Surface gratings for polarization control of single- and multi-mode oxide-confined vertical-cavity surface-emitting lasers

By etching a surface grating into the semiconductor cap-layer of top-emitting, oxide-confined VCSELs, we have fabricated polarization-stable VCSELs with an emission wavelength of 960 nm, while nominally identical devices on the same sample without a grating show polarization switches. With this technique we can define and stabilize the polarization not only for single-mode, but also for multi-mode VCSELs. We present highly multi-mode VCSELs with 10 mW output power having one common and stable polarization for all modes with a suppression of the orthogonal polarization by 15 dB up to thermal rollover. Combining the surface grating with the surface relief technique, the single-mode output power can be doubled, while the polarization of the VCSELs is well defined and stabilized.