Raman-converted Kilowatt-class ultrafast laser Solutions for microexplosion-based Silicon transformations and new 3D manufacturing technologies

• Applicant: Dr. Marwan Abdou Ahmed
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 505739526

Tightly focused ultrashort laser pulses can induce confined micro-explosions in matter that lead to strong non-equilibrium conditions with extreme pressures (>10 TPa) and temperatures (> 105 K) i.e. well beyond what can be achieved by other techniques. Recently, this has made possible a breakthrough in material science by transformation of solids into super-dense crystalline phases exhibiting unique properties. This research also encompasses current industrial processes such as laser machining because the same process can be used to create any 3D structures beneath the surface of solids. However, all these advances so far remain limited to transparent dielectrics. Attempts to translate the laser-induced micro-explosion effect into bulk silicon have failed because of nonlinear processes that strongly limit the intensity that can be delivered into materials with narrow bandgap. By joint efforts on new interaction schemes and the development of novel high-power laser solutions, the project KiSS aims at accessing the micro-explosion regime inside silicon. KiSS will capitalize on the advent of kW-class ultrafast lasers to demonstrate efficient Raman conversion in single-crystal diamond to provide >100W-class systems emitting in the transparency domain of silicon (1420 nm). A unique feature with the proposed technology is a high versatility at high power in this spectral region. The implemented system will integrate temporal and polarization shaping of the pulses so that the beam characteristics beams can be precisely adjusted (on-demand) to meet the severe requirements identified for 3D processing inside semiconductors. On the front of the interaction studies, a novel crossed-beam laser arrangement to enhance the conditions inside the material will be developed. We propose developments in which tightly focused counter-propagating pulses contribute to the interaction. Tight control of synchronizations and characteristics of each contributing pulse provide new degrees of freedom and optimization. The concept will be validated by time-resolved studies of unprecedented micro-explosion conditions achieved deep inside silicon. The proposed developments will lead to a practical solution with large volume processing capabilities. The final demonstrator, unique at the international level, will open up new and exciting opportunities for generalized explorations of the matter by laser-driven micro-explosions. This will be supported by a collaborative work (Australian National University) in which structural diagnostics of processed silicon will become possible in a volume of the order of cubic millimeter. At long term, the controlled synthesis of new dense phases of silicon will have an extraordinary impact on technologies. We also expect short or mid-term industrial relevance of the developed high-throughput manufacturing technology. This will be shown by the first direct writing demonstrations of microfluidic cooling circuits inside silicon chips.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Dr. David Grojo, Ph.D.