Geometric dispersion in integrated microresonators plays a major role in nonlinear optics applications, especially at short wavelengths, to compensate the natural material normal dispersion. Tailoring of geometric confinement allows for anomalous dispersion, which, in particular, enables the formation of microcombs that can be tuned into the dissipative Kerr soliton (DKS) regime. Due to processes like soliton-induced dispersive wave generation, broadband DKS combs are particularly sensitive to higher-order dispersion, which, in turn, is sensitive to the ring dimensions at the nanometer-level. For microrings exhibiting a rectangular cross section, the ring width and thickness are the two main control parameters to achieve the targeted dispersion. The former can be easily varied through parameter variation within the lithography mask, yet the latter is defined by the film thickness during growth of the starting material stack and can show a significant variation (few percent of the total thickness) over a single wafer. In this Letter, we demonstrate that controlled dry-etching allows for fine tuning of the device layer (silicon nitride) thickness at the wafer level, allowing multi-project wafers targeting different wavelength bands and post-fabrication trimming in air-clad ring devices. We demonstrate that such dry etching does not significantly affect either the silicon nitride surface roughness or the optical quality of the devices, thereby enabling fine tuning of the dispersion and the spectral shape of the resulting DKS states.

中文翻译：

---

通过几何色散的制造后调整来定制宽带克尔孤子微梳


集成微谐振器中的几何色散在非线性光学应用中发挥着重要作用，特别是在短波长下，以补偿自然材料的法向色散。几何限制的定制允许反常色散，特别是可以形成可调谐到耗散克尔孤子（DKS）状态的微梳。由于孤子诱导色散波生成等过程，宽带 DKS 梳对高阶色散特别敏感，而高阶色散又对纳米级的环尺寸敏感。对于具有矩形横截面的微环，环宽度和厚度是实现目标色散的两个主要控制参数。前者可以通过光刻掩模内的参数变化轻松改变，而后者则由起始材料堆叠生长期间的膜厚度定义，并且可以在单个晶圆上显示出显着的变化（总厚度的几个百分点）。在这封信中，我们证明了受控干法蚀刻可以在晶圆级微调器件层（氮化硅）厚度，从而允许针对不同波长带的多项目晶圆以及空气包覆环器件中的制造后修整。我们证明，这种干法蚀刻不会显着影响氮化硅表面粗糙度或器件的光学质量，从而能够微调所得 DKS 态的色散和光谱形状。