Concept of feedback-free high-frequency loss modulation in detuned duo-cavity vertical cavity surface-emitting laser

Abstract

The authors propose and demonstrate a novel concept for ultrahigh-speed loss modulation of a vertical cavity surface-emitting laser (VCSEL). A duo-cavity device architecture is used to optically decouple the ac feedback component of a loss-modulation section from the VCSEL active region. The elimination of feedback allows modulation of the VCSEL output far beyond the optoelectronic relaxation frequency by eliminating both resonance and intrinsic high-frequency response roll-off. Precise detuning of the resonances of both coupled cavities is used to achieve ac feedback elimination by control of thickness during molecular beam epitaxy growth. Variation in the applied bias at the multiple-quantum-well modulator section allows adjustment of detuning to change coupling between the two sections, resulting in resonance features in the modulation response. In the ideal case, the resulting resonance-free high-frequency modulation response is limited only by parasitics of the modulator section. A flat (±3 dB) modulation response up to 20 GHz and data bandwidth up to 20 GB/s are demonstrated by using this modulation method.