Superefficient microcombs at the wafer level

TL;DR

This paper presents a wafer-scale silicon nitride platform enabling high-efficiency, stable soliton microcombs with over 50% conversion efficiency and 100 lines, advancing large-scale photonic integration for diverse applications.

Contribution

It demonstrates wafer-level fabrication of soliton microcombs with high yield, spectral stability, and power efficiency, surpassing previous die-level solutions.

Findings

Achieved >50% average conversion efficiency in microcombs.

Produced 100 lines at 100 GHz repetition rate.

Enabled new sensing applications through wafer-level redundancy.

Abstract

Photonic integrated circuits utilize planar waveguides to process light on a chip, encompassing functions like generation, routing, modulation, and detection. Similar to the advancements in the electronics industry, photonics research is steadily transferring an expanding repertoire of functionalities onto integrated platforms. The combination of best-in-class materials at the wafer-level increases versatility and performance, suitable for large-scale markets, such as datacentre interconnects, lidar for autonomous driving or consumer health. These applications require mature integration platforms to sustain the production of millions of devices per year and provide efficient solutions in terms of power consumption and wavelength multiplicity for scalability. Chip-scale frequency combs offer massive wavelength parallelization, holding a transformative potential in photonic system integration, but efficient solutions have only been reported at the die level. Here, we demonstrate a silicon nitride technology on a 100 mm wafer that aids the performance requirements of soliton microcombs in terms of yield, spectral stability, and power efficiency. Soliton microcombs are reported with an average conversion efficiency exceeding 50%, featuring 100 lines at 100 GHz repetition rate. We further illustrate the enabling possibilities of the space multiplicity, i.e., the large wafer-level redundancy, for establishing new sensing applications, and show tri-comb interferometry for broadband phase-sensitive spectroscopy. Combined with heterogeneous integration of lasers, we envision a proliferation of high-performance photonic systems for applications in future navigation systems, data centre interconnects, and ranging.