暗电流在科学级电荷耦合器件(CCD)长时间曝光测试实验中是主要的噪声之一。实验测试了暗电流信号平均计数随曝光时间的变化关系,并经过计算得出-10℃和-20℃下暗电流分别为2.43ADU/(s.pixel)和0.4854ADU/(s.pixel),同时测试了暗电流随CC...暗电流在科学级电荷耦合器件(CCD)长时间曝光测试实验中是主要的噪声之一。实验测试了暗电流信号平均计数随曝光时间的变化关系,并经过计算得出-10℃和-20℃下暗电流分别为2.43ADU/(s.pixel)和0.4854ADU/(s.pixel),同时测试了暗电流随CCD制冷温度的变化特性,结果显示暗电流随温度类似指数函数形式变化。由于CCD机械快门的时间响应特性对科学级光学CCD的短时曝光计数的影响比较大,实验测试了CCD平均计数和曝光时间的关系,得出实验所用的TEK 512pixel×512pixel DB CCD的机械快门在18ms时能够完全打开。展开更多
Three new complex borate compounds K7CaBi2B15O30, K7CaLa2B15 O30 and K7BaBi2B15O30 have been synthesized by the high-temperature solution method.K7CaLa2B15O30and K7CaBi2B15O30crystallize in the chiral trigonal space g...Three new complex borate compounds K7CaBi2B15O30, K7CaLa2B15 O30 and K7BaBi2B15O30 have been synthesized by the high-temperature solution method.K7CaLa2B15O30and K7CaBi2B15O30crystallize in the chiral trigonal space group R32, while K7BaBi2B15O30 crystallizes in the noncentrosymmetric orthorhombic polar space group Pca21. All of the title compounds have similar three-dimensional crystal structures, which are composed of isolated B5 O10 groups and LaO6 or BiO6 octahedra, and K^+, Ca^2+, and Ba^2+ cations fill into the cavities to keep charge balance. Based on our research, in the system of K7 MIIRE2 B15O30(MII= Ca, Sr,Ba, Zn, Cd, Pb, K/RE0.5;RE = Sc, Y, La, Gd, Lu, Bi),K7BaBi2B15O30 is unique and crystallizes in a different space group, which enriches the structural chemistry of borate.Detailed structural analyses indicate that the structural variation is due to the difference in size and coordination number of the alkaline-earth metal cations. Besides, UV-Vis-NIR spectroscopy analysis and the second-harmonic generation(SHG) measurement on the powder samples show that K7CaBi2B15O30 exhibits a UV cutoff edge(about 282 nm) and a moderate SHG response(about 0.6 × KDP). In addition,thermal analysis and infrared spectroscopy were also presented. To better understand the structure-property relationships of the title compounds, the first-principles calculations have been performed.展开更多
Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that f...Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that fewlayers graphene has obvious nonlinear absorption and large nonlinear refraction, as investigated by the Z-scan technique in the mid-infrared（mid-IR） regime. Our study may not only, for the first time to our knowledge, verify the giant nonlinear refractive index of graphene(～10-7cm2∕W) at the mid-IR, which is 7 orders of magnitude larger than other conventional bulk materials, but also provide some new insights for graphene-based mid-IR photonics,potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.展开更多
Copper and rare earth-doped(RE = La, Gd, Nd) CuFe1.85RE0.15O4nano ferrites were prepared using the so nochemical method. The effective doping of rare-earth(La3+, Nd3+, Gd3+) ions with copper nanoferrites was confirmed...Copper and rare earth-doped(RE = La, Gd, Nd) CuFe1.85RE0.15O4nano ferrites were prepared using the so nochemical method. The effective doping of rare-earth(La3+, Nd3+, Gd3+) ions with copper nanoferrites was confirmed by X-ray diffraction. The tetrahedral and octahedral sites of the nano ferrites were identified through the Fourier transform infrared spectra. The doping of rare-earth elements enhances the optical bandgap energy of the nanoferrites that are observed through Ultraviolet-DRS spectra. The oxidation state of the elements Cu 2 p, La 3 d, Nd 3 d, Gd 3 d, Fe 2 p and O 1 s was analyzed. Scanning electron microscopy images indicate a spherical morphology with agglomeration to some elongate. The values of dielectric constant and conductivity decrease considerably due to doping rare-earth ions in copper nanoferrites. Low saturation magnetization and high coercivity values of rare earth-doped copper nanoferrites are observed from the typical hysteresis curves.展开更多
