共查询到19条相似文献，搜索用时 46 毫秒
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铁磁/非磁异质结构中的超快自旋流-电荷流转换实现相干太赫兹辐射得到了广泛研究.热自旋电子学结合了热输运与磁输运,可以有效地产生和探测自旋的非平衡输运.本文利用飞秒激光脉冲激发铁磁绝缘体钇铁石榴石(Y3Fe5O12, YIG)/Pt异质结构,通过超快自旋塞贝克效应(SSE)产生太赫兹(THz)相干辐射.实验中, THz脉冲的相位随外加磁场和激光入射样品顺序的反转而反转,表明THz辐射与界面温度梯度的方向密切相关.为了考察界面对THz辐射性能的影响,系统地研究了YIG/Pt异质结构不同退火处理后的THz辐射情况.实验发现,生长在Gd3Ga5O12(GGG)衬底上的YIG/Pt经退火处理后再原生一层Pt膜,其THz辐射强度提高了一个数量级.归因于退火后增强了YIG/Pt界面的自旋混合电导率.此外,还研究了生长在高阻Si衬底上退火后优化结构的能量密度与THz辐射强度的关系,拟合得到饱和能量密度约为1.4 mJ/cm2.实验结果表明, YIG/... 相似文献
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苏玉伦;尉正行;程亮;齐静波 《物理学报》2020,(20):36-50
太赫兹技术在成像、传感和安全等方面展现出了巨大的应用潜力和价值.传统的固态宽带太赫兹源主要依赖于非线性光学晶体和光电导天线,而下一代太赫兹技术的一个主要挑战是开发高效、超宽带和低成本的太赫兹源.最近几年,基于自旋电子学的金属磁性异质结太赫兹源获得了很大关注.本文首先将对该类太赫兹源涉及的物理机理进行讨论,主要包括超快退... 相似文献
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太赫兹科学技术在光谱、成像、传感、生物医药、安全检测等方面展现出了巨大的应用潜力和价值。基于新材料和新机理,研发高效、超宽带和低成本的太赫兹光子学器件是太赫兹科学技术的重要挑战。近年来的研究表明,太赫兹光子学和超快自旋电子学深度交叉,获得了很大的关注。本文对超快太赫兹自旋光电子学所研究的物理机理和器件设计应用进行讨论。在物理机理研究方面,阐明了太赫兹脉冲为研究超快自旋电子学提供强大工具,实现了太赫兹驱动自旋波,探测自旋输运和超快磁测量。在器件设计与应用方面,介绍了基于自旋的新型太赫兹光子学器件,包括自旋太赫兹辐射源的优化方法,自旋太赫兹调制器的工作原理,自旋太赫兹探测器的设计方案。超快太赫兹自旋光电子学不仅有助于人们理解宏观自旋电子学现象背后的微观物理机制,而且有望实现高效的太赫兹光子学器件和光谱学应用。 相似文献
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冯正;王大承;孙松;谭为 《物理学报》2020,(20):62-73
自旋太赫兹源基于铁磁/非磁纳米薄膜异质结构中的超快自旋流-电荷流转换产生太赫兹脉冲,具有超宽频谱、固态稳定、偏振可调、超薄结构、成本低廉等独特优点,近年来引起很大的关注.本文首先简要介绍太赫兹波、太赫兹自旋电子学及自旋太赫兹源;其次从自旋太赫兹源的性能提升、调控及其应用3方面对其研究进展进行详细的综述,分别为:1)基于自旋太赫兹源产生太赫兹的3个过程——超快自旋输运、光学激发、太赫兹出射的性能提升方法, 2)自旋太赫兹源偏振和频谱的主动调控, 3)自旋太赫兹源在太赫兹超宽谱测试、磁结构检测及成像、太赫兹超分辨近场成像等方面的应用;最后总结全文,指出自旋太赫兹源目前存在的问题,并展望其发展方向. 相似文献
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“中国科学院超快现象和太赫兹辐射学术研讨会”于 2 0 0 2年 7月 2 2日至 2 5日在北京中国科学院物理研究所举行 .本次会议由中国科学院主办 ,中国科学院物理研究所承办 ,中国科学院上海微系统与信息技术研究所、美国伦斯勒理工学院共同协办 .会议的三位主席分别是物理所张杰研究员、美国伦斯勒理工学院的张希成教授和上海微系统与信息技术研究所的封松林研究员 .物理所的翁羽翔研究员担任会议秘书长 .这次大会是我国在超快现象和太赫兹辐射领域组织的第一次专业学术会议 ,是对国内在超快现象和太赫兹辐射领域研究水平的一次较全面的检阅 .… 相似文献
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许涌;张帆;张晓强;杜寅昌;赵海慧;聂天晓;吴晓君;赵巍胜 《物理学报》2020,(20):8-20
太赫兹频段在电磁波谱上位于红外和微波之间,兼具宽带性、低能性、高透性、指纹性等诸多优势特性,在航空航天、无线通信、国防安全、材料科学、生物医疗等领域具有重要的应用前景.太赫兹科学与技术的发展和应用在很大程度上受限于源的水平,新型太赫兹辐射源的机理研究和器件研制至关重要.自旋太赫兹发射不仅从物理上提供了操控飞秒自旋流的可... 相似文献
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自铁磁金属在飞秒激光泵浦下的超快退磁效应发现以来,电子的自旋属性逐渐被应用于太赫兹电磁波的产生.利用逆Rashba-Edelstein效应产生太赫兹辐射首先在Ag/Bi界面得到证实,而LaAlO3/SrTiO3界面通过该效应产生直流的自旋-电荷转换效率要高于Ag/Bi界面约一个数量级,但利用该结构转化自旋流来产生太赫兹的有效性尚待系统的研究.本文制备了NiFe/LaAlO3//SrTiO3(001)系列样品,在飞秒激光泵浦下观察到了太赫兹辐射的产生及其对磁场方向的依赖效应,并通过改变LaAlO3层的厚度验证了超扩散模型与光学传输模型的有效性,观察到了在LaAlO3/SrTiO3界面由于多次反射导致太赫兹波的减弱,为进一步优化太赫兹波的产生提供了实验和理论支持. 相似文献
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非线性克尔效应对飞秒激光偏振的超快调制 总被引：1，自引：0，他引：1
研究了近红外飞秒激光的偏振在太赫兹频率的超快调制.利用抽运-探测光谱技术,通过改变两个脉冲之间的延迟时间可以控制光脉冲的旋转角.在Li：NaTb（WO4）2磁光晶体中观察到探测光的偏振随延迟时间变化的高速振荡,振荡信号的中心频率为0.19 THz.这种超快偏振调制现象可以解释为,抽运-探测实验构置中,前向传播的抽运光诱导的光学克尔非线性引起被晶体远端表面所反射的背向传播的探测光脉冲偏振面的额外旋转.通过改变抽运光的圆偏振旋性可以控制探测光调制信号的相位和振幅.实验结果表明,非线性光学克尔效应可以作为一种全新的手段,在磁光晶体中实现近红外飞秒激光以太赫兹频率的超快偏振调控.这将在超快磁光调制器等全光器件中得以应用.实验结果将有助于偏振依赖的超快动力学过程的研究. 相似文献
