Plasmonic grating structures have been shown effective at increasing near-field optical enhancement. A doublewidth plasmonic grating design is introduced, where each period has two alternating metal widths separated b...Plasmonic grating structures have been shown effective at increasing near-field optical enhancement. A doublewidth plasmonic grating design is introduced, where each period has two alternating metal widths separated by a nanogap. With this new design, analysis has shown that plasmonic resonances couple between each metal section,resulting in even greater optical enhancement compared with single-width gratings. The geometry that gives the greatest optical enhancement has been determined with a computational model. This work demonstrates that the increased enhancement is due to hybridized modes that couple between the two grating segments.展开更多
For the last few years,the research interest in magnetoelectric(ME)effect,which is the cross-coupling between ferroelectric and magnetic ordering in multiferroic materials,has experienced a significant revival.The ext...For the last few years,the research interest in magnetoelectric(ME)effect,which is the cross-coupling between ferroelectric and magnetic ordering in multiferroic materials,has experienced a significant revival.The extensive recent studies are not only conducted towards the design of sensors,actuators,transducers,and memory devices by taking advantage of the cross-control of polarization(or magnetization)by magnetic(or electric)fields,but also aim to create a clearer picture in understanding the sources of ME responses and the novel effects associated with them.Here we derive analytical models allowing to understand the striking and novel dynamics of ME effects in multiferroics and further confirm it with atomistic simulations.Specifically,the role of strain is revealed to lead to the existence of electroacoustic magnons,a new quasiparticle that mixes acoustic and optical phonons with magnons,which results in resonances and thus a dramatic enhancement of magnetoelectric responses.Moreover,a unique aspect of the dynamical quadratic ME response under a magnetic field with varying frequencies,which is the second harmonic generation(SHG),has not been discussed prior to the present work.These SHGs put emphasis on the fact that nonlinearities should be considered while dealing with such systems.展开更多
GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we ...GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we present explorative investigations of GeSn heterostructure laser diodes with various layer thicknesses and material compositions.Cap layer material was studied by using Si_(0.03)Ge_(0.89)Sn_(0.08) and Ge_(0.95)Sn_(0.05),and cap layer total thickness was also compared.The 190 nm SiGeSn-cap device had threshold of 0.6 kA/cm^(2) at 10 K and a maximum operating temperature(T_(max)) of 100 K,compared to 1.4 kA/cm^(2) and 50 K from 150 nm SiGeSn-cap device,respectively.Furthermore,the 220 nm GeSn-cap device had 10 K threshold at 2.4 kA/cm^(2) and T_(max) at 90 K,i.e.,higher threshold and lower maximal operation temperature compared to the SiGeSn cap layer,indicating that enhanced electron confinement using SiGeSn can reduce the threshold considerably.The study of the active region material showed that device gain region using Ge_(0.87)Sn_(0.13) had a higher threshold and lower T_(max),compared to Ge_(0.89)Sn_(0.11).The performance was affected by the metal absorption,free carrier absorption,and possibly defect density level.The maximum peak wavelength was measured as 2682 nm at 90 K by using Ge_(0.87)Sn_(0.13) in gain regions.The investigations provide directions to the future GeSn laser diode designs toward the full integration of group-Ⅳ photonics on a Si platform.展开更多
基金Arkansas Biosciences Institute(ABI)Iraqi Ministry of Higher Education and Scientific ResearchSPIE
文摘Plasmonic grating structures have been shown effective at increasing near-field optical enhancement. A doublewidth plasmonic grating design is introduced, where each period has two alternating metal widths separated by a nanogap. With this new design, analysis has shown that plasmonic resonances couple between each metal section,resulting in even greater optical enhancement compared with single-width gratings. The geometry that gives the greatest optical enhancement has been determined with a computational model. This work demonstrates that the increased enhancement is due to hybridized modes that couple between the two grating segments.
基金S.O.S.,B.X.,and L.B.acknowledge the DARPA Grant Number HR0011-15-2-0038(under the MATRIX program)S.P.acknowledges ONR Grant Number N00014-17-1-2818 and also appreciates support of RFBR 19-52-53030 GFEN+3 种基金C.P.thanks the ARO grant W911NF-16-1-0227B.X.also acknowledges the startup fund from Soochow University and the support from Priority Academic Program Development(PAPD)of Jiangsu Higher Education InstitutionsWe appreciate the support of MRI Grant Number 0722625 from NSF,ONR Grant Number N00014-15-1-2881(DURIP)as well as a Challenge grant from the Department of Defense,and also acknowledge the High Performance Computing Center at the University of Arkansas.
文摘For the last few years,the research interest in magnetoelectric(ME)effect,which is the cross-coupling between ferroelectric and magnetic ordering in multiferroic materials,has experienced a significant revival.The extensive recent studies are not only conducted towards the design of sensors,actuators,transducers,and memory devices by taking advantage of the cross-control of polarization(or magnetization)by magnetic(or electric)fields,but also aim to create a clearer picture in understanding the sources of ME responses and the novel effects associated with them.Here we derive analytical models allowing to understand the striking and novel dynamics of ME effects in multiferroics and further confirm it with atomistic simulations.Specifically,the role of strain is revealed to lead to the existence of electroacoustic magnons,a new quasiparticle that mixes acoustic and optical phonons with magnons,which results in resonances and thus a dramatic enhancement of magnetoelectric responses.Moreover,a unique aspect of the dynamical quadratic ME response under a magnetic field with varying frequencies,which is the second harmonic generation(SHG),has not been discussed prior to the present work.These SHGs put emphasis on the fact that nonlinearities should be considered while dealing with such systems.
基金Air Force Office of Scientific Research (FA9550-18-1-0045, FA9550-19-1-0341, FA9550-21-1-0347)。
文摘GeSn lasers enable the monolithic integration of lasers on the Si platform using all-group-Ⅳ direct-bandgap material.The GeSn laser study recently moved from optical pumping into electrical injection.In this work,we present explorative investigations of GeSn heterostructure laser diodes with various layer thicknesses and material compositions.Cap layer material was studied by using Si_(0.03)Ge_(0.89)Sn_(0.08) and Ge_(0.95)Sn_(0.05),and cap layer total thickness was also compared.The 190 nm SiGeSn-cap device had threshold of 0.6 kA/cm^(2) at 10 K and a maximum operating temperature(T_(max)) of 100 K,compared to 1.4 kA/cm^(2) and 50 K from 150 nm SiGeSn-cap device,respectively.Furthermore,the 220 nm GeSn-cap device had 10 K threshold at 2.4 kA/cm^(2) and T_(max) at 90 K,i.e.,higher threshold and lower maximal operation temperature compared to the SiGeSn cap layer,indicating that enhanced electron confinement using SiGeSn can reduce the threshold considerably.The study of the active region material showed that device gain region using Ge_(0.87)Sn_(0.13) had a higher threshold and lower T_(max),compared to Ge_(0.89)Sn_(0.11).The performance was affected by the metal absorption,free carrier absorption,and possibly defect density level.The maximum peak wavelength was measured as 2682 nm at 90 K by using Ge_(0.87)Sn_(0.13) in gain regions.The investigations provide directions to the future GeSn laser diode designs toward the full integration of group-Ⅳ photonics on a Si platform.
