Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quas...Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quasi-one-dimensional PdBr_(2) by using combined measurements of the angle-resolved polarized Raman spectroscopy(ARPRS) and anisotropic optical absorption spectrum. The analyses of ARPRS data validate the anisotropic Raman properties of the PdBr_(2) flake.And anisotropic optical absorption spectrum of PdBr_(2) nanoflake demonstrates distinct optical linear dichroism reversal. Photodetector constructed by PdBr_(2) nanowire exhibits high responsivity of 747 A·W^(-1) and specific detectivity of 5.8×10^(12) Jones. And the photodetector demonstrates prominent polarization-sensitive photoresponsivity under 405-nm light irradiation with large photocurrent anisotropy ratio of 1.56, which is superior to those of most of previously reported quasi-one-dimensional counterparts. Our study offers fundamental insights into the strong optical anisotropy exhibited by PdBr_(2), establishing it as a promising candidate for miniaturization and integration trends of polarization-related applications.展开更多
Linear dichroism (LD) spectroscopy is an important technique in the study of the orientation and organization of pigments in the photosynthetic membrane complexes in vivo and in vitro . In this work, the orient...Linear dichroism (LD) spectroscopy is an important technique in the study of the orientation and organization of pigments in the photosynthetic membrane complexes in vivo and in vitro . In this work, the orientation of the pigments in the isolated photosystem Ⅱ (PSⅡ) sub_core reaction center complexes was analyzed and characterized by means of low temperature absorption and LD spectroscopy. The preparations containing different amounts of CP47 isolated from spinach (Spinacia oleracea L.) chloroplast were used in order to investigate the orientation of pigments in the PSⅡ sub_core CP47/D1/D2/Cyt b_559 (CP47/D1/D2) complexes. Chlorophyll a (Chl a) absorbing at 680 nm in CP47/D1/D2/Cyt b_559 complex showed an orientation of the Q y transition parallel to the membrane plane. It is proposed that there are two forms of β_carotene (β_Car) in CP47/D1/D2/Cyt b_559 complex, denoted as β_Car (Ⅰ) and β_Car (Ⅱ), with different orientations, β_Car (Ⅰ) at 470 and 505 nm is roughly parallel to the membrane plane, and β_Car (Ⅱ) at 460 and 490 nm seems to be perpendicular orientation. Upon the photoinhibitory experiment β_Car (Ⅱ) was found to be photosensitive and easily photodamaged. It also showed that the positive LD signal observed at 680 nm was quite complicated. This signal is tentatively attributed to P680 and some Chl a of antenna in CP47 protein based upon our measurements.展开更多
Electronic absorption bands of conjugated linear carbon chain molecules, namely polyynes H(C≡C)nH (n=5-7), are exploited to devise light-polarizing films applicable to the UV. Laser ablated polyynes are separated in ...Electronic absorption bands of conjugated linear carbon chain molecules, namely polyynes H(C≡C)nH (n=5-7), are exploited to devise light-polarizing films applicable to the UV. Laser ablated polyynes are separated in size and dispersed in a film of polyvinyl alcohol (PVA), which is stretched to align the trapped linear polyyne molecules inside. As a nature of the structural anisotropy, transition dipole of the UV absorption for polyyne molecules is in parallel with the molecular axis and the absorption occurs only for the electromagnetic wave having the amplitude of its electric vector along the molecular axis. Aligned and fixed orientationally in the solid PVA film, polyyne molecules act as selective absorbers of one of the polarization components of incident light at particular wavelength. Using a light source of linearly polarized UV light, whose direction of polarization is rotatable, angular dependence of the absorption intensity is investigated for the stretched PVA film containing aligned polyyne molecules and analyzed in terms of an order parameter in the theory of linear dichroism.展开更多
Fluorescence polarization is related to the dipole orientation of chromophores,making fuores-cence polarization microscopy possible to_reveal structures and functions of tagged cellularorganelles and biological macrom...Fluorescence polarization is related to the dipole orientation of chromophores,making fuores-cence polarization microscopy possible to_reveal structures and functions of tagged cellularorganelles and biological macromolecules.Several recent super resolution techniques have beenapplied to fluorescence polarization microscopy,achieving dipole measurement at nanoscale.In this review,we summarize both difraction limited and super resolution fluorescence polari-zation microscopy techniques,as well as their applications in biological imaging.展开更多
