Gigahertz switchable wavefront shaping through LNOI-empowered metasurfaces

Over the past decade, metasurfaces deploying two-dimensional artificial nanostructures have emerged as breakthrough platforms for manipulating light in different degrees of freedom. These metasurfaces show great potential in basic scientific research and industrial applications.

Compared with static light field control, dynamic light field control introduces new control variables in the time domain, which can realize real-time beam shaping, spatial light modulation, information processing, etc. Active metasurfaces can manipulate light in the space and time domains at high speeds, potentially opening up new areas of photonic technology and bridging the gap between theoretical physics and practical applications.

Dynamic reconfigurability is key. Although a range of materials and techniques have been explored to enhance the tunability of metasurfaces, achieving tunable wavefronts at very high speeds remains a daunting challenge. Fortunately, the recently emerged lithium niobate-on-insulator (LNOI) technology provides a promising platform for ultrahigh-speed tunable metasurfaces.

LNOI has become a versatile material for photonic integrated circuits (PICs) due to its excellent electro-optical effect. This technology significantly improves the performance of PIC, making it a leading platform for future high-speed electro-optical modulation devices.

Recently, a joint research team from East China Normal University and Nanjing University successfully integrated electrodes, metasurfaces, and LNOI photonic waveguides into a PIC device.It is reported Advanced Photonicsthey demonstrated ultrahigh-speed wavefront-shaping metasurfaces with integrated PIC-driven metasurfaces.

By applying different electrical signals to the electrodes, the device demonstrates the ability to shape any wavefront in a reconfigurable polarization state. The researchers demonstrated high-speed tunability of a variety of features, including lateral focus position and focal length control, orbital angular momentum (OAM), and Bessel beaming.

By effectively combining the propagation and geometric phases of birefringent nanostructures in this waveguide scheme, the tunability of these features can be controlled in arbitrary orthogonal polarizations. Experimental measurements show that the system can operate at modulation speeds up to 1.4 GHz.

The authors emphasize that the current high-speed modulation results are preliminary. This device has the potential to increase the modulation speed to hundreds of gigahertz by optimizing the electrode design and utilizing the electro-optical effect of lithium niobate.

Corresponding author Professor Li Lin from the State Key Laboratory of Precision Spectroscopy at East China Normal University said: “The integration of subwavelength metasurfaces and optical waveguides provides a versatile and efficient method to manipulate light at multiple degrees of freedom at high speed. This advancement It paves the way for potential applications in optical communications, computing, sensing and imaging.