses, including information about chirp and self‐phase modulation. In contrast to traditional FROG techniques, T‐FROG represents a significant improvement as it provides temporal amplitude and phase profiles of ultrafast optical pulses directly inside photonic integrated circuits. The real‐time in situ characteristics and dynamics of optical pulses offered by T‐FROG show promise for their potential applications in the design, testing, and optimization of ultrafast photonic integrated circuits. [ABSTRACT FROM AUTHOR]

In general, a high‐quality (Q) microresonator can accommodate abundant whispering gallery modes (WGMs) with the mode number increasing with the dimensional sizes of the microresonator. Removing the unnecessary modes while reorganizing the remaining modes is of vital importance, which, however, has been proved challenging and usually results in a tradeoff with the Q of the microresonator. Here, an effective and controllable mode trimming and clustering mechanism is revealed underlying the generation of polygon and star modes in weakly perturbed tapered fiber‐coupled lithium niobate whispering gallery microresonators. Experimentally, various polygon and star modes are observed in sequence within a single microresonator by tuning the excitation wavelength or varying the coupling position between a tapered fiber and the circular microresonator, which can be well reproduced with the theoretical model. The finding offers a ubiquitous solution for a broad range of applications requiring elaborate selection and organization of the high‐Q WGMs. [ABSTRACT FROM AUTHOR]

In this paper, taking the 14837 annual audit reports of 4159 listed companies in Shanghai and Shenzhen Stock Exchanges from 2017 to 2020 as samples, and taking the information entropy value of KAM disclosures and the type of audit opinion as the agent indexes of the explanatory variable and the interpreted variable respectively, whether the disclosure of KAMs could improve audit quality had been empirically tested and analyzed. The results shown that: (1) The regression coefficient of information entropy value of KAMs disclosure was 0.1785, which shown a significant positive correlation, and was established at the level of 1% significance, that was to say, KAMs disclosure can improve audit quality. (2) The marginal effect coefficient was only 0.0081, which meant that there was some information redundancy in the KAMs disclosure and the enhancement effect on audit quality was weak. (3) In the robustness test, the interpreted variable was respectively replaced by audit cost (taking the natural logarithm of audit cost) and manipulated accrual profit (taking the absolute value of manipulated accrual profit), the regression coefficients of information entropy of KAMs were 0.0852 and 0.0017 respectively, which shown a significant positive correlation and were consistent with the results of the main regression test. (4) Further research shown that whether the industry in which the audited company was located and whether the audit institution was one of the international Big Four would affect the disclosure of KAMs, and then affect the audit quality in the same direction. The implementation effect of the new audit reporting standards was supported by these test evidences. [ABSTRACT FROM AUTHOR]

Photonic‐based low‐phase‐noise microwave generation with real‐time frequency tuning is crucial for a broad spectrum of subjects, including next‐generation wireless communications, radar, metrology, and modern instrumentation. Here, for the first time to the best of the authors' knowledge, narrow‐bandwidth dual‐wavelength microlasers are generated from nearly‐degenerate polygon modes in a high‐Q active lithium niobate microdisk. The record‐high‐Q (≈107) nearly‐degenerate polygon modes formation with independently controllable resonant wavelengths and free spectral ranges is enabled by the weak perturbation of the microdisks using a tapered fiber. Moreover, because a high spatial overlap factor between the pump and the dual‐wavelength laser modes is achieved, the gain competition between the two lasing modes spatially separated with a π‐phase difference is suppressed, leading to stable dual‐wavelength laser generation with low threshold, and in turn, the low noise microwave source. The stable beating signal confirms the low phase‐noise achieved in the tunable laser. Without the need of external phase stabilizers, the measured microwave signal shows a phase noise of −123 dBc Hz−1 and an electro‐optic tuning efficiency of −1.66 MHz V−1. The linewidth of the microwave signal is measured as 6.87 kHz, which is more than three orders of magnitude narrower than current records based on integrated dual‐lasers. [ABSTRACT FROM AUTHOR]