In this work, the magnetocrystalline anisotropy energy(MAE) on the surface of FeCoalloy film is extracted from x-ray magnetic linear dichroism(XMLD) experiments. The result indicates that the surface MAE value is nega...In this work, the magnetocrystalline anisotropy energy(MAE) on the surface of FeCoalloy film is extracted from x-ray magnetic linear dichroism(XMLD) experiments. The result indicates that the surface MAE value is negatively correlated with thickness. Through spectrum calculations and analysis, we find that besides the thickness effect, another principal possible cause may be the shape anisotropy resulting from the presence of interface roughness. These two factors lead to different electron structures on the fermi surface with different exchange fields, which produces different spin–orbit interaction anisotropies.展开更多
We used CD spectroscopy to study the conformations of three cyclic peptides (CP10E: cyclo[Glu(OBz1)-Pro-Gly-Glu(OBzl), CP10K: cyclo[Lys(Z)-Pro Gly-Lys(Z)-Gly]2, CP12K: cyclo[Phe-Lys(Z)-Pro-Gly-Lys(Z)-Gly]2 and their c...We used CD spectroscopy to study the conformations of three cyclic peptides (CP10E: cyclo[Glu(OBz1)-Pro-Gly-Glu(OBzl), CP10K: cyclo[Lys(Z)-Pro Gly-Lys(Z)-Gly]2, CP12K: cyclo[Phe-Lys(Z)-Pro-Gly-Lys(Z)-Gly]2 and their correspon dent linear peptides (LP10E: Boc-[Glu(OBzl)-Pro-Gly-Glu(OBzl)-Gly]2-OPac, LP10K: Boc-[Lys(Z)-Pro-Lys(Z)-Pro]2-OMe, LP 12K: Bao- [-Lys(Z)-Pro-Gly-Lys(Z)-Gly]2- OMe) in three solvents of different polarity (chloroform, acetonitrile, 2,2,2-triliuroethanol), and it was found that all of linear and cyclicpeptides exist as γ-turn conformation in chloroform,however, in TFE & CH3CN solutions, the three linear peptides are in β Ⅱ-turn conformations. CP10E is β Ⅰ-turn conformation, CP10K & CP12K exist in more than one types of turn conformations. On the basis of our experiments, it was concluded: 1) In the presence of conformational constrained amino acids short linear peptides form obvious secondary structure, 2) The solvent polarity has influence on the peptide conformation and this influence on linear peptides is greater than that on cyclic peptides, 3) The backbone of cyclic peptide has constraint effect on its conformation and makes the secondary structure of cyclic peptide different from that of its relative linear peptide. This information might give some clues in the design of bioactive peptides with different receptor selectivity.展开更多
Two-dimensional magnets have received increasing attention since Cr_2Ge_2Te_6 and CrI_3 were experimentally exfoliated and measured in 2017. Although layered ferromagnetic metals were demonstrated at room temperature,...Two-dimensional magnets have received increasing attention since Cr_2Ge_2Te_6 and CrI_3 were experimentally exfoliated and measured in 2017. Although layered ferromagnetic metals were demonstrated at room temperature, a layered ferromagnetic semiconductor with high Curie temperature(Tc) is yet to be unveiled. Here, we theoretically predicted a family of high Tcferromagnetic monolayers, namely MnNX and CrCX(X = Cl, Br and I; C = S, Se and Te). Their Tcvalues were predicted from over 100 K to near 500 K with Monte Carlo simulations using an anisotropic Heisenberg model. Eight members among them show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These semiconducting monolayers also show extremely large anisotropy, i.e. ~10~1 for effective masses and ~10~2 for carrier mobilities, along the two in-plane lattice directions of these layers. Additional orbital anisotropy leads to a spin-locked linear dichroism, in different from previously known circular and linear dichroisms in layered materials.Together with the mobility anisotropy, it offers a spin-, dichroism-and mobility-anisotropy locking.These results manifest the potential of this 2D family for both fundamental research and high performance spin-dependent electronic and optoelectronic devices.展开更多
Two-dimensional(2D)van der Waals(vdW)magnetic materials with strong in-plane anisotropy can make possible novel applications such as optospintronics and strain sensors.In this work,the strong in-plane optical anisotro...Two-dimensional(2D)van der Waals(vdW)magnetic materials with strong in-plane anisotropy can make possible novel applications such as optospintronics and strain sensors.In this work,the strong in-plane optical anisotropy in 2D vdW antiferromagnet VOCl has been systematically investigated.The optical brightness and absorption coefficient exhibit evident periodic variation with the change of incident polarization,unveiling the strong in-plane anisotropic optical absorption.The Raman intensity in this material shows obvious dependence on the polarization angle of incident laser,demonstrating that the phonon properties possess strong in-plane anisotropy.Besides,we have also realized in-situ visualization of in-plane optical reflection anisotropy in this material.Moreover,the strong second harmonic generation(SHG)signal can only be detected when the incident polarization is along specific in-plane crystal orientations,illustrating the presence of strong in-plane nonlinear optical anisotropy.These findings will benefit the applications of VOCl in the field of polarization-dependent electronics and spintronics.展开更多
