Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 16: Laser Developments and Applications

Q 16.1: Talk

Monday, March 11, 2019, 14:00–14:15, S SR 211 Maschb.

Theory of transient x-ray lasing in the small signal regime — •Chunhai Lyu, Stefano M. Cavaletto, Zoltán Harman, and Christoph H. Keitel — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany

Transient lasing processes are conventionally modeled by the Maxwell–Bloch equations which can not be solved analytically in the general case even for a one-dimensional model. Thus, numerical simulation of these equations is the main method to analyze the properties of the output lasers [1]. Here, we present a formal solution of the one-dimensional Maxwell–Bloch theory in the small-signal regime where the laser intensity is well below the saturation intensity. For the case of x-ray lasers pumped by an x-ray free-electron laser, direct integration of the formal solution reproduces the behaviors obtained from numerical simulations. Furthermore, in this regime, the dynamics of the polarization field in the gain medium follows the strength of the laser field adiabatically. This allows us to derive an approximate analytical solution for the time-dependent laser field, which is shown to be characterized by a Gaussian-like profile, with the duration and spectrum width determined by the population-inversion lifetime, the gain coefficient and the decoherence rate. Our results would be beneficial for the experimental design of a specific x-ray laser, i.e., by facilitating the determination of the laser parameters.

[1] C. Lyu, S. M. Cavaletto, C. H. Keitel, and Z. Harman, arXiv:1801.02503 (2018).