Dynamics of ultra small semiconductor lasers

Semiconductor lasers represent an exceptional success story of breakthroughs in fundamental physics. In particular, laser structures with small cavity volumes are becoming attractive candidates for high-speed direct... [ view full abstract ]

Semiconductor lasers represent an exceptional success story of breakthroughs in fundamental physics. In particular, laser structures with small cavity volumes are becoming attractive candidates for high-speed direct modulation, with bandwidths much beyond those of conventional semiconductor lasers due to small volume and short radiative carrier lifetime. The attractiveness of ultra small devices relies in the dimensions of the optical cavity, close to or below diffraction limit. First, this offers promise for tighter integration of optoelectronic devices on a microchip and for reduced energy consumption per transmitted bit of information, which are of vital importance for optical interconnection applications. To the best of our knowledge, little is known on the dynamics of such small devices, in particular close to their threshold where there is strong competition between spontaneous and stimulated emissions as well as potential for super-radiance effects. This work aims first at investigating the impact of the spontaneous emission rate and the Purcell factor on the static and dynamical responses of semiconductor lasers for which the cavity dimensions become close to the lasing wavelength. In the limiting case of dimensions below the diffraction limit, our analysis unveils that relaxation oscillation frequency, damping factor and 3-dB bandwidth are not necessary increased when compared to standard edge emitters (macro-lasers) or micro-lasers (VCSEL) under comparable pumping conditions. The last part will focus on the nonlinear dynamics under optical injection, which can be used to enhance the modulation dynamics. In this case, the light from an external master laser is injected into the slave laser, which can lock onto the master wavelength. The direct-modulation response of the injection-locked laser then exhibits a resonance at the frequency detuning between the master and slave lasers, which allows reaching 3-dB bandwidths much larger than the free-running bandwidth of the slave laser. Results reveal that devices with smaller size from close to below the diffraction limit allow an increase of the stable-locking area. Overall, the presented results will unveil the importance of the device miniaturization on the laser dynamics, in the context of developing novel laser sources for the aforementioned applications.