CAREER: Breaking and engineering reciprocity in magnetless THz and IR devices using 2D materials

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The propagation of electromagnetic waves has enabled modern technology and communication systems. In many practical applications, it is required that these waves propagate through nonreciprocal channels/devices able to exhibit different responses when source and observation points are interchanged. This is the case of isolators that protect sources and antennas from high-power reflections, circulators able to distribute signals to different outputs, or Faraday rotators that control the polarization of light. These components are fundamental building blocks for telecommunications, defense, health care, and space industries. Unfortunately, breaking reciprocity usually requires bulky and costly magnetic materials that are not compatible with integrated circuits. This project proposes novel approaches to break and engineer reciprocity at the micro/nano-scale by exploiting exciting properties of two-dimensional materials without requiring external magnetic fields. The findings will be applied to develop low-cost, compact, and highly-efficient nonreciprocal platforms that enable novel functionalities and are compatible with integrated circuits and other optoelectronic components. The main goal is to establish a new paradigm for nonreciprocal devices, lessening the dependence on magnetic materials and exploiting unusual responses to reshape many areas of the coming technology. The educational and outreach efforts will focus on engaging Hispanic students, ranging from K-12 to college, in science, technology, engineering and math. Summer fellowships will foster the participation of undergraduate Hispanic students in a research project about nonreciprocal antennas, allowing graduate, undergraduate, and high school students to interact and share knowledge and experiences learnt by implementing similar concepts at different frequencies. The organization of a workshop about reciprocity will bring together top experts in the field with graduate and Hispanic undergraduate and high-school students, enabling technical discussions and broadening the impact of this exciting topic on all society. This project combines and exploits unique properties of two-dimensional materials to break and manipulate time-reversal symmetry in the absence of magnetic bias. First, nonreciprocal responses far beyond what is currently attainable using magneto-optics effects will be realized by pumping two-dimensional materials subjected to uniform strain with circularly-polarized light. This platform will permit to investigate the response of many systems under effective magnetic bias much larger than those attained in common laboratories and will enable the practical development of strain engineering. Such responses will be applied to realize Faraday rotators and nonreciprocal hyperbolic/phase profile metasurfaces, enabling functionalities such as one way giant optical forces and nonreciprocal beam steering/lensing. Second, the ultrafast field effect of two-dimensional materials will be exploited to judiciously modulate in space and time their electric properties. Spatiotemporal modulations will be applied to realize low-loss, efficient, and integrated nonreciprocal photonic and plasmonic platforms able to enhance the spectrum efficiency and data-rate in the telecommunication industry. The technology proposed in this project is low-cost, compatible with integrated circuits, and aims to significantly advance the current frontiers in the field of nonreciprocity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.