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

TL;DR

This paper introduces resonant-coupling in microresonator soliton microcombs, significantly reducing power consumption while increasing spectral span and enabling octave-spanning operation at microwave repetition rates for portable applications.

Contribution

It presents a novel resonant-coupling approach that enhances spectral span and reduces power needs in microresonator soliton microcombs, facilitating practical, portable optical systems.

Findings

Threefold increase in spectral span

Up to tenfold reduction in repetition frequency

Reliable, turnkey 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.