Surfaces with micro-nanoscale structures show different optical responses,including infrared reflection,thermal radiation,and protective coloration.Direct realization of structure camouflage is important for material ...Surfaces with micro-nanoscale structures show different optical responses,including infrared reflection,thermal radiation,and protective coloration.Direct realization of structure camouflage is important for material functionalities.However,external cloaks or coatings are necessary in structure camouflage,which limits the surface functionality.Here,we propose a novel strategy for the direct structure camouflage through topography inherited removal(TIR)with ultrafast laser,featuring pristine topography preservation and scattering surface fabrication.After multistep TIR,pristine topographies are partially and uniformly removed to preserve the original designed structures.Optical response changes show the suppression of specular reflection by uniformizing reflected light intensity to a low level on the inherited surface.We produce various structure camouflages on large scaled substrates,and demonstrate applications of information encryption in code extraction and word recognition through structure camouflage.The proposed strategy opens opportunities for infrared camouflage and other technologies,such as thermal management,device security,and information encryption.展开更多
A Weyl node is characterized by its chirality and tilt.We develop a theory of how nth-order nonlinear optical conductivity behaves under transformations of anisotropic tensor and tilt, which clarifies how chirality-de...A Weyl node is characterized by its chirality and tilt.We develop a theory of how nth-order nonlinear optical conductivity behaves under transformations of anisotropic tensor and tilt, which clarifies how chirality-dependent and-independent parts of optical conductivity transform under the reversal of tilt and chirality.Built on this theory, we propose ferromagnetic Mn Bi2Te4as a magnetoelectrically regulated, terahertz optical device, by magnetoelectrically switching the chiralitydependent and-independent DC photocurrents.These results are useful for creating nonlinear optical devices based on the topological Weyl semimetals.展开更多
文摘暗电流在科学级电荷耦合器件(CCD)长时间曝光测试实验中是主要的噪声之一。实验测试了暗电流信号平均计数随曝光时间的变化关系,并经过计算得出-10℃和-20℃下暗电流分别为2.43ADU/(s.pixel)和0.4854ADU/(s.pixel),同时测试了暗电流随CCD制冷温度的变化特性,结果显示暗电流随温度类似指数函数形式变化。由于CCD机械快门的时间响应特性对科学级光学CCD的短时曝光计数的影响比较大,实验测试了CCD平均计数和曝光时间的关系,得出实验所用的TEK 512pixel×512pixel DB CCD的机械快门在18ms时能够完全打开。
基金supported by the West Light Foundation of the CAS(2016-YJRC-2 and 2015 XBQN-B-11)the National Natural Science Foundation of China(51602341 and 91622107)+2 种基金the Natural Science Foundation of Xinjiang(2016D01B061)Tianshan Innovation Team Program(2018D14001)Key research project of Frontier Science of CAS(QYZDB-SSW-JSC049)
文摘Three new complex borate compounds K7CaBi2B15O30, K7CaLa2B15 O30 and K7BaBi2B15O30 have been synthesized by the high-temperature solution method.K7CaLa2B15O30and K7CaBi2B15O30crystallize in the chiral trigonal space group R32, while K7BaBi2B15O30 crystallizes in the noncentrosymmetric orthorhombic polar space group Pca21. All of the title compounds have similar three-dimensional crystal structures, which are composed of isolated B5 O10 groups and LaO6 or BiO6 octahedra, and K^+, Ca^2+, and Ba^2+ cations fill into the cavities to keep charge balance. Based on our research, in the system of K7 MIIRE2 B15O30(MII= Ca, Sr,Ba, Zn, Cd, Pb, K/RE0.5;RE = Sc, Y, La, Gd, Lu, Bi),K7BaBi2B15O30 is unique and crystallizes in a different space group, which enriches the structural chemistry of borate.Detailed structural analyses indicate that the structural variation is due to the difference in size and coordination number of the alkaline-earth metal cations. Besides, UV-Vis-NIR spectroscopy analysis and the second-harmonic generation(SHG) measurement on the powder samples show that K7CaBi2B15O30 exhibits a UV cutoff edge(about 282 nm) and a moderate SHG response(about 0.6 × KDP). In addition,thermal analysis and infrared spectroscopy were also presented. To better understand the structure-property relationships of the title compounds, the first-principles calculations have been performed.
