Third-harmonic generation and imaging with resonant Si membrane metasurface

Dielectric metasurfaces play an increasingly important role in enhancing optical nonlinear generations owing to their ability to support strong light-matter interactions based on Mie-type multipolar resonances.Compared to metasurfaces composed of the periodic arrangement of nanoparticles,inverse,so-called,membrane metasurfaces offer unique possibilities for supporting multipolar resonances,while maintaining small unit cell size,large mode volume and high field enhancement for enhancing nonlinear frequency conversion.Here,we theoretically and experimentally investigate the formation of bound states in the continuum(BICs)from silicon dimer-hole membrane metasurfaces.We demonstrate that our BIC-formed resonance features a strong and tailorable electric near-field confinement inside the silicon membrane films.Furthermore,we show that by tuning the gap between the holes,one can open a leaky channel to transform these regular BICs into quasi-BICs,which can be excited directly under normal plane wave incidence.To prove the capabilities of such metasurfaces,we demonstrate the conversion of an infrared image to the visible range,based on the Third-harmonic generation(THG)process with the resonant membrane metasurfaces.Our results suggest a new paradigm for realising efficient nonlinear photonics metadevices and hold promise for extending the applications of nonlinear structuring surfaces to new types of all-optical near-infrared imaging technologies.

Broadband infrared imaging governed by guidedmode resonance in dielectric metasurfaces

Nonlinear metasurfaces have experienced rapid growth recently due to their potential in various applications,including infrared imaging and spectroscopy.However,due to the low conversion efficiencies of metasurfaces,several strategies have been adopted to enhance their performances,including employing resonances at signal or nonlinear emission wavelengths.This strategy results in a narrow operational band of the nonlinear metasurfaces,which has bottlenecked many applications,including nonlinear holography,image encoding,and nonlinear metalenses.Here,we overcome this issue by introducing a new nonlinear imaging platform utilizing a pump beam to enhance signal conversion through four-wave mixing(FWM),whereby the metasurface is resonant at the pump wavelength rather than the signal or nonlinear emissions.As a result,we demonstrate broadband nonlinear imaging for arbitrary objects using metasurfaces.A silicon disk-on-slab metasurface is introduced with an excitable guided-mode resonance at the pump wavelength.This enabled direct conversion of a broad IR image ranging from>1000 to 4000 nm into visible.Importantly,adopting FWM substantially reduces the dependence on high-power signal inputs or resonant features at the signal beam of nonlinear imaging by utilizing the quadratic relationship between the pump beam intensity and the signal conversion efficiency.Our results,therefore,unlock the potential for broadband infrared imaging capabilities with metasurfaces,making a promising advancement for next-generation all-optical infrared imaging techniques with chip-scale photonic devices.

Interaction between stress responses and circadian metabolism in metabolic disease

Circadian rhythms play crucial roles in orchestrating diverse physiological processes that are critical for health and disease.Dysregulated circadian rhythms are closely associated with various human metabolic diseases,including type 2 diabetes,cardiovascular disease,and non-alcoholic fatty liver disease.Modern lifestyles are frequently associated with an irregular circadian rhythm,which poses a significant risk to public health.While the central clock has a set periodicity,circadian oscillators in peripheral organs,particularly in the liver,can be entrained by metabolic alterations or stress cues.At the molecular level,the signal transduction pathways that mediate stress responses interact with the key determinants of circadian oscillation to maintain metabolic homeostasis under physiological or pathological conditions.In the liver,a number of nuclear receptors or transcriptional regulators,which are regulated by metabolites,hormones,the circadian clock,or environmental stressors,serve as direct links between stress responses and circadian metabolism.In this review,we summarize recent advances in the understanding of the interactions between stress responses(endoplasmic reticulum stress response,oxidative stress response,and inflammatory responses)and circadian metabolism,and the role of these interactions in the development of metabolic diseases.

Entity and relation extraction with rule-guided dictionary as domain knowledge

Entity and relation extraction is an indispensable part of domain knowledge graph construction,which can serve relevant knowledge needs in a specific domain,such as providing support for product research,sales,risk control,and domain hotspot analysis.The existing entity and relation extraction methods that depend on pretrained models have shown promising performance on open datasets.However,the performance of these methods degrades when they face domain-specific datasets.Entity extraction models treat characters as basic semantic units while ignoring known character dependency in specific domains.Relation extraction is based on the hypothesis that the relations hidden in sentences are unified,thereby neglecting that relations may be diverse in different entity tuples.To address the problems above,this paper first introduced prior knowledge composed of domain dictionaries to enhance characters’dependence.Second,domain rules were built to eliminate noise in entity relations and promote potential entity relation extraction.Finally,experiments were designed to verify the effectiveness of our proposed methods.Experimental results on two domains,including laser industry and unmanned ship,showed the superiority of our methods.The F1 value on laser industry entity,unmanned ship entity,laser industry relation,and unmanned ship relation datasets is improved by+1%,+6%,+2%,and+1%,respectively.In addition,the extraction accuracy of entity relation triplet reaches 83%and 76%on laser industry entity pair and unmanned ship entity pair datasets,respectively.