The discovery that externally driven nonlinear optical resonators can sustain ultrashort pulses (solitons) corresponding to coherent optical frequency combs has enabled landmark advances in applications from telecommunications to sensing. Most previous research has focused on resonators with purely cubic (Kerr-type) nonlinearity that are externally driven with a monochromatic continuous-wave laser—in such systems, the solitons manifest themselves as unique attractors whose carrier frequency coincides with that of the external driving field. Recent experiments have, however, shown that a qualitatively different type of temporal soliton can arise via parametric downconversion in resonators with simultaneous quadratic and cubic nonlinearity. In contrast to conventional solitons in pure-Kerr resonators, these parametrically driven solitons come in two different flavours with opposite phases, and they are spectrally centred at half of the frequency of the driving field. Here we theoretically predict and experimentally demonstrate that parametrically driven solitons can also arise in resonators with pure-Kerr nonlinearity under conditions of bichromatic driving. In this case, the solitons arise through four-wave-mixing-mediated phase-sensitive amplification, come with two distinct phases and have a carrier frequency in between the two external driving fields. Our experiments are performed in an integrated silicon nitride microcavity, and we observe frequency comb spectra in remarkable agreement with theoretical predictions. In addition to representing the discovery of a new type of temporal dissipative soliton, our results constitute an unequivocal realization of parametrically driven soliton frequency combs in a microcavity platform that is compatible with foundry-ready mass fabrication.

外部驱动的非线性光学谐振器可以维持与相干光学频率梳相对应的超短脉冲（孤子）的发现使得从电信到传感的应用取得了里程碑式的进步。以前的大多数研究都集中在具有纯立方（克尔型）非线性的谐振器上，这些谐振器由单色连续波激光器从外部驱动——在此类系统中，孤子表现为独特的吸引子，其载波频率与外部驱动场的载波频率一致。然而，最近的实验表明，通过同时具有二次和三次非线性的谐振器中的参数下变频，可以产生性质不同类型的时间孤子。与纯克尔谐振器中的传统孤子相比，这些参数驱动的孤子有两种不同的风格，具有相反的相位，并且它们的频谱中心位于驱动场频率的一半。在这里，我们从理论上预测并通过实验证明，在双色驱动条件下，参数驱动的孤子也可以出现在具有纯克尔非线性的谐振器中。在这种情况下，孤子通过四波混合介导的相敏放大产生，具有两个不同的相位，并且具有位于两个外部驱动场之间的载波频率。我们的实验是在集成氮化硅微腔中进行的，我们观察到的频率梳光谱与理论预测非常一致。除了代表了新型时间耗散孤子的发现之外，我们的结果还明确地实现了微腔平台中参数驱动的孤子频率梳，该平台与代工厂大规模制造兼容。