Abstract: Made up of two-dimensional (2D) layers that are weakly bound in the third dimension, Van der Waals (vdW) materials present a unique opportunity for integration into photonic structures via exfoliation and transfer. In this talk, I will present several applications of single monolayer and multilayer vdW materials, transition metal dichalcogenides (TMDCs) and hexagonal boron nitride (hBN), for enhanced and enriched light-matter interactions, which enable unprecedented control over optical and solid-state degrees of freedom. In the first part of my talk, I will discuss a giant photoinduced circular dichroism we recently discovered in monolayers of transition metal dichalcogenide WS2. I will show that the dichroism originates from the valley polarization of photoexcited free carriers and excitons, and it effectively breaks time-reversal symmetry, thus enabling applications in nonreciprocal photonic devices. Examples of designs of all-optically controllable optical isolators based on chiral light-matter interactions with monolayer WS2 will be presented. In the second part of my talk, I will discuss interactions of structured light with vdW materials integrated into topological metasurface waveguides. First, I will show that, thanks to the chiral nature of guided modes in such the waveguides, one can selectively couple forward and backward propagating modes to the valley polarized excitons in monolayer TMDCs [2]. The resultant exciton-polaritons thus allow a directional transfer of the valley degree of freedom and spin of excitons, which are guided along with the electromagnetic wave. Second, I will demonstrate that a similar approach can be applied to phonons in mid-IR, where transverse vibrations in hBN films can be directionally guided by the chiral waveguide modes in a resilient manner, avoiding backscattering due to sharp bends [3]. The demonstrated approach to use structured light to control light-matter interactions offers a new pathway to manipulate solid-state excitations and their degrees of freedom, and it can find application in spintronics/valleytronics and in phononic devices, e.g., for heat management on a chip.
Biography: Dr. Khanikaev has received PhD degree in Physics from the M. V. Lomonosov Moscow State University in 2003. After graduation Dr. Khanikaev spent five years at the Department of Electrical and Electronic Engineering of Toyohashi University of Technology, Japan, as a postdoctoral scholar and then as a senior researcher, where he worked on the topics of magnetic photonic crystals and plasmonic nanostructures. From 2009 Dr. Khanikaev held a position of a research scientist at the Department of Physics at the University of Texas at Austin and contributed to the fields of infrared photonics and plasmonic and all-dielectric metamaterials, biosensing, and graphene photonics. In 2012 he pioneered the concept of photonic topological insulators. In 2013 Dr. Khanikaev joined the City University of New York as the faculty member. Dr. Khanikaev’s research focus is on design and experimental studies of photonic nanostructures and metamaterials. His major research directions include optical nonreciprocity, topological properties, and light-matter interactions in novel and engineered optical materials. Dr. Khanikaev presently is the Full Professor at the City College, the Graduate Center, and Advanced Science Research Center of CUNY. He is a Fellow of the Optical Society of America and recipient of the NSF Special Creativity Award (2021).
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