Versatile tuning of Kerr soliton microcombs in crystalline microresonators

TL;DR

This paper demonstrates broad spectral tuning of Kerr soliton microcombs in crystalline microresonators, achieving significant frequency adjustments through thermal control, which enhances their applicability in optical technologies.

Contribution

It introduces a method for large, reliable spectral tuning of Kerr microcombs in crystalline microresonators using thermal effects with pump-detuning stabilization.

Findings

Spectral tuning of the center frequency up to -48.8 GHz.

Repetition frequency tuning up to -5.85 MHz.

Carrier-envelope offset frequency tuning up to -386 MHz.

Abstract

Microresonator-based optical frequency combs emitted from high-quality-factor microresonators, also known as microcombs, have opened up new horizons to areas of optical frequency comb technology including frequency metrology, precision sensing, and optical communication. To extend the capability of microcombs for such applications, large and reliable tunability is of critical importance. Here, we show broad spectral tuning of Kerr soliton microcombs in a thermally controlled crystalline microresonator with pump-detuning stabilization. The fundamental elements composing frequency combs, namely the center frequency, repetition frequency, and carrier-envelope offset frequency, are spectrally tuned by up to -48.8 GHz, -5.85 MHz, and -386 MHz, respectively, leveraging thermal effects in ultrahigh-Q crystalline magnesium fluoride resonators. We further demonstrate a 3.4-fold enhancement of soliton comb power resulting from thermal expansion with a temperature change of only 28 K by employing quantitative analyses of the fiber-to-resonator coupling efficiency.