We describe how a direct combination of an axicon and a lens can represent a simple and efficient beam-shaping solution for laser material processing applications.We produce high-angle pseudo-Bessel micro-beams at 155...We describe how a direct combination of an axicon and a lens can represent a simple and efficient beam-shaping solution for laser material processing applications.We produce high-angle pseudo-Bessel micro-beams at 1550 nm,which would be difficult to produce by other methods.Combined with appropriate stretching of femtosecond pulses,we access optimized conditions inside semiconductors allowing us to develop high-aspect-ratio refractive-index writing methods.Using ultrafast microscopy techniques,we characterize the delivered local intensities and the triggered ionization dynamics inside silicon with 200-fs and 50-ps pulses.While similar plasma densities are produced in both cases,we show that repeated picosecond irradiation induces permanent modifications spontaneously growing shot-after-shot in the direction of the laser beam from front-surface damage to the back side of irradiated silicon wafers.The conditions for direct microexplosion and microchannel drilling similar to those today demonstrated for dielectrics still remain inaccessible.Nonetheless,this work evidences higher energy densities than those previously achieved in semiconductors and a novel percussion writing modality to create structures in silicon with aspect ratios exceeding~700 without any motion of the beam.The estimated transient change of conductivity and measured ionization fronts at near luminal speed along the observed microplasma channels support the vision of vertical electrical connections optically controllable at GHz repetition rates.The permanent silicon modifications obtained by percussion writing are light-guiding structures according to a measured positive refractive index change exceeding 10-2.These findings open the door to unique monolithic solutions for electrical and optical through-silicon-vias which are key elements for vertical interconnections in 3D chip stacks.展开更多
中子照相是一种重要的无损检测技术,它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器,完成了一个用于快中子照相的准直屏蔽体系统(BSA)的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型,采用MCNP4C蒙特...中子照相是一种重要的无损检测技术,它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器,完成了一个用于快中子照相的准直屏蔽体系统(BSA)的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型,采用MCNP4C蒙特卡罗程序,模拟了准直屏蔽体系统中中子和γ射线的输运,准直中子束相对于单位源中子的中子注量可以达到9.30×10^(-6)cm^(-2),准直中子束中主要是能量大于10 Me V的快中子;在设置的样品平面直径14 cm的照射视野范围,准直束中子注量的不均匀度为4.30%,准直束中中子注量与γ注量的比值为17.20,中子通量和中子注量比值J/Φ为0.992,说明准直中子束有好的平行性;准直屏蔽体外的泄露中子注量率与准直束中子注量率相比降低了2个量级。所设计的准直屏蔽体能满足快中子照相的要求。展开更多
基金conducted using LaMP facilities at LP3.The project received funding from the French National Research Agency(ANR-22-CE92-0057-0,KiSS project)and the European Union’s Horizon 2020 research and innovation program under grant agreements No.101034324(MSCA-COFUND)and No.724480(ERC).
文摘We describe how a direct combination of an axicon and a lens can represent a simple and efficient beam-shaping solution for laser material processing applications.We produce high-angle pseudo-Bessel micro-beams at 1550 nm,which would be difficult to produce by other methods.Combined with appropriate stretching of femtosecond pulses,we access optimized conditions inside semiconductors allowing us to develop high-aspect-ratio refractive-index writing methods.Using ultrafast microscopy techniques,we characterize the delivered local intensities and the triggered ionization dynamics inside silicon with 200-fs and 50-ps pulses.While similar plasma densities are produced in both cases,we show that repeated picosecond irradiation induces permanent modifications spontaneously growing shot-after-shot in the direction of the laser beam from front-surface damage to the back side of irradiated silicon wafers.The conditions for direct microexplosion and microchannel drilling similar to those today demonstrated for dielectrics still remain inaccessible.Nonetheless,this work evidences higher energy densities than those previously achieved in semiconductors and a novel percussion writing modality to create structures in silicon with aspect ratios exceeding~700 without any motion of the beam.The estimated transient change of conductivity and measured ionization fronts at near luminal speed along the observed microplasma channels support the vision of vertical electrical connections optically controllable at GHz repetition rates.The permanent silicon modifications obtained by percussion writing are light-guiding structures according to a measured positive refractive index change exceeding 10-2.These findings open the door to unique monolithic solutions for electrical and optical through-silicon-vias which are key elements for vertical interconnections in 3D chip stacks.
文摘中子照相是一种重要的无损检测技术,它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器,完成了一个用于快中子照相的准直屏蔽体系统(BSA)的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型,采用MCNP4C蒙特卡罗程序,模拟了准直屏蔽体系统中中子和γ射线的输运,准直中子束相对于单位源中子的中子注量可以达到9.30×10^(-6)cm^(-2),准直中子束中主要是能量大于10 Me V的快中子;在设置的样品平面直径14 cm的照射视野范围,准直束中子注量的不均匀度为4.30%,准直束中中子注量与γ注量的比值为17.20,中子通量和中子注量比值J/Φ为0.992,说明准直中子束有好的平行性;准直屏蔽体外的泄露中子注量率与准直束中子注量率相比降低了2个量级。所设计的准直屏蔽体能满足快中子照相的要求。
