Ultra-broadband Kerr microcomb through soliton spectral translation
Gregory Moille, Edgar Perez, Jordan Stone, Ashutosh Rao, Xiyuan Lu, Tahmid Rahman, Yanne Chembo, Kartik Srinivasan
Broad bandwidth and stable microresonator frequency combs are critical for optical atomic clocks, optical frequency synthesis, dual comb spectroscopy, and a host of other applications that require accurate and precise optical frequency measurements in a compact and deployable format. Typically, broad bandwidths (e.g., close to one octave) are achieved by tailoring the geometric dispersion of the microresonator in the spectral region surrounding the pump laser that drives Kerr soliton formation. Here, we demonstrate that the addition of a second pump laser at a suitable frequency results in a substantial increase of the frequency comb bandwidth through non-degenerate four-wave mixing that results in new sets of generated dispersive waves on both side of the spectrum. We model this behavior through numerical simulation of the multi-pump system and develop a linear approximation that explains the creation of new dispersive waves through the concept of synthetic dispersion, in which the multiple pumps effectively alter the starting dispersion landscape set by the resonator geometry. We experimentally demonstrate this concept by pumping a silicon nitride microring resonator at 1060 nm and 1550 nm, resulting in a single soliton microcomb whose bandwidth approaches two octaves (137 THz to 407 THz). Such broad bandwidths provide new opportunities for stabilization of microcombs through self-referencing, and for extending microcombs to visible wavelengths for which pure geometric dispersion engineering is challenging.
, Perez, E.
, Stone, J.
, Rao, A.
, Lu, X.
, Rahman, T.
, Chembo, Y.
and Srinivasan, K.
Ultra-broadband Kerr microcomb through soliton spectral translation, [online], https://doi.org/10.1038/s41467-021-27469-0
(Accessed November 29, 2022)