设计了包含双层空竹的超表面,通过调节其晶格周期实现了不同阶晶格模式与超表面本征模式间的耦合,获得了3个强耦合区,并在两个晶格周期处实现了弗里德里希–温特根型连续域束缚态(Friedrich-Wintgen bound states in the continuum,FW-B...设计了包含双层空竹的超表面,通过调节其晶格周期实现了不同阶晶格模式与超表面本征模式间的耦合,获得了3个强耦合区,并在两个晶格周期处实现了弗里德里希–温特根型连续域束缚态(Friedrich-Wintgen bound states in the continuum,FW-BIC)。基于耦合模理论对其进行分析,理论分析结果与模拟结果吻合,进一步证明了结构的有效性。讨论了在介质间隔层中基于强耦合和FW-BIC的局域磁场增强,发现最大磁场强度是入射太赫兹波磁场强度的41 209倍,且该值是单纯的由超表面电磁共振产生的磁场强度的4倍。这项研究将为强场太赫兹产生和太赫兹非线性研究提供参考。展开更多
Using THz emission spectroscopy,we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond timescale.We demonstrate that THz radiation changes its polarity with reversal of the ma...Using THz emission spectroscopy,we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond timescale.We demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic field.In addition,it is found that the sign of THz polarity excited from different sides is defined by the thickness of the Fe layer and Fe/dielectric interface.Based on the thickness and symmetry dependences of THz emission,we experimentally distinguish between the two major contributions:ultrafast demagnetization and the anomalous Hall effect.Our experimental results not only enrich understanding of THz electromagnetic generation induced by femtosecond laser pulses but also provide a practical way to access laser-induced ultrafast spin dynamics in magnetic structures.展开更多
Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy togeth...Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy together,we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb_(2)Te_(3)-GeTe superlattices.Sample orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric,shift and injection currents contribute to the THz generation in Sb_(2)Te_(3)-GeTe superlattices.By decreasing the thickness and increasing the number of GeTe and Sb_(2)Te_(3) layer,the interlayer coupling can be enhanced,which significantly reduces the contribution from circular photo-galvanic effect(CPGE).A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of~1100 nm to~1400 nm further demonstrates a gapped state resulting from the interlayer coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.展开更多
文摘设计了包含双层空竹的超表面,通过调节其晶格周期实现了不同阶晶格模式与超表面本征模式间的耦合,获得了3个强耦合区,并在两个晶格周期处实现了弗里德里希–温特根型连续域束缚态(Friedrich-Wintgen bound states in the continuum,FW-BIC)。基于耦合模理论对其进行分析,理论分析结果与模拟结果吻合,进一步证明了结构的有效性。讨论了在介质间隔层中基于强耦合和FW-BIC的局域磁场增强,发现最大磁场强度是入射太赫兹波磁场强度的41 209倍,且该值是单纯的由超表面电磁共振产生的磁场强度的4倍。这项研究将为强场太赫兹产生和太赫兹非线性研究提供参考。
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFF0719200 and 2022YFA1404004)the National Natural Science Foundation of China(Grant Nos.61988102,62322115,61975110,and 62335012)+3 种基金the 111 Project(Grant No.D18014)the Key Project supported by Science and Technology Commission Shanghai Municipality(Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality(Grant No.22JC1400200)General Administration of Customs People’s Republic of China(Grant No.2019HK006)。
文摘Using THz emission spectroscopy,we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond timescale.We demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic field.In addition,it is found that the sign of THz polarity excited from different sides is defined by the thickness of the Fe layer and Fe/dielectric interface.Based on the thickness and symmetry dependences of THz emission,we experimentally distinguish between the two major contributions:ultrafast demagnetization and the anomalous Hall effect.Our experimental results not only enrich understanding of THz electromagnetic generation induced by femtosecond laser pulses but also provide a practical way to access laser-induced ultrafast spin dynamics in magnetic structures.
基金the National Key Research and Development Program of China(2022YFA1404004,2023YFF0719200)the National Nat⁃ural Science Foundation of China(61805140,62335012,61988102).
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFF0719200 and 2022YFA1404004)the National Natural Science Foundation of China(Grant Nos.62322115,61988102,61975110,62335012,and 12074248)+3 种基金111 Project(Grant No.D18014)the Key Project supported by Science and Technology Commission Shanghai Municipality(Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality(Grant Nos.22JC1400200 and 21S31907400)General Administration of Customs People’s Republic of China(Grant No.2019HK006)。
文摘Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy together,we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb_(2)Te_(3)-GeTe superlattices.Sample orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric,shift and injection currents contribute to the THz generation in Sb_(2)Te_(3)-GeTe superlattices.By decreasing the thickness and increasing the number of GeTe and Sb_(2)Te_(3) layer,the interlayer coupling can be enhanced,which significantly reduces the contribution from circular photo-galvanic effect(CPGE).A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of~1100 nm to~1400 nm further demonstrates a gapped state resulting from the interlayer coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.
