Towards fibre-like loss for photonic integration from violet to near-infrared.

Abstract

Over the past decades, remarkable progress has been made in reducing the loss of photonic integrated circuits (PICs) within the telecom band^1-4, facilitating on-chip applications spanning low-noise optical⁵ and microwave synthesis⁶, to lidar⁷ and photonic artificial intelligence engines⁸. However, several obstacles arise from the marked increase in material absorption and scattering losses at shorter wavelengths^9,10, which prominently elevate power requirements and limit performance in the visible and near-visible spectrum. Here we present an ultralow-loss PIC platform based on germano-silicate-the material underlying the extraordinary performance of optical fibre-but realized by a fully CMOS-foundry-compatible process. These PICs achieve resonator Q factors surpassing 180 million from violet to telecom wavelengths. They also attain a 10-dB higher quality factor without thermal treatment in the telecom band, expanding opportunities for heterogeneous integration with active components¹¹. Other features of this platform include readily engineered waveguide dispersion, acoustic mode confinement and large-mode-area-induced thermal stability-each demonstrated by soliton microcomb generation, stimulated Brillouin lasing and low-frequency-noise self-injection locking, respectively. The success of these germano-silicate PICs can ultimately enable fibre-like loss onto a chip, leading to an additional 20-dB improvement in waveguide loss over the current highest performance photonic platforms. Moreover, the performance abilities demonstrated here bridge ultralow-loss PIC technology to optical clocks¹², precision navigation systems¹³ and quantum sensors¹⁴.