Temperature dependent polarization switch of 850-nm VCSELs with different apertures

• The aperture of VCSELs is formed by wet oxidation technology.
• The I–P curves of VCSELs with different apertures are measured and analyzed.
• We measured the polarization and spectrum characteristics at different temperatures.
• The change of polarization switch points for single transverse-mode is simulated and analyzed theoretically.

Temperature greatly affects the polarization properties of VCSELs. In this paper, these polarization properties of top-emitting 850-nm VCSELs are simulated by numerical calculation and then they are verified by experimental measurement. For a 4-μm aperture VCSEL, polarization switch current reduces from 1.4 mA to 0.4 mA as the temperature increases from 273 K to 323 K, which is caused by the change of the reflectivity of DBR and differential gain for LP01 transverse-mode. For VCSELs with 8-μm aperture, the first polarization switch current reduces from 2.1 mA to 0.8 mA as temperature increases from 273 K to 313 K. However, the second polarization switch current increases from 3.8 mA to 6.3 mA for the same increase in temperature because of the competition and polarization selection among several higher-order transverse modes. When the device aperture is further increased to 12 μm or 16 μm, there are several high-order transverse modes emitting even at small injection current, resulting in a serious competition and selection among themselves. This is why the polarization characteristics of VCSELs with 12 μm or larger aperture are irregular and different from those of smaller aperture devices. Our research results provide useful guidelines for the application of VCSELs operating at different ambient temperatures.