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.

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.

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