Breaking the barriers to ultrafast laser 3D structuring deep inside silicon

David Grojo
LP3-Lasers, Plamas et Procédés Photoniques
CNRS / Aix-Marseille University

An important challenge in the field of three-dimensional ultrafast laser processing is to achieve in the bulk structuring of silicon (Si) and narrow gap materials. Attempts by increasing the energy of infrared femtosecond pulses have simply failed because of nonlinear delocalization of light before reaching the focal region. We have developed a solution inspired by solid-immersion microscopy to produce hyper-focused beams that are intrinsically free from aberrations. It allows extreme energy confinement up to breakdown deep into Si. Other solutions rely on temporal optimizations to reduce the strong detrimental nonlinear effects while taking benefit from heat-accumulated-based-effects for efficient local absorption. The validity of the solutions are demonstrated by controlled refractive index modifications achieved inside Si wafers. These investigations open perspectives for 3D laser solutions in Si that may, in particular, drastically change how things are designed and fabricated in the important field of silicon photonics.

Coffee/tea and cake from 10:00.