Contactless integrated photonic probes: A non-invasive on-chip optical monitor

On-chip optical power monitors are indispensable for functional implementation and stabilization of large-scale and complex photonic integrated circuits (PICs). Traditional on-chip optical monitoring is implemented by tapping a small portion of optical power from the waveguide, which leads to significant loss. Due to its advantages like non-invasive nature, miniaturization, and complementary metal-oxide-semiconductor (CMOS) process compatibility, a transparent monitor named contactless integrated photonic probes (CLIPP), has been attracting great attention in recent years. The CLIPP indirectly monitors the optical power in the waveguide by detecting the conductance variation of the local optical waveguide caused by the surface state absorption (SSA) effect.

The team led by Prof. Jian Wang from Huazhong University of Science and Technology (HUST) has written a review paper on the research of the CLIPP, providing a comprehensive summary of the fundamentals, characteristics, and applications of the CLIPP. The review first introduces the fundamentals of the CLIPP including the concept, the equivalent electric model and the impedance read-out method, and then summarizes some characteristics of the CLIPP. Finally, the functional applications of the CLIPP on the identification and feedback control of optical signal are discussed, followed by a brief outlook on the prospects of the CLIPP. The review entitled “Contactless integrated photonic probes: fundamentals, characteristics, and applications” was published on Frontiers of Optoelectronics (published on Aug. 5, 2024).