Femtosecond laser induced breakdown spectroscopy of Cu at the micron/sub-micron scale

• Femtosecond LIBS was studied at small crater lengthscales.
• Limits of detection, plasma properties and spectral emission efficiency of Cu were measured at the micron/submicron scale.
• Less efficient spectral emission per ablated volume was demonstrated as we scale down in laser energy and crater sizes.

While femtosecond Laser Induced Breakdown Spectroscopy has been studied in the macro-scale (i.e. ablation crater sizes of tens to hundreds of micrometers), the spectral emission mechanisms at the micron/sub-micron scale remain largely unknown, mainly because of the challenges associated with spectral emission acquisition from the limited amounts of ablated mass at these small lengthscales. In this work we study the limits of detection, the laser-induced plasma properties and spectral emission efficiency of Cu at the micron/submicron scale. Although the corresponding number electron densities and temperatures are similar to those reported for macroscale laser ablation, our findings suggest less efficient luminous spectral emission per ablated volume as we scale down in laser energy and crater sizes. These results provide a first insight into fs laser-induced plasma properties at the micron/sub-micron scale regime.