The electro-optic spatial light modulator of lithium niobate metasurface based on plasmonic quasi-bound states in the continuum.

Metasurface has attracted massive interest owing to its ability to control light arbitrarily in a wide range of applications, such as high-speed imaging, optical interconnection, and spectroscopy. Here we propose a free space light modulator combined with a gold grating metasurface based on lithium niobate (LiNbO3). The quasi-bound states in the continuum (quasi-BIC) are achieved in the metasurface. In addition, the plasmonic quasi-BIC and the guided-mode resonance (GMR) can be modulated by controlling the polarization of the incident light without any geometric adjustment. Thus, the working wavelength range from 1480 nm to 1620 nm was achieved, and the maximum resonance depth reached about 51% at the resonant wavelength. In addition, the insertion loss of the device was -2.8 dB at a wavelength of 1510 nm. Furthermore, the dynamic modulation speed reached up to 190 MHz and the highest signal-to-noise ratio (SNR) could reach about 49 dB at a frequency of 65 MHz. The data showed potential for the material for applications such as near-infrared imaging, beam steering, and free-space optical communication links.

Electrically controllable optical switch metasurface based on vanadium dioxide.

We report a voltage-tunable reflective gold wire grid metasurface on vanadium dioxide thin film, which consists of a metal-insulator-metal (MIM) structure. We excite surface plasmon polariton (SPP) modes on the gold surface by fabricating a one-dimensional structured gold wire grid. Joule heating of laser-induced graphene (LIG) can be controlled by the voltage at the bottom, allowing vanadium dioxide in the structure to complete the transition from the insulating state to the metallic state. The phase transition of vanadium dioxide strongly disrupts the plasmon modes excited by the gold wire grid above, thereby realizing a huge change in the reflection spectrum. This acts as a tunable metasurface optical switch with a maximum modulation depth (MD) of over 20 dB. We provide a more effective and simple method for creating tunable metasurfaces in the near-infrared band, which can allow metasurfaces to have wider applications in optical signal processing, optical storage, and holography.

Multifunctional optoelectronic device based on graphene-coupled silicon photonic crystal cavities.

We present a hybrid device based on graphene-coupled silicon (Si) photonic crystal (PhC) cavities, featuring triple light detection, modulation, and switching. Through depositing single-layer graphene onto the PhC cavity, the light-graphene interaction can be enhanced greatly, which enables significant detection and modulation of the resonant wavelength. The device is designed to generate a photocurrent directly by the photovoltaic effect and has an external responsivity of ∼14 mA/W at 1530.8 nm (on resonance), which is about 10 times higher than that off-resonance. Based on the thermo-optical effect of silicon and graphene, the device is also demonstrated in electro-optical and all-optical modulation. Also, due to the high-quality (Q) factor of the resonate cavity, the device can implement low threshold optical bistable switching, and it promises a fast response speed, with a rise (fall) time of ∼0.4 µs (∼0.5 µs) in the all-optical switch and a rise (fall) time of ∼0.5 µs (∼0.5 µs) in the electro-optical hybrid switch. The multifunctional photodetector, modulator, and optical bistable switch are achieved in a single device, which greatly reduces the photonic overhead and provides potential applications for future integrated optoelectronics.