Abstract
To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irradiation can be controlled via the Lorentz force , where is velocity of charge e, is the applied electrical bias and is the magnetic flux density. The external electric E-field was applied during laser ablation using suspended micro-electrodes above a glass substrate with an air gap for the incident laser beam. The counter-facing Al-electrodes on Si surface were used to study debris formation patterns on Si. Debris was deposited preferentially towards the negative electrode in the case of glass and Si ablation. Also, an external magnetic field was applied during laser ablation of Si in different geometries and is shown to affect ripple formation. Chemical analysis of ablated areas with and without a magnetic field showed strong chemical differences, revealed by synchrotron near-edge X-ray absorption fine structure (NEXAFS) measurements. Harnessing the vectorial nature of the Lorentz force widens application potential of surface modifications and debris formation in external E-/B-fields, with potential applications in mass and charge spectroscopes.
Highlights
Ablation using ultra-short sub-1 ps laser pulses has become a popular method for three-dimensional (3D) material structuring: cutting, dicing, hole-drilling, surface- and volume-patterning with nanogratings [1,2,3,4], optical waveguide inscription in glasses and crystals [5], non-erasable optical memory and photonic crystals [6], creation of new materials and their high pressure and temperature phases by 3D confined micro-explosions [7], thermal morphing of laser fabricated 3D structures [8], laser-assisted etching [9], and light-induced back-side wet-etching [10]
Ablation using ultra-short sub-1 ps pulses at high irradiance 5–10 TW/cm2 begins with removal of electrons from the surface with heavier ions following after the negative charge [16]
This is of a particular interest since the ablation plasma is overall charge neutral
Summary
Ablation using ultra-short sub-1 ps laser pulses has become a popular method for three-dimensional (3D) material structuring: cutting, dicing, hole-drilling, surface- and volume-patterning with nanogratings [1,2,3,4], optical waveguide inscription in glasses and crystals [5], non-erasable optical memory and photonic crystals [6], creation of new materials and their high pressure and temperature phases by 3D confined micro-explosions [7], thermal morphing of laser fabricated 3D structures [8], laser-assisted etching [9], and light-induced back-side wet-etching [10]. Ablation using ultra-short sub-1 ps pulses at high irradiance 5–10 TW/cm begins with removal of electrons from the surface with heavier ions following after the negative charge [16] This dynamic removal of material takes place in electrostatically coupled electron-ion systems. A valid question is whether an externally applied E-field (voltage V over a gap of ∆d) or externally applied B-field can influence the dynamics of the ablation plume with asymmetry during the initial stage of negative-positive charge removal from the surface. This is of a particular interest since the ablation plasma is overall charge neutral
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