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本文采用光抽运-太赫兹探测技术系统研究了低温生长砷化镓(LT-GaAs)中光生载流子的超快动力学过程.光激发LT-GaAs薄层电导率峰值随抽运光强增加而增加,最后达到饱和,其饱和功率为54μJ/cm~2.当载流子浓度增大时,电子间的库仑相互作用将部分屏蔽缺陷对电子的俘获概率,从而导致LT-GaAs的快速载流子俘获时间随抽运光强增加而变长.光激发薄层电导率的色散关系可以用Cole-Cole Drude模型很好地拟合,结果表明LT-GaAs内部载流子的散射时间随抽运光强增加和延迟时间(产生光和抽运光)变长而增加,主要来源于电子-电子散射以及电子-杂质缺陷散射共同贡献,其中电子-杂质缺陷散射的强度与光激发薄层载流子浓度密切相关,并可由散射时间分布函数α来描述.通过对光激发载流子动力学、光激发薄层电导率以及迁移率变化的研究,我们提出适当增加缺陷浓度,可以进一步降低载流子迁移率和寿命,为研制和设计优良的THz发射器提供了实验依据. 相似文献
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Jacques Hawecker Thi-Huong Dang Enzo Rongione James Boust Sophie Collin Jean-Marie George Henri-Jean Drouhin Yannis Laplace Romain Grasset Jingwei Dong Juliette Mangeney Jerome Tignon Henri Jaffrès Luca Perfetti Sukhdeep Dhillon 《Advanced Optical Materials》2021,9(17):2100412
Terahertz (THz) spin-to-charge conversion has become an increasingly important process for THz pulse generation and as a tool to probe ultrafast spin interactions at magnetic interfaces. However, its relation to traditional, steady state, ferromagnetic resonance techniques is poorly understood. Here, nanometric trilayers of Co/X/Pt (X = Ti, Au or an Au:W alloy) are investigated as a function of the “X” layer thickness, where THz emission generated by the inverse spin Hall effect is compared to the Gilbert damping of the ferromagnetic resonance. Through the insertion of the “X” layer it is shown that the ultrafast spin current injected in the non-magnetic layer defines a direct-spin-conductance, whereas the Gilbert damping leads to an effective spin-mixing-conductance of the trilayer. Importantly, it is shown that these two parameters are connected to each other and that spin-memory-losses can be modeled via an effective Hamiltonian with Rashba fields. This work highlights that magneto-circuit concepts can be successfully extended to ultrafast spintronic devices, as well as enhancing the understanding of spin-to-charge conversion processes through the complementarity between ultrafast THz spectroscopy and steady state techniques. 相似文献
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This paper shows that a substantial amount of dissipationlessspin-Hall current contribution may exist in the extrinsic spin-Halleffect, which originates from the spin-orbit coupling induced bythe applied external electric field itself that drives the extrinsicspin-Hall effect in a nonmagnetic semiconductor (or metal). Byassuming that the impurity density is in a moderate range such thatthe total scattering potential due to all randomly distributedimpurities is a smooth function of the space coordinate, it is shownthat this dissipationless contribution shall be of the same ordersof magnitude as the usual extrinsic contribution from spin-orbitdependent impurity scatterings (or may even be larger than thelatter one). The theoretical results obtained are in good agreementwith recent relevant experimental results. 相似文献
