New Approaches for Birefringence Tuning in Vertical-Cavity Surface-Emitting Lasers

Using the elasto-optic effect we increase the frequency difference between the two orthogonally polarized modes, the so-called birefringence splitting, in standard single-mode oxideconfined GaAs-based vertical-cavity surface-emitting lasers (VCSELs). The birefringence may play an important role in the realization of ultrafast polarization modulation for highspeed data transmission. For practical implementation it is necessary to miniaturize the strain-inducing mechanism for birefringence tuning in VCSELs. The goal is the realization of integrated structures on the VCSEL chip. In this article we discuss our work on miniaturized bending devices as the next step in achieving extremely high birefringence splitting. Furthermore measurements with integrated hotspot structures on VCSEL chips were made to reach much smaller scales for birefringence fine-tuning.