Spectral extension and synchronization of microcombs in a single microresonator

Abstract

Broadband optical frequency combs are extremely versatile tools for precision spectroscopy, ultrafast ranging, as channel generators for telecom networks, and for many other metrology applications. Here, we demonstrate that the optical spectrum of a soliton microcomb generated in a microresonator can be extended by bichromatic pumping: one laser with a wavelength in the anomalous dispersion regime of the microresonator generates a bright soliton microcomb while another laser in the normal dispersion regime both compensates the thermal effect of the microresonator and generates a repetition-rate-synchronized second frequency comb. Numerical simulations agree well with experimental results and reveal that a bright optical pulse from the second pump is passively formed in the normal dispersion regime and trapped by the primary soliton. In addition, we demonstrate that a dispersive wave can be generated and influenced by cross-phase-modulation-mediated repetition-rate synchronization of the two combs. The demonstrated technique provides an alternative way to generate broadband microcombs and enables the selective enhancement of optical power in specific parts of a comb spectrum.

Ultra-broadband Kerr microcomb through soliton spectral translation

“…The use of an auxiliary pump enables straightforward access to soliton states, through an effective temperature compensation mechanism that bypasses the thermal bistability 27 – 29 . Moreover, simultaneous spectral broadening of the comb, attributed to cross-phase modulation (XPM) effects, has also recently been observed 30 , though the magnitude of the effect was limited. Here, we consider a dual-pumped system in a regime where much more significant spectral broadening is realized.…”

“…Zhang and colleagues have recently realized a similar dual pumping configuration, in which an auxiliary laser at 1330 nm spectrally broadens a 1550 nm soliton microcomb down to wavelengths of around 1275 nm 30 , considerably increasing the bandwidth of such low repetition rate DKS solitons. The spectrum extends from 1275 to 1720 nm (taken at the −50 dB points relative to the maximum), an extent of 60 THz, and the auxiliary laser is responsible for about 22 THz of spectral extension on the high frequency side, resulting in about a factor 1.5 × increase of the bandwidth of the comb.…”

“…In ref. 30 , spectral broadening is generally attributed to XPM effects, which leaves open many questions about the relationship between the original comb and the spectrally broadened region—in particular, whether any offset between the two regions is indicative of independent frequency combs. Here, we show that the dominant process behind spectral broadening in our system is FWM-BS, so that soliton comb teeth generated by the primary pump are spectrally translated to both the low frequency and high frequency sides of the spectrum.…”

Thermal Behaviors and Optical Parametric Oscillation in 4H‐Silicon Carbide Integrated Platforms

“…As shown in Figure 5a, there are four new frequencies beside the two pumps, based on the cascaded FWM. The OPO spectrum is expected to be symmetric, as shown in Figure 5b, which is simulated based on the Lugiato-Lefever equation using the same conditions as in the experiment [45]…”

Frequency comb generation in silicon nitride resonators with amplitude modulated pump

“…On the other hand, in [29] a fraction of the soliton light generated in a first resonator was injected into a second resonator, and a soliton with identical repetition rate than the one in the master resonator could still be generated, even when their FSRs were dissimilar by up to ~8 MHz. In [30] a micro-resonator was pumped with two pumps 220nm apart, to generate solitons that had their repetition rate synchronized thanks to cross-phase modulation (XPM), even when pumping different mode families with dissimilar dispersion values. It has also been reported that modulating a pump with a 20 MHz signal resulted in the generation of soliton molecules with different constituent intensities, but with their repetition rates locked via XPM [31].…”