Ultralow-loss silicon nitride waveguides for nonlinear optics
Doctoral thesis, 2021

The field of nonlinear optics relies on the interaction between high-intensity optical waves and nonlinear media. An integrated waveguide with large refractive index contrast allows to highly confine optical waves in a sub-μm^2 area, thus enhancing the optical intensity. However, such a high optical confinement increases the susceptibility to scattering losses induced from nanometer-level inhomogeneities.
Silicon nitride is a dielectric material featuring a relatively large nonlinear-index coefficient and a broadband transparency window, from ultraviolet to mid-infrared. Its refractive index contrast to silica allows high confinement and controlling the dispersion with the waveguide geometry. This material platform has emerged in the past years as a workhorse for nonlinear optics applications that rely on the Kerr effect, from microcomb generation to parametric amplification. In this thesis work, we focused on the development of advanced manufacturing techniques for the realization of ultralow-loss silicon nitride waveguides. Meter long high-confinement waveguides with record low losses in the order of 1.4 dB/m and dispersion-engineered microresonators with quality factors of 19 million are reported. Based on this technology, we demonstrated octave-spanning coherent microcombs and microcombs with photodetectable repetition rates occupying a device area less than 1 mm^2, i.e., one order of magnitude smaller than state of the art. The high yield and ultralow-loss silicon nitride waveguides also allowed us to achieve, for the first time, continuous-wave parametric amplification in an integrated waveguide, with a demonstrated gain of 9.5 dB and noise figure of 1.2 dB when operated in phase-sensitive mode.

parametric amplifier

DKS microcombs

ultralow loss

integrated waveguides

Kerr nonlinear optics

silicon nitride

Kollektorn, MC2, Chalmers. Zoom (Password: ZYdefence)
Opponent: Prof. John E. Bowers, UCSB, United States


Zhichao Ye

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Low-loss high-Q silicon-rich silicon nitride microresonators for Kerr nonlinear optics

Optics Letters,; Vol. 44(2019)p. 3326-3329

Journal article

High-Q Si3N4 microresonators based on a subtractive processing for Kerr nonlinear optics

Optics Express,; Vol. 27(2019)p. 35719-35727

Journal article

Octave-Spanning Frequency Comb Generation in All-Normal-Dispersion Silicon-Rich Silicon Nitride Waveguide

Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS,; Vol. 2020-May(2020)

Paper in proceedings

Zhichao Ye. Ping Zhao. Krishna Twayana. Magnus Karlsson. Victor Torres-Company. and Peter A. Andrekson, "Low-noise continuous-wave-pumped parametric amplifier using a silicon-nitride waveguide"

Zhichao Ye. Fuchuan Lei. Krishna Twayana. Marcello Girardi. Peter A. Andrekson. and Victor Torres-Company, "Integrated, ultra-compact high-Q silicon nitride microresonators for low-repetition-rate soliton microcombs"

Mohammed S. Alshaykh. Cong Wang. Nathan P. O’Malley. Zhichao Ye. Abdullah Al Noman. Daniel E. Leaird. Minghao Qi. Victor Torres-Company. and Andrew M. Weiner, "Optical Dual-Comb Vernier Division of an Octave-Spanning Kerr Microcomb"

Subject Categories

Nano Technology



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4925


Chalmers University of Technology

Kollektorn, MC2, Chalmers. Zoom (Password: ZYdefence)


Opponent: Prof. John E. Bowers, UCSB, United States

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