# Towards visible soliton microcomb generation

## TL;DR

This paper reports the creation of visible-spectrum soliton microcombs using silica microresonators, achieving high optical quality factors and low power operation, opening new possibilities for miniature optical clocks and extending spectral reach.

## Contribution

Demonstration of mode-locked silica microcombs near the visible spectrum with high Q factors and low power requirements, advancing microcomb technology into shorter wavelengths.

## Key findings

- Achieved visible-spectrum soliton microcombs with high Q factors (~80 million).
- Demonstrated low-power (as low as 5.4 mW) soliton mode locking at 20 GHz.
- Extended spectral reach of microcombs into the visible and potentially ultraviolet bands.

## Abstract

Frequency combs have applications that extend from the ultra-violet into the mid-infrared bands. Microcombs, a miniature and often semiconductor-chip-based device, can potentially access most of these applications, but are currently more limited in spectral reach. Here, we demonstrate mode-locked silica microcombs with emission near the edge of the visible spectrum. By using both geometrical and mode-hybridization dispersion control, devices are engineered for soliton generation while also maintaining optical $Q$ factors as high as 80 million. Electronics-bandwidth-compatible (20 GHz) soliton mode locking is achieved with low pumping powers (parametric oscillation threshold powers as low as 5.4 mW). These are the shortest wavelength soliton microcombs demonstrated to date and could be used in miniature optical clocks. The results should also extend to visible and potentially ultra-violet bands.