Abstract
Soliton formation in on-chip micro-comb generation balances cavity dispersion and nonlinearity and allows coherent, low-noise comb operation. We study the intracavity waveform of an on-chip microcavity soliton in a silicon nitride microresonator configured with a drop port. Whereas combs measured at the through port are accompanied by a very strong pump line which accounts for >99% of the output power, our experiments reveal that inside the microcavity, most of the power is in the soliton. Time-domain measurements performed at the drop port provide information that directly reflects the intracavity field. Data confirm a train of bright, close to bandwidth-limited pulses, accompanied by a weak continuous wave (CW) background with a small phase shift relative to the comb.
Highlights
Comb generation in high quality factor (Q) microresonators has attracted increasing attention
We study the intracavity waveform of an on-chip microcavity soliton in a silicon nitride microresonator configured with a drop port
The very strong pump line observed in all cases at the through port is explained by several factors: (1) the input bus is under-coupled; (2) power transfer into combs aggravates the under-coupling condition [13]; (3) soliton formation is accompanied by a strong effective reddetuning [2, 6, 7] and the power difference is further enhanced after the transition
Summary
Comb generation in high quality factor (Q) microresonators has attracted increasing attention. The pump line is 11 dB stronger than the adjacent comb spectrum in Fig. 4(a) and 8 dB, in both cases nearly a 30 dB difference compared to the through port This suggests that under soliton operation, most of the strong pump power at the through port results from the pump being transmitted directly through the bus waveguide without coupling into the microring. The very strong pump line observed in all cases at the through port is explained by several factors: (1) the input bus is under-coupled; (2) power transfer into combs aggravates the under-coupling condition [13]; (3) soliton formation is accompanied by a strong effective reddetuning [2, 6, 7] and the power difference is further enhanced after the transition. Chaotic State @ 1551.27 nm Input Port Through Port (output) Drop Port (output) Intracavity Single Soliton @ 1551.27 nm Input Port Through Port (output) Drop Port (output) Intracavity
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