Abstract
The femtosecond laser ablation of silicon amidst an externally applied magnetic field in different orientations was investigated with respect to the scanning direction and polarisation of the laser beam, by observation of ablation patterns and debris displacement in a range of fluences, magnetic fields strengths, and geometries. Ultra-short fs laser pulses of 1030 nm wavelengths were utilised in the single and multi-pulse irradiation modes. Ablation with an externally applied magnetic B-field T was shown to strongly affect debris formation and deposition. The mechanism of surface plasmon polariton (SPP) wave can explain the ablated periodic patterns observed with alignment along the magnetic field lines. The application potential of external field controlled ablation is discussed.
Highlights
Both of those recent studies used externally applied fields fabricated with laser pulses that heavily overlapped with larger focal volumes than that used in this study
Patterns of periodic small ablation pits were formed along the applied B-field lines, extending well beyond the focal spot diameter, with the ablation site on the central axis of the magnets and central on the sample surface relative to its shape
It was demonstrated that by externally applying a magnetic B-field of B ∼ 0.1–0.2 T across a 5–2 mm gap with a Si sample placed inside it, the field of ablation debris and surface morphology of ablation is strongly affected
Summary
Ultra-short laser pulses provide nanoscale resolution in 3D polymerisation, optical waveguide inscription in glasses and crystals [1], non-erasable optical memory and photonic crystals [2,3,4], nano-structuring of surfaces and in the bulk [5,6,7,8], creation of new materials and their high pressure/temperature phases by 3D confined micro-explosions [9,10,11], thermal morphing of laser fabricated 3D structures [12], and laser assisted etching [13,14,15]. Plasma-assisted surface processing of Si at low NA focusing conditions using 0.3 ps pulses with ethanol as the medium and in the presence of an externally applied repulsive magnetic field showed the benefit of producing smoother surfaces; the ablation volume was smaller [22]. Both of those recent studies used externally applied fields fabricated with laser pulses that heavily overlapped with larger focal volumes than that used in this study. Small tens-of-nm nanoparticles of Si have promising applications in optical and bio-medical sensing due to support of electric and magnetic dipole modes in light scattering [23]
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