Abstract
A dielectric material’s response to light is microscopically defined by field-cycle-driven motion of electron densities in the restoring forces of the atomic environment. Here we apply single-cycle mid-infrared pulses to drive the nonlinear motion of valence electrons in a heteronuclear crystal with asymmetric structure and report how the macroscopic optical response can be tracked back to the real-space electron dynamics in the symmetry-breaking potential along the chemical bonds. Whether our single-cycle field drives electrons from the less electronegative to the more electronegative element or vice versa controls the appearance of a smooth nonlinear output spectrum or one with even and odd harmonic orders. Crystal angle scans reveal the absolute orientation of the asymmetric bonds. Directional motion of valence charges controlled by a single cycle of light can therefore be used for spectroscopically exploring the binding potential, to understand and design novel materials for nonlinear optics, or to eventually process information at the frequency of light.
Highlights
When a light wave interacts with a transparent material, such as gas-phase atoms, molecules, liquid, or a dielectric solid, electron densities are driven by the electric field of the optical cycles and move in the restoring forces of the atomic environment
[16,17], the shape of the nonlinear output spectrum is directly related to the absolute orientation of the chemical bonds, and no measurements in time domain are required to understand the basics of the nonlinear response of valence electrons in real space
The peak field strength inside the crystal is 1.4 V/nm, and the electric field is parallel to the Ga–Se bonds in the a −b plane [Fig. 1(c)]; see Supplement 1
Summary
When a light wave interacts with a transparent material, such as gas-phase atoms, molecules, liquid, or a dielectric solid, electron densities are driven by the electric field of the optical cycles and move in the restoring forces of the atomic environment. Materials for cycle-based nonlinear optics and information processing should have low absorption losses, a complex potential energy landscape, and a direct nonlinear response to single-cycle excitation. Researchers aim at reconstructing the band structure and the potential of a crystalline material by all-optical nonlinear spectroscopy [22,23,24] For both objectives, and for comprehending the foundations of nonlinear optics, we need to understand the nonlinear response of a complex material to an impulsive single-cycle excitation and determine the relevant connections to the atomic structure. [16,17], the shape of the nonlinear output spectrum is directly related to the absolute orientation of the chemical bonds, and no measurements in time domain are required to understand the basics of the nonlinear response of valence electrons in real space
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
