High-speed wavefront shaping integrated on a chip
In the realm of optical information and scientific research, achieving high-speed spatiotemporal control of light has always been a fascinating challenge. Traditional methods have been limited either by their modulation speed or by the degrees of freedom they offer for control. However, a recent breakthrough in this field has been made by a collaborative effort from researchers at East China Normal University, Nanjing University, China Jiliang University, Shanxi University, and the Chinese Academy of Sciences in China.
Their innovative approach involves integrating metasurfaces with an electrically controlled lithium niobate on insulator (LNOI) photonic integrated circuit (PIC) chip to showcase dynamic control of free-space wavefront shaping and switching at incredibly fast gigahertz rates. The device is meticulously designed on an X-cut LNOI platform to ensure optimal electro-optical performance. By combining a waveguide with two orthogonally propagated modes and nano-scatterers at specific positions, the researchers are able to generate arbitrary polarized light.
Through the strategic incorporation of a Mach–Zehnder interferometer (MZI) and a phase shifter, along with pairs of electrodes, they can control both the amplitude and phase of the two orthogonal modes, enabling the generation of light with arbitrary polarizations across the Poincaré sphere surface at high speeds. A specially crafted silicon metasurface is then placed on the slab waveguide to achieve desired functionalities and facilitate rapid modulation or switching by adjusting voltages on the MZI and phase shifter electrodes.
By employing different designs of silicon metasurfaces, the team has successfully demonstrated tunable focusing with variable lateral focal positions and focal lengths, the generation of orbital angular momentum light beams with diverse topological numbers, and Bessel beams. Importantly, the tunability of these functionalities covers a wide range of orthogonal polarizations. This groundbreaking approach not only significantly enhances modulation speed but also combines the strengths of metasurfaces and PICs, allowing for efficient management of multiple light degrees of freedom at high speeds.
Although the current work is limited to switchable functionalities in orthogonal polarization states, the researchers envision expanding this capability by incorporating complex unit cells, artificial intelligence design, and multiple input waveguide modes. By doing so, the number of switchable functionalities could be substantially increased, with the potential to extend polarization states to non-orthogonal configurations.
The researchers anticipate that their integration of high-speed electrical modulated PICs and metasurfaces will pave the way for achieving tunable functionalities with unparalleled modulation speed. With the current modulation bandwidth already reaching 1.4 GHz, they believe this could be further enhanced to hundreds of gigahertz based on the electro-optical effect of lithium niobate. This successful integration opens up a myriad of applications in high-capacity optical communications, rapid optical computation, advanced imaging techniques, and cutting-edge sensing technologies.
In conclusion, this research represents a significant leap forward in the field of optical manipulation and control, offering tremendous potential for revolutionizing various technological applications reliant on high-speed light modulation and shaping.
Source: https://www.nature.com/articles/s41566-024-01404-3
Their innovative approach involves integrating metasurfaces with an electrically controlled lithium niobate on insulator (LNOI) photonic integrated circuit (PIC) chip to showcase dynamic control of free-space wavefront shaping and switching at incredibly fast gigahertz rates. The device is meticulously designed on an X-cut LNOI platform to ensure optimal electro-optical performance. By combining a waveguide with two orthogonally propagated modes and nano-scatterers at specific positions, the researchers are able to generate arbitrary polarized light.
Through the strategic incorporation of a Mach–Zehnder interferometer (MZI) and a phase shifter, along with pairs of electrodes, they can control both the amplitude and phase of the two orthogonal modes, enabling the generation of light with arbitrary polarizations across the Poincaré sphere surface at high speeds. A specially crafted silicon metasurface is then placed on the slab waveguide to achieve desired functionalities and facilitate rapid modulation or switching by adjusting voltages on the MZI and phase shifter electrodes.
By employing different designs of silicon metasurfaces, the team has successfully demonstrated tunable focusing with variable lateral focal positions and focal lengths, the generation of orbital angular momentum light beams with diverse topological numbers, and Bessel beams. Importantly, the tunability of these functionalities covers a wide range of orthogonal polarizations. This groundbreaking approach not only significantly enhances modulation speed but also combines the strengths of metasurfaces and PICs, allowing for efficient management of multiple light degrees of freedom at high speeds.
Although the current work is limited to switchable functionalities in orthogonal polarization states, the researchers envision expanding this capability by incorporating complex unit cells, artificial intelligence design, and multiple input waveguide modes. By doing so, the number of switchable functionalities could be substantially increased, with the potential to extend polarization states to non-orthogonal configurations.
The researchers anticipate that their integration of high-speed electrical modulated PICs and metasurfaces will pave the way for achieving tunable functionalities with unparalleled modulation speed. With the current modulation bandwidth already reaching 1.4 GHz, they believe this could be further enhanced to hundreds of gigahertz based on the electro-optical effect of lithium niobate. This successful integration opens up a myriad of applications in high-capacity optical communications, rapid optical computation, advanced imaging techniques, and cutting-edge sensing technologies.
In conclusion, this research represents a significant leap forward in the field of optical manipulation and control, offering tremendous potential for revolutionizing various technological applications reliant on high-speed light modulation and shaping.
Source: https://www.nature.com/articles/s41566-024-01404-3
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