Thermally induced birefringence in VCSELs: approaching the limits

Polarization dynamics in vertical-cavity surface-emitting lasers (VCSELs) are much faster than their intensity driven counterparts and can be a potential approach to overcome the bandwidth limitation in short-distance data transmission. The birefringence splitting B as the frequency difference between the two fundamental polarization modes is an important factor determining the polarization dynamics in spin-VCSELs. Although B can be strongly influenced by mechanical bending, for later applications an on-chip solution for birefringence tuning is favored. With an electrically driven asymmetric heating device we have demonstrated a thermally induced tuning range of Delta B = 45 GHz. The maximum achievable birefringence tuning was not limited by the laser but by material parameters and the fabrication process. In this paper We present an optimized design for thermally induced birefringence tuning and additional possibilities to increase the efficiency of the mechanism.