Spatial frequency comb generation in a microresonator using various saturable absorbers: a comparative study

In this paper, we theoretically demonstrate the generation of an optical spatial frequency comb (SFC) in the microresonator cavity, particularly the cavity of a vertical cavity surface-emitting laser containing a saturable absorber (SA) layer and coupled with frequency-selective feedback. To determine the operational region of the microresonator cavity, we analytically characterize the relevant parameters. The intracavity field equation, a complex Ginzburg–Landau equation, is numerically solved using the split-step Fourier method to generate SFC. We investigated SFC generation with five different SAs: semiconductor saturable absorber, graphene saturable absorber, graphene flakes saturable absorber, black phosphorus, and carbon nanotube. For each SA, we identify the parametric zone that supports a distinct SFC. We compiled a comprehensive table that specifies the range of system parameters favorable to stable SFC formation for each SA. A comparative analysis of the resulting SFC bandwidth profiles and the number of SFC teeth across different SAs is also presented. The role of the operating wavelength on the SFC bandwidth is also determined.