Electric Current Tuning the Self-Oscillation Frequency of EC-VCSELs

We demonstrate a new way to electrically tune the self-oscillation frequency of an external cavity VCSEL by changing the electrical current injected into the VCSEL, without using any mechanical moving parts. We found that for a self-oscillation frequency from 500 MHz to 4 GHz, the tuning range is up to 15% and the tuning rate is up to 800 MHz/mA. Our experiments and simulation show that the injection current tuning of self-oscillation frequency is due to a change in the VCSEL birefringence induced by changing the injection current.