Laser-induced assembly is a promising technology for advancing micro/nano photonic devices.However,the dynamic process and the photothermal interaction in laser-induced assembly technique,as well as the role of laser ...Laser-induced assembly is a promising technology for advancing micro/nano photonic devices.However,the dynamic process and the photothermal interaction in laser-induced assembly technique,as well as the role of laser illumination pattern on the assembly structure have not been well investigated.In this paper,we prepare dark MoSe_(2) nanospheres with a facile solvothermal synthesis method and grow a concentric ring-shaped assembly with incident light following Fresnel circular-aperture diffraction.The impact of the illumination light filed on the structure of the assembly is investigated.The concentric ring-shaped assembly reveals focusing effect with about 4.87 times intensity amplification.Optical trap effect,photothermal effect,and tension effect are proved to synergistically enhance the trap stiffness and broaden trap region.This work gives an insight into the production of laser induced assembly,hence broadens the potential application of nanoparticles and assembly in micro-optics and photonic devices.展开更多
Metasurfaces composed of meta-atoms provide promising platforms for manipulating amplitude,phase,and polarization of light.However,the traditional design methods of metasurfaces are time consuming and laborious.Here,w...Metasurfaces composed of meta-atoms provide promising platforms for manipulating amplitude,phase,and polarization of light.However,the traditional design methods of metasurfaces are time consuming and laborious.Here,we propose a bidirectional cascaded deep neural network with a pretrained autoencoder for rapid design of dielectric metasurfaces in the range of 450 nm to 850 nm.The forward model realizes a prediction of amplitude and phase responses with a mean absolute error of 0.03.Meanwhile,the backward model can retrieve patterns of meta-atoms in an inverse-design manner.The availability of this model is demonstrated by database establishment,model evaluation,and generalization testing.Furthermore,we try to reveal the mechanism behind the model in a visualization way.The proposed approach is beneficial to reduce the cost of computation burden and improve nanophotonic design efficiency for solving electromagnetic on-demand design issues automatically.展开更多
Long period fiber gratings （LPFGs） with different spectral characteristics were fabricated with 1 kHz, 50 fs laser pulses. The contrast of resonant rejection band can be significantly increased by a proper amount of...Long period fiber gratings （LPFGs） with different spectral characteristics were fabricated with 1 kHz, 50 fs laser pulses. The contrast of resonant rejection band can be significantly increased by a proper amount of axial stress along a fiber during laser writing or post- processing with lower energy density laser irradiation. Variations of focal condition, pulse energy of laser irradiation and the number of grating periods lead to the generation of resonance rejection band of LPFGs from single-peak to multi-peak plus larger out-of-band loss. The out-of-band loss is primarily caused by Mie scattering from the laser processed cites, and it can be reduced by decreasing the duty cycle of grating pitch instead of lowing down the actual power of laser irradiation.展开更多
基金The research was funded by Natural Science Foundation of Tianjin City(No.18JCZDJC38200)the Fundamental Research Funds for the Central Universities,Nankai University(No.63201178)。
文摘Laser-induced assembly is a promising technology for advancing micro/nano photonic devices.However,the dynamic process and the photothermal interaction in laser-induced assembly technique,as well as the role of laser illumination pattern on the assembly structure have not been well investigated.In this paper,we prepare dark MoSe_(2) nanospheres with a facile solvothermal synthesis method and grow a concentric ring-shaped assembly with incident light following Fresnel circular-aperture diffraction.The impact of the illumination light filed on the structure of the assembly is investigated.The concentric ring-shaped assembly reveals focusing effect with about 4.87 times intensity amplification.Optical trap effect,photothermal effect,and tension effect are proved to synergistically enhance the trap stiffness and broaden trap region.This work gives an insight into the production of laser induced assembly,hence broadens the potential application of nanoparticles and assembly in micro-optics and photonic devices.
基金Fundamental Research Funds for the Central UniversitiesNankai University(63201178)+1 种基金Natural Science Foundation of Tianjin City(18JCZDJC38200)Nankai University-Taishan University cooperative project(F1033851)。
文摘Metasurfaces composed of meta-atoms provide promising platforms for manipulating amplitude,phase,and polarization of light.However,the traditional design methods of metasurfaces are time consuming and laborious.Here,we propose a bidirectional cascaded deep neural network with a pretrained autoencoder for rapid design of dielectric metasurfaces in the range of 450 nm to 850 nm.The forward model realizes a prediction of amplitude and phase responses with a mean absolute error of 0.03.Meanwhile,the backward model can retrieve patterns of meta-atoms in an inverse-design manner.The availability of this model is demonstrated by database establishment,model evaluation,and generalization testing.Furthermore,we try to reveal the mechanism behind the model in a visualization way.The proposed approach is beneficial to reduce the cost of computation burden and improve nanophotonic design efficiency for solving electromagnetic on-demand design issues automatically.
文摘Long period fiber gratings （LPFGs） with different spectral characteristics were fabricated with 1 kHz, 50 fs laser pulses. The contrast of resonant rejection band can be significantly increased by a proper amount of axial stress along a fiber during laser writing or post- processing with lower energy density laser irradiation. Variations of focal condition, pulse energy of laser irradiation and the number of grating periods lead to the generation of resonance rejection band of LPFGs from single-peak to multi-peak plus larger out-of-band loss. The out-of-band loss is primarily caused by Mie scattering from the laser processed cites, and it can be reduced by decreasing the duty cycle of grating pitch instead of lowing down the actual power of laser irradiation.