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Giacomo Balistreri Alessandro Tomasino Junliang Dong Aycan Yurtsever Salvatore Stivala José Azaña Roberto Morandotti 《Laser u0026amp; Photonics Reviews》2021,15(8):2100051
In this work, the time-domain integration of broadband terahertz (THz) pulses via a tapered two-wire waveguide (TTWWG) is reported. Such a guiding structure consists of two metallic wires separated by a variable air gap that shrinks down to a subwavelength size as the movement takes from the waveguide input to its output. It is shown that while an input THz pulse propagates toward the subwavelength output gap, it is reshaped into its first-order time integral waveform. In order to prove the TTWWG time integration functionality, the THz pulse is detected directly within the output gap of the waveguide, so as to prevent the outcoupling diffraction from altering the shape of the time-integrated THz transient. Since the time-domain integration is due to the tight geometrical confinement of the THz radiation in a subwavelength gap volume, the TTWWG operational spectral range can easily be tuned by judiciously changing both the output gap size and the tapering angle. The results lead to the physical realization of a broadband, analog THz time integrator device, which is envisioned to serve as a key building block for the implementation of complex and ultrahigh-speed analog signal processing operations in THz communication systems. 相似文献
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We report a theoretic study on modulating the spin polarization of charge current in a mesoscopic four-terminal device of cross structure by using the inverse spin hall effect. The scattering region of device is a two-dimensional electron gas (2DEG) with Rashba spin orbital interaction (RSOI), one of lead is ferromagnetic metal and other three leads are spin-degenerate normal metals. By using Landauer-Büttiker formalism, we found that when alongitudinal charge current flows through 2DEG scattering region from FM lead by external bias, the transverse current can be either a pure spin current or full-polarized charge current due to the combined effect of spin hall effect and its inverse process, and the polarization of this transverse current can be easily controlled by several device parameters such as the Fermi energy, ferromagnetic magnetization, and the RSOI constant. Our method may pave a new way to control the spin polarization of a charge current. 相似文献
