Novel physics in photonic crystal nanolasers : Dynamics and Coherence

The development of nanoscale sources of coherent light is a key element in the route towards nanoscale optical circuits. Because of their reduced size, nanoscale lasers sustain a very small number of optical modes and can contain only a few emitting dipoles as gain material. This has a strong impact on the laser characteristics. For instance, the laser can be subject to Cavity Quantum ElectroDynamics (CQED) effects, such as spontaneous emission enhancement and preferential funneling of spontaneous emission into the useful mode, so that the fraction β of spontaneous emission in the useful mode may be of the order of few 10^-1, in contrast to conventional lasers with β of the order of 10-⁵. As a consequence, the number of photons at threshold (equal to 1/ v/3) is very small, typically 1 to 10. For such small numbers, fluctuations are large (of the order of the average values), occur only in integral multiples of a base value (corresponding to a change of a single unit), are asymmetric (as excursions into negative values are impossible) and cause the nanolaser output to deviate from that predicted by the traditional laser rate equations.