We experimentally demonstrate a new electro-optic SRAM element fully CMOS compatible. Inspired by the Esaki diode, presenting negative differential resistance (NDR), we designed a new type of NDR diode based on a horizontal PN junction and a region with higher acceptor concentration, P+, in silicon. We embedded the new NDR into a photonic micro-ring resonator to enable a bistable device with electrical and optical readout capabilities. Our device is remarkable for its simplicity, CMOS compatibility and its low power consumption around the nanowatt, but it’s also an important steppingstone on the way to new nonlinear electro-optic and neuromorphic computing structures.
In the present talk, we discuss strategies to design both plasmonic and all-dielectric active metasurfaces, which can dynamically manipulate the wavefront of the transmitted light in the near-infrared wavelength range. Our active transmissive metasurfaces feature an array of amorphous silicon (a-Si) pillars on a silica (SiO2) substate, which, in some cases, are hybridized with a thin metallic layer. The optical response of the designed metasurface is either tuned thermo-optically or by integrating active materials such as lithium niobate (LNO), indium tin oxide (ITO), or tungsten disulfide (WS2) into the metasurface structure.
Space-time metasurfaces employ a spatial and temporal phase-gradient to impart momentum to input light in space and frequency. In this work, we used a reflective gate-tunable ITO-based metasurface operating at 1530 nm to generate diffraction of frequency-shifted light up to 1 MHz. Our device consists of an array of interdigitated plasmonic nanoantennas with two electrical contacts that are modulated with identical electrical waveforms, time-delayed by half a period, to diffract frequency-shifted light. The simultaneous control of spatial and spectral properties of light enabled by space-time metasurfaces is highly desired in applications such as LiDAR, LiFi, and space communication.
Laser communications hold the potential to bring internet-like speeds (exceeding Gb/s) to data transmission in space. One of the major challenges of the laser communications is the necessity to accurately direct narrow beams. In the present talk, we discuss how electrically reconfigurable active metasurfaces can address this challenge. We perform an optical link budget analysis and discuss how the link range can be extended by increasing the aperture diameter or the input optical power. To assess maximal available output powers from realistic metasurface-based apertures, we experimentally probe the gate-tunable performance of indium tin oxide (ITO)-based active metasurfaces upon high-power illumination.
Chip-scale beam steering units, which would replace currently used mechanical gimbals, could revolutionize the field of free space optical communications. We review chip-scale technologies, which enable electronic beam reconfigurations and steering without mechanically moving parts. We assess the feasibility of using different electrically steerable apertures such as active metasurfaces and optical phased arrays for laser communications. Our optical link budget analysis shows that, for metasurface apertures of 1 cm in diameter and input powers of 5 W, the free space link range can approach ~ 10,000 km. We also provide an outlook how the link range can be increased further.
Active metasurfaces designed to operate at optical frequencies are a new class of flat optical elements that can dynamically control the wavefront of the reflected or transmitted light at a subwavelength scale. Here, we estimate the feasibility of using gate-tunable conducting oxide metasurfaces as electrically steerable apertures for free space optical communications. Our optical link budget analysis shows that for pulse energies of 1 mJ, free space optical communication at distances of 100000 km is possible. We further elaborate our analysis by adopting a system design approach and refining our optical link budget analysis.
We report an all-dielectric active metasurface based on indium phosphide (InP) multiple quantum wells (MQWs) operating at telecom wavelengths (λ=1.55μm). Our design exhibits high reflectance of >80% and is based on localized Mie supported by the metasurface. Our calculations show that the proposed metasurface can steer the beam up to polar angles of 35° while maintaining high efficiency of >80% and a side mode suppression ratio of 7 dB. The anticipated modulation frequencies are >1 MHz. Our metasurface can be used in future chip-scale light detection and ranging systems as well as for free-space optical communications.
Active metasurfaces represent a new class of flat optical elements, which can dynamically control the wavefront of the reflected or transmitted light at a subwavelength scale. Here, we theoretically investigate thermal performance of gate-tunable conducting oxide metasurfaces, which are illuminated with high-power laser beams (~kW/cm2). We develop strategies to mitigate and limit temperature increase of our active metasurfaces. To anchor our approach, we experimentally investigate the short pulse laser-induced damage of thin gold, indium tin oxide, and titanium nitride films. Our analysis reveals that our metasurfaces can support irradiances necessary for free space optical communication or light detection and ranging applications.
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