Investigating the thermal robustness of soliton crystal microcombs.

Soliton crystals are a novel form of microcomb, with relatively high conversion efficiency, good thermal robustness, and simple initiation among the methods to generate them. Soliton crystals can be easily generated in microring resonators with an appropriate mode-crossing. However, fabrication defects can significantly affect the mode-crossing placement and strength in devices. To enable soliton crystal states to be harnessed for a broader range of microcomb applications, we need a better understanding of the link between mode-crossing properties and the desired soliton crystal properties. Here, we investigate how to generate the same soliton crystal state in two different microrings, how changes in microring temperature change the mode-crossing properties, and how mode-crossing properties affect the generation of our desired soliton crystal state. We find that temperature affects the mode-crossing position in these rings but without major changes in the mode-crossing strength. We find that our wanted state can be generated over a device temperature range of 25 ∘C, with different mode-crossing properties, and is insensitive to the precise mode-crossing position between resonances.

Optimising microring resonator based optical frequency comb distillation for optical communications systems.

Microring resonators (MRR) can be used as devices for filtering out broadband noise on optical frequency combs, in cases where significant amplification of a generated comb is required. While comb distillation has been demonstrated experimentally for optical communication systems, approaches to optimise device and sub-system parameters have not been explored. Here, we investigate how the performance of comb distillation through micro-ring filtering depends on device parameters. We also explore device parameter dependent performance when the comb and MRR are misaligned in line spacing. For the device platform we investigate, we find that the required optical signal-to-noise ratio (OSNR) of a comb line can be reduced by 16 dB, independent of modulation format, using a MRR with a resonance bandwidth of 100 MHz and coupling loss of 3 dB.