Development and numerical simulation of spherical microresonators based on SiO2 – GeO2 germanosilicate glasses for generation of optical frequency combs

We propose and theoretically investigate the possibility of using spherical, whispering gallery mode microresonators based on germanosilicate glasses with different GeO₂ contents for generating optical frequency combs in the dissipative soliton regime under pumping at a wavelength of 1.55 or 2 μm. The dispersion and nonlinearity of microspheres of different radii are calculated and analysed, and their optimal characteristics and the expected parameters of the output radiation are determined. It is shown that the spectral widths of optical frequency combs formed in 0.8SiO₂ – 0.2GeO₂ and GeO₂ glass microspheres pumped at λ = 1.55 and 2 μm can be ~200 and ~300 nm, respectively. In these cases, in addition to the dissipative soliton with a duration of ~100 fs, the generation of dispersive waves is also observed.