Tailoring Broadband Kerr Soliton Microcombs via Post-Fabrication Tuning of the Geometric Dispersion

Abstract

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 which 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.

References in corpus (17)

• An Integrated-Photonics Optical-Frequency Synthesizer
• Photonic chip based optical frequency comb using soliton induced Cherenkov radiation
• Breaking the Loss Limitation of On-chip High-confinement Resonators
• Optical combs with a crystalline whispering gallery mode resonator
• Stably accessing octave-spanning microresonator frequency combs in the soliton regime
• Efficient and low-noise single-photon-level frequency conversion interfaces using silicon nanophotonics
• Ultra-low power nonlinear optics in a high Q CMOS compatible integrated micro-ring resonator
• Observation of dispersive wave emission by temporal cavity solitons
• Broadband Resonator-Waveguide Coupling for Efficient Extraction of Octave Spanning Microcombs
• Dissipative Kerr Solitons in a III-V Microresonator
• On-chip optical parametric oscillation into the visible: generating red, orange, yellow, and green from a near-infrared pump
• Tuning Kerr-Soliton Frequency Combs to Atomic Resonances
• Dissipative Kerr solitons and Cherenkov radiation in optical microresonators with third order dispersion
• Kerr Microresonator Soliton Frequency Combs at Cryogenic Temperatures
• A universal frequency engineering tool for microcavity nonlinear optics: multiple selective mode splitting of whispering-gallery resonances
• Measurements and modeling of atomic-scale sidewall roughness and losses in integrated photonic devices
• pyLLE: a Fast and User Friendly Lugiato-Lefever Equation Solver