Chirped mirrors have underpinned advances in ultra-fast lasers based on bulk optics but have yet to be fully exploited in integrated photonics, where they could provide a means to engineer otherwise unattainable dispersion profiles for a range of nonlinear optical applications, including soliton frequency comb generation. The vast majority of integrated resonators for frequency combs make use of microring geometries, in which only waveguide width and height are varied to engineer dispersion. Here, we present an integrated photonic-crystal Fabry–Pérot resonator made of gallium phosphide (GaP), a material exhibiting a Kerr nonlinearity 200 times larger than that of silicon nitride and a high refractive index that permits the creation of strongly chirped photonic-crystal mirrors. Leveraging the additional degrees of freedom provided by integrated chirped mirrors, we disentangle optical losses from dispersion. We obtain an overall dispersion that is more anomalous than that achievable in both silicon nitride and gallium phosphide ring resonators with the same free-spectral range (FSR), while simultaneously obtaining higher quality factors than those of GaP ring resonators. With subharmonic pulsed pumping at an average power of 23.6 mW, we are able to access stable dissipative Kerr frequency combs in a device with a FSR of 55.9 GHz. We demonstrate soliton formation with a 3-dB bandwidth of 3.0 THz, corresponding to a pulse duration of 60 fs. This approach to cavity design based on photonic-crystal reflectors offers nearly arbitrary dispersion engineering over the optical transparency window of the nonlinear material.

中文翻译：

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在磷化镓中集成啁啾光子晶体腔，用于宽带孤子生成


啁啾镜为基于体光学的超快激光器的进步奠定了基础，但尚未在集成光子学中得到充分利用，在集成光子学中，它们可以为一系列非线性光学应用（包括孤子频率梳生成）设计原本无法实现的色散分布。绝大多数用于频率梳的集成谐振器都使用微环几何形状，其中只有波导的宽度和高度会发生变化，以设计色散。在这里，我们提出了一种由磷化镓 （GaP） 制成的集成光子晶体法布里-佩罗谐振器，这种材料表现出比氮化硅大 200 倍的克尔非线性和高折射率，允许产生强啁啾光子晶体镜。利用集成啁啾镜提供的额外自由度，我们消除了色散中的光损耗。我们获得的整体色散比具有相同自由光谱范围 （FSR） 的氮化硅和磷化镓环形谐振器所能实现的更异常，同时获得比 GaP 环形谐振器更高的品质因数。借助平均功率为 23.6 mW 的次谐波脉冲泵浦，我们能够在 FSR 为 55.9 GHz 的设备中获得稳定的耗散 Kerr 频率梳。我们演示了 3 dB 带宽为 3.0 THz 的孤子形成，对应于 60 fs 的脉冲持续时间。这种基于光子晶体反射器的腔体设计方法在非线性材料的光学透明窗口上提供了几乎任意的色散工程。