Design of Partially Etched GaP-OI Microresonators for Two-Color Kerr Soliton Generation at NIR and MIR

We present and theoretically investigate a dispersion engineered GaP-OI microresonator containing a partially-etched gap of 250 nm x 410 nm in a 600 nm x 2990 nm waveguide. This gap enables a 3.25 {\mu}m wide anomalous dispersion spectral span covering both the near-infrared and the mid-infrared spectra. This anomalous dispersion is manifested by two mechanisms, being the hybridization of the fundamental TE modes around 1550 nm and the geometric dispersion of the higher order TE mode around the 3100 nm wavelengths, respectively. Two Kerr soliton combs can be numerically generated with 101 GHz and 97 GHz teeth spacings at these spectral windows. The proposed structure demonstrates the design flexibility thanks to the partially etched gap and paves the way towards potential coherent multicolor frequency comb generation in the emerging GaP-OI platform

Investigation of <italic>&#x03C7;</italic>⁽²⁾-Translated Optical Frequency Combs Tunability in Gallium Phosphide-on- Insulator Resonators

We describe a synergistic optimization approach that enables highly efficient frequency translation of a Kerr optical frequency comb (OFC) from 1550 nm to 775 nm in a gallium phosphide-on-insulator (GaP-OI) microresonator. Key distinctions from previous GaP-OI works which focused on individual optical nonlinearity are that this work not only emphasizes the interaction between the second- and third-order nonlinearity, but also explores the tunability of the &#x03C7;(2)-translated OFC through geometric and temperature tuning. We apply this approach to the burgeoning GaP-OI platform and demonstrate that a 50 &#x03BC;m-radius ring resonator with a cross-section of 555 nm &#x00D7; 600 nm has an intracavity second harmonic (SH) generation efficiency as high as 71.5&#x0025;&#x002F;W, 3 times larger compared to the state-of-the-art designs. The sum-frequency (SF) comb at 775 nm has a geometric tuning sensitivity of 354 GHz&#x002F;nm, and a thermal tuning sensitivity of 24.8 GHz&#x002F;K, paving the way for post-fabrication trimming and in-situ spectral shaping, with a broader potential to realize highly efficient, wide-spectrum, and tunable on-chip nonlinear sources