BACKGROUND The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a notorious pest that transmits the causal agent of huanglongbing (also called citrus greening disease). Resistance to insecticide in this destructive pest poses a serious threat to the citrus industry. To date, no systemic studies on genes coding for detoxification enzymes has been carried out on D. citri. RESULTS: Multiple transcriptomes were generated through deep sequencing of RNA libraries. Candidate genes potentially involved in detoxification including cytochrome P450 monooxygenases (CYPs), glutathione S‐transferases (GSTs), and esterases (ESTs) were systematically identified by searching the transcriptomes and a draft genome assembly. A total of 49, 14 and 20 genes were found encoding CYPs, GSTs, and ESTs, respectively, in D. citri. The total numbers of candidate detoxification genes were much smaller than the counterparts reported in other insect species, which may reflect the strict oligophagy of this insect species. Developmental stage‐ and tissue‐specific expression patterns of the identified genes as well as their responses to insecticide treatments identified a small set of genes that could participate in detoxifying plant secondary metabolites and insecticides. CONCLUSION: Our studies represent the most comprehensive investigation to date on identification, characterization and expression profiling of detoxification genes in D. citri. The information revealed in this study shall be useful in designing strategies to manage this important insect pest. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

High-quality lithium niobate (LN) thin-film microresonators provide an ideal platform for on-chip nonlinear optical applications. The strict phase-matching condition should be satisfied for an efficient nonlinear optical process, which requires dispersion engineering with an LN microresonator. However, this is challenging in single microresonator, resulting from the fabrication error. Here, we demonstrate strong nonlinear effects in a photonic molecule (PM) structure composed of two strongly coupled lithium niobate microdisks. The size mismatch of the microdisks enables phase matching by employing coupling-induced frequency splitting to compensate for the material and geometric dispersion. With a continuous wave excitation, rich nonlinear optical phenomena including cascaded four-wave mixing and stimulated Raman scattering were observed around the second harmonic signal. Meanwhile, an ultra-high four-wave mixing absolute conversion efficiency of 14% as obtained when the second harmonic signal power is at microwatts level. The LN PM is of great potential for applications in nonlinear integrated photonics. [ABSTRACT FROM AUTHOR]

Optical true delay lines (OTDLs) of low propagation losses, small footprints and high tuning speeds and efficiencies are of critical importance for various photonic applications. Here, we report fabrication of electro-optically switchable OTDLs on lithium niobate on insulator using photolithography assisted chemo-mechanical etching. Our device consists of several low-loss optical waveguides of different lengths which are consecutively connected by electro-optical switches to generate different amounts of time delay. The fabricated OTLDs show an ultra-low propagation loss of ∼ 0.03 dB/cm for waveguide lengths well above 100 cm. [ABSTRACT FROM AUTHOR]

The red palm weevil Rhynchophorus ferrugineus is a devastating, invasive pest that causes serious damages to palm trees, and its invasiveness depends on its strong ability of physiological and behavioral adaptability. Neuropeptides and their receptors regulate physiology and behavior of insects, but these protein partners have not been identified from many insects. Here, we systematically identified neuropeptide precursors and the corresponding receptors in the red palm weevil, and analyzed their tissue expression patterns under control conditions and after pathogen infection. A total of 43 putative neuropeptide precursors were identified, including an extra myosuppressin peptide was identified with amino acid substitutions at two conserved sites. Forty-four putative neuropeptide receptors belonging to three classes were also identified, in which neuropeptide F receptors and insulin receptors were expanded compared to those in other insects. Based on qRT-PCR analyses, genes coding for several neuropeptide precursors and receptors were highly expressed in tissues other than the nervous system, suggesting that these neuropeptides and receptors play other roles in addition to neuro-reception. Some of the neuropeptides and receptors, like the tachykinin-related peptide and receptor, were significantly induced by pathogen infection, especially sensitive to Bacillus thuringiensis and Metarhizium anisopliae. Systemic identification and initial characterization of neuropeptides and their receptors in the red palm weevil provide a framework for further studies to reveal the functions of these ligand- and receptor-couples in regulating physiology, behavior, and immunity in this important insect pest species. [ABSTRACT FROM AUTHOR]