Realization of One-Dimensional Dynamic Broadband Router

This program seeks to demonstrate an engineered metamaterial-based router capable of continuously tuning the angle of reflection via an externally applied bias across the infrared spectrum. Such a dynamic broadband optical router, if realized, would enable the far-field steering of beams, enabling new optical system functionalities such as signal multiplexing and routing. Today, the closest state-of-the-art solutions to the proposed system are ones based on MEMS micro-mirrors and liquid crystal spatial light modulators. In comparison to these known systems, the proposed device would be revolutionary in terms of switching speed, compactness, and versatile reconfigurability with the benefit of no moving parts. The physical and design principles, large-area manufacturing technologies, and software developed in this program will prove invaluable for future developments of the proposed dynamic achromatic optical router. All co-investigators will supervise undergraduate students, including individuals belonging to under-represented groups in sciences and engineering, building on their extensive track record in this important area. Co-PIs will employ a unified plan of action to incorporate nanophotonics into curricula, including classes in nanophotonics and openly accessible lecture notes. Furthermore, co-PIs will organize and establish a summer experience workshop for K-12 students in their respective community e.g. in Science Museums and Science Fair, an activity that will be closely coordinated with the institution and reported to NSF annually. They will also organize summer school, with emphasis on minority and under-represented participants.

Conventional approaches to the design of metasurfaces rely on subwavelength, near-resonance, metallic or dielectric scatterers as building blocks. The major drawback of such an approach is that the shaping of the wavefront can only be engineered for a frequency, since the scattered phase for each resonator depends on frequency in a highly nonlinear fashion. Indeed, the implementation of metasurfaces that function achromatically across a broad range of frequencies remains a formidable challenge. In conjunction, the electrical tunability of such anomalous reflection would represent a truly revolutionary device concept which can potentially employed in a variety of optical systems in a disruptive manner. Here, co-PIs propose novel strategies to do just that. The anomalous reflections required to achieve this tuning are induced by a phase gradient along a sub-wavelength-scale nanostructured metasurface mediated by gap plasmons within ITO based nanogap structures. Electrical tuning is achieved through ITO materials, which modifies the phase velocity of the gap plasmons and exhibits true time delay which allows for electro-optic control. This program will design the above-mentioned one-dimensional dynamic achromatic optical router, fabricate the device, evaluate its performance and fundamental limits, and perform scatterometry measurement to corroborate with theory. The device will be realized with a unique high-throughput nanomanufacturing method, atomic layer lithography that allows us to realize ultrahigh-aspect-ratio metal trenches needed for this work. If realized, the proposed device constitutes an electrically controllable plasmonic optical router that can be employed in a variety of optical systems, specifically where achromatic control of the light path on a pixel-by-pixel basis is essential, and cannot otherwise be achieved with current state-of-the-art.

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.