Dynamics of 1.55 μm Buried Tunnel Junction VCSELs under optical injection around threshold

An investigation into the carrier and spectral dynamics of a 1.55 μm Buried Tunnel Junction (BTJ) VCSEL was carried out by examining the emission spectra under high resolution and the voltage across the junction as polarisation resolved light from a tunable laser source was injected into the cavity. The VCSEL combines an epitaxial InGaAlAs distributed Bragg reflector with a Si/ZnS dielectric reflector and an oval shaped BTJ leading to a predominantly single transverse polarisation mode and laser linewidths as low as 20 MHz. Around lasing threshold and injecting into the primary mode, the voltage required to maintain the current drops due to stimulated emission and a consequent reduction in the carrier density. Locking behaviour associated with this characteristic is measured with increased input power. Voltage drops as large as 6 mV are measured. Above threshold, injection locking is measured in addition to features associated with the relaxation oscillations of the carriers.