Analysis of metal-interlaced-grating vertical-cavity surface-emitting lasers using the modal method by modal expansion

It is analyzed by the modal method by modal expansion (MMME) that the strong polarization discrimination of a vertical-cavity surface-emitting laser (VCSEL) can be effectively obtained by using the metal-interlaced grating on the topmost layer of the VCSEL. The MMME is used to overcome the problems coming from the large permittivity discontinuities at GaAs-Al-air-Al interfaces. The analyses predict the correct direction of dominant polarization and the mode-suppression ratio. The calculated transmission efficiencies explain the characteristics of the VCSEL's below threshold. It is found that the difference in phase and amplitude between the two orthogonal polarization generated by the grating plays important roles for the selection of a dominant polarization through mirror reflectivities and mirror losses. In addition, the influence of various thin metal layers on polarization stabilization is demonstrated.