Coherent terahertz needle radiation emission mechanism from nanostructured ferromagnetic metal films excited by femtosecond laser pulses

球霰石纳米胶囊的光热无针注射

Optothermal needle-free injection of vaterite nanocapsules

本研究提出了一种基于介孔球霰石纳米颗粒异常光热膨胀的激光诱导粒子加速机制，实现了2微米粒子在0.5瓦飞秒激光下克服范德华力获得15米/秒速度，成功完成无针注射进入体模层，推动了光响应纳米胶囊的发展。

Coulomb interactions and the spatial coherence of femtosecond nanometric electron pulses

The transverse coherence of electrons is of utmost importance in high resolution electron microscopes, point-projection microscopes, low-energy electron microscopy and various other applications. Pulsed versions of many of these have recently been realized, mostly relying on femtosecond laser-triggering electron emission from a sharp needle source. We here observe electron interference fringes and measure how the interference visibility becomes reduced as we increase the electron bunch charge. Due to the extremely strong spatio-temporal confinement of the electrons generated here, we observe t…

飞秒光脉冲诱导的纳米尺度电荷分布的电子成像

Electron Imaging of Nanoscale Charge Distributions Induced by Femtosecond Light Pulses

本文研究了非导电样品在原位透射电子显微镜中的表面充电现象，通过飞秒多光子光发射后的电子光学成像，定量提取光诱导静电势并分析充电动力学，提出描述电子与光诱导过程相互作用的模型，并展示通过同步光学照明缓解样品充电的方法。

Three-dimensional femtosecond laser nanolithography of crystals

Nanostructuring hard optical crystals has so far been exclusively feasible at their surface, as stress induced crack formation and propagation has rendered high precision volume processes ineffective. We show that the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by more than five orders of magnitude by means of direct laser writing. The process allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture. To showcase the unique potential of the technique, we fabricate phot…

Diffraction of Ultrashort Pulse on a Nanoscale Conductive Cone

Surface plasmon polariton is collective oscillation of the free electrons at metal dielectric interface. As a wave phenomenon, surface plasmon polaritons can be focused using appropriate excitation geometry of metallic structures. We theoretically demonstrate the possibility of controlling nanoscale short pulse superfocusing based on the generation of radially polarized surface plasmon polariton mode of conical metallic tip. Numerical simulation for femtosecond pulse propagation along a silver nano-needle is discussed. The spatial distribution for a near field strongly depends on a linear chir…

All femtosecond optical pump and X-ray probe: holey-axicon for free electron laser

We put forward a co-axial pump(optical)-probe(X-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 micrometers-diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-X-ray free electron laser (X-FEL) beam of sub-1 micrometer diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different …

利用（高斯-）贝塞尔飞秒激光束烧蚀黑硅

Ablation of black-Si by (Gauss-)Bessel femtosecond laser beams

本文比较了高斯与高斯-贝塞尔飞秒激光对黑硅的改性效果，发现贝塞尔光束可在低50倍能量密度下实现更窄改性并获更高深宽比沟槽，且双面织构黑硅近红外透射率超95%。

Slow Light Nanocoatings for Ultrashort Pulse Shaping

Transparent materials do not absorb light but have profound influence on the phase evolution of transmitted radiation. One consequence is chromatic dispersion, i.e., light of different frequencies travels at different velocities, causing ultrashort laser pulses to elongate in time while propagating. Here we experimentally demonstrate ultrathin nanostructured coatings that resolve this challenge: we tailor the dispersion of silicon nanopillar arrays such that they temporally reshape pulses upon transmission using slow light effects and act as ultrashort laser pulse compressors. The coatings ind…

超短双电子脉冲的空间与能量关联

Spatial and energetic correlations of ultrashort two electron pulses

本文表征了针尖处双电子脉冲的三维库仑关联，发现横向空间间距小的电子对存在3.3 eV能隙，结合光阑与能量滤波可将多电子脉冲抑制至g(2)=0.02，为相关研究及仪器设计提供基础。

Evidence of coherence in strong-field electron photoemission from a semiconductor

Strong-field quantum electronics is emerging as a potential candidate in information processing but still coherence vs decoherence is a primary concern of the concept. Strong-field coherent processes in band gap materials have led during the last decade to the emergence of high harmonic generation in semiconductors, petahertz electronics, or strong-field quantum states. However, the coherent behavior of the sub-optical cycle-driven electrons has never been directly observed. We report here on the experimental evidence of coherent ultrashort emission of hot electrons from a nanostructured semic…

Partial Quantum Coherence, Ultrashort Electron Pulse Statistics, and a Plasmon-Enhanced Nanotip Emitter Based on Metallized Optical Fibers

The present dissertation covers two related research projects. The first topic was initiated with the ultimate goal of observing quantum degeneracy in ultrashort free electron pulses. This constitutes a thorough theoretical analysis of the problem involving partial quantum coherence and spin polarization of the source in light of a path-integral treatment of the phenomenon of matter-wave diffraction-in-time. Subsequently, results of a trailblazing experiment, to be superseded by a Hanbury Brown-Twiss type conclusive test of free fermion antibunching with electrons, is reported. In this experim…