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We report a theoretic study on the inverse spin-Hall effect （ISHE） in a two-terminal nano-device that consists of a two-dimensional electron gas （2DEG） with Rashba spin-orbit coupling （RSOC） and two ideal leads. Based on a two-site toy model and Keldysh Green＇s function method, we derive an analytic result of ISHE, which shows clearly that a nonzero transverse charge current stems from the combined effect of the RSOC, the spin bias, and its spin polarization direction in spin space. Our further numerical calculations in a larger system other than two-site lattice model demonstrate that the transverse charge current, dependent on the strength of the RSOC, the Fermi energy of the system, as well as the system size, can exhibit oscillating behavior and even reverse its sign due to Rashba spin precession. These properties may be helpful for eficient detection of the spin current （spin bias） by measuring the transverse charge current in a spin-orbital coupling system. 相似文献
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We report a theoretic study on modulating the spin polarization of charge current in a mesoscopic fourterminal device of cross structure by using the inverse spin hall effect. The scattering region of device is a two-dimensional electron gas （2DEG） with Rashba spin orbital interaction （RSOI）, one of lead is ferromagnetic metal and other three leads are spin-degenerate normal metals. By using Landauer-Biittiker formalism, we found that when a longitudinal charge current flows through 2DEG scattering region from FM lead by external bias, the transverse current can be either a pure spin current or full-polarized charge current due to the combined effect of spin hall effect and its inverse process, and the polarization of this transverse current can be easily controlled by several device parameters such as the Fermi energy, ferromagnetic magnetization, and the RSOI constant. Our method may pave a new way to control the spin polarization of a charge current. 相似文献
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太赫兹时域光谱技术(THz-TDS)广泛应用于材料、生物医学、化学、药学、安检等诸多领域。传统扫描式THz-TDS技术需要通过改变探测光延时逐点扫描并重构时域信号,仅适合于具有较高重复频率且稳定的太赫兹辐射源情形下的样品探测。在低重复频率或涨落较大的太赫兹辐射源情形下和不可逆过程中样品的探测,扫描式THz-TDS不再适用,需要使用单发THz-TDS技术,单发THz-TDS技术原则上仅需要一个激光脉冲就可以获取一个完整的太赫兹时域脉冲波形。介绍几种主要的单发THz-TDS探测技术,这些技术都利用了电光晶体的泡克尔斯效应,通过测量探测光的某个物理量的变化来提取太赫兹信号。根据探测方法不同可分为光谱编码、空间编码和互相关等技术。在光谱编码技术中,探测光不同频率成分在时间上发生分离,不同时间成分分别被太赫兹脉冲不同时刻电场调制,通过测量探测光各个频率被太赫兹脉冲调制前后的光谱的变化提取太赫兹脉冲波形。该方法光路简单,测量结果直观,有较高的信噪比,但其时间分辨率较低,且被测太赫兹信号容易产生失真。为提高被测信号的时间分辨率,有人提出了空间编码技术,即不同位置探测光分别被太赫兹脉冲不同时刻电场调制,通过测量探测光各个位置太赫兹脉冲调制前后的光强变化提取太赫兹脉冲波形。根据不同空间展开方法可分为一维空间编码技术和二维空间编码技术。空间编码技术中虽然有较高的时间分辨率,但由于探测光在空间展开能量分散使得其信噪比相对较低。此外,还有一种较高时间分辨率的技术即互相关技术,可分为共线互相关和非共线互相关技术。在非共线互相关技术中,被太赫兹脉冲调制的激光啁啾脉冲与短脉冲互相关作用产生二次谐波,通过太赫兹脉冲调制前后二次谐波空间分布变化来提取太赫兹信号;在共线互相关技术中被太赫兹脉冲调制的啁啾脉冲与短脉冲共线入射到光谱仪,通过干涉条纹提取太赫兹信号,该技术提高了时间分辨率和信噪比,但光路布置复杂,不能进行实时监测。回顾了这几种单发THz-TDS探测技术的发展历程,综述探测技术的原理、实验方案和测量结果,并讨论了这些探测技术的优势和不足。 相似文献
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Jonas Kiemle Paul Seifert Alexander W. Holleitner Christoph Kastl 《physica status solidi b》2021,258(1):2000033