Rational Design of Tunable Anisotropic Chalcogenides for Optics

• Applicant: Professor Dr. Carsten Ronning
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566192676

We propose to rationally design and synthesize stable chalcogenides with large static anisotropy, modulate their anisotropy spatially, and, in select cases, introduced dynamic tunability of optical anisotropy in visible (VIS), near-infrared (near-IR), and mid-infrared (mid-IR) spectral ranges, while maintaining very low optical losses. These materials class is referred to as Tunable Anisotropic Chalcogenides for Optics, or TACOs. The central hypothesis to be tested is that quasi low-dimensional chalcogenides with transition-metal cations can serve as ideal candidates for TACOs. A combination of first-principles density-functional theory and materials informatics will be used to identify synthesizable materials with either high static optical anisotropy and in some cases, electrically tunable optical anisotropy at desired frequencies. The screened chalcogenides will be synthesized as single crystals using vapor-transport, and when needed, as thin films using pulsed-laser deposition. The material structure and composition will be characterized using a combination of X-ray, neutron, and electron-based probes that are sensitive to both long-range order and local atomic structures. Their linear and circular anisotropy will be characterized using a range of optical spectroscopic techniques. Their static anisotropy will be modified by alloying and ion bombardment, this leading to a high-dimensional space of materials characteristics that will be investigated using an iterative, closed-feedback loop approach. The proposed research is motivated by a series of discoveries by the PIs showing world-record optical anisotropy and excellent transparency in the mid-IR and long-wave IR ranges in quasi-one-dimensional chalcogenide perovskites along with new mechanisms to achieve such large anisotropy. The proposed research will efficiently sift through the largely unexplored, vast phase space of chalcogenides and screen the ones that have a desirable combination of formability, band gap, linear and circular anisotropies, and, in some cases, dynamic tunability of the optical anisotropy due to electrically switchable ferroelectric transitions. These functional semiconductors will open a route to new types of free-space and on-chip electro-optical modulators, tunable metasurfaces, displays, adaptable imagers and sensors.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partners: Professor Dr. Mikhail Kats; Professor Dr. Rohan Mishra; Dr. Jayakanth Ravichandran