Versatile THz Electric Field Sampling for Controlling and Employing Structural Dynamics

The advent of high-field terahertz (THz) sources opened the field of nonlinear THz physics and unlocked access to fundamental low energy excitations for ultrafast control of quantum materials, correlated systems and other novel functional materials [1]. Nonlinear driving schemes thereby extend these methods of contemporary IR-spectroscopy even to non-IR-active modes [2, 3]. Recent concepts employing angular momentum of THz light, e.g. for driving chiral excitations, further rely on the undistorted measurement of intense THz fields and on the precise knowledge about sophisticated THz helicity states. For this, we established simple α-quartz plates as a precise electrooptic THz detector for full amplitude, phase and polarization measurement of intense THz fields, all at a fraction of costs of conventional THz detectors [4]. Determining quartz’ complex detector response function, allowed us to develop a swift and reliable 2D electro-optic sampling protocol to precisely measure arbitrary THz helicity states, a prerequisite for the preparation of phonon trajectories with tailored angular momentum. Eventually, we translate the benefits of electro-optic sampling to electromagnetic cavities with the capability of measuring intra-cavity THz fields [5].

[1] M. Frenzel et al, Sci. Adv. 9, eadg3856 (2023)
[2] S. F. Maehrlein et al., Phys. Rev. Lett. 119, 12, 127402 (2017)
[3] D. M. Juraschek and S. F. Maehrlein, PRB 97, 17, p. 174302 (2018)
[4] M. Frenzel et al., Optica 11, 3, 362-370 (2024)
[5] M. S. Spencer et al., in preparation (2024)

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