基金supported by the National 973 Program of China (Grant No. 2012CB315701)the National Natural Science Foundation of China (Grant Nos. 61205125, 61222505, and 61475102)
文摘Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that fewlayers graphene has obvious nonlinear absorption and large nonlinear refraction, as investigated by the Z-scan technique in the mid-infrared（mid-IR） regime. Our study may not only, for the first time to our knowledge, verify the giant nonlinear refractive index of graphene(～10-7cm2∕W) at the mid-IR, which is 7 orders of magnitude larger than other conventional bulk materials, but also provide some new insights for graphene-based mid-IR photonics,potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.
基金Project supported by the Science and Engineering Research Board(SERB)New Delhi,India(SR/FTP/PS-068/2014)
文摘Copper and rare earth-doped(RE = La, Gd, Nd) CuFe1.85RE0.15O4nano ferrites were prepared using the so nochemical method. The effective doping of rare-earth(La3+, Nd3+, Gd3+) ions with copper nanoferrites was confirmed by X-ray diffraction. The tetrahedral and octahedral sites of the nano ferrites were identified through the Fourier transform infrared spectra. The doping of rare-earth elements enhances the optical bandgap energy of the nanoferrites that are observed through Ultraviolet-DRS spectra. The oxidation state of the elements Cu 2 p, La 3 d, Nd 3 d, Gd 3 d, Fe 2 p and O 1 s was analyzed. Scanning electron microscopy images indicate a spherical morphology with agglomeration to some elongate. The values of dielectric constant and conductivity decrease considerably due to doping rare-earth ions in copper nanoferrites. Low saturation magnetization and high coercivity values of rare earth-doped copper nanoferrites are observed from the typical hysteresis curves.
基金supported by the National Natural Science Foundation of China(No.52075289).
文摘Surfaces with micro-nanoscale structures show different optical responses,including infrared reflection,thermal radiation,and protective coloration.Direct realization of structure camouflage is important for material functionalities.However,external cloaks or coatings are necessary in structure camouflage,which limits the surface functionality.Here,we propose a novel strategy for the direct structure camouflage through topography inherited removal(TIR)with ultrafast laser,featuring pristine topography preservation and scattering surface fabrication.After multistep TIR,pristine topographies are partially and uniformly removed to preserve the original designed structures.Optical response changes show the suppression of specular reflection by uniformizing reflected light intensity to a low level on the inherited surface.We produce various structure camouflages on large scaled substrates,and demonstrate applications of information encryption in code extraction and word recognition through structure camouflage.The proposed strategy opens opportunities for infrared camouflage and other technologies,such as thermal management,device security,and information encryption.
基金Project supported by the National Key R&D Program of China (Grant Nos.2018YFA, 0305601, and 2021YFA1400100)the National Natural Science Foundation of China (Grant Nos.12274003, 11725415, and 11934001)the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0302600)。
文摘A Weyl node is characterized by its chirality and tilt.We develop a theory of how nth-order nonlinear optical conductivity behaves under transformations of anisotropic tensor and tilt, which clarifies how chirality-dependent and-independent parts of optical conductivity transform under the reversal of tilt and chirality.Built on this theory, we propose ferromagnetic Mn Bi2Te4as a magnetoelectrically regulated, terahertz optical device, by magnetoelectrically switching the chiralitydependent and-independent DC photocurrents.These results are useful for creating nonlinear optical devices based on the topological Weyl semimetals.
基金supported by the National Natural Science Foundation of China(62175061,52172140,52221001,and 52072117)the Natural Science Foundation of Hunan Province(2022JJ30167)+1 种基金the Outstanding Scholarship Program of Hunan Province(2021JJ10021)China Postdoctoral Science Foundation(BX20220104,2022M720046 and 2022TQ0100)。
