Phase transformations in a Ge1Sb2Te4 system induced by a single femtosecond laser exposure were investigated. The system has a multilayer structure of air/10 nm ZnS–SiO2/80 nm Ge1Sb2Te4/80 nm ZnS–SiO2/0.6 mm polycar...Phase transformations in a Ge1Sb2Te4 system induced by a single femtosecond laser exposure were investigated. The system has a multilayer structure of air/10 nm ZnS–SiO2/80 nm Ge1Sb2Te4/80 nm ZnS–SiO2/0.6 mm polycarbonate substrate. The morphology and contrast of marks written in both amorphous and crystalline backgrounds by single femtosecond pulses were characterized using an optical microscope. X-ray diffraction (XRD) was applied to identify the crystal structures transformed by single 108 fs shots. The characteristics and the conditions of phase transitions in the multilayer structure triggered by single shots were investigated. The pulse energy window for the crystallization in the Ge1Sb2Te4 system was established. The mechanism of phase change triggered by 108 fs laser pulses was discussed.展开更多
Metasurfaces have emerged as a flexible platform for shaping the electromagnetic field via the tailoring phase,amplitude,and polarization at will.However,the chromatic aberration inherited from building blocks’diffra...Metasurfaces have emerged as a flexible platform for shaping the electromagnetic field via the tailoring phase,amplitude,and polarization at will.However,the chromatic aberration inherited from building blocks’diffractive nature plagues them when used in many practical applications.Current solutions for eliminating chromatic aberration usually rely on searching through many meta-atoms to seek designs that satisfy both phase and phase dispersion preconditions,inevitably leading to intensive design efforts.Moreover,most schemes are commonly valid for incidence with a specific spin state.Here,inspired by the Rayleigh criterion for spot resolution,we present a design principle for broadband achromatic and polarization-insensitive metalenses using two sets of anisotropic nanofins based on phase change material Ge2Sb2Se4Te1.By limiting the rotation angles of all nanofins to either 0 deg or 90 deg,the metalens with a suitable numerical aperture constructed by this fashion allows for achromatic and polarization-insensitive performance across the wavelength range of 4–5μm,while maintaining high focusing efficiency and diffraction-limited performance.We also demonstrate the versatility of our approach by successfully implementing the generation of broadband achromatic and polarization-insensitive focusing optical vortex.This work represents a major advance in achromatic metalenses and may find more applications in compact and chip-scale devices.展开更多
基金Project(05PJ14037) supported by Foundations of Pujiang Talented Person Plans of Shanghai Science and Technology Project(0519) supported by Shanghai-Applied Materials Research and Development Fund Project(0552nm042) supported by the Shanghai Science and Technology Committee
文摘Phase transformations in a Ge1Sb2Te4 system induced by a single femtosecond laser exposure were investigated. The system has a multilayer structure of air/10 nm ZnS–SiO2/80 nm Ge1Sb2Te4/80 nm ZnS–SiO2/0.6 mm polycarbonate substrate. The morphology and contrast of marks written in both amorphous and crystalline backgrounds by single femtosecond pulses were characterized using an optical microscope. X-ray diffraction (XRD) was applied to identify the crystal structures transformed by single 108 fs shots. The characteristics and the conditions of phase transitions in the multilayer structure triggered by single shots were investigated. The pulse energy window for the crystallization in the Ge1Sb2Te4 system was established. The mechanism of phase change triggered by 108 fs laser pulses was discussed.
基金supported by the National Natural Science Foundation of China(Grant No.12004347)the Scientific and Technological Project in Henan Province(Grant Nos.222102210063 and 232102320057)+2 种基金the Aeronautical Science Foundation of China(Grant Nos.2020Z073055002 and 2019ZF055002)the Innovation and Entrepreneurship Training Program for College Students(Grant Nos.202210485007 and 202210485044)the Graduate Education Innovation Program Foundation(Grant No.2022CX53).
文摘Metasurfaces have emerged as a flexible platform for shaping the electromagnetic field via the tailoring phase,amplitude,and polarization at will.However,the chromatic aberration inherited from building blocks’diffractive nature plagues them when used in many practical applications.Current solutions for eliminating chromatic aberration usually rely on searching through many meta-atoms to seek designs that satisfy both phase and phase dispersion preconditions,inevitably leading to intensive design efforts.Moreover,most schemes are commonly valid for incidence with a specific spin state.Here,inspired by the Rayleigh criterion for spot resolution,we present a design principle for broadband achromatic and polarization-insensitive metalenses using two sets of anisotropic nanofins based on phase change material Ge2Sb2Se4Te1.By limiting the rotation angles of all nanofins to either 0 deg or 90 deg,the metalens with a suitable numerical aperture constructed by this fashion allows for achromatic and polarization-insensitive performance across the wavelength range of 4–5μm,while maintaining high focusing efficiency and diffraction-limited performance.We also demonstrate the versatility of our approach by successfully implementing the generation of broadband achromatic and polarization-insensitive focusing optical vortex.This work represents a major advance in achromatic metalenses and may find more applications in compact and chip-scale devices.
