Light control of orbital domains: case of the prototypical manganite La0.5Sr1.5MnO4

Control of electronic and structural ordering in correlated materials on the ultrafast timescale with light is a new and emerging approach to disentangle the complex interplay of the charge, spin, orbital and structural degree of freedom. In this paper we present an overview of how orbital order and orbital domains can be controlled by near IR and THz radiation in the layered manganite La0.5Sr1.5MnO4. We show how near-IR pumping can efficiently and rapidly melt orbital ordering. However, the nanoscale domain structure recovers unchanged demonstrating the importance of structural defects for the orbital domain formation. On the contrary, we show that pulsed THz fields can be used to effectively orientate the domains. In this case the alignment depends on the in-plane electric field polarisation and is induced by an energy penalty that arises from THz field induced hopping of the localised charges.Peer ReviewedPostprint (author's final draft

Superradiant Undulator Radiation for Selective THz Control Experiments at XFELs

The generation of frequency-tunable, narrow-bandwidth and carrier-envelope-phase stable THz pulses with fields in the MV/cm regime that can be appropriately timed to the femtosecond X-ray pulses from free-electron-lasers is of highest scientific interest. It will enable to follow the electronic and structural dynamics stimulated by (non)linear selective excitations of matter on few femtosecond time and {\AA}ngstrom length scales. In this article, a scheme based on superradiant undulator radiation generated just after the XFEL is proposed. The concept utilizes cutting edge superconducting undulator technology and provides THz pulses in a frequency range between 3 and 30 THz with exceptional THz pulse energies. Relevant aspects for realization and operation are discussed point by point on the example of the European XFEL

Terahertz Nonlinear Optics of Graphene: From Saturable Absorption to High-Harmonics Generation

Eid HAH, Kovalev S, Tielrooij K-J, Bonn M, Gensch M, Turchinovich D. Terahertz Nonlinear Optics of Graphene: From Saturable Absorption to High-Harmonics Generation. Advanced optical matierals. 2020;8(3): 1900771.Graphene has long been predicted to show exceptional nonlinear optical properties, especially in the technologically important terahertz (THz) frequency range. Recent experiments have shown that this atomically thin material indeed exhibits possibly the largest nonlinear coefficients of any material known to date, paving the way for practical graphene-based applications in ultrafast (opto-)electronics operating at THz rates. Here the advances in the booming field of nonlinear THz optics of graphene are reported, and the state-of-the-art understanding of the nature of the nonlinear interaction of graphene with the THz fields based on the thermodynamic model of electron transport in graphene is described. A comparison between different mechanisms of nonlinear interaction of graphene with light fields in THz, infrared, and visible frequency ranges is also provided. Finally, the perspectives for the expected technological applications of graphene based on its extraordinary THz nonlinear properties are summarized. This report covers the evolution of the field of THz nonlinear optics of graphene from the very pioneering to the state-of-the-art works. It also serves as a concise overview of the current understanding of THz nonlinear optics of graphene and as a compact reference for researchers entering the field, as well as for the technology developers

Shock Wave Expansion, Decoupling and Acoustic Signals in LIBS Measurements under Martian Atmospheric Conditions

In laboratory studies, we investigated the generation of laser-induced shock waves and the accompanying acoustic signal in a simulated martian atmosphere

SHOCK WAVE EXPANSION, DECOUPLING AND ACOUSTIC SIGNALS IN LIBS MEASUREMENTS UNDER MARTIAN ATMOSPHERIC CONDITIONS

In laboratory studies, we investigated the generation of laser-induced shock waves and the accompanying acoustic signal in a simulated martian atmosphere