Research Project
I study the optical properties of semiconductor quantum dots embedded in photonic crystal nanocavities. We have shown that this system can be used to achieve ultra-efficient lasers and to realize key quantum information tasks in the solid state. The unique optical properties arise because the photonic crystal cavity can confine single particles of light (photons) in ultra-small, nanoscale volumes. When light is confined so well, the interaction between photons and embedded quantum dots is enhanced by orders of magnitude.
For lasing applications, we have shown that a few randomly-positioned quantum dots can couple to the cavity mode irrespective of spectral detuning with high efficiency. We have measured threshold pump powers in the nanoWatts and Beta factos of ~0.8.
To study quantum information in these structures, we found that it was critical to place a single quantum dot very precisely in the cavity. Only in this way could we achieve an effective two-state system and observe coherent interaction between a single photon in the cavity and a single quantum-dot exciton. We have observed the Strong Coupling regime in which the two states hybridize to form mixed "polariton" states. These entangled states can be used to encode and transmit quantum information or to convert quantum information between light and matter.