17 GHz Lossless InP-Membrane Active Metasurface

TL;DR

This paper demonstrates a high-speed, low-loss active metasurface operating at 17.5 GHz using an InP membrane platform, enabling advanced optical control with minimal optical absorption and high modulation bandwidth.

Contribution

It introduces a novel InP-membrane active metasurface achieving record-high bandwidth and low optical loss, surpassing silicon-based devices in speed and efficiency.

Findings

Achieved 17.5 GHz modulation bandwidth.

Maintained a high Q factor of 102.

Optical loss of only 0.56 dB.

Abstract

High-speed active metasurfaces enable spatiotemporal control of incident light within an ultra-thin layer, offering new possibilities for optical communication, computing, and sensing. However, a fundamental tradeoff between electrical conductivity and optical absorption of the material has hindered the realization of active metasurfaces that simultaneously achieve broad modulation bandwidth and low optical loss. Here, we experimentally demonstrate a high-speed active metasurface operating in the 1.5-{\mu}m wavelength range that realizes a record-high modulation bandwidth of 17.5 GHz, while maintaining a high quality (Q) factor of 102 and an ultra-low optical loss of 0.56 dB. The key enabling technology is the indium-phosphide (InP) membrane platform; an n-type InP offers both high electron mobility and low free-carrier optical absorption, making it an ideal material for active metasurface devices. The high-Q Friedrich-Wintgen quasi-bound-states-in-the-continuum mode inside the InP-membrane high-contrast grating (HCG) is utilized to trap the normally incident light within an organic electro-optic (OEO) material, enabling efficient modulation. InP HCG also serves as an ultralow-resistance interdigitated electrodes for applying high-speed electrical signals to the OEO material, thereby offering 50-fold improvement in modulation bandwidth compared to conventional silicon-based counterparts. Our work paves the way towards high-speed, low-loss active metasurfaces for spatiotemporal control of light beyond the gigahertz regime.