Investigation of nonlinear propagation of ultrafast infrared laser pulses inside narrow-bandgap semiconductors

• Applicant: Professor Dr. Stefan Nolte
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545531713

Ultrashort laser pulses are widely used for precision processing of dielectrics with applications that include integrated optoelectronics, lab-on-a-chip devices, and data storage. However, laser processing in narrow-gap semiconductors such as silicon (Si) and gallium arsenide (GaAs) presents considerable challenges due to extreme nonlinear absorption and refraction. Despite their key role in modern electronics, so far sufficient energy deposition to reach the internal modification regime in these materials could not be realized in general, as a direct consequence of nonlinear propagation effects. Additionally, the current theoretical models used for dielectrics are inadequate for describing the nonlinear propagation of ultrafast laser pulses inside semiconductors due to oversimplified semi-classical approximations. Consequently, progress in this field is hindered by a lack of fundamental understanding which would lead to the development of novel techniques to exalt energy deposition. The main objective of this project is to address this problem and improve the understanding of nonlinear propagation of ultrashort laser pulses inside narrow-gap semiconductors. This will allow us to propose new ways to maximize energy deposition in these materials. To achieve this objective, the French partner (LabHC, Saint-Etienne) will develop a computationally efficient quantum-mechanical model. This model will incorporate the coupling between the unidirectional pulse propagation equation (UPPE), semiconductor Bloch equations (SBE), and density functional theory (DFT). The model will be refined and validated using unique experimental techniques developed by the German team (IAP, Jena). Subsequently, the model will be used to predict the optimal laser conditions, and plan new experiments to achieve exalted energy deposition. The original solutions proposed in this project consist of spatial, temporal, and spatio-temporal shaping. The success of this project relies on the exceptional complementarity of the partners and the uniqueness of their expertise in this field. The French team possesses the necessary theoretical expertise on laser pulse propagation modeling and quantum simulations of ultrafast photoexcitation. They are renowned for their theoretical work in laser processing of semiconductor surfaces and nanostructures. On the other hand, the German partner performed pioneering experiments on in-volume laser-semiconductor interaction. Their findings led to first applications including ultrafast waveguide inscription in silicon, and semiconductor–metal ultrafast laser welding.

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