Optical frequency combs are lightwaves composed of a large number of equidistant spectral lines. They are important for metrology, spectroscopy, communications and fundamental science. Frequency combs are most often generated by exciting dissipative solitons in lasers or in passive resonators, both of which suffer from important limitations. Here we show that the advantages of each platform can be combined. We introduce a novel kind of soliton (called an active cavity soliton) hosted in coherently driven lasers pumped below the lasing threshold. We use an active fibre resonator and measure high-peak-power solitons on a low-power background, in excellent agreement with simulations of a generalized Lugiato–Lefever equation. Moreover, we find that amplified spontaneous emission has negligible impact on the soliton’s stability. Our results open up novel avenues for frequency comb formation by showing that coherent driving and incoherent pumping can be efficiently combined to generate a high-power ultra-stable pulse train.

光频梳是由大量等距谱线组成的光波。它们对于计量学、光谱学、通信和基础科学很重要。频率梳通常是由激光器或无源谐振器中的激发耗散孤子产生的，两者都受到重要限制。在这里，我们展示了每个平台的优势可以结合起来。我们介绍了一种新型孤子（称为有源腔孤子），它位于激光阈值以下泵浦的相干驱动激光器中。我们使用有源光纤谐振器并在低功率背景下测量高峰值功率孤子，这与广义 Lugiato-Lefever 方程的模拟非常一致。此外，我们发现放大的自发辐射对孤子稳定性的影响可以忽略不计。