The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,th...The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,these applications are significantly limited by the challenges of air-stability,response time,and linearly dichroic ratio.Interestingly,palladium diselenide(PdSe2)with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure.We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation,and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements.Such unique linear dichroism,endows the PdSe2 photodetector powerful ability to detect polarized light.The photodetector based on 5L PdSe2,as tested with polarization-dependent photocurrent mapping,exhibited competitive capability to detect polarized light,achieving a significant photocurrent on/off ratio(>10^2),the quite fast response time(<11 ms)and robust linearly dichroic ratios(/max//min≈1.9 at 532 nm).These results are essential advance in the development of polarization-sensitive photodetector,a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.展开更多
Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional (2D) layered black phosphorus (BP) exh...Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional (2D) layered black phosphorus (BP) exhibits outstanding in-plane optical anisotropy with distinct linear dichroism and optical birefringence in the visible region, which are superior characteristics for ultrathin polarizing optics. Herein, taking advantage of polarized Raman spectroscopy, we demonstrate that layered BP with a nanometer thickness can remarkably alter the polarization state of a linearly-polarized laser and behave as an ultrathin optical polarization element in a BP-Bi2Se3 stacking structure by inducing the exceptionally polarized Raman scattering of isotropic Bi2Se3. Our findings provide a promising alternative for designing novel polarization optics based on 2D anisotropic materials, which can be easily integrated in micro- sized all-optical and optoelectronic devices.展开更多
The selection rule for angle-resolved polarized Raman(ARPR)intensity of phonons from standard grouptheoretical method in isotropic materials would break down in anisotropic layered materials(ALMs)due to birefringence ...The selection rule for angle-resolved polarized Raman(ARPR)intensity of phonons from standard grouptheoretical method in isotropic materials would break down in anisotropic layered materials(ALMs)due to birefringence and linear dichroism effects.The two effects result in depth-dependent polarization and intensity of incident laser and scattered signal inside ALMs and thus make a challenge to predict ARPR intensity at any laser incidence direction.Herein,taking in-plane anisotropic black phosphorus as a prototype,we developed a so-called birefringence-linear-dichroism(BLD)model to quantitatively understand its ARPR intensity at both normal and oblique laser incidences by the same set of real Raman tensors for certain laser excitation.No fitting parameter is needed,once the birefringence and linear dichroism effects are considered with the complex refractive indexes.An approach was proposed to experimentally determine real Raman tensor and complex refractive indexes,respectively,from the relative Raman intensity along its principle axes and incident-angle resolved reflectivity by Fresnel’s law.The results suggest that the previously reported ARPR intensity of ultrathin ALM flakes deposited on a multilayered substrate at normal laser incidence can be also understood based on the BLD model by considering the depth-dependent polarization and intensity of incident laser and scattered Raman signal induced by both birefringence and linear dichroism effects within ALM flakes and the interference effects in the multilayered structures,which are dependent on the excitation wavelength,thickness of ALM flakes and dielectric layers of the substrate.This work can be generally applicable to any opaque anisotropic crystals,offering a promising route to predict and manipulate the polarized behaviors of related phonons.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant Nos. 2022YFA1403203 and 2021YFA1600201)the National Natural Science Foundation of China (Grant No. 12274414)the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures (Contract No. JZHKYPT-2021-08)。
文摘Perpendicular optical reversal of the linear dichroism transition has promising applications in polarization-sensitive optoelectronic devices. We perform a systematical study on the in-plane optical anisotropy of quasi-one-dimensional PdBr_(2) by using combined measurements of the angle-resolved polarized Raman spectroscopy(ARPRS) and anisotropic optical absorption spectrum. The analyses of ARPRS data validate the anisotropic Raman properties of the PdBr_(2) flake.And anisotropic optical absorption spectrum of PdBr_(2) nanoflake demonstrates distinct optical linear dichroism reversal. Photodetector constructed by PdBr_(2) nanowire exhibits high responsivity of 747 A·W^(-1) and specific detectivity of 5.8×10^(12) Jones. And the photodetector demonstrates prominent polarization-sensitive photoresponsivity under 405-nm light irradiation with large photocurrent anisotropy ratio of 1.56, which is superior to those of most of previously reported quasi-one-dimensional counterparts. Our study offers fundamental insights into the strong optical anisotropy exhibited by PdBr_(2), establishing it as a promising candidate for miniaturization and integration trends of polarization-related applications.
