VCSEL with intracavity modulator: Fast modulation options

An integrated optoelectronic device, comprising VCSEL and intracavity electro-absorption modulator within the same epitaxial structure, has been previously developed by several research groups. Such a combination device, despite having relatively weak DC modulation, exhibits strong optical feedback, resulting in strong optoelectronic resonance feature in small-signal modulation response characteristic . At large modulation amplitude, device demonstrates pulsed response. Similar to Q-switching operation, energy accumulated in the gain medium over full modulation cycle is released in a single short pulse once cavity Q-factor is increased. As a result, traditional NRZ amplitude modulation becomes ineffective. We are proposing a phase-pulse modulation approach to drive this device, when strong optical feedback is used for obtaining very fast rise and fall times of short pulses. Such transient times can be on the order of few photon lifetimes, e.g. few picoseconds. Gain medium depletion can be avoided by variation of Q-factor both above and below steady-state value and keeping total emitted energy per cycle at a constant level. Data showing modulation properties (pulse energy >100 fJ, FWHM 40 ps non-controlled pulse length at 4 GHz,) and device characteristics, along with numerical analysis of such device for different modulation waveforms is presented.