# Power-efficient ultra-broadband soliton microcombs in resonantly-coupled microresonators

## TL;DR

Researchers developed a new method to make soliton microcombs more power-efficient, enabling broader use in portable optical devices.

## Contribution

Introducing resonant coupling to soliton microcombs, significantly reducing pump power requirements.

## Key findings

- Resonant coupling increases spectral span threefold compared to conventional designs.
- Octave-spanning combs can now operate at up to tenfold lower repetition frequencies.
- The design is compatible with laser integration and enables reliable soliton generation.

## Abstract

The drive to miniaturize optical frequency combs for practical deployment has spotlighted microresonator solitons as a promising chip-scale candidate. However, these soliton microcombs could be very power-hungry when their span increases, especially with fine comb spacings. As a result, realizing an octave-spanning comb at microwave repetition rates for direct optical-microwave linkage is considered not possible for photonic integration due to the high power requirements. Here, we introduce the concept of resonant-coupling to soliton microcombs to reduce pump consumption significantly. Compared to conventional waveguide-coupled designs, we demonstrate (i) a threefold increase in spectral span for high-power combs and (ii) up to a tenfold reduction in repetition frequency for octave-spanning operation. This configuration is compatible with laser integration and yields reliable, turnkey soliton generation. By eliminating the long-standing pump-power bottleneck, microcombs will soon become readily available for portable optical clocks, massively parallel data links, and field-deployable spectrometers.