基金Commissaire Energie de Atomique de Francethe 9th Five-Year Major Program of the National Natural Science Foundation of China(39890390)+1 种基金the State Key Basic Research Development Plan of China(973)(G1998010100)Innovation of Laboratory of Photosynthests Basic Research,Institute of Botany,The Chinese Acadeny of Sciences
文摘Linear dichroism (LD) spectroscopy is an important technique in the study of the orientation and organization of pigments in the photosynthetic membrane complexes in vivo and in vitro . In this work, the orientation of the pigments in the isolated photosystem Ⅱ (PSⅡ) sub_core reaction center complexes was analyzed and characterized by means of low temperature absorption and LD spectroscopy. The preparations containing different amounts of CP47 isolated from spinach (Spinacia oleracea L.) chloroplast were used in order to investigate the orientation of pigments in the PSⅡ sub_core CP47/D1/D2/Cyt b_559 (CP47/D1/D2) complexes. Chlorophyll a (Chl a) absorbing at 680 nm in CP47/D1/D2/Cyt b_559 complex showed an orientation of the Q y transition parallel to the membrane plane. It is proposed that there are two forms of β_carotene (β_Car) in CP47/D1/D2/Cyt b_559 complex, denoted as β_Car (Ⅰ) and β_Car (Ⅱ), with different orientations, β_Car (Ⅰ) at 470 and 505 nm is roughly parallel to the membrane plane, and β_Car (Ⅱ) at 460 and 490 nm seems to be perpendicular orientation. Upon the photoinhibitory experiment β_Car (Ⅱ) was found to be photosensitive and easily photodamaged. It also showed that the positive LD signal observed at 680 nm was quite complicated. This signal is tentatively attributed to P680 and some Chl a of antenna in CP47 protein based upon our measurements.
基金supported by the MEXT-Supported Program for the Strategic Research Foundation at Private Universities entitled Establishing a Best-Energy-Mix Research Center to Promote the Use of Solar Energy subsidized from the Ministry of Education, Culture, Sports, Science and Technology of Japan and Kindai University
文摘Electronic absorption bands of conjugated linear carbon chain molecules, namely polyynes H(C≡C)nH (n=5-7), are exploited to devise light-polarizing films applicable to the UV. Laser ablated polyynes are separated in size and dispersed in a film of polyvinyl alcohol (PVA), which is stretched to align the trapped linear polyyne molecules inside. As a nature of the structural anisotropy, transition dipole of the UV absorption for polyyne molecules is in parallel with the molecular axis and the absorption occurs only for the electromagnetic wave having the amplitude of its electric vector along the molecular axis. Aligned and fixed orientationally in the solid PVA film, polyyne molecules act as selective absorbers of one of the polarization components of incident light at particular wavelength. Using a light source of linearly polarized UV light, whose direction of polarization is rotatable, angular dependence of the absorption intensity is investigated for the stretched PVA film containing aligned polyyne molecules and analyzed in terms of an order parameter in the theory of linear dichroism.
基金supported by the National Instrument Development Special Program(2013YQ03065102)the Natural Science Foundation of China(614-75010,61428501)Science and Technology Commission of Shanghai Municipality(16DZ-1100300).
