近日，新西兰奥克兰大学的Miro Erkintalo及其研究团队取得一项新进展。经过不懈努力，他们发现芯片集成微腔中参数驱动的纯克尔时间孤子。相关研究成果已于2024年3月14日在国际知名学术期刊《自然—光子学》上发表。

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)，这一发现使从电信到传感的应用取得了里程碑式的进步。以往的研究大多集中在由单色连续波激光外部驱动的纯三次克尔型非线性谐振器上，在这种系统中，孤子表现为独特的吸引子，其载流子频率与外部驱动场的载流子频率一致。然而，最近的实验表明，在同时具有二次和三次非线性的谐振器中，通过参数下转换可以产生一种性质不同的时间孤子。与纯克尔谐振器中的传统孤子相比，这些参数驱动孤子有两种不同的相位，它们的频谱中心位于驱动场频率的一半。

本文从理论上预测和实验上证明，在双色驱动条件下，参数驱动孤子也可以出现在纯克尔非线性谐振腔中。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，并且在两个外部驱动场之间具有载流子频率。该实验是在集成的氮化硅微腔中进行的，研究人员观察到的频率梳谱与理论预测非常吻合。这项研究结果不仅揭示了新型时间耗散孤子的存在，还实现了在微腔平台中明确参数驱动孤子频率梳的制备，这一平台与铸造厂批量制造的成熟技术相兼容。

附：英文原文

Title: Parametrically driven pure-Kerr temporal solitons in a chip-integrated microcavity

Author: Moille, Grgory, Leonhardt, Miriam, Paligora, David, Englebert, Nicolas, Leo, Franois, Fatome, Julien, Srinivasan, Kartik, Erkintalo, Miro

Issue&Volume: 2024-03-14

Abstract: 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.

DOI: 10.1038/s41566-024-01401-6

Source: https://www.nature.com/articles/s41566-024-01401-6