Phys. Rev. Lett. 113, 163901 (2014)

A miniature photonic crystal laser capable of being modulated at terahertz speeds has been designed by scientists in Denmark. Jesper Mork and co-workers say that their photonic crystal Fano laser uses a mirror based on a Fano resonance between a photonic crystal cavity and a photonic crystal defect waveguide. The Fano mirror has a narrow reflection band centred at the nanocavity resonance. The other mirror that forms the laser cavity is made by a simple termination of the defect waveguide. Inducing small amplitude changes in the nanocavity resonance allows the laser to be modulated at frequencies that are well beyond the carrier dynamics and bandwidth of conventional lasers. In contrast, introducing larger changes in the resonance yields the generation of a train of ultrashort pulses. It is thought that the laser design may prove useful for conducting fundamental investigations of the nonlinear dynamics of coupled lasers that share a common mirror. The laser's modulation bandwidth can be increased by reducing the length of the cavity, which leads to a rise in the laser threshold gain, reduces its output power and increases its relative intensity noise.