文摘Fluorescence polarization is related to the dipole orientation of chromophores,making fuores-cence polarization microscopy possible to_reveal structures and functions of tagged cellularorganelles and biological macromolecules.Several recent super resolution techniques have beenapplied to fluorescence polarization microscopy,achieving dipole measurement at nanoscale.In this review,we summarize both difraction limited and super resolution fluorescence polari-zation microscopy techniques,as well as their applications in biological imaging.
基金supported by the National Natural Science Foundation of China(Grant Nos.11075176 and 11375131)
文摘In this work, the magnetocrystalline anisotropy energy(MAE) on the surface of FeCoalloy film is extracted from x-ray magnetic linear dichroism(XMLD) experiments. The result indicates that the surface MAE value is negatively correlated with thickness. Through spectrum calculations and analysis, we find that besides the thickness effect, another principal possible cause may be the shape anisotropy resulting from the presence of interface roughness. These two factors lead to different electron structures on the fermi surface with different exchange fields, which produces different spin–orbit interaction anisotropies.
文摘We used CD spectroscopy to study the conformations of three cyclic peptides (CP10E: cyclo[Glu(OBz1)-Pro-Gly-Glu(OBzl), CP10K: cyclo[Lys(Z)-Pro Gly-Lys(Z)-Gly]2, CP12K: cyclo[Phe-Lys(Z)-Pro-Gly-Lys(Z)-Gly]2 and their correspon dent linear peptides (LP10E: Boc-[Glu(OBzl)-Pro-Gly-Glu(OBzl)-Gly]2-OPac, LP10K: Boc-[Lys(Z)-Pro-Lys(Z)-Pro]2-OMe, LP 12K: Bao- [-Lys(Z)-Pro-Gly-Lys(Z)-Gly]2- OMe) in three solvents of different polarity (chloroform, acetonitrile, 2,2,2-triliuroethanol), and it was found that all of linear and cyclicpeptides exist as γ-turn conformation in chloroform,however, in TFE & CH3CN solutions, the three linear peptides are in β Ⅱ-turn conformations. CP10E is β Ⅰ-turn conformation, CP10K & CP12K exist in more than one types of turn conformations. On the basis of our experiments, it was concluded: 1) In the presence of conformational constrained amino acids short linear peptides form obvious secondary structure, 2) The solvent polarity has influence on the peptide conformation and this influence on linear peptides is greater than that on cyclic peptides, 3) The backbone of cyclic peptide has constraint effect on its conformation and makes the secondary structure of cyclic peptide different from that of its relative linear peptide. This information might give some clues in the design of bioactive peptides with different receptor selectivity.
基金supported by the National Natural Science Foundation of China(11274380,91433103,11622437 and 61674171)the Fundamental Research Funds for the Central Universities of China+2 种基金the Research Funds of Renmin University of China(16XNLQ01)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2017 of Renmin University of China
文摘Two-dimensional magnets have received increasing attention since Cr_2Ge_2Te_6 and CrI_3 were experimentally exfoliated and measured in 2017. Although layered ferromagnetic metals were demonstrated at room temperature, a layered ferromagnetic semiconductor with high Curie temperature(Tc) is yet to be unveiled. Here, we theoretically predicted a family of high Tcferromagnetic monolayers, namely MnNX and CrCX(X = Cl, Br and I; C = S, Se and Te). Their Tcvalues were predicted from over 100 K to near 500 K with Monte Carlo simulations using an anisotropic Heisenberg model. Eight members among them show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These semiconducting monolayers also show extremely large anisotropy, i.e. ~10~1 for effective masses and ~10~2 for carrier mobilities, along the two in-plane lattice directions of these layers. Additional orbital anisotropy leads to a spin-locked linear dichroism, in different from previously known circular and linear dichroisms in layered materials.Together with the mobility anisotropy, it offers a spin-, dichroism-and mobility-anisotropy locking.These results manifest the potential of this 2D family for both fundamental research and high performance spin-dependent electronic and optoelectronic devices.
基金S.X.Y.is supported by the National Natural Science Foundation of China(NSFC)(No.51972007).
