The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex...The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.展开更多
In the printing industry,the common method of coloring relies on inks,which contains amounts of chemical agents,causing environment pollution.However,structural color achieves coloration through the refraction and dif...In the printing industry,the common method of coloring relies on inks,which contains amounts of chemical agents,causing environment pollution.However,structural color achieves coloration through the refraction and diffraction of light by periodic structure,offering eco-friendly and fade-resistant advantages,as well as colorful.In this study,screen printing was used to create patterned mask on paper substrates.Then,coated SiO_(2)microspheres on the mask to create structural color patterns with angle-dependent color characteristics.The patterns showed color changes from rose-red to orange to green by changing the viewing angle.By changing the color grayscale,the absorption of stray light by the substrate was enhanced,thereby the brightness and saturation of the structural color improved too.This method is simple,cost-effective,and environmentally friendly,and it has highly promising for the application in printing and anti-counterfeiting.展开更多
A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top ...A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top output with a high extinction ratio. Compared to filters consisting of the conventional Panda polarization maintaining fibre, filters based on a high birefringence photonic crystal fibre loop mirror have better temperature stability. This kind of filter can be expected to be used widely in Wavelength-division-multiplexing(WDM) systems in the future.展开更多
As a new type optical fiber,because of its particular optical properties,photonic crystal fibers(PCFs) have attracted the academic and industrial field widespread attention.So,the researches about PCFs have made great...As a new type optical fiber,because of its particular optical properties,photonic crystal fibers(PCFs) have attracted the academic and industrial field widespread attention.So,the researches about PCFs have made great progress in recent decade.In this paper,two kinds of PCFs constructions are numerically investigated and its leakage-loss properties are simulated.Based on the results of calculations,both the two types of PCFs are fabricated using glass capillary tube stacking.And the process of fiber drawing is described in this paper.展开更多
The one-dimensional photonic crystals of Ag/SiO_(2) system are studied to investigate the photonic band gaps (PBG). The samples were prepared by the ultra-high vacuum electron beam evaporation. The clear band gaps wer...The one-dimensional photonic crystals of Ag/SiO_(2) system are studied to investigate the photonic band gaps (PBG). The samples were prepared by the ultra-high vacuum electron beam evaporation. The clear band gaps were observed. Satisfactory agreement between experimental and calculated results was obtained without fitting. The thickness of SiO_(2 )film has influence on the photonic band gap, as well as it awfully affects the transmittance of Ag. More layers can get clearer PBG.展开更多
High-pressure crystallization behavior of poly(ethylene terephthalate)(PET)/biphenol-A polycarbonate(PC) blends were investigated by scanning electron microscopy(SEM) and atomic force microscopy(AFM).Two novel spherul...High-pressure crystallization behavior of poly(ethylene terephthalate)(PET)/biphenol-A polycarbonate(PC) blends were investigated by scanning electron microscopy(SEM) and atomic force microscopy(AFM).Two novel spherulitic structures,i.e.bamboo-shoot-like spherulite and brain-like spherulite,were observed in the polyester extended-chain crystals.The extended-chain lamellar crystal may be the substructure of these spherulites.This morphology,which is quite different from that of usual spherulite and extended-chain crystal,may promote the understanding of formation process and mechanism for both polymer spherulites and extended-chain crystals.展开更多
基金supported by the National Nat-ural Science Foundation of China(Nos.12192251,12174185,92163216,and 62288101).
文摘The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs.
文摘In the printing industry,the common method of coloring relies on inks,which contains amounts of chemical agents,causing environment pollution.However,structural color achieves coloration through the refraction and diffraction of light by periodic structure,offering eco-friendly and fade-resistant advantages,as well as colorful.In this study,screen printing was used to create patterned mask on paper substrates.Then,coated SiO_(2)microspheres on the mask to create structural color patterns with angle-dependent color characteristics.The patterns showed color changes from rose-red to orange to green by changing the viewing angle.By changing the color grayscale,the absorption of stray light by the substrate was enhanced,thereby the brightness and saturation of the structural color improved too.This method is simple,cost-effective,and environmentally friendly,and it has highly promising for the application in printing and anti-counterfeiting.
基金supported by the"100 Projects"of Creative Research for the Undergraduates of Nankai University under Grant(BX6-224)
文摘A novel all-fibre flat-top comb filter based on a high birefringence photonic crystal fibre loop mirror is proposed and demonstrated. We simulate theoretically its output spectra and experimentally realize a flat-top output with a high extinction ratio. Compared to filters consisting of the conventional Panda polarization maintaining fibre, filters based on a high birefringence photonic crystal fibre loop mirror have better temperature stability. This kind of filter can be expected to be used widely in Wavelength-division-multiplexing(WDM) systems in the future.
文摘As a new type optical fiber,because of its particular optical properties,photonic crystal fibers(PCFs) have attracted the academic and industrial field widespread attention.So,the researches about PCFs have made great progress in recent decade.In this paper,two kinds of PCFs constructions are numerically investigated and its leakage-loss properties are simulated.Based on the results of calculations,both the two types of PCFs are fabricated using glass capillary tube stacking.And the process of fiber drawing is described in this paper.
基金Supported by the National High Technology Development Program of China(Grant No.2003AA32720)Shanghai Nanotechnology Promotion Center(0352nm016, 0359nm204,0252nm084)+2 种基金Science and Technology Council of Shanghai(03dz11009)Fore-research of basic research project(2001CCA02800)the special Foundation for State Major Basic Research Programmeof China(Grant No.001CB610408)
文摘The one-dimensional photonic crystals of Ag/SiO_(2) system are studied to investigate the photonic band gaps (PBG). The samples were prepared by the ultra-high vacuum electron beam evaporation. The clear band gaps were observed. Satisfactory agreement between experimental and calculated results was obtained without fitting. The thickness of SiO_(2 )film has influence on the photonic band gap, as well as it awfully affects the transmittance of Ag. More layers can get clearer PBG.
文摘High-pressure crystallization behavior of poly(ethylene terephthalate)(PET)/biphenol-A polycarbonate(PC) blends were investigated by scanning electron microscopy(SEM) and atomic force microscopy(AFM).Two novel spherulitic structures,i.e.bamboo-shoot-like spherulite and brain-like spherulite,were observed in the polyester extended-chain crystals.The extended-chain lamellar crystal may be the substructure of these spherulites.This morphology,which is quite different from that of usual spherulite and extended-chain crystal,may promote the understanding of formation process and mechanism for both polymer spherulites and extended-chain crystals.
