On‐Chip Terahertz Optoelectronic Transmission‐Modulators

ABSTRACT The transmission and modulation of terahertz (THz) waves play a key role in the THz‐links. The current research on THz transmission‐modulators is no longer limited to free‐space. Due to the advancement of THz sources and detectors, as well as the maturity of micro‐nano process technology, on‐chip electronics and photonics technologies have synchronously migrated to the THz band, thereby promoting research on on‐chip THz transmission‐modulators. We have found that the development of on‐chip THz transmission‐modulators has significantly accelerated in the past decade, giving rise to multiple research directions, including: i) on‐chip THz dielectric waveguides migrated from integrated photonics; ii) THz metal transmission lines developed from electronic technology, as well as metal‐based THz surface plasmon transmission; iii) on‐chip THz photonic crystal systems; iv) on‐chip THz time‐domain systems; v) on‐chip dynamic THz modulation; vi) THz coupling between free‐space and on‐chip; vii) on‐chip THz‐to‐optical conversion, and viii) inverse design of on‐chip THz optoelectronic devices based on machine learning. We provide this immediate and systematic review on the field of on‐chip THz transmission‐modulators, aiming to reflect the state‐of‐the‐art in the integration of electronic and photonics technologies in the THz field, and accelerate the development of on‐chip THz optoelectronic devices.