Resonant electro-optic metasurfaces and integrated photonics: Shaping light in space and time
David Barton
Northwestern University
DIPC Josebe Olarra Seminar Room
Aitzol Garcia-Etxarri
Dynamical control of the optical properties of materials lays the groundwork for reconfigurable flat optical devices, tunable devices that can learn from optical inputs, and energy-efficient chip-scale communications and computation platforms that promise to reduce the energy consumption of the modern telecommunications infrastructure. One particularly appealing method to achieve this relies on electro-optics, which provides a direct connection between driving electronics and optical properties of materials. Integrating electro-optic materials into micro and nanostructures heralds a new generation of devices with light-matter-microwave interactions much stronger than bulk devices, creating a platform for new and unprecedented photonic devices. I will discuss a few device demonstrations and opportunities using thin-film Lithium Niobate on Insulator (LNOI) to advance dynamical operation of optical devices, as well as an outlook of emerging materials and composite systems that can be enabled by these devices. First, I will show how we can control the frequency of light with amplitude and phase modulators, yielding a femtosecond pulse generator on a chip the size of a penny, driven entirely by microwaves. This uses the concept of a “time lens” that maps the operation of a lens (which focuses light to a point in space), to the time domain (“focusing” light to a point in time), and requires the development of high performanceamplitude modulators, phase modulators, and dispersion control on-chip. We demonstrate the generation of ~500 fs laser pulses with theoretical efficiency up to 25% with this system, which can enable frequency-agile pulse generation in a small footprint and without resonant structures. Next, we will discuss the development of resonant nanophotonics interfaced with electro-optic materials for reconfigurable wavefront shaping. High index dielectric antennas evanescently coupled to an electro-optic material can lead to individual nanoantenna addressability, potentially enabling a high efficiency universally reconfigurable optical element. En route to this, we demonstrate reconfigurable beamsplitters based on guided mode resonant silicon nanoantennas on thin-film lithium niobate. Here, the modulation bandwidth is limited by the RC delays of the device, demonstrating a 3 dB bandwidth of > 1 GHz. As an outlook, we discuss potential opportunities with emerging electro-optic materials and nanofabrication strategies. Together, these results show the power of micro and nanostructuring of electro-optic materials to control the amplitude, phase, and dispersion of light amenable for a variety of integrated devices and systems.