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Chengying Bao

Publications and source records attributed to Chengying Bao.

25 records · Page 2Linked to original sources
arXiv2017

Thermo-Optical Chaos and Direct Soliton Generation in Microresonators

We investigate, numerically and experimentally, the effect of thermo-optical (TO) chaos on direct soliton generation (DSG) in microresonators. When the pump laser is scanned from blue to red and then stopped at a fixed wavelength, we find that the solitons generated sometimes remain (survive) and sometimes annihilate subsequent to the end of the scan. We refer to the possibility of these different outcomes arising under identical laser scan conditions as coexistence of soliton annihilation and survival. Numerical simulations that include the thermal dynamics show that the coexistence of soliton annihilation and survival is explained by TO chaos accompanying comb generation. The random fluctuations of the cavity resonance occurring under TO chaos are also found to trigger spontaneous soliton generation after the laser scan ends. The coexistence of soliton annihilation and survival as well as spontaneous soliton generation are observed experimentally in a silicon-nitride microresonator. The elucidation of the role of TO chaos provides important insights into the soliton generation dynamics in microresonators, which may eventually facilitate straightforward soliton generation in fully-integrated microresonators.

physics.optics↗
arXiv2016

Soliton repetition rate in a silicon-nitride microresonator

The repetition rate of a Kerr comb comprising a single soliton in an anomalous dispersion silicon nitride microcavity is measured as a function of pump frequency tuning. The contributions from the Raman soliton self-frequency shift (SSFS) and from thermal effects are evaluated both experimentally and theoretically; the SSFS is found to dominate the changes in repetition rate. The relationship between the changes in repetition rate and pump frequency detuning is found to be independent of the nonlinearity coefficient and dispersion of the cavity. Modeling of the repetition rate change by using the generalized Lugiato-Lefever equation is discussed; the Kerr shock is found to have only a minor effect on repetition rate for cavity solitons with duration down to ~50 fs.

physics.optics↗
arXiv2016

Observation of Fermi-Pasta-Ulam Recurrence Induced by Breather Solitons in an Optical Microresonator

We present, experimentally and numerically, the observation of Fermi-Pasta-Ulam recurrence induced by breather solitons in a high-Q SiN microresonator. Breather solitons can be excited by increasing the pump power at a relatively small pump phase detuning in microresonators. Out of phase power evolution is observed for groups of comb lines around the center of the spectrum compared to groups of lines in the spectral wings. The evolution of the power spectrum is not symmetric with respect to the spectrum center. Numerical simulations based on the generalized Lugiato-Lefever equation are in good agreement with the experimental results and unveil the role of stimulated Raman scattering in the symmetry breaking of the power spectrum evolution. Our results shows that optical microresonators can be exploited as a powerful platform for the exploration of soliton dynamics.

physics.optics↗
arXiv2016

Frequency Comb Generation in 300 nm Thick SiN Concentric-Racetrack-Resonators: Overcoming the Material Dispersion Limit

Kerr nonlinearity based frequency combs and solitons have been generated from on-chip optical microresonators with high quality factors and global or local anomalous dispersion. However, fabrication of such resonators usually requires materials and/or processes that are not standard in semiconductor manufacturing facilities. Moreover, in certain frequency regimes such as visible and ultra-violet, the large normal material dispersion makes it extremely difficult to achieve anomalous dispersion. Here we present a concentric racetrack-shaped resonator that achieves anomalous dispersion in a 300 nm thick silicon nitride film, suitable for semiconductor manufacturing but previously thought to result only in waveguides with high normal dispersion, a high intrinsic Q of 1.5 million, and a novel mode-selective coupling scheme that allows coherent combs to be generated. We also provide evidence suggestive of soliton-like pulse formation in the generated comb. Our method can achieve anomalous dispersion over moderately broad bandwidth for resonators at almost any wavelength while still maintaining material and process compatibility with high-volume semiconductor manufacturing.

physics.optics↗
arXiv2016

Intracavity characterization of micro-comb generation in the single-soliton regime

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.

physics.optics↗
arXiv2015

Carrier envelope phase dynamics of cavity solitons: soliton stability and scaling law

The relationship between carrier envelope phase (CEP) slip of cavity soliton (CS) and pump phase detuning is derived analytically and numerically. To preserve the stability of CS, CEP slip always equals to the pump phase detuning. When CEP slip fails to follow the pump phase detuning, CS becomes unstable. The locking between CEP slip and pump phase detuning results in a scaling law for CS.

physics.optics↗