Single-mode, single-polarization and dispersion-flattened waveguides based on silicon carbide and diamond

•Low loss, flexible dispersion engineering, and pure single-polarization and single-mode operation are achieved at the same time.•Ultra-low and flat dispersion that varies from −1 to 1 ps/nm/km is obtained over an octave-spanning bandwidth from 1.81 to 3.63 μm, with four zero-dispersion wavelengths (ZDWs).•In comparison with a standard strip waveguide, scattering loss is greatly reduced by 8.6 times.•The proposed waveguides are easier to process without dry etching SiC and diamond and show better fabrication tolerance. Fundamental properties of an optical waveguide are mainly related to its guided modes and associated loss, dispersion, polarization and nonlinearity. Single-mode and single-polarization waveguiding has long been of interest, i.e., so-called truly single mode. We propose SiC- and diamond-based waveguides, which are truly single-mode and simultaneously dispersion-flattened. This is preferred for broadband nonlinear applications, such as octave-spanning supercontinuum and frequency comb generation. An ultra-low and flat dispersion profile with four zero-dispersion wavelengths (ZDWs) can be obtained over an octave-spanning bandwidth from 1.8 to 3.6 μm. Meanwhile, only TE00 mode is supported in the proposed waveguide over the low-dispersion bandwidth. Scattering loss of the waveguide is greatly reduced by 8.6 times, compared to a standard strip waveguide. Fabrication of the proposed waveguide is easier than previous dispersion-tailored waveguides, without dry etching SiC and diamond. It is expected that the proposed waveguides can find applications in nonlinear photonics, optomechanics and quantum optics.