Efficient and Reconfigurable Soliton Microcomb Source Based on the 400-nm-Thick Si₃N₄ Platform

Dark soliton microcombs with a high repetition rate and high line power can be generated in a nonlinear ring with normal group velocity dispersion (GVD), making them suitable for various applications. This study explores the impact of pump power, coupling coefficient, waveguide loss, and GVD on the dark soliton spectral profile, including the power level of the comb lines and the extent of the flat spectral range. A dark soliton microcomb is experimentally generated based on a 400-nm-thick Si<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> microring, demonstrating an off-chip −10-dBm bandwidth of 28 nm. Spectral reconstruction of the efficient dark soliton is also achieved. By changing the temperature by 2 °C, the −10-dBm bandwidth is varied from 23 nm to 28 nm and the spectral flatness is modified. Furthermore, the comb spacing of the generated dark soliton can be changed from one free spectral range (FSR) to three FSRs by properly adjusting the pump power and wavelength. The proposed scheme offers a straightforward method for creating an efficient soliton microcomb source with a customizable spectral shape on the 400-nm-thick Si<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> platform, suitable for a variety of applications.