文摘Two-dimensional(2D)van der Waals(vdW)magnetic materials with strong in-plane anisotropy can make possible novel applications such as optospintronics and strain sensors.In this work,the strong in-plane optical anisotropy in 2D vdW antiferromagnet VOCl has been systematically investigated.The optical brightness and absorption coefficient exhibit evident periodic variation with the change of incident polarization,unveiling the strong in-plane anisotropic optical absorption.The Raman intensity in this material shows obvious dependence on the polarization angle of incident laser,demonstrating that the phonon properties possess strong in-plane anisotropy.Besides,we have also realized in-situ visualization of in-plane optical reflection anisotropy in this material.Moreover,the strong second harmonic generation(SHG)signal can only be detected when the incident polarization is along specific in-plane crystal orientations,illustrating the presence of strong in-plane nonlinear optical anisotropy.These findings will benefit the applications of VOCl in the field of polarization-dependent electronics and spintronics.
基金This work was supported by the National Natural Science Foundation of China(No.61775241)Youth Innovation Team(No.2019012)+3 种基金of CSU,Hunan province key research and development project(No.2019GK2233)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)the Project of State Key Laboratory of High-Performance Complex Manufacturing,Central South University(No.ZZYJKT2020-12)Z.W.L.acknowledges the funding support from the Australian Research Council(ARC Discovery Projects,DP180102976).
文摘The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,these applications are significantly limited by the challenges of air-stability,response time,and linearly dichroic ratio.Interestingly,palladium diselenide(PdSe2)with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure.We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation,and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements.Such unique linear dichroism,endows the PdSe2 photodetector powerful ability to detect polarized light.The photodetector based on 5L PdSe2,as tested with polarization-dependent photocurrent mapping,exhibited competitive capability to detect polarized light,achieving a significant photocurrent on/off ratio(>10^2),the quite fast response time(<11 ms)and robust linearly dichroic ratios(/max//min≈1.9 at 532 nm).These results are essential advance in the development of polarization-sensitive photodetector,a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.
文摘Manipulating the polarization of light at the nanoscale is essential for the development of nano-optical devices. Owing to its corrugated honeycomb structure, two-dimensional (2D) layered black phosphorus (BP) exhibits outstanding in-plane optical anisotropy with distinct linear dichroism and optical birefringence in the visible region, which are superior characteristics for ultrathin polarizing optics. Herein, taking advantage of polarized Raman spectroscopy, we demonstrate that layered BP with a nanometer thickness can remarkably alter the polarization state of a linearly-polarized laser and behave as an ultrathin optical polarization element in a BP-Bi2Se3 stacking structure by inducing the exceptionally polarized Raman scattering of isotropic Bi2Se3. Our findings provide a promising alternative for designing novel polarization optics based on 2D anisotropic materials, which can be easily integrated in micro- sized all-optical and optoelectronic devices.
基金the support from the National Key Research and Development Program of China(2016YFA0301204)the National Natural Science Foundation of China(11874350 and 51702352)+2 种基金the CAS Key Research Program of Frontier Sciences(ZDBS-LY-SLH004)China Postdoctoral Science Foundation(2019TQ0317)support from Youth Innovation Promotion Association Chinese Academy of Sciences(2020354)。
文摘The selection rule for angle-resolved polarized Raman(ARPR)intensity of phonons from standard grouptheoretical method in isotropic materials would break down in anisotropic layered materials(ALMs)due to birefringence and linear dichroism effects.The two effects result in depth-dependent polarization and intensity of incident laser and scattered signal inside ALMs and thus make a challenge to predict ARPR intensity at any laser incidence direction.Herein,taking in-plane anisotropic black phosphorus as a prototype,we developed a so-called birefringence-linear-dichroism(BLD)model to quantitatively understand its ARPR intensity at both normal and oblique laser incidences by the same set of real Raman tensors for certain laser excitation.No fitting parameter is needed,once the birefringence and linear dichroism effects are considered with the complex refractive indexes.An approach was proposed to experimentally determine real Raman tensor and complex refractive indexes,respectively,from the relative Raman intensity along its principle axes and incident-angle resolved reflectivity by Fresnel’s law.The results suggest that the previously reported ARPR intensity of ultrathin ALM flakes deposited on a multilayered substrate at normal laser incidence can be also understood based on the BLD model by considering the depth-dependent polarization and intensity of incident laser and scattered Raman signal induced by both birefringence and linear dichroism effects within ALM flakes and the interference effects in the multilayered structures,which are dependent on the excitation wavelength,thickness of ALM flakes and dielectric layers of the substrate.This work can be generally applicable to any opaque anisotropic crystals,offering a promising route to predict and manipulate the polarized behaviors of related phonons.